An upper level low riding along a stalled front to the south of Virginia could bring significant snowfall to all of Central Virginia tomorrow night. Hints at the potential for a winter storm were noted earlier in the week in some of the major weather models. Model disagreements were based on the timing of the cold air arrival and how much moisture would overspread into Central Virginia. Both NAM and GFS point to the possibility of significant snowfall amounts for tomorrow night. Current thoughts from Wakefield include:
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/…
STRONG MID/UPPER LOW WILL LOCATE OVER THE LOWER MS VALLEY THURSDAY
MORNING AS THE SFC LOW STRENGTHENS ALONG THE STALLED BOUNDARY.
RAIN WILL BE ONGOING ACROSS THE PIEDMONT INTO SRN VA IN AREA OF
ISENTROPIC LIFT/DIVERGENCE ALOFT. STRONG DYNAMICS AND ABUNDANT
MOISTURE WILL ACCOMPANY THE UPPER LOW/PV ANOMALY AS IT LIFTS OUT
OF THE DEEP SOUTH AND INTO THE MID ATLANTIC THURSDAY AFTERNOON.
PRECIP WATERS WILL BE NEARLY ONE INCH WITH HIGH RH VALUES IN THE
IMPORTANT DGZ. SHARP HEIGHT FALLS WILL RESULT IN STRONG
FRONTOGENETIC FORCING AT THE SFC THURSDAY AFTERNOON AS A 200+ KT
JET EXISTS ACROSS THE NE. THIS WILL LEAD TO WIDESPREAD
RAIN…POSSIBLY HEAVY AT TIMES…OVER MUCH OF THE AFTERNOON
ACROSS THE ENTIRE FA. THE STRONGEST FRONTOGENETIC
FORCING/DIVERGENCE ALOFT WILL LOCATE OVER THE WRN AND NRN
FA…WHERE THE HIGHEST QPF AMOUNTS WILL OCCUR.THE UPPER LEVEL SHORTWAVE WILL PHASE WITH THE NRN STREAM TROUGH
THURSDAY EVENING AS COLD SFC HIGH PRESSURE EXPANDS EWD FROM THE
GREAT PLAINS. AS THE SFC LOW TRACKS SOUTH OF THE FA THURSDAY
EVENING/OVERNIGHT…COLD AIR WILL ALLOW TEMPS TO DROP RAPIDLY
ALONG THE NRN PERIPHERY OF THE PRECIP. COLD AIR WORKING INTO THIS
DYNAMIC OF A SYSTEM WILL RESULT IN A QUICK CHANGE OVER TO SNOW
LATE THURSDAY AFTERNOON…FIRST ACROSS THE NW. HAVE GONE UNDER
MODEL GUIDANCE ON SNOW ACCUMULATIONS BASED ON THE ANTECEDENT
RAINFALL/MILD WEATHER WHICH HAS KEPT GROUND TEMPERATURES WARM.
HOWEVER…STRONG UVM IN THE DGZ WILL ALLOW FOR LARGER FLAKES AND
HEAVIER SNOWFALL RATES. THIS WILL HELP SNOW ACCUMULATE REGARDLESS
OF THE WARM GROUND CONDITIONS. ANOTHER THING TO OVERCOME IS LOW
LEVEL TEMPS HOVERING RIGHT AROUND FREEZING…TO SLIGHTLY ABOVE.
HAVE GONE UNDER MODEL GUIDANCE ON TEMPS TOMORROW EVENING AS PRECIP
FALLING INTO THE LOWER LEVELS WILL HELP COOL THE LOW LEVELS. AS
THE LOW PUSHES OUT OVER THE WATERS AND INTENSIFIES AS IT LIFTS
NE…COLD AIR WILL CONTINUE TO MOVE TO THE SW ALLOWING RAIN TO
CHANGE OVER TO SNOW ALL THE WAY TO THE COAST BY LATE THURSDAY
NIGHT/EARLY FRIDAY MORNING. AS DRY/COLD W/NW FLOW WORKS INTO THE
REGION…PRECIP WILL END QUICKLY NW TO SE THURSDAY NIGHT/EARLY
FRIDAY MORNING…UNDER CLEARING SKIES. WHEN ALL IS SAID AND
DONE…SNOWFALL AMOUNTS WILL RANGE FROM AROUND 4 TO 5 INCHES IN
THE NW TO HALF AN INCH ACROSS SE VA/NE NC. LOCATIONS ALONG THE
COAST WILL REMAIN WARM ENOUGH FOR LITTLE…IF ANY…SNOWFALL
ACCUMULATIONS. WITH THE POSSIBILITY OF WARNING CRITERIA BEING MET
(SREF PROBABILITIES OF >4 INCHES EXCEEDS 50 PCT)…HAVE OPTED TO
ISSUE A WINTER WEATHER WATCH AS OPPOSED TO A WINTER WEATHER
ADVISORY. ANOTHER THING TO CONSIDER IN THE HIGHLY DYNAMIC SYSTEM
IS PRECIP BANDING. STRONG FRONTOGENETIC FORCING AND SLIGHTLY
NEGATIVE SAT GEO POT VORT INDICATE BANDING WILL BE POSSIBLE AND
SOMETHING TO WATCH. BANDING WILL LEAD TO LOCALLY HIGHER SNOWFALL
AMOUNTS. GRASSY SURFACES WILL SEE THE MOST SNOWFALL WITH SOME
ACCUMULATION ON AREA ROADS AND HIGHWAYS. TOTAL QPF AMOUNTS WILL
RANGE FROM AN INCH TO AN INCH AND A HALF…WHICH ON ALREADY
SATURATED SOILS MAY LEAD TO ADDITIONAL HYDRO CONCERNS. A FLOOD
WATCH MAY BE NEEDED.STRONG CAA ON FRIDAY (850 TEMPS FALL TO -7 TO -9C AND LOW LEVEL
THICKNESSES FALL OVER 20 M) AND AN EXISTING SNOW PACK WILL PREVENT
TEMPS FROM REACHING 40 ANY MANY LOCALES. WHILE SKIES WILL FINALLY
CLEAR FOR THE FIRST TIME IN SEVERAL DAYS…NORTHWEST WINDS 10 TO
15 MPH…STRONGER NEAR THE COAST…WILL MAKE IT FEEL EVEN COLDER.Some other images of the possible storm:
