Update, Morning of 1/21/2014:

 

.SYNOPSIS…

LOW PRESSURE WILL INTENSIFY ACROSS NORTH CAROLINA LATER TODAY. AN

ARCTIC COLD FRONT CROSSES THE AREA THIS AFTERNOON AND EVENING…WITH

THE ENTIRE SYSTEM MOVING OFF THE MID ATLANTIC COAST TONIGHT. CANADIAN

HIGH PRESSURE BUILDS INTO THE AREA FOR THE MID WEEK PERIOD BRINGING

WELL BELOW NORMAL TEMPERATURES TO THE AREA.

 

&&

 

.NEAR TERM /THROUGH WEDNESDAY/…

HIGH IMPACT WINTER EVENT TODAY THROUGH TONIGHT…

 

THE BIG PICTURE…

A COLD FRONT CURRENTLY DRAPED ACROSS THE VA/NC BORDER INTO NC

EARLY THIS MORNING WILL BECOME STALLED ALONG THE CAROLINAS BY

DAYBREAK. LOW PRESSURE STARTS TO DEEPEN ALONG THIS BOUNDARY DURING

THE MORNING…WHICH WILL THEN TRACK NORTHEAST JUST OFF THE MID

ATLANTIC COAST TUE AFTN/EARLY EVENING AND THEN SHIFT WELL EAST OF

THE DELMARVA AFTER MIDNIGHT. MEANWHILE…A CANADIAN HIGH WILL

BRING A VERY COLD ARCTIC AIRMASS INTO THE NE STATES WHICH WILL

RUSH INTO THE MID ATLANTIC REGION LATE IN THE DAY THROUGH WED. THE

COASTAL LOW FINALLY MOVES INTO NOVA SCOTIA BY WED AFTN/EVENING AS

SFC HIGH PRESSURE BUILDS INTO THE MID ATLANTIC REGION FROM THE SW.

SEVERAL IMPACTS ARE EXPECTED TODAY THROUGH TONIGHT DUE TO THE

INTERACTION OF THE COASTAL LOW WITH THE VERY COLD ARCTIC AIR TO

THE NORTH. THEY ARE AS FOLLOWS:

 

TEMPERATURES…

HIGH TEMPERATURES WILL REACH THEIR PEAK LATE THIS MORNING WITH TEMPS

IN THE MID 30S FAR NW TO AROUND 50 FAR SE. TEMPERATURES WILL THEN

FALL THROUGH THE AFTN AS A COLD ARCTIC AIRMASS GETS PULLED INTO THE

REGION ON THE BACK SIDE OF THE COASTAL LOW. STRONG COLD AIR

ADVECTION PROCESSES TAKE OVER BY EARLY THIS EVENING AS THE LOW PULLS

AWAY TO THE NORTHEAST…CAUSING TEMPERATURES TO PLUMMET QUICKLY.

TEMPS SHOULD RANGE FROM THE LOW-MID 20S NW TO UPPER 30S/LOWER 40S

SE. OVERNIGHT LOWS ARE EXPECTED TO BOTTOM OUT IN THE SINGLE DIGITS

NW TO MID-UPPER TEENS SE.

 

