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Late December Discussion and Christmas um Event


Cold Rain

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Euro in the long range has our new years storm a little quicker -coming on 12/30 now. looks like a miller a and temps look decent.

On 12/29, the primary surface low heads to St. Louis, tho there is another weak sfc low signature over Mobile....so, it looks Miller B-ish, with the coastal low forming and sitting east of DC on 12/30. Damming signature is lacking, but overall look is not bad especially if the 12/27 storm bombs out.

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On 12/29, the primary surface low heads to St. Louis, tho there is another weak sfc low signature over Mobile....so, it looks Miller B-ish, with the coastal low forming and sitting east of DC on 12/30. Damming signature is lacking, but overall look is not bad especially if the 12/27 storm bombs out.

That is not the event.. the actual storm that the GFS has shown is backing out into the Pacific on the 12z Euro. It typically does this a lot, so don't fret just yet!

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Big difference from 0z Euro to 12z Euro. 0z closed off the vort at NM/ TX border....12z was at MS River.

12z GEM doesn't fully close it off until eastern NC.

12z GEM is a thing of beauty for western Carolina/ N GA snow fans.

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Big difference from 0z Euro to 12z Euro. 0z closed off the vort at NM/ TX border....12z was at MS River.

12z GEM doesn't fully close it off until eastern NC.

12z GEM is a thing of beauty for western Carolina/ N GA snow fans.

I agree with. 850's are marginal in NGA but any small strength in dynamics would take care of that. I believe the 12z Euro would throw some snow underneath that strong sfc low pulling just to the north of GA. Of course I'm saying that without looking at any of the QPF maps but rather just by looking at how the 850s are wrapping around underneath the storm and the strength of the low.

To top that off the 12z EURO also shows a nice ice storm on the 29th with snow north of Atlanta.

It's so nice to actually see fantasy storms showing up.

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MRX thinks it's of interest:

000

FXUS64 KMRX 212001

AFDMRX

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE MORRISTOWN TN

243 PM EST FRI DEC 21 2012

.SHORT TERM (TONIGHT AND SATURDAY)...LIGHT SNOW SHOWERS WILL CONTINUE

ACROSS NE TN AND SW VIRGINIA THIS EVENING. BRISK WEST TO NORTHWEST

WINDS WILL WEAKEN THIS EVENING. SURFACE LOW PRESSURE WILL CONTINUE

TO MOVE NORTHEAST THROUGH THE EASTERN GREAT LAKES INTO SE CANADA

THROUGH THE PERIOD. HIGH PRESSURE AND A DRIER AIRMASS WILL BUILD

INTO THE REGION FROM THE WEST. TEMPERATURE ADVECTION BECOME NEUTRAL

TONIGHT AND IS WEAKLY WARM ON SATURDAY. TONIGHT MINS WILL BE RANGE

FROM THE TEENS TO THE LOW 20S ACROSS MOST AREAS WITH COLDER READINGS

IN THE HIGHER ELEVATIONS. SATURDAY WITH SUNNY SKIES TEMPERATURES

WILL APPROACH NORMAL LATE.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)...ACTIVE EXTENDED

FORECAST. SURFACE RIDGING SATURDAY NIGHT WILL MOVE EAST ALLOWING A

PLUME OF GULF MOISTURE TO PULL NORTHEAST TOWARD THE TENNESSEE

VALLEY/SOUTHERN APPALACHIANS ON SUNDAY. A FAST MOVING SOUTHERN

STREAM WAVE WILL PRODUCE WEAK CYCLONGENESIS OVER THE MID-MISSISSIPPI

VALLEY SUNDAY NIGHT WITH A FRONTAL PASSAGE LATE MONDAY. ISENTROPIC

LIFT AND FRONTO-GENETIC FORCING WILL FOCUS THE GULF MOISTURE TO

PRODUCE AN AREA OF GENERALLY LIGHT RAIN.

