Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 260838
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
438 AM EDT SUN APR 26 2015

.SYNOPSIS...
WITH THE DEPARTURE OF AN UPPER LEVEL SYSTEM FROM THE MID ATLANTIC
THIS MORNING...HIGH PRESSURE BUILDING IN FROM THE MIDWEST REGION
WILL BECOME THE MAIN WEATHER FEATURE FOR OUR AREA TODAY. ANOTHER LOW
PRESSURE SYSTEM IS EXPECTED TO AFFECT THE SOUTHEAST AND MID ATLANTIC
REGION DURING THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 345 AM EDT SUNDAY...

KEEPING AN EYE ON AN AREA OF RAIN...WITH THE OCCASIONAL EMBEDDED
THUNDERSTORM...MAKING ITS WAY EAST ACROSS CENTRAL VIRGINIA THIS
MORNING AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE REGION. RAPID
UPDATE MODELS INDICATE THAT THE MAJORITY OF THIS RAIN WILL EXIT OUR
AREA FOR THE COASTAL PLAIN BY 7 AM...LEAVING ONLY ISOLATED
SHOWERS...WHICH WILL BE INTERMIXED WITH AREAS OF FOG AND DRIZZLE
THROUGH LATE MORNING.

WITH THE DEPARTURE OF THE UPPER LEVEL DISTURBANCE...HIGH PRESSURE
BUILDING IN FROM THE MIDWEST STATES WILL GRADUALLY TAKE OVER AS OUR
DOMINATING WEATHER FEATURE...CAUSING WINDS ACROSS OUR AREA TO SLOWLY
SHIFT NORTHWEST THROUGH THE DAY. THE VERY SLOW ARRIVAL OF DRIER AIR
MEANS THAT LOW CLOUDS WILL REMAIN ACROSS OUR FORECAST AREA THROUGH
MUCH OF THE DAY...KEEPING A FIRM LID ON DAYTIME HEATING. ALTHOUGH
SLIGHTLY WARMER THAN THOSE OBSERVED ON SATURDAY...HIGH TEMPERATURES
THIS AFTERNOON WILL REMAIN WELL BELOW NORMAL FOR LATE APRIL...
GENERALLY HOLDING IN THE LOW TO MID 50S MOST LOCATIONS...WITH UPPER
40S POSSIBLE IN A FEW SPOTS NEAR THE INTERSTATE 64 CORRIDOR.

CLOUDS WILL START TO BREAK UP DURING LATE AFTERNOON/EARLY EVENING
EAST OF THE BLUE RIDGE...WITH CLOUD COVER DECREASING ACROSS THE
MOUNTAINS AFTER DARK. THE ARRIVAL OF HIGH PRESSURE WILL ALSO CAUSE
THE PRESSURE GRADIENT TO INCREASE FOR THE CENTRAL APPALACHIANS...AND
WE CAN EXPECT WINDS TO BECOME BREEZY AFTER MIDNIGHT. LOOKING ONCE
AGAIN AT ANOTHER COOL NIGHT...WITH SUNDAY NIGHT LOWS RANGING FROM
THE MID 40S ACROSS THE FOOTHILLS IN NORTH CAROLINA...TO THE LOW AND
MID 30S ALONG THE INTERSTATE 64 CORRIDOR. MAY BE A FEW SPOTS WHERE
TEMPERATURES FALL BELOW FREEZING IN THE NORTH...HOWEVER THE
INCREASED WIND SPEEDS WILL LIKELY PREVENT FROST FORMATION. WILL LET
THE DAY SHIFT TAKE A LOOK AT ANOTHER BATCH OF MODEL DATA...AND
DETERMINE IF ANY FROST/FREEZE STATEMENTS ARE NECESSARY FOR TONIGHT.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
AS OF 400 AM EDT SUNDAY...