PRECIPITATION…

PRECIPITATION MOVES INTO THE AREA FROM THE NW THIS MORNING AND

OVERSPREADS THE ENTIRE FORECAST AREA BY MID-LATE AFTN. THERE IS

AMPLE LIFT PRESENT TODAY…ESPECIALLY THROUGH THE DENDRITIC GROWTH

ZONE. AS THE WET BULB ZERO LINE FALLS BELOW ZERO THROUGH THE MORNING

IN THE NORTH…EXPECT PRECIP TO START OFF AS SNOW NW AND RAIN SE

WITH A BRIEF RAIN/SNOW MIX CAUGHT IN THE MIDDLE. WET BULB ZEROES

WILL FALL BELOW ZERO THROUGH THE AFTN IN THE SOUTH…THUS PRECIP

WILL TRANSITION FROM RAIN TO SNOW IN A NW TO SE ORIENTATION. THIS

TRANSITION LINES UP WELL WITH THE FALLING TEMPERATURES EXPECTED

TODAY. PRECIP WILL BECOME ALL SNOW BTWN 21-00Z TODAY. MEANWHILE…

THE BEST FRONTOGENESIS AND Q-VECTOR CONVERGENCE IS FOCUSED ACROSS

NRN VA AND CTRL/NRN MD THIS AFTN…WHERE THE BEST POTENTIAL FOR

ENHANCED SNOWFALL RATES WILL BE FOCUSED. A DEFORMATION ZONE WILL

ALSO DEVELOP ACROSS THE AREA THIS EVENING. THIS ZONE OF DEFORMATION

WILL OCCUR JUST BEHIND THE COASTAL LOW AS IT STARTS TO LIFT NE

AWAY FROM THE COAST AND AS THE COLD AND DRY ARCTIC AIRMASS QUICKLY

POURS INTO THE REGION FROM THE NNW. THE DEFORMATION ZONE INITIALLY

BECOMES FOCUSED OVER CTRL VA THIS EVENING (AROUND 00Z) AND THEN

SHIFTS ALONG THE COAST BY MIDNIGHT. MEANWHILE…A SECONDARY (AND

WEAKER) AREA OF FRONTOGENESIS/CONVERGENCE AND ENHANCED LIFT IS

EXPECTED TO DEVELOP ACROSS SE VA/NE NC DURING THE EVENING. THIS

WILL RESULT IN ENHANCED SNOWFALL AND QUICK SNOW ACCUMULATIONS

ACROSS THE ENTIRE FORECAST AREA DURING THIS TIME. ROADS WILL

QUICKLY BECOME SNOW-COVERED AND LEAD TO HAZARDOUS TO DANGEROUS

DRIVING CONDITIONS. PERIODS OF MODERATE SNOWFALL (POSSIBLY HEAVY)

ARE LIKELY IN THE AFOREMENTIONED AREAS DURING THIS TIMEFRAME…

ESPECIALLY ACROSS THE EASTERN SHORE WHERE THE DEFORMATION ZONE IS

STRONGEST AND ALSO DUE TO GUSTY NORTH WINDS PRODUCE AREAS OF

BLOWING SNOW (SEE WIND SECTION BELOW). AS THE LOW TRACKS NE TWD

NEW ENGLAND AFTER MIDNIGHT…SNOW WILL START TO TAPER OFF FROM

WEST TO EAST…LINGERING NEAR THE COAST BEFORE DAYBREAK. THE

POTENTIAL EXISTS FOR SNOW BANDS TO DEVELOP AS PRECIP STARTS TO

WANE…HOWEVER THE ARCTIC AIR INTRUSION MAY ACT TO SHUT OFF THE

PRECIP COMPLETELY. ALSO…A NARROW BAND OF BAY EFFECT SHOWERS ARE

POSSIBLE TONIGHT AS GUSTY NORTH WINDS AND COLD AIR MOVE OVER THE

WARMER WATERS OF CHES BAY.

 

TOTAL SNOWFALL AMOUNTS WILL VARY FROM 5 TO 8 INCHES ACROSS NRN

COUNTIES (GENERALLY NORTH OF INTERSTATE 64) AND THE MD/VA EASTERN

SHORE AND THE PREVIOUSLY ISSUED WINTER STORM WARNINGS WILL REMAIN IN

EFFECT FROM MID MORNING THROUGH MIDNIGHT. ACROSS PORTIONS OF CTRL/SE

VA…STORM TOTAL SNOWFALL AMOUNTS OF 3 TO 5 INCHES ARE EXPECTED AND

ADDITIONAL WARNINGS HAVE BEEN ISSUED FOR TODAY THROUGH MIDNIGHT. FOR

SW COUNTIES OF THE CWA AND NE NC…TO 1 TO 3 INCHES OF SNOWFALL IS

EXPECTED AND WINTER WEATHER ADVISORIES HAVE BEEN ISSUED FOR THIS

AREA TODAY THROUGH LATE TONIGHT. IT IS LIKELY THAT WINTER HEADLINES

WILL NEED TO BE REPLACED WITH WIND CHILL ADVISORIES TONIGHT INTO

WED AS SNOW COMES TO AN END LATER TONIGHT. PLEASE REFER TO

WWW.ERH.NOAA.GOV/AKQ FOR THE MOST UP-TO-DATE INFORMATION REGARDING

THE ADVERSE WEATHER TODAY THROUGH WEDNESDAY.

