The March 6 Storm- The (last) Great White Hope, Part II

[SeminoleSullivan]

Big takeaway is not adding to gfs 850 confidence. Never want to be fighting uphill with consensus.

Its been a great day. May not feel *perfect* but it never will. Let's just break the f***ing streak and drink gravy from there.

 

Might I suggest everyone in the mid-atlantic shutting off their lights/power for the next 36 hours? This will greatly help in the larger cities...

 

Beyond that, there's really nothing we can do. Personally, I'd rather see a marginal threat...it prepares us for what could be 'worst case.'  I'd probably hate to be on here tomorrow if 850s/9s were modeled to be -8 or better, and then we end up not verifying.

[SeminoleSullivan]

Elevation is best bet.

Elevation is best bet, but since we can't rapidly build a mountain for DC/BWI...Speed is best. If we can cool the column before the morning hours, then the uphill battle becomes a little easier.

[Bob Chill]

Might I suggest everyone in the mid-atlantic shutting off their lights/power for the next 36 hours? This will greatly help in the larger cities...

Beyond that, there's really nothing we can do. Personally, I'd rather see a marginal threat...it prepares us for what could be 'worst case.' I'd probably hate to be on here tomorrow if 850s/9s were modeled to be -8 or better, and then we end up not verifying.

Tomorrow is when the real fun starts. We get to compare actual thermals to models. I'm a #s guy too...lol.

And the rap comes into play. Good times never end man.

[SeminoleSullivan]

Tomorrow is when the real fun starts. We get to compare actual thermals to models. I'm a #s guy too...lol.

And the rap comes into play. Good times never end man.

 

Agreed, I posted a day or two ago about numbers. I'm huge on holding models accountable. Just going on blind data is a terrible idea. I would never trust my financial guy if he said:

 

"Well, we talked it over with the 5 guys here at the firm, one says you have between 100 and 300 dollars, a couple say you have a few thousand, and others say you lost all of your money"

 

I'll say it once more, and then I'm done (not to you, just in general): Take your favorite model from yesterday, look at projected 850s for the time frame that exists now, compare 850s, surface, current observations...Probably a sure fire way to verify is to see what's happening in the MW with your favorite model.

 

Granted, that's not an indicator of what will happen here, tomorrow...this is a tight gradient. But it is an indicator of what you're investing your money in. Same thing you'd do with your investment banker...everyone's profile is different, but you can learn a lot from a little work.

 

Sidenote: I'm A believer in about 80% of the NAMs temperature profiles, and almost wholly in the camp for the GFS' QPF if anyone cares. 

[Bob Chill]

One last note before I faint from exhaustion. The euro is pasting ORH now. This is good because it's a full cave and the gfs made the euro look like a jv model for the last 2-3 days. DT looking like junior high too.

But now we don't want the euro looking like the gfs temp wise. Nothing comes easy. Especially on March. But its been a fun ride and its going to snow. Life is good.

[Bari]

i wonder what tonight temperature profiles will do to help to hurt initial temperatures, probably almost nothing.

[Arnold214]

thanks....we really need 950 temps because that is where the problem lies....plus there is no cold air within 800 miles

EC 950 temps hover right at 0c 12z wed onward.

[SeminoleSullivan]

Just discussing with EasternUSWX - the SREFs are wet wet wet. But a touch warmer than many of us would like to see (GFS-esque)

 

Should be enough to push some of the local WFOs to turn those watches to warnings, though.

[tdmorrow]

NAM looks juicier and like it might actually track closer to the coast this run.

[tdmorrow]

and further north.....

[Jebman]

Isn't it getting close to nowcasting time? Check out the radars - precip already forming in southwest VA

http://radar.weather.gov/Conus/full_loop.php

[orangewx]

06z NAM is another crushing blow with its qpf output. W and SW of DC seems to be the jackpot area of 2"+ liquid. Culpeper, Madison, Greene counties up towards winchester.....someone in that area is going to get reemed some kinda good.

[Bari]

06z NAM is another crushing blow with its qpf output. W and SW of DC seems to be the jackpot area of 2"+ liquid. Culpeper, Madison, Greene counties up towards winchester.....someone in that area is going to get reemed some kinda good.

DC has a mixing issue concern, may end up being mostly rain.

[Jebman]

I'm SW of DC lol

[SeminoleSullivan]

Take it for what it's worth. 

 

Looking at where the frozen stuff actually starts for DC/Balt is somewhere around the 36-39 hour mark per soundings. If you subtract the wet stuff from the overall QPF totals, then do some fancy calculatin' and drop ~.35 QPF from the overall totals for what the ground will eat up due to moisture...

 

You end up with ~.5 of frozen QPF. for DC, .6 or so for BWI. 

 

...Per the NAM, anyhow.

[snowdude]

Just ridiculous snow maps. No way it's mostly rain sorry.

[tmagan]

The new HPC (Weather Prediction Center) heavy snowfall maps just released should make you guys happy.

[Jebman]

Take it for what it's worth. 

 

Looking at where the frozen stuff actually starts for DC/Balt is somewhere around the 36-39 hour mark per soundings. If you subtract the wet stuff from the overall QPF totals, then do some fancy calculatin' and drop ~.35 QPF from the overall totals for what the ground will eat up due to moisture...

 

You end up with ~.5 of frozen QPF. for DC, .6 or so for BWI. 

 

...Per the NAM, anyhow.

Per the nam clown map - I should see 4 inches tops.

 

It isnt 12 inches but that 4 inches is the best I've seen all winter.

 

I'll take it 

Big amts were always well west, in the mountains. Let them enjoy huge branches bisecting their homes and a week with no power in cold windy weather.

