January 31-February 2 Historic Winter Storm part 6

[csnavywx]

csnavy, I'm thinking we could see some localized amounts topping 30" from the IL shore over into northwest Indiana. What say you?

Along the lake? Absolutely. Some great delta-Ts behind this one, so no doubt we'll be seeing some lake enhanced snow or just plain lake effect after the synoptic stuff leaves.

[OceanStWx]

What do you think of the 18Z NAM height field changes?

I'm suspicious. It had about 3 really good consistent runs, then this. I'll chalk it up to a one run stumble right now.

[Thundersnow12]

looks like some 2.5 inches amounts for me

waiting for people to post more detailed info

I'll believe it when i see it though

2.19" liquid

PIA

MON 7P 31-JAN -4.7 -2.1 1021 92 94 0.11 554 537

TUE 1A 01-FEB -4.9 -2.9 1021 92 54 0.10 554 537

TUE 7A 01-FEB -6.1 -4.5 1022 89 83 0.02 553 536

TUE 1P 01-FEB -5.0 -4.5 1020 89 94 0.05 553 537

TUE 7P 01-FEB -4.5 -7.1 1014 91 98 0.77 549 538

WED 1A 02-FEB -5.3 -9.6 1005 89 100 0.71 539 536

WED 7A 02-FEB -6.1 -14.4 1008 90 93 0.32 531 525

WED 1P 02-FEB -6.5 -14.3 1019 87 89 0.09 536 521

WED 7P 02-FEB -6.8 -13.2 1027 87 76 0.02 541 520

[talaub]

It wouldn't be the winter season if this map wasn't any hooter than it, hotter than it is.

Good one "Clark"

[JoMo]

I hope that is more of a euphemism than a reality. I think the idea behind a winter storm warning is that it is already particularly dangerous, especially in the OUN area.

I think it's going to have 'more dangerous' type wording. They are even mentioning the Blizzard word and mentioning Dec 2009 blizzard and how this could be as bad or worse.

[baroclinic_instability]

Hi BI, Congrats on your new job, You will be a gr8 forcaster as you are here! So Im currently thinking some colder air will make it further south to me, making this a more serious icing for us? Thanks

I haven't been looking at detailed soundings in that location through the storm--I think BeauDodson may be your man there since he forecasts near that region specifically.

[Hoosier]

LOT still going with up to 2 feet but leaving the door open for higher amounts.

[A-L-E-K]

LOT still going with up to 2 feet but leaving the door open for higher amounts.

Hard to call for amounts well over the all time record.

[janetjanet998]

ilx saying snowfall of only 6-12 inches and "up to" 12 in NW zones (me)

[cyclone77]

Yesterday's 18z NAM was a bogus run, so that makes you wonder about today's with the way things look.

[Thundersnow12]

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL

310 PM CST SUN JAN 30 2011

DISCUSSION

309 PM CST

STRONG SFC RIDGE CONTINUES TO DRIFT SOUTH ACROSS THE CANADIAN

PRAIRIES LATE TONIGHT AND STRETCH EAST ACROSS SOUTHWEST ONTARIO.

THIS HAS PROVIDED THE CONTINUED THE LIGHT NORTH/NORTHEAST FLOW

ACROSS THE SOUTHERN GREAT LAKES REGION. IN ADDITION THIS HAS ALLOWED

A NARROW CHANNEL OF LAKE EFFECT SNOW TO TRAVERSE FROM NORTH TO SOUTH

OVER LAKE MICHIGAN...PUSHING INLAND ACROSS THE CHICAGO METRO AREA.