THIS BOUNDARY WILL MOVE SOUTH OF THE AREA MONDAY NIGHT...BUT A

NORTHERN AND SOUTHERN STREAM WAVES WILL PHASE OVER THE PLAIN STATES

TUESDAY THEN MOVE EAST/NORTHEAST ACROSS THE TENNESSEE VALLEY AND

SOUTHERN APPALACHIANS FOR TUESDAY NIGHT AND WEDNESDAY. THE GFS/ECMWF

ARE IN GENERAL AGREEMENT IN TRACKING THE SURFACE LOW ACROSS THE

TENNESSEE VALLEY. A DOUBLE JET STRUCTURE OF THE NORTHERN AND

SOUTHERN STREAM JETS WILL PRODUCE STRONG LIFT OVER THE AREA

ENHANCING FRONTO-GENETIC FORCING. LATEST RUN SHOWS A MORE

PROGRESSIVE SYSTEM WHICH WILL LIMIT FLOODING POTENTIAL.

HOWEVER...AS THE SURFACE LOW MOVES NORTHEAST...COLD AIR WILL SPILL

INTO THE FORECAST AREA WEDNESDAY CHANGING PRECIPITATION TO SNOW.

SNOWFALL IS POSSIBLE WEDNESDAY AFTERNOON THROUGH THURSDAY NIGHT...

ESPECIALLY ACROSS THE MOUNTAINS.

We'll probably see some flakes in Knoxville - but I wonder if we'll get any accumulations.

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Nashville:

PREV DISCUSSION.../ISSUED 353 AM CST FRI DEC 21 2012/

DISCUSSION...STRONG HIGH PRESSURE QUICKLY BUILDING INTO MIDDLE

TENNESSEE FROM THE SW THIS MORNING, WITH MUCH DRIER AIR WORKING

ITS WAY INTO THE MID STATE. CLOUDS STILL BLANKET THE UPPER

PLATEAU, BUT CLEARING SHOULD TAKE PLACE LATER THIS MORNING. AM

EXTENDING THE WIND ADVISORY OUT TO 22Z, AS WINDS DON`T SEEM TO LET

UP UNTIL THE AFTERNOON, AND WILL FURTHER DIMINISH THIS EVENING.

COLD TEMPERATURES WILL BE AROUND INTO THE WEEKEND, AT LEAST UNTIL

THE SURFACE RIDGE PUSHES EAST OF MIDDLE TENNESSEE LATE SATURDAY.

MODELS BRING A QUICK SYSTEM INTO THE AREA SUNDAY NIGHT THAT MAY

PRODUCE SCATTERED SHOWERS, WITH A GREATER CHANCE ON MONDAY AS AN

UPPER TROUGH AMPLIFIES THIS SYSTEM AND ADDS TS TO THE FORECAST.

THE BIG STORY THIS FORECAST CYCLE IS A POSSIBLE WINTER WEATHER

SYSTEM THAT DEVELOPS OUT OF THE GULF AND TRACKS TOWARD THE NE ON

CHRISTMAS DAY. PRECIPITATION WILL START OFF AS RAIN, WITH A

POSSIBLE CHANGE TO SNOW ON WEDNESDAY, DEPENDING ON WHICH TRACK THE

STORM TAKES. THE GFS AND ECMWF HAVE BOTH COME TOGETHER IN BRINGING

THE LOW DIRECTLY ACROSS MIDDLE TENNESSEE, BUT A SLIGHTLY MORE

EASTERN TRACK WOULD TEND TO PRODUCE MORE SNOW THAN RAIN. AT ANY

RATE, WE COULD GET SNOW JUST OUT OF THE WRAP-AROUND MOISTURE,

REGARDLESS. FOR NOW, WE`LL GO WITH A SAFE RAIN/SNOW MIXTURE

WEDNESDAY AND WEDNESDAY NIGHT, WITH A CLOSE EYE ON FUTURE MODEL

SOLUTIONS.

It looks like west and middle TN may do better than east TN at this point?

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NWS Raleigh Still thinking that any wintery precipitation will be North and West of their forecast area per latest AFD. They are also talking about the possibility of severe weather as well.

.LONG TERM /MONDAY THROUGH FRIDAY/...