[orangewx]

Winter Storm Warnings have expanded eastward a bit into the piedmont of virginia (including the counties i just mentioned above, and the city of Charlottesville).

[SeminoleSullivan]

Per the nam clown map - I should see 4 inches tops.

 

It isnt 12 inches but that 4 inches is the best I've seen all winter.

 

I'll take it 

Big amts were always well west, in the mountains. Let them enjoy huge branches bisecting their homes and a week with no power in cold windy weather.

 

Apparently, LWX has the goggles on 

[blazeKing]

Amazingly my NWS forecast has 3-5" Tues night and a county west of me (culpeper) has a WSW ...And I hear around here it's going to be mostly rain and you've got to believe it with experts showing the soundings and everything. What the in the world are they looking at that we aren't?

[Jebman]

Where do I get a pair of them goggles lol?

 

If we can resolve the mixing issues - those amts could verify.

[snowdude]

06z GFS looks good to be. 850s crash quickly again. I just don't believe these very warm profiles. This is a classic looking track and even without arctic air the rates will be strong and enough to overcome the warm BL. But that's just me and that's what LWX is leaning towards. They're just scared and waiting for 12z before shifting warnings east.

[SeminoleSullivan]

06z GFS looks good to be. 850s crash quickly again. I just don't believe these very warm profiles. This is a classic looking track and even without arctic air the rates will be strong and enough to overcome the warm BL. But that's just me and that's what LWX is leaning towards. They're just scared and waiting for 12z before shifting warnings east.

Almost entirely concur. I'd just like to see those totals in my yard rather than in my gauge or on my board

[nw baltimore wx]

A great disco out of LWX this morning explaining the components of this system and their concerns.

[Voyager]

Wind concerns for me since I drive a high profile vehicle. Sustained? Gusts? The US50 Bay Bridge?

[Jebman]

000

FXUS61 KLWX 050855

AFDLWX

http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=AFD&format=CI&version=1&glossary=1&highlight=off

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

355 AM EST TUE MAR 5 2013

.SYNOPSIS...

HIGH PRESSURE WILL MOVE INTO THE WESTERN ATLANTIC TODAY. STRONG

LOW PRESSURE WILL IMPACT THE AREA LATE THIS AFTERNOON THROUGH

WEDNESDAY NIGHT. THE LOW WILL MOVE AWAY FROM THE AREA THURSDAY.

HIGH PRESSURE WILL BUILD OVERHEAD LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...

HIPRES RDG FM GRTLKS TO VA ATTM. HWVR...CLDS FM WAA/OVERRUNNING

ALREADY ACRS VA/WVA...AND READY TO CROSS THE PTMC INTO MD. PCPN IN

SRN WV WAS MORE MIXED THAN SNW. HWVR...AS IT REACHES THE DRY AMS

ACRS CWFA /DEWPTS IN THE TEENS/...IT SHUD DSPT. THEREFORE...AM NOT

EMPHASIZING IT IN THE MRNG GRIDS...BUT DO RECOGNIZE THAT POP S OF

W99-OMH IS NONZERO.

TEMPS THE KEY TO FCST TDA-TNGT. AS HIPRES SHIFTS OFFSHORE...AN

ELY/SELY FLOW WL ENSUE. THAT/LL BE THE PRIMARY PCPN GENERATOR FOR

THE DAYTIME HRS. MEANWHILE...UPR LOW/JET STREAK AND ITS SFC LOW

REFLECTION WL BE DROPPING FM THE PLAINS/MIDWEST TO THE MID OHVLY...

INCRSG UVV. SINCE PCPN SHUD BE RATHER LGT AT FIRST AND WAA WL BE

PRESENT ALOFT...SFC TEMPS WL BE ABLE TO WARM INTO THE 40S. THAT

MAKES ONSET PCPN TYPE FCST MORE CHALLENGING. SUSPECT EVAP COOLING

/TOP-DOWN/ WL COOL COLUMN AND THEREFORE SUPPORT SNW...BLYR TEMPS WL

BE SUPPORTIVE OF MELTING. AM THEREFORE EMPHASIZING EITHER RA /E/ OR

RASN /W/ FOR THE AFTN HRS. POPS WL BE HIEST S OF CHO/SHD...W/ A DRY

FCST TDA N OF DCA-MRB.

TNGT DYNAMIC PROCESSES FM THE CYCLONE TAKE OVER...INCL AN INCRSGLY

STRONG /60-70 KT/ COLD CONVEYOR BELT. THE SFC LOW WL BE PASSING EWD

SOMEWHERE NEAR THE NC/VA BRDR...PLACING CWFA IN THE AREA OF BEST

LIFT AND MSTR INFLUX. SFC TEMPS REMAIN PESKY THO. SHUD HV COOLING OF

THE COLUMN...BUT THERE/S NO REAL COLD AIR ANYWHERE...AS SFC FLOW WL

BE INCRSG OFF OF THE RATHER WARM ATLC. AM SEEING PTYPE DIFFS IN GDNC

INCREASE BY LT TNGT. WL FAVOR STRONG DYNAMIC COOLING...MARCHING THE

RA-SN LINE EWD TO SOMEWHERE E OF I-95 BY DAWN. AM NOT REAL CERTAIN

WHERE IT WL END UP THO...AND HV A FAIRLY WIDE SWATH OF RASN IN GRIDS

TO DEPICT THAT UNCERTAINTY.