CURRENTLY NOT ANTICIPATING THAT THIS WILL PRODUCE MUCH MORE THAN A

TENTH OR TWO OF SNOWFALL. TEMPS SHUD COOL OFF TONIGHT INTO THE

TEENS/LOW 20S. CONSIDERABLE SOLAR FILTERING FOR MUCH OF MON...SHUD

PREVENT TEMPS FROM WARMING BEYOND THE LOW/MID 20S. IT APPEARS ENOUGH

DRY AIR WILL ENTRAIN INTO THE NEAR SFC ENVIRONMENT EARLY MON TO

PREVENT SN FROM ARRIVING UNTIL MIDDAY MON. THEN ANTI-CYCLONIC FLOW

DEPARTS AND ALLOWS ADDTL LLVL MOISTURE WILL POOL EAST AND

RE-SATURATE THE ENVIRONMENT BY MIDDAY MON AND WILL THEN PERSIST THRU

MON NGT. SNOW OVERSPREADS THE AREA MON AFTN THRU OVERNIGHT...AND QPF

TOTALS APPEAR TO BE BTWN 0.05 AND 0.10 INCHES. CURRENT THINKING IS

THAT SNOW TOTALS WITH THE FIRST WAVE WILL BE BTWN 2-4 INCHES. FOR

NOW HAVE HELD OFF ON ANY ISSUANCE OF A WINTER WEATHER ADV WITH THIS

FORECAST ISSUANCE. THEN THE FOCUS TURNS TOWARDS THE IMPENDING MAJOR

WINTER STORM.

TUESDAY THROUGH TUESDAY NIGHT...

MAJOR WINTER STORM EXPECTED TO IMPACT MUCH OF THE GREAT LAKES

REGION...WITH SIGNIFICANT SNOW ACCUMULATIONS AND CONSIDERABLE

BLOWING AND DRIFTING SNOW TUESDAY EVENING THROUGH WEDNESDAY MORNING.

HAVE UPGRADED THE WINTER STORM WATCH TO A BLIZZARD WATCH.

SETTING THE STAGE FOR THE IMPENDING WINTER STORM WILL BE A

PERSISTENT NORTHEAST WINDS TUESDAY MORNING. A BROAD SURFACE RIDGE

WILL BECOME CENTERED ACROSS THE NORTHERN PLAINS AND STRETCHING

NORTHEAST INTO SOUTHERN ONTARIO. THIS WILL AID IN TIGHTENING THE

PRESSURE GRADIENT ACROSS THE SOUTHERN GREAT LAKES REGION...AND

PRODUCING BREEZY CONDITIONS FOR NORTHERN IL/NORTHWEST IN. EXPECT THE

BETTER WIND GRADIENT TO ARRIVE AFTER NOON TUE WITH A STEADY RAMPING

UP IN THE WINDS AND TIGHTENING PRESSURE GRADIENT. SFC LOW HAS

CONTINUED TO WOBBLE BETWEEN A MEMPHIS/INDIANAPOLIS/TOLEDO...WITH THE

850MB LOW TRACKING JUST TO THE NORTHWEST OF THIS PATH. AS THE SFC

LOW CONTINUES TO STRENGTHEN ACROSS EASTERN TEXAS/ARKANSAS...GULF

MOISTURE IS EXPECTED TO ENTRAIN INTO THIS SYSTEM.

IT APPEARS THAT DURING THE DAY TUE A LULL IN THE SNOW WILL

OCCUR...PRIMARILY BETWEEN 12Z AND 18Z. BY THE AFTN HRS THE LOW SHUD

LIFT NORTH TO MEMPHIS WITH LGT SN OVERSPREADING THE CWFA FROM SOUTH

TO NORTH. THE CAVEAT WILL BE THAT WITH THE PERSISTENT NE FLOW OFF OF

LAKE MICHIGAN...WE MAY SEE LAKE EFFECT SN BEGIN FOR THE IMMEDIATE

LAKESHORE COUNTIES MIDDAY TUE.

CONDITIONS WILL CONTINUE TO DETERIORATE TUESDAY NIGHT AS THE LOW

STEADILY LIFTS NORTH/NORTHEAST. INSTABILITY ALOFT APPEARS DECENT

WITH CAPE VALUES AT 850MB PROGGED ARND 200-400J/KG LATE TUE NGT.

THIS COUPLED WITH STRENGTH OF 850MB LOW...COULD PRODUCE SNOWFALL

RATES FOR A PERIOD TUE NGT BETWEEN 2-3IN/HR. 850MB JET CONTINUES TO

BE PROGGED BETWEEN 40-50KTS AND A MIXED LYR SHUD EASILY TOUCH AND

FILTER TO THE SFC THIS CORE OF WINDS TUE NGT INTO WED. SO EXPECT

SUSTAINED WINDS TUE NGT OF 20 TO 30 MPH...WITH GUSTS UP TO 45 MPH.