 

 

WINDS/WIND CHILL…

THE SIGNIFICANT AIRMASS DIFFERENCES BTWN THE CANADIAN HIGH AND THE

COASTAL LOW WILL CAUSE THE SFC TEMP/PRESSURE GRADIENTS TO TIGHTEN

DRAMATICALLY BY THIS AFTN. NORTH WINDS WILL GENERALLY BECOME BREEZY

WITH GUSTS TO 20 MPH ACROSS FAR S-SW COUNTIES AND UP TO 25 MPH

ACROSS CTRL VA. CLOSER TO THE COASTAL AREAS OF CHES BAY AND THE

ATLANTIC OCEAN…NORTH WINDS WILL BECOME STRONG AND GUSTY THIS AFTN

WITH SUSTAINED SPEEDS OF 25-30 MPH WITH GUSTS UP TO 35 MPH. AS STRONG

COLD AIR ADVECTION PROCESSES OCCUR THIS EVENING WITH THE MAIN ARCTIC

BLAST…NORTH WINDS WILL STRENGTHEN ALL AREAS. GUSTS OF 25 MPH ARE

ANTICIPATED ACROSS INLAND AREAS…WHILE LOCATIONS NEAR THE COAST

SHOULD EXPERIENCE WIND GUSTS OF 35-45 MPH. THE COMBINATION OF

STRONG WINDS…SNOWFALL…AND TEMPERATURES FALLING BELOW FREEZING

WILL PRODUCE AREAS OF BLOWING SNOW AND FALLING WIND CHILL VALUES.

WIND CHILLS WILL BE NEAR 20 TO THE UPPER 30S THIS AFTN…FALLING

INTO THE TEENS THIS EVENING…AND THEN DROPPING TO VALUES OF

5-10 DEGREES BELOW ZERO TO NEAR ZERO. BREEZY WINDS WILL PERSIST

THROUGH THE DAY WED…THEN GRADUALLY DIMINISH THROUGH THE AFTN AS

HIGH PRESSURE BUILDS INTO THE AREA. EXPECT WIND CHILLS TO REMAIN

IN THE SINGLE DIGITS TO LOW TEENS ON WED.

 

SUMMARY OF IMPACTS…

* FALLING TEMPERATURES WILL CHANGE PRECIPITATION TO ALL SNOW BY

  EARLY THIS EVENING.

 

* SNOW WILL ACCUMULATE QUICKLY THIS EVENING AS ATMOSPHERIC CONDITIONS

  ENHANCE SNOWFALL RATES.

 

* STRONG AND GUSTY NORTH WINDS WILL PRODUCE AREAS OF BLOWING SNOW

  (ESPECIALLY NEAR THE COAST) AND ALSO WIND CHILLS THAT WILL FALL BELOW

  ZERO AFTER MIDNIGHT TONIGHT.

 

* THE COMBINATION OF GUSTY WINDS…FALLING TEMPERATURES…AND

  SNOW/BLOWING SNOW WILL CREATE HAZARDOUS TO DANGEROUS DRIVING

  CONDITIONS BEGINNING THIS AFTN THROUGH EARLY WED MORNING.

FLUVANNA-PRINCE EDWARD-CUMBERLAND-GOOCHLAND-NOTTOWAY-AMELIA-

POWHATAN-CHESTERFIELD-HENRICO-DINWIDDIE-PRINCE GEORGE-

CHARLES CITY-NEW KENT-

INCLUDING THE CITIES OF…FARMVILLE…GOOCHLAND…CREWE…

COLONIAL HEIGHTS…RICHMOND…PETERSBURG…HOPEWELL

736 AM EST TUE JAN 21 2014

 

…WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT EST

TONIGHT…

 

A WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT EST

TONIGHT.