IN THE END...IT/LL BE THE POSITION OF THAT TRANSITION WHICH

DETERMINES SNFL ACCUMS. AM COMFY THAT SGFNT SNW WL MAKE IT E OF THE

BLURDG BTWN MIDNGT AND DAWN. CONCERNED ABOUT THE RA/SN LINE...AM MUCH

LESS CERTAIN OF THE END RESULT IN THE I-95 CORRIDOR. SNOW WL BE

WET...WITH RATHER LOW SLR /LESS THAN 10-1/. WRNGS WERE EXPANDED

EWD...AS DETAILED IN SHORT TERM DSCN BLO.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...

AS WITH MOST CONTINENTAL STORM SYSTEMS THAT APPROACH AND EVENTUALLY

DEVELOP A SUBSEQUENTLY STRONGER COASTAL LOW BEFORE LEAVING THE EAST

COAST...THE INCOMING STORM SHOULD BE LOOKED-AT IN AT LEAST TWO MAIN

PHASES. THE FIRST PHASE WILL BE LARGELY RESPONSIBLE FOR DROPPING

SEVERAL INCHES OF THE SNOW ALONG AND WEST OF THE BLUE RIDGE

OVERNIGHT AND INTO EARLY WED. THE SECOND PHASE WILL BE GEARING UP AS

THE FIRST IS WINDING DOWN...AFFECTING THE ERN HALF OF THE CWA

BASICALLY FROM THE PREDAWN HRS WED THRU THE REMAINDER OF THE DAY.

PHASE II...

GULF STREAM WATER TEMPS JUST A COUPLE HUNDRED MILES OFF THE VA

TIDEWATER ARE IN THE 60S/NEAR 70...TAPERING OFF BACK INTO THE

40S/L50S CLOSER TO THE ATLC COASTLINE. THIS LARGE TEMP

STRATIFICATION WILL QUICKLY INTENSIFY THE SFC LOW AFTER IT MOVES OFF

THE COAST...BUT EVEN BEFORE REACHING THE VA TIDEWATER REGION...THE

LOW WILL BE QUICKLY INTENSIFY MOVING OFF THE LEE OF THE SRN VA BLUE

RIDGE AND BEGIN TO TRANSFORM THE STORM SYSTEM INTO ITS SECOND PHASE.

THIS WILL CONVERT THE LARGE BATCH OF PRECIP THAT WILL HAVE DRIFTED

FROM SW-TO-NE OVER THE SHEN VLY TO A MORE ELY DRIVEN FLOW AND

DEVELOP INTENSE AND CONCENTRATED SNOW BANDS THAT WILL BE WRAPPING

AROUND THE BACKSIDE OF THE DEVELOPING COASTAL LOW.

HEADLINE CHANGES...

THE WINTER STORM WARNING HAS EXPANDED A TIER TOWARD THE EAST -

ACROSS THE FOOTHILLS OF THE BLUE RIDGE/CATOCTINS. THE WS WATCH

REMAINS IN EFFECT FOR THE REMAINDER OF THE CWA INCLUDING ALL OF THE

I-95 CORRIDOR. THOUGH SNOWFALL TOTALS WERE INCREASE AREA

WIDE...CONFIDENCE ACROSS THE METRO AREAS FOR THESE HIGHER AMOUNTS

REMAINS LOWER THAN NECESSARY FOR FURTHER EXPANSION.

THE I-95 CORRIDOR QUESTION-MARK...

THE 00Z GFS HAS TRENDED WARMER AND IN-FACT SHOWS LONGER PERIODS OF

RAIN ALONG AND E OF I-95 INTO WED MRNG BOTH THAN ITS OWN PREVIOUS

RUNS AND W/ OTHER NEAR-TERM MEMBERS. HOWEVER...A STILL BULLISHLY

COLD NAM DOESN`T SEEM LIKE SUCH AN OUTLIER AND WAS USED MORE SO

IN-CONCERT W/ THE EURO THAN WEIGHING-IN THE GFS. WITH THIS

TRANSFORMATION OF THE SYSTEM INTO ITS SECOND PHASE...THIS MAY ALLOW

FOR A BRIEF PERIOD OF WARMER TEMPS/LIQUID PRECIP TO RETREAT BACK

TOWARD THE WEST - W OF I-95...EVEN IF SNOW BEGINS TO FALL IN THE

IMMEDIATE DC/BALT AREA AND POINTS EAST. THE RAIN-SNOW LINE WILL

CONTINUE TO WAVER DURING THE POST-DAWN HOURS OF WED ACROSS THE METRO

AREAS.

DYNAMIC COOLING WILL THEN BE THE DIFFERENCE IN PRODUCING ALL-SNOW

BACK INTO THE METRO AREAS...AS THE LOW SHIFTS OFF THE COAST TOWARD

THE MIDDAY HRS WED. DURING AND BEFORE THIS TIME...THE MTNS/SHEN

VLY/BLUE RIDGE AND EVEN THE WRN DC/BALT SUBURBS WILL HAVE BEEN IN AN

ALL-SNOW REGIME...BUT THE DYNAMIC COOLING OF THE LOWEST FEW THOUSAND

FEET FROM THE RESULTANT STRENGTHENING OF THE LOW WILL USHER IN A

PERIOD OF HEAVY SNOW ACROSS THE METRO AREAS. THOUGH ACCUMULATION MAY

HAVE A SLOW START ACROSS THESE AREAS THAT SAW RAIN FOR LONGER

PERIODS...THE SNOW RATIO/THE HEAVY-WET FLAKES AND INTENSITY WILL

QUICKLY OVERCOME THIS AND SFC TEMPS THAT WILL LIKELY BE HOVERING IN

THE 33-36 RANGE. THE MORE INTENSE SNOW FALLS...THE QUICKER THESE

TEMPS WILL THEN START TO DROP TOWARD FREEZING. WHILE THIS IS

OCCURRING DURING THE LATE AFTN/EVE HRS WED...THE LOW WILL BE MOVING

OFF THE COAST AND DRAGGING THE SNOW BANDS WITH IT.