THIS COMBINED WITH HIGH SNOWFALL RATES WILL PRODUCE LIFE THREATENING

SITUATIONS WITH WHITE OUT CONDITIONS. ANOTHER BY-PRODUCT IS THE

CONSIDERABLE BLOWING AND DRIFTING SNOW. TOTAL SNOWFALL IS CURRENTLY

FORECASTED FOR THE EVENT IN EXCESS OF ONE FOOT TO SOME LOCATIONS

RECEIVING UP TO TWO FEET. THERE CONTINUES TO BE A FEW MODEL

SOLUTIONS THAT HAVE SUGGESTED SNOW RATIOS WOULD BE SLIGHTLY

HIGHER...WHICH COULD LEAD TO STORM TOTALS MUCH HIGHER. CONFIDENCE

GOING ABOVE THE CURRENT FORECAST IS MUCH LOWER WITH THIS FORECAST

PKG.

[OceanStWx]

I think it's going to have 'more dangerous' type wording. They are even mentioning the Blizzard word and mentioning Dec 2009 blizzard and how this could be as bad or worse.

My opinion there is word your WSW more strongly. I understand and support PDS wording for convective season, where watches are quite frequent in that part of the country. But WSWs already aren't that common in OK, so just by issuing one suggests this is particularly dangerous. I just worry because there is no national policy on that currently, and its use could get out of hand quickly.

[prinsburg_wx]

fwiw: 18Z RGEM at 48

[Kevin Askew]

I haven't been looking at detailed soundings in that location through the storm--I think BeauDodson may be your man there since he forecasts near that region specifically.

Thank you BI, we have discussed it, its so close to call. Right on a thin line very difficult to forcast... Will have generator ready in case.

[Moneyman]

Green Bay AFD said they expect the storm to head farther north and said the GEM may be onto something with the qpf shield.

Here's what they say:

ATTENTION THEN TURNS TO MAJOR...AND I MEAN MAJOR WINTER STORM THAT

WILL STRIKE THE CENTRAL UNITED STATES TUESDAY INTO WEDNESDAY WITH

SOME LOCATIONS EXPECTING OVER A FOOT OF SNOW. LATEST MODEL RUNS TODAY

HAVE PUSHED THEN SYSTEM FURTHER NORTH. 500MB PATTERN INDICATING

TWO UPPER LEVEL FEATURES. THE FIRST FEATURE IS ASSOCIATED WITH THE

DEVELOPING STORM. THE SYSTEM FEATURE WAS MOVING DOWN THE BACKSIDE

OF THE TROUGH. THIS FEATURE COULD HELP DIG THE TROUGH ACROSS THE

ROCKIES WITH MORE RIDGING DOWNSTREAM ACROSS THE OHIO VALLEY THAT

WOULD HELP PUSH THE SYSTEM EVEN FURTHER NORTH. ALSO...LOOKING AT

THE BEST 850MB THERMAL GRADIENT WOULD SUGGEST AN EVEN FURTHER

NORTHWARD TREND OVER THE NEXT SEVERAL DAYS. THE CANADIAN HAS

TRENDED IN THIS DIRECTION AND HAVE INCREASED CHANCES FOR SNOW

TUESDAY NIGHT OVER THE SOUTHEAST THIRD OF THE FORECAST AREA. OF

CONCERN...ALL MODELS INDICATED A VERY DISTINCT CUT OFF OF THE

PRECIPITATION SHIELD ON THE NORTHERN EDGE WITH VERY DRY AIR AT

850MB NORTH OF THE SYSTEM. THIS SITUATION IS STILL VERY FLUID...