 

* AREAS AFFECTED: PORTIONS OF CENTRAL VIRGINIA…INCLUDING METRO

  RICHMOND.

 

* HAZARDS: SNOW…BLOWING SNOW…AND GUSTY WINDS.

 

* ACCUMULATIONS: 3 TO 6 INCHES.

 

* WINDS: NORTH WINDS OF 15 TO 20 MPH WITH GUSTS TO AROUND 30 MPH

  THIS AFTERNOON AND EVENING.

 

* TEMPERATURES AND WIND CHILL: TEMPERATURES WILL FALL BELOW

  FREEZING THIS AFTERNOON…THEN FALL TO AROUND 10 DEGREES BY

  EARLY WEDNESDAY MORNING. THE COMBINATION OF GUSTY WINDS AND

  COLD TEMPERATURES WILL PRODUCE WIND CHILL VALUES TO AROUND

  FIVE BELOW ZERO BY WEDNESDAY MORNING.

 

* TIMING: SNOW WILL BEGIN IN THE WEST THIS MORNING WITH RAIN OR

  A RAIN/SNOW MIX FARTHER EAST. PRECIPITATION WILL CHANGE TO ALL

  SNOW DURING THIS AFTERNOON. THE PERIOD OF HEAVIEST SNOWFALL IS

  EXPECTED THIS AFTERNOON THROUGH EARLY THIS EVENING.

 

* IMPACTS: ROADS WILL BECOME SNOW COVERED AND SLIPPERY. THE

  COMBINATION OF SNOW AND GUSTY WINDS WILL PRODUCE BLOWING SNOW

  THAT WILL REDUCE VISIBILITY TO BELOW ONE MILE AT TIMES. TRAVEL

  CONDITIONS WILL BECOME DANGEROUS THIS AFTERNOON THROUGH THIS

  EVENING.

 

PRECAUTIONARY/PREPAREDNESS ACTIONS…

 

A WINTER STORM WARNING FOR HEAVY SNOW MEANS SEVERE WINTER WEATHER

CONDITIONS ARE EXPECTED OR OCCURRING. SIGNIFICANT AMOUNTS OF SNOW

ARE FORECAST THAT WILL MAKE TRAVEL DANGEROUS. ONLY TRAVEL IN AN

EMERGENCY. IF YOU MUST TRAVEL…KEEP AN EXTRA FLASHLIGHT…

FOOD…AND WATER IN YOUR VEHICLE IN CASE OF AN EMERGENCY.

1/20/2014 Forecast Grpahics and Discussion:

An arctic front is set to move through the area tonight and stall across North Carolina. Once it passes and stalls south of Central Virginia, a clipper system will pass nearby Tuesday morning into the afternoon that will likely give the area some accumulating snow. A winter storm watch was issues for most of the immediate metro Richmond area:

DORCHESTER-WICOMICO-SOMERSET-INLAND WORCESTER-MARYLAND BEACHES-
FLUVANNA-LOUISA-CUMBERLAND-GOOCHLAND-HANOVER-CAROLINE-AMELIA-
POWHATAN-CHESTERFIELD-HENRICO-KING WILLIAM-KING AND QUEEN-ESSEX-
WESTMORELAND-RICHMOND-NORTHUMBERLAND-LANCASTER-CHARLES CITY-
NEW KENT-MIDDLESEX-
INCLUDING THE CITIES OF...CAMBRIDGE...SALISBURY...CRISFIELD...
PRINCESS ANNE...SNOW HILL...OCEAN CITY...LOUISA...GOOCHLAND...
ASHLAND...COLONIAL HEIGHTS...RICHMOND...TAPPAHANNOCK
352 AM EST MON JAN 20 2014

...WINTER STORM WATCH IN EFFECT FROM TUESDAY MORNING THROUGH
TUESDAY EVENING...

