March 5, 2013: Update

It looks like the impact from this storm is growing less and less…

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/…
FOR THE UPCOMING STORM SYSTEM TO AFFECT THE LOCAL AREA…GENLY
FOLLOWING HPC`S LEAD AND BLENDED SEVERAL OF THE 05/00Z MODELS
INCLUDING THE NAM/ECMWF/GFS. MAIN CHANGE WITH THIS FORECAST
PACKAGE IS DELAYING THE TRANSITION FROM RAIN TO RAIN/SNOW TO
SNOW…AND DECREASING SNOW TOTALS IN SOME AREAS.

WHAT HAS REMAINED FAIRLY CONSISTENT OVER THE PAST FEW DAYS
W/ THIS UPCOMING EVENT: MODELS HAVE BEEN SHOWING ABOUT 5 STD
DEVIATION ANOMALIES WITH RESPECT TO U COMPONENT OF 850 MB WIND
(I.E. STRONG/ANOMALOUS EASTERLY WINDS). ALTHOUGH EXACT LOCATION
HAS VARIED (GENLY BEING LOCATED OVER THE NRN MID ATLC REGION OR
FAR SOUTHERN NJ/PA). THIS TENDS TO BE A STRONG INDICATOR OF A
SIGNIFICANT EVENT ACRS AKQ CWA. THE OTHER FACTOR IS THE VERY
IMPRESSIVE FRONTOGENETIC FORCING OCCURRING ON THE NW SIDE OF THE
LOW TRACK…AND POTENTIAL FOR BANDING OF PRECIP. THE HIGHEST SNOW
AMOUNTS WILL BE LOCATED WITHIN THE NARROW BAND OF STRONGEST
FORCING AND ANY DEVIATION IN THE LOCATION OF THIS BAND WILL
DRASTICALLY CHANGE WHERE THE HIGHEST SNOWFALL ACCUMULATION OCCURS.
FOR NOW…THIS APPEARS TO RESIDE OVER THE FAR NWRN PART OF THE
CWA. THE LAST FACTOR…WHICH WILL BE INHIBITING AT LEAST IN TERMS
OF SNOWFALL ACCUMULATION WILL BE A WARM BOUNDARY LAYER…AND FACT
THAT ENTIRE FA WILL SEE SIGNIFICANT ACCUMULATION OF RAIN TUE
NGT/WED MRNG BEFORE THE CHANGEOVER. STILL..THINK DYNAMICALLY
DRIVEN COOLING DUE TO INTENSE LIFT AND PRECIP RATES WILL BE ABLE
TO OVERCOME THE WARMTH AT THE SFC. WHEN THIS OCCURS THE LOWER
LEVELS WILL BECOME COLD ENOUGH FOR THE PRECIP TO REMAIN
FROZEN…AND WITH THE STRONG FORCING AND HEAVY PRECIP RATES…SNOW
COULD BEGIN TO ACCUMULATE. WITH THE SFC LO TRENDING NORTH…THE
BEST CHC FOR WARNING–LVL SNOWFALL WILL BE OVER LOUISA AND
FLUVANNA…WHERE THE TRANSITION FROM RAIN TO SNOW WILL OCCUR IN
THE MRNG/MIDDAY HRS WED. FOR RICHMOND METRO…WITH HI LO-LVL
THICKNESSES AND THE H85/H5 LO PASSING DIRECTLY OVER THE AREA
(INSTEAD OF OFF TO THE SOUTH)…TRANSITION FROM RAIN TO SNOW MAY
BE DELAYED UNTIL THE AFTN HRS.

CONCERNING HEADLINES…WINTER STORM WATCH REMAINS ACRS THE
PIEDMONT FROM FVX TO LOUISA AND A FEW COUNTIES EAST. WATCH HAS NOT
BEEN EXPANDED SOUTH/EAST…WITH THE RICHMOND AREA MORE LIKELY TO
RECEIVE ONLY 1-2 INCHES. HAVE ADDED DORCHESTER COUNTY TO THE
WATCH WITH THIS PACKAGE WHERE 3-4 INCHES IS POSSIBLE.