THEREFORE IF MY CURRENT THOUGHTS ARE CORRECT...LATER SHIFTS MAY

NEED TO INCREASE AND PUSH THE SNOW EVEN FURTHER NORTHWARD. CURRENT

DEPICTION OF THE SNOW GRIDS WOULD SUGGEST 1 TO 3 INCHES FOR GREEN

BAY AND APPLETON WITH LITTLE OR NO ACCUMULATION TO THE NORTH AND

WEST WHILE I HAVE 3 TO 6 INCHES FOR KEWAUNEE AND MANITOWOC COUNTIES.

EVEN FURTHER NORTHWARD JOG OF THE SYSTEM COULD INCREASE SNOW

TOTALS. AS THE SYSTEM PASSES TO THE SOUTH...GUSTY NORTHEAST TO

NORTH WINDS ARE EXPECTED TO CAUSE CONSIDERABLE BLOWING AND DRIFTING

OF THE SNOW...ESPECIALLY ALONG THE LAKESHORE. IF THIS REGION DOES

GET 3 TO 6 INCHES OF SNOW...BLIZZARD CONDITIONS CAN BE EXPECTED

ALONG THE HIGHWAY 43 CORRIDOR. SNOW WILL TAPER OFF WEDNESDAY MORNING

ACROSS NORTHEAST WISCONSIN.

[turtlehurricane]

The sub-zero snowfall in ND is cranking, up to 4.5" being measured in spots now.

[baroclinic_instability]

Thank you BI, we have discussed it, its so close to call. Right on a thin line very difficult to forcast... Will have generator ready in case.

Being prepared is the best way to go

18Z NAM for now should be tossed with its odd changes. Still a significant icing event either way.

[janetjanet998]

DVN

329 PM CST SUN JAN 30 2011

SYNOPSIS

A BROAD REGION OF WEST NORTHWEST 500MB FLOW COVERED MUCH OF THE

NORTHERN U.S. FROM THE ROCKIES EAST WITH A DEEP TROF DIGGING SOUTH

ALONG THE WEST COAST. AT THE SURFACE SLOW PRESSURE WAS TAKING SHAPE

OVER THE SOUTHWEST AHEAD OF THE DIGGING TROF. OVER THE MID

MISSISSIPPI VALLEY A WEAK INVERTED SURFACE TROF ORIENTED NORTHWEST

THROUGH SOUTHEAST HAS BEEN WORKING IS WAY SLOWLY SOUTHWEST ACROSS

THE CWFA. THE CONVERGENCE NEAR THE TROF WAS ALLOWING DENSE FOG TO

FORM...DROPPING VISIBILITIES TO AROUND 1/4 MILE AS IT MOVES

THROUGH. ..DLF..

SHORT TERM...TONIGHT AND MONDAY

SURFACE WINDS OVER THE REGION ARE EXPECTED TO CONTINUE VEERING TO A

MORE EASTERLY DIRECTION THIS EVENING AS LOW PRESSURE CONTINUES TO

FORM OVER SOUTHERN ROCKIES AND SOUTHERN PLAINS. AS THIS HAPPENS THE

INVERTED TROF SHOULD FILL ALLOWING ANY FOG DISSIPATE.

A 300MB JET STREAK FROM THE NORTHERN PLAINS INTO THE GREAT LAKES

WILL MOVE EAST OVERNIGHT. SNOW OCCURRING IN THE ENTRANCE REGION OF

THE JET OVER THE MONTANA AND NORTH DAKOTA WILL SLIDE EAST AND

SOUTHEAST REACHING THE MID MISSISSIPPI VALLEY BY MONDAY MORNING. THE

SNOW WILL ENCOUNTER DRY EASTERLY LOW LEVEL FLOW AS IT NEARS THE

REGION...SO KEPT POPS OUT OF THE FORECAST FOR TONIGHT. SNOW IS

EXPECTED TO SPREAD OVER THE REGION ON MONDAY AS A WEAK S/W MOVES

THROUGH THE REGION ENHANCING THE FORCING ASSOCIATED WITH THE JET

STREAK. UPPER DIVERGENCE AHEAD OF THE WESTERN TROF WILL HELP

SUPPORT ADDITIONAL SNOWS FROM MONDAY NIGHT INTO TUESDAY MORNING.