THE NATIONAL WEATHER SERVICE IN WAKEFIELD HAS ISSUED A WINTER
STORM WATCH...WHICH IS IN EFFECT FROM TUESDAY MORNING THROUGH
TUESDAY EVENING.

* AREAS AFFECTED: PORTIONS OF CENTRAL AND EASTERN VIRGINIA...AND
  THE LOWER EASTERN SHORE.

* HAZARDS: SNOW.

* ACCUMULATIONS: SNOWFALL ACCUMULATIONS OF 3 TO 6 INCHES OF SNOW
  ARE POSSIBLE ACROSS THE WATCH AREA.

* WINDS: NORTH WINDS WILL AVERAGE 10 TO 20 MPH...WITH GUSTS TO
  AROUND 30 MPH EXPECTED TUESDAY AFTERNOON AND EVENING.

* TIMING: LIGHT SNOW WILL BEGIN BY MID MORNING ON
  TUESDAY...CONTINUING INTO EARLY TUESDAY EVENING. THE PERIOD OF
  HEAVIEST SNOWFALL IS EXPECTED TUESDAY AFTERNOON THROUGH EARLY
  EVENING.

* IMPACTS: ACCUMULATING SNOWFALL COULD CAUSE PERIODS OF HAZARDOUS
  TRAVEL ACROSS THE AREA TUESDAY AFTERNOON AND EVENING.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW ACCUMULATIONS THAT MAY IMPACT TRAVEL. CONTINUE TO MONITOR
THE LATEST FORECASTS.

Discussion from the NWS:

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...

BUSINESS LOOKS TO PICK UP ACROSS THE LOCAL AREA TO BEGIN THE DAY
TUESDAY. MODELS CONTINUE TO TREND TOWARDS A MORE MOIST SOLUTION AS
THE SHORTWAVE/CLIPPER AMPLIFIES SE INTO THE CAROLINAS THROUGH THE
DAY TUESDAY BEFORE EJECTING THE SYSTEM NORTHEAST TOWARDS ATLANTIC
CANADA EARLY WEDNESDAY.

OVERALL, WHILE THE NAM TRACKS THE SYSTEM FARTHEST SOUTH, WE STAYED
CLOSER TO A GGEM/UKMET/GFS BLEND WHICH IS FARTHER NORTH WITH THE
SLUG OF BEST CONVERGENCE/LIFT. RIGHT ENTRANCE REGION OF H3 (UPPER
JET), ALONG WITH 285K PRESSURE ADVECTION/RH FIELD PER THE ABOVE
MODEL CONSENSUS WOULD PAINT A VERY MESSY PICTURE LATE TUESDAY
MORNING THROUGH EARLY EVENING AS THE CLIPPER AND TRAILING COLD
FRONT MOVE THROUGH. STRONG CAA STILL PROGGED TO KICK IN DURING
THE AFTN. THUS...EXPECT MAX TEMPS AROUND NOON/SHORTLY THEREAFTER
SOUTHEAST WITH FALLING READINGS IN THE AFTN. POPS HAVE BEEN
SHUNTED UPWARD INTO HIGH LIKELY RANGE ACROSS THE FAR NORTHERN CWA
FOR TUESDAY.