NEARLY ALL GUIDANCE IN AGREEMENT THAT AT LEAST SOME LIGHT SNOW WILL

BE FALLING ALONG THE WRN PERIPHERY OF THE HEAVIER BANDS ALL THE WAY

INTO THE EARLY MRNG HRS THU...JUST AFTER MIDNIGHT AND DISSIPATING

FROM THERE. THE HEAVIEST ACCUMULATIONS WILL HAVE ALREADY OCCURRED

EARLIER IN THE EVE ACROSS THE REGION - W/ A POSSIBLE 6-10 INCHES

ACROSS THE VA/MD PIEDMONT W OF I-95...A QUICK COUPLE-FEW INCHES FROM

THE SRN MD COAST TO THE DC AND BALT AREAS.

NEARLY ALL THIS TIME...STRONG AND GUSTY WINDS WILL BE AFFECTING THE

AREA - WRAPPING AROUND THE LOW AS IT STRENGTHENS...REDUCING

VISIBILITIES AND DROPPING WIND CHILLS. THIS WILL ALSO BE ADVERSE FOR

DRIVING AND FOR TREES/POWERLINES. WIDESPREAD POWER OUTAGES COULD

RESULT FROM TREE BRANCHES SNAPPING UNDER THE HEAVY-WET SNOW AND

GUSTY WINDS. MODELS QPFS CONTINUE TO SHOW BETWEEN AN 1.0-1.5 INCHES

OF QPF ACROSS THE AREA. SNOWFALL RATIOS WILL LIKELY BE BETWEEN 7-8:1

FURTHER SOUTH AND 10:1 FURTHER WEST AND NORTH.

WILL CONTINUE TO MONITOR THE POTENTIAL FLOODING THREAT FROM THESE

HIGHER QPF AREAS...ESPECIALLY POST-EVENT AS RUNOFF AND QUICK MELTING

COULD CREATE RIVER FLOODING IN THE DAYS FOLLOWING.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...

ANOTHER CHANGE FROM THIS TIME YESTERDAY IS THAT GUIDANCE IS NOW

KEEPING THE COASTAL STORM JUST OFF THE COAST FOR A LONGER PERIOD OF

TIME AND NOT MOVING AWAY UNTIL LATE FRI. FROM THU NIGHT INTO

FRI...THE LOW COULD CONTINUE TO SLIDE A COUPLE MORE WAVES OF LIGHT

PRECIP OVER THE NY/NJ AREAS AND PORTIONS OF DELMARVA. LITTLE IF ANY

OF THIS IS EXPECTED TO PUSH BACK INTO THE CHES BAY/MD ZONES. WINDS

WILL CONTINUE TO GUST OUT OF THE N-NW FROM THU INTO FRI...BUT A TIER

LESS EACH DAY AND NOT AS COLD W/ HIGH PRESSURE GRADUALLY BUILDING IN

TO CLOSE OUT THE WEEK.

A LARGE UPPER RIDGE WILL DOMINATE THE MIDDLE PORTIONS OF THE CONUS

LATE THIS WEEK INTO THE WEEKEND. THE RIDGE AXIS WILL DRAW UP WARMER

AIR FROM THE SOUTH...OUT AHEAD OF YET ANOTHER STORM SYSTEM BACK

ACROSS THE ROCKIES. THIS AXIS OF WARMER AIR WILL POKE INTO THE EAST

COAST AND ERN SEABOARD ON SAT...JUST AS THE STORM FROM THE MTN WEST

QUICKLY PUSHES TOWARD THE PLAINS AND MS VLY. LONG TERM GUIDANCE

STILL DIFFERING ON WHAT HAPPENS FROM HERE...NAMELY BECAUSE OF THEIR

DIFFERENT DEPICTIONS OF THE CHARACTERISTICS OF THE DEEP SHORTWAVE

TROUGH. THE GFS KEEPS IT AN OPEN WAVE FOR LONGER AND MAKING A

QUICKER ZONAL FLOW PASSAGE...WHILE THE LATEST EURO MAKES THE SYSTEM

A LARGE CUT-OFF UPPER LOW THAT TAKES MUCH LONGER TO EVEN APPROACH

THE EAST COAST BY EARLY NEXT WEEK.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...

VFR CONDS FOR MOST OF TDA...BUT PCPN WL BE PUSHING IN FM SW-NE LT

AFTN-EVE. INIT PTYPE RA OR RASN...BUT THEN ENUF COLD AIR WL WORK IN

FM THE W FOR PCPN TO CHG OVER TO SNW. THE CHGOVER MAY HOLD OFF ACRS

DC/BALT METROS TIL AFTR MIDNGT. FLGT CONDS DROPPING TO MVFR...AND

EVENTUALLY DOWN TO IFR BY DAYBREAK. AS LOPRES PASSES S OF TERMINALS

TOWARD DAWN...WNDS AT FL 020 WL BE INCRSG FM THE E AT 40-50 KT...

PRODUCING PROBABLE LLWS.