THIS INITIAL ROUND OF SNOW IS EXPECTED TO PRODUCE A BROAD REGION OF

2 TO 3 INCH AMOUNTS OVER THE SOUTHERN THREE FOURTHS OF THE CWFA BY

NOON TUESDAY WITH AMOUNTS NEAR THE HIGHWAY 20 CORRIDOR EXPECTED TO

BE IN THE 3 TO 5 INCH RANGE. A WINTER WEATHER ADVISORY WILL BE

ISSUED TO COVER HIGHER SNOW AMOUNTS ACROSS THE NORTH FOR MONDAY INTO

TUESDAY MORNING. ..DLF..

LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY

..MAJOR WINTER STORM TO IMPACT THE AREA TUE AND WED

WILL BE KEEPING THE CURRENT WINTER STORM WATCH RUNNING FROM 18Z TUE

THROUGH 00Z WED. CONFIDENCE IS INCREASING THAT THIS WILL BE A HIGH

IMPACT WINTER STORM...WITH HEAVY SNOW AND BLOWING SNOW ISSUES OVER

THE ENTIRE AREA ESPECIALLY TUE NIGHT INTO EARLY WED MORNING.

ALTHOUGH LIGHT SNOW WILL BE ON-GOING MON NIGHT INTO TUE MORNING FROM

THE PASSING INVERTED SURFACE TROUGH...STILL LOOKS AS THOUGH THERE

WILL BE A SEVERAL HOUR CUT-OFF OF LITTLE IF ANY SNOW BEFORE THE

SHIELD OF SNOW FROM THE ADVANCING SURFACE LOW OVERSPREADS THE AREA

FROM SOUTH TO NORTH TUESDAY. FOR SIMPLICITY...WILL KEEP THE WATCH

FOCUSED ON THE MAIN...STRONGER STORM LIFTING OUT OF THE SOUTHEAST

AND ITS IMPACTS TUE AFTERNOON THROUGH WED.

NO MAJOR ISSUES WERE NOTED WITH MODEL INITIALIZATION THIS MORNING.

UPPER LEVEL CIRCULATIONS OUT WEST THAT EVENTUALLY MERGE AND

INTERACT TO PRODUCE THE WINTER STORM WERE NOW ON-SHORE AND BETTER

SAMPLED BY 12Z MODELS. LIKEWISE...NO GLARING ISSUES WERE SEEN IN

MOISTURE FIELDS THIS MORNING. 12Z ANALYSIS INDICATED GULF

MOISTURE...THAT WILL BE INFLUENTIAL IN THE VERY LARGE SNOW

AMOUNTS...WAS BEGINNING TO BUILD ALONG THE TX COAST AS SHOWN BY 850

MB DEWPOINTS AROUND 10 CELSIUS AND DEWPOINTS AT THE SURFACE IN THE

50S AND 60S ACROSS EASTERN TX...LA AND SOUTHERN AR.

12Z MODELS ARE IN CLOSE AGREEMENT WITH A COMPLEX INTERACTION OF THE

UPPER LEVEL LOW OVER CENTRAL CA PROGRESSING EAST AND THEN

NORTHEAST...WHILE A SEPARATE SHORTWAVE OVER BC THIS MORNING DROPS

NEARLY DUE SOUTH TO CARVE OUT AN UPPER LOW OVER THE 4 CORNERS REGION

BY WED. THE CA SHORTWAVE IS SHOWN CONTINUING EAST...WITH THE HELP OF

A 100 PLUS KT JET AT 300 MB APPROACHING THE CA COAST THIS

MORNING...AND THEN EJECTING NORTHEAST AND STRENGTHENING INTO A

CLOSED LOW AS IT LIFTS THROUGH MO THEN NRN IL TUE NIGHT INTO WED.