WHEREAS SNOW ACCUMULATIONS WILL LIKELY BE A BIT MORE CUT AND DRIED
FARTHER NORTH AS ARCTIC AIR SURGES SOUTHEAST, THEY APPEAR TO BE A
BIT MORE TRICKY ACROSS OUR AREA, ESPECIALLY ALONG AND SOUTH/EAST OF
THE RICHMOND METRO. ONE LOOK AT LATEST SREF PLUMES SHOWS A WIDE
ARRAY OF POTENTIAL SOLUTIONS FORWARDED BY MEMBER ENSEMBLES...WHICH
DOES NOT INSPIRE FORECAST CONFIDENCE, ESPECIALLY GIVEN THE FACT
THAT MODEL SOLUTIONS WERE LESS THAN ENTHUSIASTIC ABOUT QPF TOTALS
JUST 12-18 SHORT HOURS AGO. HOWEVER, WITH BETWEEN 0.2 AND 0.4" OF
QPF...AND SNOW-LIQUID RATIOS A BIT HIGHER THAN NORMAL CONSIDERING
THE IMMINENT INCURSION OF AN ARCTIC AIRMASS...WARNING CRITERIA
SNOWS ARE CERTAINLY FEASIBLE AS BEST FGEN FORCING PUSHES ACROSS
THE REGION TUESDAY AFTN. WL GO WITH WINTER STORM WATCH OVER
RICHMOND METRO NORTH TO THE LOWER EASTERN SHORE...INCLUDING
NORTHERN NECK. FARTHER SOUTH, WEAKER PCPN RATE AWAY FROM BEST FGEN
FORCING WILL MAKE ACCUMULATING SNOWFALL A BIT MORE PROBLEMATIC.
CERTAINLY, THESE AREAS WILL BE MONITORED...BUT GIVEN PREFERRED
MODEL SOLUTION, EXPECT BEST SNOWFALL TOTALS NORTH OF RIC METRO
OVER TO THE NORTHERN NECK AND EASTERN SHORE. A GENERAL 3-6
INCLUDED IN WSW...BUT COULD CERTAINLY SEE HIGHER TOTALS OVER
NORTHEASTERN MOST PORTIONS OF THE AREA.

THE SNOW SHOULD END ACROSS THE NORTH EARLY TUESDAY EVENING WITH MUCH
COLDER ARCTIC AIR CONTINUING TO MOVE INTO THE AREA. ATTENTION
QUICKLY SHIFTS TO THE SOUTHEAST, WITH POTENTIAL FOR A QUICK (LIGHT)
SNOW ACCUMULATION ACROSS HAMPTON ROADS AND TIDEWATER AREAS. WIND
TRAJECTORY QUICKLY TURNS 350-360 AS THICKNESSES CRASH AND H92-85
TEMPS FALL TO ~-18C. STILL QUITE WARY OF POTENTIAL FOR BAY
ENHANCEMENT OF SNOW SHRAS TUESDAY NIGHT...AND HV GONE WITH SNOW
WORDING ACROSS THE TIDEWATER. CERTAINLY NOT CERTAIN ENOUGH FOR ANY
HEADLINES AT THIS STAGE...BUT JUMP IN SREF PROBABILITIES AND
SYNOPTIC SETUP WARRANTS A BIT HARDER WORDING IN DIGITAL FORECAST.

BECAUSE OF THE COMBINATION OF A STRONGER SURFACE LOW (TIGHTER
GRADIENT BRINGS MORE WIND) AND EXPECTED SNOW ON THE GROUND, TEMPS
HAVE BEEN DROPPED FOR TUESDAY NIGHT AND ESPECIALLY WED/THU NIGHT.
EXPECT WIND CHILL VALUES TO NUDGE BELOW ZERO TUESDAY NIGHT AND EARLY
WED.

STRONG CAA KICKS IN CONTINUES WED MORNING BEFORE SLOWLY DIMINISHING
LATE. DESPITE PLENTY OF SUNSHINE...A VERY COLD DAY IS EXPECTED. THE
STRONG/GUSTY N-NW FLOW WILL KEEP TEMPS ABOUT 1.5-2 STD DEV BELOW
NORMAL. KEPT SC CLOUD DECK ALONG THE COASTAL ZONES ERY WED AS H8
TEMPS PLUMMET TO -16 TO -18C. ALTHOUGH NOT THE PERFECT WIND
DIRECTION (340 VS 360)...SOME BAY EFFECT STREAMERS AND ADDITIONAL
SNOW SHRAS POSSIBLE ACROSS HAMPTON ROADS WED MORN. KEPT SLIGHT CHC
POP FOR NOW. HIGHS WEDNESDAY IN THE 20S.