PRECIP DOES COME TO AN END FROM WEST TO EAST WED NIGHT INTO
THURSDAY MORNING WITH THE POTENTIAL FOR A SNEAKY WRAP-AROUND BAND
OF SNOW ON THE EASTERN SHORE BEFORE ALL IS SAID AND DONE.

AS FAR AS TEMPS…HIGHS WEDNESDAY IN THE MID 30S NW TO UPR 40S
SERN COASTAL AREAS. THURSDAY`S HIGHS IN THE MID TO UPR 40S. LOW
TEMPS GENERALLY IN THE 30S.

March 4, 2013: Updates

New images and discussion regarding the storm from the NWS:

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/…
FOR THE UPCOMING STORM SYSTEM TO AFFECT THE LOCAL AREA…GENLY
FOLLOWING A SOLUTION BLENDING THE 04/00Z RUNS OF THE NAM/ECMWF/GFS.
OVERALL THINGS HAVE NOT CHANGED THAT MUCH…THE GFS STILL IS A
FASTER AND FARTHER NORTH SFC LOW TRACK SOLUTION TENDING TO BE ON
THE NORTH EDGE OF ALL GUIDANCE. IT WOULD SUGGEST THE MAIN IMPACT
FOR ACCUMULATING SNOW WOULD BE OVER FAR NORTHERN PORTIONS OF THE
CWA. THE 00Z NAM SOLUTION WOULD FAVOR A MUCH MORE SIGNIFICANT SNOW
ACCUMULATION OVER CENTRAL AND EVEN SOUTHERN VA. NOTE…LATEST 06Z
NAM HAS TRENDED NORTH TO THE GFS…ALTHOUGH DO NOT GENLY FAVOR THE
06/18Z MODEL RUNS.

WHAT HAS REMAINED FAIRLY CONSISTENT OVER THE PAST FEW DAYS W/
THIS UPCOMING EVENT: MODELS HAVE BEEN SHOWING ABOUT 5 STD
DEVIATION ANOMALIES WITH RESPECT TO U COMPONENT OF 850 MB WIND
(I.E. STRONG/ANOMALOUS EASTERLY WINDS). ALTHOUGH EXACT LOCATION
HAS VARIED (GENLY BEING LOCATED OVER THE NRN MID ATLC REGION OR
FAR SOUTHERN NJ/PA). THIS TENDS TO BE A STRONG INDICATOR OF A
SIGNIFICANT EVENT ACRS AKQ CWA. THE OTHER FACTOR IS THE VERY
IMPRESSIVE FRONTOGENETIC FORCING OCCURRING ON THE NW SIDE OF THE
LOW TRACK…AND POTENTIAL FOR BANDING OF PRECIP. THE HIGHEST SNOW AMOUNTS
WILL BE LOCATED WITHIN THE NARROW BAND OF STRONGEST FORCING AND
ANY DEVIATION IN THE LOCATION OF THIS BAND WILL DRASTICALLY CHANGE
WHERE THE HIGHEST SNOWFALL ACCUMULATION OCCURS. FOR NOW…AND THIS
HAS BEEN FAIRLY CONSISTENT…THIS APPEARS TO RESIDE OVER NRN 1/2
TO 1/3 OF THE CWA. THE LAST FACTOR…WHICH COULD BE INHIBITING AT
LEAST IN TERMS OF SNOWFALL ACCUMULATION WILL BE WARM BOUNDARY
LAYER…AND FACT THAT ENTIRE REGION EXCEPT FOR POSSIBLY THE FAR NW
WILL SEE SIGNIFICANT ACCUMULATION OF RAIN TUE NIGHT BEFORE THE
CHANGEOVER. STILL..THINK DYNAMICALLY DRIVEN COOLING DUE TO INTENSE
LIFT AND PRECIP RATES WILL BE ABLE TO OVERCOME THE WARMTH AT THE
SFC. WHEN THIS OCCURS THE LOWER LEVELS WILL BECOME COLD ENOUGH FOR
THE PRECIP TO REMAIN FROZEN…AND WITH THE STRONG FORCING AND
HEAVY PRECIP RATES…SNOW COULD BEGIN TO ACCUMULATE VERY QUICKLY.