IFR CONDS WEDNESDAY AND WILL EVEN REDUCE FROM THERE UNDER HEAVIER

BANDS OF SNOW THAT DEVELOP ACROSS THE REGION WED MRNG/AFTN. A RAIN

TO RAIN/SNOW MIX IS EXPECTED EARLY WED BUT GRADUALLY CHANGE TO

ALL-SNOW LATER IN THE MRNG/AFTN WED. INTERMITTENT LIGHT-MODERATE

SNOW AND GUSTY WINDS WILL CONTINUE WED AFTN EVE. SNOW WILL TAPER OFF

WED NIGHT THOUGH WINDS WILL STAY GUSTY WELL INTO THE WED NIGHT...THU

AND A TIER LOWER ON FRI. VFR CONDITIONS RETURN BY THU MRNG AND

LINGER THRU THE UPCOMING WEEKEND.

&&

.MARINE...

LGT WNDS TDA...MAINLY FM THE E...BUT WNDS INCRSG LT TAFTN-TNGT AS

STORM SYSTEM APPROACHES FM THE W. AN ELY FLOW WL BE INCRSG TNGT AS

LOPRES PASSES S OF THE WATERS. HV RAISED SCA FOR THE OVNGT HRS ALL

WATERS.

GALE FORCE WIND GUSTS ARE EXPECTED TO BEING WED MRNG ACROSS THE

BAY/TP AND CONTINUE TO SPREAD OVER THE WATERS ALL-DAY AND INTO THE

NIGHTTIME HRS. A SFC LOW THAT WILL PASS JUST SOUTH OF THE BAY/TP

INLET REGION WILL BE STRENGTHENING AS IT MOVES EWD WED AFTN/EVE. AS

IT MOVES OFF THE COAST...WINDS WILL CONTINUE TO BE STRONG ACROSS THE

WATERS FROM THE RELATIVE PROXIMITY TO THE FEATURE. GALE FORCE GUSTS

WILL STILL POSSIBLE ON THU AFTN - ESPEC OVER THE MIDDLE/LOWER

PORTIONS OF THE BAY W/ SOLID SCA GUSTS ELSEWHERE. THE LOW WILL

REMAIN OFFSHORE INTO FRI...CONTINUING TO STREAM GUSTY SCA WINDS OVER

THE WATERS UNTIL IT MOVES AWAY FRI NIGHT W/ HIGH PRESSURE BUILDING

IN OVER THE AREA.

&&

.TIDES/COASTAL FLOODING...

A STRONG AREA OF LOW PRES WL IMPACT THE REGION TUE NIGHT INTO WED.

WITH ONSHORE FLOW DEVELOPING...MINOR COASTAL FLOODING IS LIKELY

DURING THE WED MRNG HIGH TIDE CYCLE ALONG THE WRN SHORE OF THE MD

CHSPK BAY FROM ANNAPOLIS SWD INTO ST MARYS COUNTY. FARTHER NORTH

TOWARD BALTIMORE AND HAVRE DE GRACE...LATEST CBOFS GUIDANCE

INDICATES A LOWER THREAT. SAME GOES FOR COASTAL AREAS ALONG THE

TIDAL POTOMAC RIVER. ANOMALIES FORECAST TO DECREASE WED AFTN AS NLY

FLOW DEVELOPS...SO THREAT OF COASTAL FLOODING APPEARS TO BE VERY LOW

FOR SUBSEQUENT HIGH TIDE CYCLE.

&&

[blizzardmeiser]

000

FXUS61 KLWX 050855

AFDLWX

http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=AFD&format=CI&version=1&glossary=1&highlight=off

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

355 AM EST TUE MAR 5 2013

.SYNOPSIS...

HIGH PRESSURE WILL MOVE INTO THE WESTERN ATLANTIC TODAY. STRONG

LOW PRESSURE WILL IMPACT THE AREA LATE THIS AFTERNOON THROUGH

WEDNESDAY NIGHT. THE LOW WILL MOVE AWAY FROM THE AREA THURSDAY.

HIGH PRESSURE WILL BUILD OVERHEAD LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...

HIPRES RDG FM GRTLKS TO VA ATTM. HWVR...CLDS FM WAA/OVERRUNNING

ALREADY ACRS VA/WVA...AND READY TO CROSS THE PTMC INTO MD. PCPN IN

SRN WV WAS MORE MIXED THAN SNW. HWVR...AS IT REACHES THE DRY AMS

ACRS CWFA /DEWPTS IN THE TEENS/...IT SHUD DSPT. THEREFORE...AM NOT

EMPHASIZING IT IN THE MRNG GRIDS...BUT DO RECOGNIZE THAT POP S OF

W99-OMH IS NONZERO.

TEMPS THE KEY TO FCST TDA-TNGT. AS HIPRES SHIFTS OFFSHORE...AN

ELY/SELY FLOW WL ENSUE. THAT/LL BE THE PRIMARY PCPN GENERATOR FOR

THE DAYTIME HRS. MEANWHILE...UPR LOW/JET STREAK AND ITS SFC LOW

REFLECTION WL BE DROPPING FM THE PLAINS/MIDWEST TO THE MID OHVLY...

INCRSG UVV. SINCE PCPN SHUD BE RATHER LGT AT FIRST AND WAA WL BE

PRESENT ALOFT...SFC TEMPS WL BE ABLE TO WARM INTO THE 40S. THAT

MAKES ONSET PCPN TYPE FCST MORE CHALLENGING. SUSPECT EVAP COOLING

/TOP-DOWN/ WL COOL COLUMN AND THEREFORE SUPPORT SNW...BLYR TEMPS WL

BE SUPPORTIVE OF MELTING. AM THEREFORE EMPHASIZING EITHER RA /E/ OR

RASN /W/ FOR THE AFTN HRS. POPS WL BE HIEST S OF CHO/SHD...W/ A DRY

FCST TDA N OF DCA-MRB.