THE BRUNT OF STRONG UPPER FORCING FROM POSITIVE VORTICITY ADVECTION

AHEAD OF THE SHORTWAVE...AND JET COUPLET REGION OF SEPARATE 300 MB

JET CORES OVER THE SRN PLAINS AND UPPER GREAT LAKES...TAKES DIRECT

AIM OVER THE ESPECIALLY THE EAST AND SE HALF OF THE FORECAST AREA

TUE NIGHT. AT THE SURFACE...LOW PRESSURE DEVELOPS OVER TX MON

NIGHT...THEN LIFTS NORTHEAST ACROSS SOUTHERN IL TOWARD CENTRAL

INDIANA BY WED MORNING. THIS IS ALONG THE LINES OF THE MORE

NORTHERLY TRACKS SHOWN BY EARLIER ECMWF RUNS AND PERHAPS A BIT

SLOWER. AHEAD OF THE SURFACE LOW...AND THE MORE NORTHWESTERLY

TRACKING LOW AT 850 MB...A 50 TO 70 KT LOW LEVEL JET IS DEPICTED

FEEDING GULF MOISTURE INTO THE WARM CONVEYOR BELT. THIS RESULTS IN

SEASONABLY HEAVY MODEL QPF FIELDS IN THE LOW LEVEL DEFORMATION ZONE

NORTHWEST OF THE SURFACE LOW...REACHING WELL INTO CENTRAL AND

EASTERN IA TUE NIGHT INTO WED. AROUND 1 INCH TO NEARLY 1.25 INCHES

IS SHOWN BY MODELS ACCUMULATING OVER MUCH OF THE FORECAST AREA

BETWEEN 18Z TUE AND 12Z WED MORNING. WHILE SOME OF THIS MAY BE

CONVECTIVE FEEDBACK...ESPECIALLY CLOSER TO THE LOW TRACK WITH

SUFFICIENTLY STEEP MID LEVEL LAPSE RATES...GIVEN THE MOISTURE

AVAILABILITY FROM AN OPEN GULF THAT WE HAVE NOT SEEN IN A LONG

TIME...THE HIGH QPF VALUES CANNOT BE ENTIRELY DISCOUNTED.

USING ROUGHLY 70 PERCENT OF BLENDED MODEL QPF AND APPLYING SEVERAL

SNOWFALL TECHNIQUES...HAVE COME UP WITH SNOWFALL TOTALS IN THE RANGE

OF 8 10 10 INCHES ACROSS THE NW HALF OF THE FORECAST AREA...TO 10 TO

14 INCHES IN THE SOUTH. THIS COULD OBVIOSLY BE EVEN HIGHER IF THE

MODEL QPF FIELDS VERIFY. NUMEROUS TECHNIQUES...AND HPC FORECASTS...

SUGGEST AN AXIS OF 15 TO 18 INCHES OR GREATER TOTALS POSSIBLE ALONG

A LINE FROM OUR MO COUNTIES THROUGH MACOMB TO PRINCETON IL.

MODELS ARE NOW ADVERTISING 20 TO 30 KT SUSTAINED SURFACE WINDS

WRAPPING AROUND THIS SURFACE LOW AS IT PASSES TO THE SOUTHEAST TUE

NIGHT. AT THE SAME TIME...850 MB WINDS PUSH 65 KTS FROM THE

NORTHEAST. RESULTING WIDESPREAD BLOWING SNOW AND LOW VISIBILITIES IN

THE PERIODS OF HEAVY SNOWFALL TUE NIGHT MAY EASILY RESULT IN

BLIZZARD LIKE CONDITIONS...ESPECIALLY ACROSS THE SOUTHEAST HALF OF

THE FORECAST AREA. MKX AND LOT HAVE UPGRADED TO BLIZZARD WATCHES IN

ADJACENT FORECAST AREAS TO THE EAST AND IF THE CURRENT MODELS STAY

THE COURSE...OUR AREAS AT LEAST EAST OF THE MS RIVER MAY BE WORTHY

OF A BLIZZARD WATCH AS WELL. ALSO...ALTHOUGH NOT IN THE FORECAST...

CANNOT RULE OUT THUNDERSNOW GIVEN THE SUFFICIENTLY UNSTABLE MID

LEVEL LAPSE RATES AND VERY STRONG UPPER LEVEL FORCING TUE NIGHT.

[Trent]

From CLE discussion:

THERE IS THE POTENTIAL FOR

SIGNIFICANT ICE ACCUMULATIONS OVER THE EASTERN HALF OF THE AREA. IN

THE EXTREME...ICE ACCUMULATIONS COULD APPROACH THREE QUARTERS OF AN

INCH WITH AN EARLY CHANGEOVER.