CONVOLUTED UPPER AIR PATTERN REMAINS IN PLACE THROUGH THE PERIOD.
THE MAIN FEATURES BEING A DEEP 529DM UPPER LOW OFF THE NORTHEAST
U.S. COAST EXTENDING WELL BACK INTO THE OH VALLEY/MID-ATLANTIC
REGION...A CLOSED LOW COMING OUT OF THE DESERT SOUTHWEST INTO
TEXAS...AND A ELONGATED RIDGE IN BETWEEN BETWEEN THE CENTRAL
CANADIAN PROVINCES DOWN INTO THE CENTRAL U.S...THEN THE SOUTHEAST
U.S. FOR MON AND TUE...OUR REGION WILL REMAIN LARGELY UNDER THE
INFLUENCE OF THE NORTHEAST U.S./NORTHERN MID-ATLANTIC UPPER LOW. A
SPOKE OF PVA/SHORT WAVE WILL ROTATE THROUGH THE REGION FROM THE
NORTH ON THE WEST SIDE OF THE ELONGATED UPPER LOW. WITH 850MB
TEMPS CONTINUING TO HOVER NEAR 0C AND COLD 500MB TEMPS -20 TO -24C...
THE ATMOSPHERE WILL BE QUITE UNSTABLE. ANY MORNING SUNSHINE WILL
QUICKLY RESULT IN CU/SC DEVELOPING AND LIKELY -SHRA ACROSS THE
MOUNTAINS BY LATE MORNING THROUGH THE EARLY EVENING. TEMPERATURES
WILL REMAIN WELL BELOW NORMAL...AND ANY SHOWERS WILL EASILY BRING
THOSE AREAS BACK DOWN INTO THE 40S DURING THE AFTERNOON. IN
FACT...850MB TEMPS COULD SUPPORT SOME -SN AT THE HIGHEST ELEVATIONS
MON MORNING...BUT HAVE NOT INCLUDED IN THE GRIDS AT THIS TIME.
SHOWERS WILL BE CONSIDERABLY LESS LIKELY IN THE DOWNSLOPE PIEDMONT
AREAS. LESS CLOUDS IN THIS AREA WILL ALSO ALLOW MAX TEMPS TO WARM
BACK INTO THE 60S...YET STILL BELOW NORMAL.

FOR TUE...THE DEEP UPPER LOW FINALLY BEGINS TO DRIFT EAST FURTHER
OUT TO SEA...WHILE THE UPPER LOW ACROSS TX DRIFTS INTO THE
ARKLATEX REGION. A NEW UPPER LOW BEGINS TO DRIFT SOUTH OUT OF THE
CENTRAL CANADIAN PROVINCES...WHILE THE SKINNY/COMPLICATED UPPER
RIDGE DRIFTS INTO OUR REGION. THIS SHOULD BE THE ONE DAY WITH
LITTLE TO NO -SHRA ACTIVITY WITH NO FORCING EVIDENT ALOFT AND WEAK
RIDGING. INCREASED SUNSHINE SHOULD ALLOW TEMPS TO WARM A TAD
CLOSER TO NORMAL...BUT 850MB TEMPS ONLY WARM A FEW DEGREES TO
ABOUT +4C ACROSS MUCH OF THE CWA.

FOR WED...THE ARKLATEX UPPER LOW DRIFTS INTO THE SOUTHEAST STATES
WHILE LOW PRESSURE ALOFT DRIFTS SOUTHWARD INTO THE GREAT LAKES.
THESE TWO SYSTEM WILL MERGE ACROSS THE REGION INTO THU AS YET
ANOTHER UPPER LOW FORMS ACROSS THE MID-ATLANTIC BY THU. LIGHT
RAIN WILL BEGIN TO SPREAD INTO THE REGION WED AS HEIGHTS ALOFT
LOWER AS THE UPPER LOWS CONVERGE ACROSS THE REGION. THIS...ALONG
WITH CLOUD COVER AND INCREASED PRECIPITATION WILL ENSURE CONTINUED
WELL BELOW NORMAL TEMPERATURES. QPF DOES NOT APPEAR TO BE AN ISSUE
AT THIS POINT AS THE HEAVIEST RAINFALL WILL REMAIN WELL SOUTH OF
THE REGION.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 430 AM EDT SUNDAY...