TNGT DYNAMIC PROCESSES FM THE CYCLONE TAKE OVER...INCL AN INCRSGLY

STRONG /60-70 KT/ COLD CONVEYOR BELT. THE SFC LOW WL BE PASSING EWD

SOMEWHERE NEAR THE NC/VA BRDR...PLACING CWFA IN THE AREA OF BEST

LIFT AND MSTR INFLUX. SFC TEMPS REMAIN PESKY THO. SHUD HV COOLING OF

THE COLUMN...BUT THERE/S NO REAL COLD AIR ANYWHERE...AS SFC FLOW WL

BE INCRSG OFF OF THE RATHER WARM ATLC. AM SEEING PTYPE DIFFS IN GDNC

INCREASE BY LT TNGT. WL FAVOR STRONG DYNAMIC COOLING...MARCHING THE

RA-SN LINE EWD TO SOMEWHERE E OF I-95 BY DAWN. AM NOT REAL CERTAIN

WHERE IT WL END UP THO...AND HV A FAIRLY WIDE SWATH OF RASN IN GRIDS

TO DEPICT THAT UNCERTAINTY.

IN THE END...IT/LL BE THE POSITION OF THAT TRANSITION WHICH

DETERMINES SNFL ACCUMS. AM COMFY THAT SGFNT SNW WL MAKE IT E OF THE

BLURDG BTWN MIDNGT AND DAWN. CONCERNED ABOUT THE RA/SN LINE...AM MUCH

LESS CERTAIN OF THE END RESULT IN THE I-95 CORRIDOR. SNOW WL BE

WET...WITH RATHER LOW SLR /LESS THAN 10-1/. WRNGS WERE EXPANDED

EWD...AS DETAILED IN SHORT TERM DSCN BLO.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...

AS WITH MOST CONTINENTAL STORM SYSTEMS THAT APPROACH AND EVENTUALLY

DEVELOP A SUBSEQUENTLY STRONGER COASTAL LOW BEFORE LEAVING THE EAST

COAST...THE INCOMING STORM SHOULD BE LOOKED-AT IN AT LEAST TWO MAIN

PHASES. THE FIRST PHASE WILL BE LARGELY RESPONSIBLE FOR DROPPING

SEVERAL INCHES OF THE SNOW ALONG AND WEST OF THE BLUE RIDGE

OVERNIGHT AND INTO EARLY WED. THE SECOND PHASE WILL BE GEARING UP AS

THE FIRST IS WINDING DOWN...AFFECTING THE ERN HALF OF THE CWA

BASICALLY FROM THE PREDAWN HRS WED THRU THE REMAINDER OF THE DAY.

PHASE II...

GULF STREAM WATER TEMPS JUST A COUPLE HUNDRED MILES OFF THE VA

TIDEWATER ARE IN THE 60S/NEAR 70...TAPERING OFF BACK INTO THE

40S/L50S CLOSER TO THE ATLC COASTLINE. THIS LARGE TEMP

STRATIFICATION WILL QUICKLY INTENSIFY THE SFC LOW AFTER IT MOVES OFF

THE COAST...BUT EVEN BEFORE REACHING THE VA TIDEWATER REGION...THE

LOW WILL BE QUICKLY INTENSIFY MOVING OFF THE LEE OF THE SRN VA BLUE

RIDGE AND BEGIN TO TRANSFORM THE STORM SYSTEM INTO ITS SECOND PHASE.

THIS WILL CONVERT THE LARGE BATCH OF PRECIP THAT WILL HAVE DRIFTED

FROM SW-TO-NE OVER THE SHEN VLY TO A MORE ELY DRIVEN FLOW AND

DEVELOP INTENSE AND CONCENTRATED SNOW BANDS THAT WILL BE WRAPPING

AROUND THE BACKSIDE OF THE DEVELOPING COASTAL LOW.

HEADLINE CHANGES...

THE WINTER STORM WARNING HAS EXPANDED A TIER TOWARD THE EAST -

ACROSS THE FOOTHILLS OF THE BLUE RIDGE/CATOCTINS. THE WS WATCH

REMAINS IN EFFECT FOR THE REMAINDER OF THE CWA INCLUDING ALL OF THE

I-95 CORRIDOR. THOUGH SNOWFALL TOTALS WERE INCREASE AREA

WIDE...CONFIDENCE ACROSS THE METRO AREAS FOR THESE HIGHER AMOUNTS

REMAINS LOWER THAN NECESSARY FOR FURTHER EXPANSION.

THE I-95 CORRIDOR QUESTION-MARK...

THE 00Z GFS HAS TRENDED WARMER AND IN-FACT SHOWS LONGER PERIODS OF

RAIN ALONG AND E OF I-95 INTO WED MRNG BOTH THAN ITS OWN PREVIOUS

RUNS AND W/ OTHER NEAR-TERM MEMBERS. HOWEVER...A STILL BULLISHLY

COLD NAM DOESN`T SEEM LIKE SUCH AN OUTLIER AND WAS USED MORE SO

IN-CONCERT W/ THE EURO THAN WEIGHING-IN THE GFS. WITH THIS

TRANSFORMATION OF THE SYSTEM INTO ITS SECOND PHASE...THIS MAY ALLOW

FOR A BRIEF PERIOD OF WARMER TEMPS/LIQUID PRECIP TO RETREAT BACK

TOWARD THE WEST - W OF I-95...EVEN IF SNOW BEGINS TO FALL IN THE

IMMEDIATE DC/BALT AREA AND POINTS EAST. THE RAIN-SNOW LINE WILL

CONTINUE TO WAVER DURING THE POST-DAWN HOURS OF WED ACROSS THE METRO

AREAS.