With a region of 3+ million, this would be devastating. I can only imagine the power outages. If this does play out like this I don't think the region could handle nor do they have capacity to provide warming shelters for potentially hundreds of thousands without heat and temps falling to near zero.

[patrick7032]

AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 417 PM EST SUN JAN 30 2011

.LONG TERM...MONDAY THROUGH SUNDAY MAJOR WINTER STORM WILL HIGHLIGHT THE FORECAST THIS WEEK. THIS STORM SYSTEM CAN BE SEEN ON SATELLITE CHURNING ACROSS CALIFORNIA/NEVADA THIS AFTERNOON ON WAY TO ROUNDING THE BASE OF AN AMPLIFYING WESTERN CONUS UPPER TROUGH. ALSO NOTED ON WATER VAPOR PIX IS THE NORTHERN STREAM SHORTWAVE SETTLING SOUTH/SOUTHEAST INTO MONTANA. WITH TIME...THIS FEATURE WILL DROP SOUTH ALONG THE ROCKY MOUNTAIN RANGE AS THE MAIN SOUTHERN STREAM STORM SYSTEM PIVOTS NORTHEAST IN ADVANCE OF IT. THE MODEL SOLUTIONS HAVE TRENDED FURTHER NORTHWEST WITH THE EVOLUTION OF THE OVERALL STORM SYSTEM WITH THE MAIN UPPER LOW LIFTING THROUGH THE MID MISSISSIPPI VALLEY BEFORE REACHING THE SOUTHERN GREAT LAKES AND THEN SHEARING MORE EASTERLY ALONG THE UPPER LEVEL CONFLUENT FLOW SITUATED ALONG BASE OF MEAN UPPER TROUGH CENTERED OVER EASTERN CANADA. THIS SHIFT TO THE NORTH AND WEST IS SUPPORTED BY A MAJORITY OF 12Z MODEL RUNS...INCLUDING A MAJORITY OF BOTH THE GFS AND GEM ENSEMBLE MEMBERS SO WILL ADJUST THE FORECAST AS SUCH. AS IT PERTAINS TO THE FORECAST...WILL BRING THE HEAVIER SNOWFALL FIELD NORTH THROUGH THE CWA AND EXTEND THE WINTER STORM WATCH TO INCLUDE THE NORTHERN CWA AS WELL...STILL TIMED FROM TUESDAY EVENING INTO WEDNESDAY. WILL ALSO HAVE TO WATCH FOR THE POTENTIAL OF SLEET/FREEZING RAIN MIXED WITH THE SNOW AT TIMES ACROSS THE SOUTHERN CWA (SOUTH OF DETROIT ATTM). SO FAR...IT STILL APPEARS THAT A MAJORITY OF THE PRECIPITATION WILL REMAIN SNOW OR A SNOW/SLEET MIX...BUT ANY ADDITIONAL SHIFT NORTH WOULD BRING A BETTER CHANCE OF ICY CONDITIONS. EITHER WAY...THE BOUNDARY LAYER IS SUFFICIENTLY COLD THAT THE RESULTANT MIX OF WINTRY PRECIPITATION WILL WARRANT THE CONTINUATION OF THE WATCH AS ANY REDUCING IN SNOW AMOUNTS WILL BE DUE TO GREATER ACCUMULATIONS OF SLEET AND/OR ICE. THE MORE NORTHERN TRACK OF THIS SYSTEM INTO THE FACE OF THE LARGE DOME OF POLAR/ARCTIC AIR OVER THE REGION WILL ACT TO TIGHTEN THE PRESSURE GRADIENT ACROSS THE AREA...SO NORTHEAST WINDS WILL BECOME RATHER GUSTY TUESDAY NIGHT INTO WEDNESDAY. WILL INCLUDE BLOWING SNOW IN THE FORECAST AND ALSO ATTEMPT TO DELINEATE THE PERIOD OF HEAVY SNOW...WHICH WILL SHIFT NORTH/NORTHEAST THROUGH THE AREA...FIRST ARRIVING OVER THE SOUTHERN CWA TUESDAY EVENING...ENCOMPASSING MUCH OF THE AREA OVERNIGHT...AND THEN FOCUSING OVER THE NORTHEASTERN CWA AS WEDNESDAY PROGRESSES. GIVEN THE AMOUNT OF MOISTURE THIS SYSTEM WILL PICK UP FROM THE GULF/MEXICO...STILL FEEL AT LEAST 8-12 INCHES OF SNOW SEEMS QUITE REASONABLE AND WOULD GUESS THAT A SWATH OF 12+ INCHES WILL BE POSSIBLE IF THE CURRENT FORECAST TRACK/INTENSITY OF THE STORM DOES NOT CHANGE MUCH.