THE GFS AND CANADIAN HAVE COME INTO BETTER AGREEMENT WITH THE
ECMWF ON DEVELOPMENT AND EVOLUTION OF A COASTAL LOW/ALMOST
MILLER-A TYPE SETUP OFF THE SOUTHEAST U.S. COAST THU. THIS WILL
SPREAD RAIN INTO THE REGION FROM THE SOUTH. AS THE SOUTHERN STREAM
LOW BECOMES ABSORBED INTO SOUTHWARD MOVING UPPER LOW FROM THE
GREAT LAKES...A DEEP 540DM UPPER LOW WILL EVOLVE ACROSS WV/VA INTO
EARLY FRI. THIS WILL PROLONG THE LIGHT RAIN...NORTHERLY FLOW...AND
UNSEASONABLY COOL TEMPERATURES RIGHT INTO FRI. WITH THE REGION
LARGELY UNDER A COOL/STABLE/NORTHERLY FLOW...PWATS ACROSS THE
REGION ARE GENERALLY AROUND 1/2 INCH DURING THIS TIME FRAME...SO
HEAVY RAIN DOES NOT APPEAR TO BE A CONCERN. THAT SHOULD REMAIN
WELL SOUTHEAST ALONG COASTAL AREAS AND THEN OFF THE VA/MD COAST
WITH TIME. BUT...850MB TEMPS WILL CONTINUE TO HOVER NEAR 0C
THROUGHOUT THE PERIOD AS THE UPPER LOW DUMBBELLS ACROSS THE MID-
ATLANTIC...KEEPING MAX TEMPS FOR SURE WELL BELOW NORMAL...BUT MIN
TEMPS SLIGHTLY BELOW NORMAL BECAUSE OF CLOUD COVER

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
AS OF 200 AM EDT SUNDAY...

AREA OF RAIN...WITH A FEW EMBEDDED THUNDERSTORMS WEST OF THE
INTERSTATE 77 CORRIDOR...WILL PASS EAST ACROSS THE FORECAST
REGION THROUGH 6 AM AS AN UPPER LEVEL DISTURBANCE MOVES OVERHEAD.
AS THE DISTURBANCE EXITS AFTER 6 AM...RAINFALL WILL BE REDUCED TO
SPOTTY LIGHT SHOWER ACTIVITY...WITH OTHERWISE AREAS OF DRIZZLE.
WINDS WILL GRADUALLY SHIFT MORE NORTH TO NORTHWESTERLY IN THE WAKE
OF THIS DISTURBANCE...BUT DO NOT EXPECT THE WIND SHIFT TO
INFLUENCE THE LIFR/VLIFR CEILINGS AND AREAS OF FOG CURRENTLY IN
PLACE...AND EXPECT THESE CONDITIONS AREAWIDE THROUGH LATE SUNDAY
MORNING.

AS WINDS GRADUALLY BACK MORE NORTHWESTERLY AFTER SUNRISE...EXPECT
A SLOW IMPROVEMENT TO MVFR CEILINGS DURING LATE MORNING AND EARLY
AFTERNOON...AND TO LOW END VFR AROUND SUNSET...ALTHOUGH RESIDUAL
POCKETS OF MVFR/IFR WILL LINGER ACROSS THE MOUNTAINS UNTIL EARLY
MONDAY...ESPECIALLY THE NORTHWEST UPSLOPE AREAS ALONG THE WESTERN
RIDGES.

EXTENDED AVIATION DISCUSSION...

BREEZY NORTHWEST FLOW IS EXPECTED FOR MONDAY AND EARLY TUESDAY
AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST...SUPPORTING VFR
CONDITIONS.

STILL KEEPING AN EYE ON A LOW PRESSURE SYSTEM PASSING ACROSS THE
SOUTHEAST STATES...WHICH WILL AFFECT THE MID ATLANTIC ON
WEDNESDAY INTO THURSDAY. CONFIDENCE IS GROWING THAT THIS SYSTEM
WILL RESULT IN WIDESPREAD RAIN FOR THE FORECAST AREA...AS WELL AS
PERSISTENT MVFR/IFR CONDITIONS.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...NF
NEAR TERM...NF
SHORT TERM...RAB
LONG TERM...PM/RAB
AVIATION...AMS/NF


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