DYNAMIC COOLING WILL THEN BE THE DIFFERENCE IN PRODUCING ALL-SNOW

BACK INTO THE METRO AREAS...AS THE LOW SHIFTS OFF THE COAST TOWARD

THE MIDDAY HRS WED. DURING AND BEFORE THIS TIME...THE MTNS/SHEN

VLY/BLUE RIDGE AND EVEN THE WRN DC/BALT SUBURBS WILL HAVE BEEN IN AN

ALL-SNOW REGIME...BUT THE DYNAMIC COOLING OF THE LOWEST FEW THOUSAND

FEET FROM THE RESULTANT STRENGTHENING OF THE LOW WILL USHER IN A

PERIOD OF HEAVY SNOW ACROSS THE METRO AREAS. THOUGH ACCUMULATION MAY

HAVE A SLOW START ACROSS THESE AREAS THAT SAW RAIN FOR LONGER

PERIODS...THE SNOW RATIO/THE HEAVY-WET FLAKES AND INTENSITY WILL

QUICKLY OVERCOME THIS AND SFC TEMPS THAT WILL LIKELY BE HOVERING IN

THE 33-36 RANGE. THE MORE INTENSE SNOW FALLS...THE QUICKER THESE

TEMPS WILL THEN START TO DROP TOWARD FREEZING. WHILE THIS IS

OCCURRING DURING THE LATE AFTN/EVE HRS WED...THE LOW WILL BE MOVING

OFF THE COAST AND DRAGGING THE SNOW BANDS WITH IT.

NEARLY ALL GUIDANCE IN AGREEMENT THAT AT LEAST SOME LIGHT SNOW WILL

BE FALLING ALONG THE WRN PERIPHERY OF THE HEAVIER BANDS ALL THE WAY

INTO THE EARLY MRNG HRS THU...JUST AFTER MIDNIGHT AND DISSIPATING

FROM THERE. THE HEAVIEST ACCUMULATIONS WILL HAVE ALREADY OCCURRED

EARLIER IN THE EVE ACROSS THE REGION - W/ A POSSIBLE 6-10 INCHES

ACROSS THE VA/MD PIEDMONT W OF I-95...A QUICK COUPLE-FEW INCHES FROM

THE SRN MD COAST TO THE DC AND BALT AREAS.

NEARLY ALL THIS TIME...STRONG AND GUSTY WINDS WILL BE AFFECTING THE

AREA - WRAPPING AROUND THE LOW AS IT STRENGTHENS...REDUCING

VISIBILITIES AND DROPPING WIND CHILLS. THIS WILL ALSO BE ADVERSE FOR

DRIVING AND FOR TREES/POWERLINES. WIDESPREAD POWER OUTAGES COULD

RESULT FROM TREE BRANCHES SNAPPING UNDER THE HEAVY-WET SNOW AND

GUSTY WINDS. MODELS QPFS CONTINUE TO SHOW BETWEEN AN 1.0-1.5 INCHES

OF QPF ACROSS THE AREA. SNOWFALL RATIOS WILL LIKELY BE BETWEEN 7-8:1

FURTHER SOUTH AND 10:1 FURTHER WEST AND NORTH.

WILL CONTINUE TO MONITOR THE POTENTIAL FLOODING THREAT FROM THESE

HIGHER QPF AREAS...ESPECIALLY POST-EVENT AS RUNOFF AND QUICK MELTING

COULD CREATE RIVER FLOODING IN THE DAYS FOLLOWING.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...

ANOTHER CHANGE FROM THIS TIME YESTERDAY IS THAT GUIDANCE IS NOW

KEEPING THE COASTAL STORM JUST OFF THE COAST FOR A LONGER PERIOD OF

TIME AND NOT MOVING AWAY UNTIL LATE FRI. FROM THU NIGHT INTO

FRI...THE LOW COULD CONTINUE TO SLIDE A COUPLE MORE WAVES OF LIGHT

PRECIP OVER THE NY/NJ AREAS AND PORTIONS OF DELMARVA. LITTLE IF ANY

OF THIS IS EXPECTED TO PUSH BACK INTO THE CHES BAY/MD ZONES. WINDS

WILL CONTINUE TO GUST OUT OF THE N-NW FROM THU INTO FRI...BUT A TIER

LESS EACH DAY AND NOT AS COLD W/ HIGH PRESSURE GRADUALLY BUILDING IN

TO CLOSE OUT THE WEEK.

A LARGE UPPER RIDGE WILL DOMINATE THE MIDDLE PORTIONS OF THE CONUS

LATE THIS WEEK INTO THE WEEKEND. THE RIDGE AXIS WILL DRAW UP WARMER

AIR FROM THE SOUTH...OUT AHEAD OF YET ANOTHER STORM SYSTEM BACK

ACROSS THE ROCKIES. THIS AXIS OF WARMER AIR WILL POKE INTO THE EAST

COAST AND ERN SEABOARD ON SAT...JUST AS THE STORM FROM THE MTN WEST

QUICKLY PUSHES TOWARD THE PLAINS AND MS VLY. LONG TERM GUIDANCE

STILL DIFFERING ON WHAT HAPPENS FROM HERE...NAMELY BECAUSE OF THEIR

DIFFERENT DEPICTIONS OF THE CHARACTERISTICS OF THE DEEP SHORTWAVE

TROUGH. THE GFS KEEPS IT AN OPEN WAVE FOR LONGER AND MAKING A

QUICKER ZONAL FLOW PASSAGE...WHILE THE LATEST EURO MAKES THE SYSTEM

A LARGE CUT-OFF UPPER LOW THAT TAKES MUCH LONGER TO EVEN APPROACH

THE EAST COAST BY EARLY NEXT WEEK.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...