I am about to start looking at sounds but believe these amounts are under-done.

[csnavywx]

These forecasted totals are so high that I can't fathom them going much higher. One would think that we'd have to be nearing a theoretical maximum soon. I mean, we're already talking about a 1 in 50 year event (at the least).

This storm has so many positives going for it.

[csnavywx]

These forecasted totals are so high that I can't fathom them going much higher. One would think that we'd have to be nearing a theoretical maximum soon. I mean, we're already talking about a 1 in 50 year event (at the least).

This storm has so many positives going for it.

On this note, something else I posted elsewhere about SLR:

+ Positives

Very deep dendritic growth zone/ice crystal formation zone, in some cases approaching 400mb, especially early Wednesday near the peak.

Very cold profiles (850s around -10 to -15C)

Deep/strong and persistent omega field intersected with DGZ

High wind shear aloft in deep DGZ will cause enhanced dendritic/ice crystal shattering, which will actually help seed snow production in the lower cold layers (seeder-feeder type process).

- Negatives

High winds and wind shear will shatter dendrites as they hit the ground, tempering the ratio somewhat.

Compaction from large amounts of snow

Still thinking an average of 16-17:1 after this all shakes out. I do think we could get past 20:1 in the early morning hours of Wednesday as the DGZ approaches 400mb and the peak of the storm arrives.

[Hoosier]

These forecasted totals are so high that I can't fathom them going much higher. One would think that we'd have to be nearing a theoretical maximum soon. I mean, we're already talking about a 1 in 50 year event (at the least).

This storm has so many positives going for it.

Yeah, there's been some discussion about theoretical maximums in the past. It's hard to say. For Chicago, I've thought it was somewhere in the 24-30" range, and this one looks like it could be the one.

[A-L-E-K]

On this note, something else I posted elsewhere about SLR:

+ Positives

Very deep dendritic growth zone/ice crystal formation zone, in some cases approaching 400mb, especially early Wednesday near the peak.

Very cold profiles (850s around -10 to -15C)

Deep/strong and persistent omega field intersected with DGZ

High wind shear aloft in deep DGZ will cause enhanced dendritic/ice crystal shattering, which will actually help seed snow production in the lower cold layers (seeder-feeder type process).

- Negatives

High winds and wind shear will shatter dendrites as they hit the ground, tempering the ratio somewhat.

Compaction from large amounts of snow

Still thinking an average of 16-17:1 after this all shakes out. I do think we could get past 20:1 in the early morning hours of Wednesday as the DGZ approaches 400mb and the peak of the storm arrives.

what badass negatives

[Hoosier]

fwiw, RGEM precip type at 48 hours

[OceanStWx]

what badass negatives

The negatives actually make the public impacts of this storm worse! The blowing, drifting and white out conditions are going to make travel, snow removal, etc. impossible.

[snowstormcanuck]

18z GFS roughly similar through 48. Looks a touch sharper with the s/w in the southern Plains.

[Hoosier]

[B-Rent]

Just woke up to see two facebook posts from TV mets in Indy (different station)

One is talking about the stormtrack, and how the Indy area is looking at our biggest ice event since 04....

The other says the low has shifted W enough that the main threat of damaging contions goes from Laf to Fort Wayne.

Talk about a confusing message!

Sent from my Droid using Tapatalk

[Thundersnow12]

18z GFS looks the same at 48hr