CONCERNING HEADLINES…HAVE RAISED A WINTER STORM WATCHACRS THE
PIEDMONT FROM FVX TO LOUISA AND A FEW COUNTIES EAST. THIS IS DUE
TO POTENTIAL FOR ACCUMULATING SNOW TO BEGIN WITHIN 48HRS…PRIOR
TO 12Z/WED. FARTHER EAST…THE CHANGEOVER/OR AT LEAST TIME WHEN
SNOW BEGINS TO ACCUMULATE IS GENLY EXPECTED AFTER 12Z. THIS IS THE
REASON FOR NO WATCH AT THIS TIME IN THESE AREAS (LATER SHIFTS WILL
NEED TO CONSIDER EXPANDING DEPENDING ON MODEL TRENDS). FCST GENLY HAS
SNOW BECOMING MAIN P-TYPE ACRS MUCH OF METRO RICHMOND SOMETIME
BETWEEN 12-18Z/WED…ALTHOUGH THIS IS UNCERTAIN AND WOULD NOT BE
SURPRISED TO SEE SHARP CUTOFF WITHIN THE METRO AREA ITSELF. EXPECT
A SIGNIFICANT SNOWFALL/SEVERAL INCHES FOR MUCH OF CENTRAL AND
POSSIBLY EAST CENTRAL VA AND INTO DORCHESTER MD SOMETIME LATER
WED-WED EVENING.

THE KEY POINT OF THIS EVENT IS THAT THIS STORM WILL CREATE A
HIGHLY DYNAMIC ENVIRONMENT AND THE LACK OF COLD AIR AT THE SURFACE
COULD BE OVERCOME BY COOLING FROM ALOFT WITH A PERIOD OF VERY
HEAVY SNOW RESULTING OVER PORTIONS OF THE FORECAST AREA WEST AND
NORTH OF A FARMVILLE-RICHMOND-SALISBURY LINE. ALTHOUGH THERE HAS
BEEN SOME MODEL RUN TO RUN CONSISTENCY…THIS WX SCENARIO IS
HIGHLY VARIABLE AND PINPOINTING SPECIFICS IN
TIMING/LOCATION/AMOUNTS IS EXTREMELY DIFFICULT.

__________________________________________________

March 2, 2013: The weather models have the lower mid-Atlantic pegged for a substantial weather system next week that is spurred by a system dropping through the Rockies, into Kentucky and Tennessee and then rapidly redeveloping off the North Carolina Coast. Being March, temperatures and intensity of the storm are going to be critical in the forecast for any snowfall in Central Virginia. The Euro model has piled up impressive snow amounts for Virginia in the last two days. As always, following the latest trends is going to be key in making a forecast for next week. As of Saturday morning, a HWO has been issued by the NWS in Wakefield:

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.
STRONG LOW PRESSURE WILL INTENSIFY OFF THE MID ATLANTIC OR SOUTHEAST
COAST WEDNESDAY THROUGH THURSDAY. MAINLY RAIN IS ANTICIPATED LATE TUESDAY
NIGHT THROUGH WEDNESDAY MORNING...BEFORE THE PRECIPITATION MIXES
WITH OR CHANGES TO WET SNOW WEDNESDAY AFTERNOON THROUGH WEDNESDAY
NIGHT.

Accuweather’s image for the upcoming storm:

An arctic cold front will swing through central Virginia tonight and usher in a new round of cold air for the weekend. Along the cold front, a low pressure system may develop during the day on Saturday to bring some light rain and snow showers to the area. Accumulations will likely be light. The system bears watching for some accumulating snowfall.