AS OF 330 PM FRIDAY...

FORECAST RATIONALE SIMILAR TO PREVIOUS DAYS...WITH ABOVE AVERAGE

CONFIDENCE. A LEAD S/W TROUGH FORECAST TO BUCKLE THE FLOW ON SUNDAY

WILL PIVOT FROM THE CENTRAL PLAINS TO THE GREAT LAKES AND BE

ACCOMPANIED BY A RELATIVELY WEAK SURFACE FRONTAL WAVE THAT WILL

MIGRATE THROUGH THE MIDDLE ATLANTIC STATES MON-MON NIGHT. A

PRECEDING WARM CONVEYOR/ISENTROPICALLY- DRIVEN CLOUD BAND AND AXIS

OF SHOWERS WILL SPREAD EASTWARD ACROSS CENTRAL NC THROUGH MON

EVENING. THE EARLIER DAY ARRIVAL OF THE CLOUDS AND SHOWERS WILL

PRODUCE A 8-10 DEGREE GRADIENT FROM NW TO SE ACROSS THE RAH CWFA -

AROUND 50 NW TO NEAR 60 SE.

FOR MID-WEEK: AS HAS BEEN NOTED...SURFACE EVOLUTION WILL BE HIGHLY

SENSITIVE TO THE STRENGTH AND LOCATION OF BOTH THE AFOREMENTIONED

HIGH LATITUDE BLOCKING FORECAST TO DEVELOP INVOF BAFFIN ISLAND...AND

AN ELONGATED VORTEX ACROSS SOUTHERN CANADA. THE STRONG HIGH LATITUDE

BLOCKED FLOW WILL SUPPRESS THE NORTHERN BRANCH OF THE WESTERLIES

SOUTHWARD ACROSS THE MIDDLE ATLANTIC/NORTHEAST STATES...WHERE IT

WILL BE MET WITH AN ACTIVE AND INCREASINGLY AMPLIFIED SOUTHERN

BRANCH JET. THE ASSOCIATED CONFLUENT FLOW ALOFT WILL SERVE TO

MAINTAIN CONTINENTAL POLAR HIGH PRESSURE FROM SOUTHEAST CANADA

SOUTHWARD INTO PIEDMONT OF THE CAROLINAS THE MIDDLE ATLANTIC

PIEDMONTS.

THE LEADING EDGE OF THE CP HIGH WILL ARRIVE ON CHRISTMAS...COURTESY

OF THE COLD FRONT TRAILING THE LEAD FRONTAL WAVE FROM MON-MON NIGHT.

WHILE THE COLD FRONT WILL PRESS SOUTH TOWARD THE SAVANNAH BASIN

DURING THE DAY...TEMPERATURES SHOULD REMAIN RELATIVELY MILD OWING TO

PARTIAL SUNSHINE IN ADVANCE OF THE A STRONGER WAVE SCHEDULED FOR

CHRISTMAS NIGHT AND WED. THE PRESENCE OF THE CAD HIGH -- ONE

MAINTAINED BY THE LARGE SCALE FLOW -- WILL CAUSE THE INCIPIENT LOW

LIFTING FROM THE WESTERN GOM TO YIELD TO A MILLER TYPE-B COASTAL LOW

THAT WILL SUBSEQUENTLY TRACK UP THE MIDDLE ATLANTIC COAST AND

NORTHEAST COASTS.