VFR CONDS FOR MOST OF TDA...BUT PCPN WL BE PUSHING IN FM SW-NE LT

AFTN-EVE. INIT PTYPE RA OR RASN...BUT THEN ENUF COLD AIR WL WORK IN

FM THE W FOR PCPN TO CHG OVER TO SNW. THE CHGOVER MAY HOLD OFF ACRS

DC/BALT METROS TIL AFTR MIDNGT. FLGT CONDS DROPPING TO MVFR...AND

EVENTUALLY DOWN TO IFR BY DAYBREAK. AS LOPRES PASSES S OF TERMINALS

TOWARD DAWN...WNDS AT FL 020 WL BE INCRSG FM THE E AT 40-50 KT...

PRODUCING PROBABLE LLWS.

IFR CONDS WEDNESDAY AND WILL EVEN REDUCE FROM THERE UNDER HEAVIER

BANDS OF SNOW THAT DEVELOP ACROSS THE REGION WED MRNG/AFTN. A RAIN

TO RAIN/SNOW MIX IS EXPECTED EARLY WED BUT GRADUALLY CHANGE TO

ALL-SNOW LATER IN THE MRNG/AFTN WED. INTERMITTENT LIGHT-MODERATE

SNOW AND GUSTY WINDS WILL CONTINUE WED AFTN EVE. SNOW WILL TAPER OFF

WED NIGHT THOUGH WINDS WILL STAY GUSTY WELL INTO THE WED NIGHT...THU

AND A TIER LOWER ON FRI. VFR CONDITIONS RETURN BY THU MRNG AND

LINGER THRU THE UPCOMING WEEKEND.

&&

.MARINE...

LGT WNDS TDA...MAINLY FM THE E...BUT WNDS INCRSG LT TAFTN-TNGT AS

STORM SYSTEM APPROACHES FM THE W. AN ELY FLOW WL BE INCRSG TNGT AS

LOPRES PASSES S OF THE WATERS. HV RAISED SCA FOR THE OVNGT HRS ALL

WATERS.

GALE FORCE WIND GUSTS ARE EXPECTED TO BEING WED MRNG ACROSS THE

BAY/TP AND CONTINUE TO SPREAD OVER THE WATERS ALL-DAY AND INTO THE

NIGHTTIME HRS. A SFC LOW THAT WILL PASS JUST SOUTH OF THE BAY/TP

INLET REGION WILL BE STRENGTHENING AS IT MOVES EWD WED AFTN/EVE. AS

IT MOVES OFF THE COAST...WINDS WILL CONTINUE TO BE STRONG ACROSS THE

WATERS FROM THE RELATIVE PROXIMITY TO THE FEATURE. GALE FORCE GUSTS

WILL STILL POSSIBLE ON THU AFTN - ESPEC OVER THE MIDDLE/LOWER

PORTIONS OF THE BAY W/ SOLID SCA GUSTS ELSEWHERE. THE LOW WILL

REMAIN OFFSHORE INTO FRI...CONTINUING TO STREAM GUSTY SCA WINDS OVER

THE WATERS UNTIL IT MOVES AWAY FRI NIGHT W/ HIGH PRESSURE BUILDING

IN OVER THE AREA.

&&

.TIDES/COASTAL FLOODING...

A STRONG AREA OF LOW PRES WL IMPACT THE REGION TUE NIGHT INTO WED.

WITH ONSHORE FLOW DEVELOPING...MINOR COASTAL FLOODING IS LIKELY

DURING THE WED MRNG HIGH TIDE CYCLE ALONG THE WRN SHORE OF THE MD

CHSPK BAY FROM ANNAPOLIS SWD INTO ST MARYS COUNTY. FARTHER NORTH

TOWARD BALTIMORE AND HAVRE DE GRACE...LATEST CBOFS GUIDANCE

INDICATES A LOWER THREAT. SAME GOES FOR COASTAL AREAS ALONG THE

TIDAL POTOMAC RIVER. ANOMALIES FORECAST TO DECREASE WED AFTN AS NLY

FLOW DEVELOPS...SO THREAT OF COASTAL FLOODING APPEARS TO BE VERY LOW

FOR SUBSEQUENT HIGH TIDE CYCLE.

&&

Excellent write up. A lot of variables with this storm

[TowsonWeather]

Good news for everyone waking up (for the DC area) ...the 6z GFS looks like it is digging south more ...mirroring the EURO from last night (and previous runs). The NAM looks like the outlier now with a more northerly solution. Thus, temps look much better overall.

 

Your analysis is poor.

[WxMan1]

Well fellas...I have to say that the EC and EC ensembles have been rock solid with their runs of late. The EC, like the UK and CMC, do *not* jog the surface low from SEVA up into the Lower Eastern Shore like the NAM and GFS do (I didn't see the 06Z GFS)...which would result in a more prolonged period of a mix or rain in the metro region.

Moreover, talk about a model of consistency. The EC ensemble mean has DCA in the 5-7" zone, though with not one of the 50 members showing more than 9". That's pretty darn good continuity to have that kind of average without a heavier outlier.

This is not to say the EC won't trend at tad north with the 12Z run around that 12-18Z timeframe, which would result in a warmer, more easterly flow profile btwn 1000-900 mb, but it probably won't be a drastic change at this point like the NAM and GFS have shown of late.

Stick with the EC...where have we heard this before? ;-)