WHILE ANY ASSOCIATED WINTRY WEATHER THREAT IS STILL FORECAST TO HOLD

TO THE NORTH AND WEST OF CENTRAL NC...THE PRESENCE OF THE DEEP

MILLER B LOWS AND WEDGE FRONT WILL PROVIDE FOR WET...AND

INCREASINGLY WINDY CONDITIONS WITH THE PASSAGE OF THE WEDGE BOUNDARY

AND INFLUX OF WINDY WARM SECTOR AIR ON WED - QUITE SIMILAR TO THE

EPISODE OF THURSDAY. UNLIKE THURSDAY...HOWEVER...MARITIME TROPICAL

AIR WILL BE MORE ABUNDANT FROM BOTH THE GOM AND SOUTHWESTERN

ATLANTIC...WHICH WILL FUEL A HIGHER PROBABILITY OF STRONG TO SEVERE

THUNDERSTORMS IN THE ADVANCING WARM SECTOR...CHARACTERIZED BY MID

60S TO NEAR 70 DEGREES TEMPS AND DEWPOINTS IN THE 60S...AHEAD OF THE

TRIPLE POINT/MILLER B LOW. MEANWHILE THE NORTHWEST PIEDMONT WILL

LIKELY REMAIN LOCKED IN THE WEDGE REGIME...IN THE 40S. MUCH COOLER

AND DRIER CONDITIONS WILL PREVAIL IN THE WAKE OF THE STORM BY WED

NIGHT...LASTING THROUGH THE END OF THE WORK WEEK.

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In my opinion, that gives the run more weight.

definitely does but models are all over the place. It will be a few days before we can pinpoint the exact track but its fun to watch it unfold. I enjoy this process almost as much as watching it in my backyard..okay not really but I am usually too tired to care at that point :santa:

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Stumbled upon this afternoon long term afd from MOB. They are leaning towards a gfs/euro forecast but, not yet ready to throw out the other model runs.

BY CHRISTMAS DAY AS ANOTHER POWERFUL SHORTWAVE AMPLIFIES OVER

TEXAS. THE GFS AND ECMWF HAVE COME INTO MUCH BETTER AGREEMENT ON THE

TIMING AND TRACK OF THE SYSTEM...BUT THERE ARE STILL DIFFERENCES IN

THE STRENGTH OF THE LOW. THE LATEST GUIDANCE SHOWS THE SURFACE LOW

DEVELOPING OVER EAST CENTRAL TEXAS CHRISTMAS MORNING WITH THE LOW

DEEPENING AND MOVING QUICKLY INTO NORTH CENTRAL MS/AL BY THE EVENING

HOURS ON CHRISTMAS DAY. IF THIS TRACK WAS TO VERIFY...OUR REGION

WOULD BE PLACED IN THE UNSTABLE...HIGHLY SHEARED WARM SECTOR...AND

SEVERE WEATHER (INCLUDING TORNADOES) ON CHRISTMAS DAY WOULD BECOME A

DISTINCT POSSIBILITY. HOWEVER...SOME OF THE GFS ENSEMBLES AND THE

OPERATIONAL CANADIAN/UKMET SHOW A STRONGER LEAD SHORTWAVE ON MONDAY

WHICH ACTUALLY PUSHES THE COLD FRONT ALL THE WAY TO THE COAST. THIS

MAKES THE SECONDARY/STRONG SURFACE LOW TRACK FURTHER SOUTH ACROSS OUR

AREA...GREATLY REDUCING THE THREAT OF SEVERE WEATHER. SINCE THE

INITIAL SHORTWAVE IS STILL OVER THE PACIFIC OCEAN...IT WILL NOT BE

PROPERLY SAMPLED BY OUR UPPER AIR NETWORK UNTIL LATER THIS WEEKEND.

THEREFORE...WE ARE LIKELY TO SEE ADDITIONAL SHIFTS TO THE TRACK OF

THIS WEATHER SYSTEM. HOWEVER...GIVEN THE AGREEMENT OF THE ECMWF/GFS...

WE WILL CONTINUE TO MENTION THE POSSIBILITY OF A FEW STRONG/SEVERE

STORMS IN OUR HAZARDOUS WEATHER OUTLOOK AND URGE EVERYBODY TO STAY

TUNED TO FORECASTS THIS WEEKEND INTO CHRISTMAS EVE. REGARDLESS OF THE

SEVERE POTENTIAL...CHRISTMAS EVE INTO CHRISTMAS DAY LOOK

WET...ESPECIALLY ON CHRISTMAS DAY. IF THE TRACK OF THE LOW STAYS TO

OUR NORTH...IT WILL BE MILD AND HUMID AS WELL.

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