Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 261452
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1052 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 1045 AM EDT SUNDAY...

MORNING SOUNDING FROM RNK SHOWS THE WEDGE STILL VERY WELL
ENTRENCHED ACROSS THE AREA WITH A FAIRLY DEEP LAYER OF COOL AND
MOIST AIR IN THE BOUNDARY LAYER. RADAR HAS BEEN SHOWING MAINLY
LIGHT RETURNS IN SPRINKLES/DRIZZLE WITH SOME STEADIER LIGHT
SHOWERS AROUND THE NC/VA BORDER. AS LOW PRESSURE TO OUR SOUTH
WITH AN INVERTED EXTENDING INTO OUR AREA CONTINUES TO PULL AWAY
AND WINDS BACK TO NORTH AND NORTHWEST...BELIEVE THE TREND WILL BE
FOR AREAS OF FOG AND DRIZZLE TO MORPH INTO SPRINKLES FROM THE BLUE
RIDGE WEST DURING THE AFTERNOON. SATELLITE IMAGES SHOW A GOOD
AMOUNT OF CLEARING JUST TO OUR NORTH MOVING IN OUR DIRECTION BUT
GUIDANCE INDICATES THIS WILL BE A VERY SLOW PROCESS SO WILL GO A
BIT MORE PESSIMISTIC WITH CLOUD COVER TODAY AND EXPECT SOME
GENERAL BRIGHTENING INSTEAD OF CLEARING WITH SOME LATE DAY BREAKS
FAR NORTH. THE GENERAL BRIGHTENING AND LESSENING PRECIPITATION
SHOULD HELP TEMPERATURES SLOWLY INCH UPWARD BUT IT WILL STILL BE A
VERY COOL AND DAMP DAY.

PREVIOUS AFD...

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. 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 /15Z SUNDAY THROUGH THURSDAY/...
AS OF 745 AM EDT SUNDAY...

DEEP UPPER LOW OFF THE NORTHEAST U.S. COAST WILL SINK SLOWLY
SOUTHWARD TO OFF THE MID-ATLANTIC COAST BY MONDAY. ASSOCIATED
WEST-EAST ORIENTED FRONTAL BOUNDARY FROM TYS-RDU...WILL SINK
SLOWLY SOUTH AS WELL. WRAP AROUND -SHRA WILL CONTINUE ACROSS THE
CWA WITH WEAK FORCING FROM THE NORTH ON BACK SIDE OF UPPER LOW.
DOUBLE BARREL SFC LOW...ONE IN THE EASTERN TN VALLEY AND THE OTHER
OFF THE NC COAST WILL SHIFT SOUTHEAST WITH TIME. WINDS WILL BACK
FROM NE TO NW THROUGH THE TAF VALID PERIOD. THIS WILL KEEP A MOIST
ATLANTIC FLOW EAST OF THE BLUE RIDGE UNTIL EVENING AND A MOIST
UPSLOPE FLOW WEST OF THE BLUE RIDGE. -SHRA WILL CONTINUE
THROUGHOUT THE DAY...BUT GRADUALLY DIMINISH AND SHIFT SOUTHEAST BY
AFTERNOON. WILL DROP DEFINITE -SHRA FROM FM GROUPS AFT 18Z...BUT
INCLUDE VCSH THROUGH THE REMAINDER OF THE AFTERNOON. IFR-LIFR CIGS
THROUGH 15Z WILL GRADUALLY IMPROVE TO MVFR BY EARLY-MID AFTERNOON
EAST OF THE BLUE RIDGE...BUT LIKELY ONLY TO IFR TO LOW END MVFR
WEST OF THE BLUE RIDGE IN UPSLOPE FLOW. VSBYS GENERALLY NOW VFR
EAST OF THE BLUE RIDGE...BUT LINGERING MVFR-IFR WEST OF THE BLUE
RIDGE. EXPECT MOST AREAS TO IMPROVE TO VFR BY LATE MORNING/EARLY
AFTERNOON...WITH THE EXCEPTION OF BLF WHICH COULD LINGER WITH
IFR-MVFR VSBYS MUCH LONGER...AND WHICH MAY RETURN AFT 00Z. WILL
NEED TO WATCH SPOKE OF PVA/SHORT WAVE APPROACHING FROM THE NORTH
LATE TONIGHT WITH POSSIBLE RENEWED SHOWER ACTIVITY ACROSS THE
MOUNTAINS OF WV AT THAT TIME. WINDS NE 5-7KTS THROUGH MID-
DAY...BACKING TO NW 6-8KTS DURING THE AFTERNOON/EVENING.

MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD.
MEDIUM CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...
BREEZY NORTHWEST FLOW IS EXPECTED FOR MONDAY AND EARLY TUESDAY AS
HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. AS NOTED ABOVE...A
SHORT WAVE WILL ROTATE AROUND THE BACK SIDE OF THE NORTHERN
ATLANTIC UPPER LOW...WHICH WILL KEEP VARIABLE CLOUDS AND SCT -SHRA
ACROSS THE MOUNTAINS...ESPECIALLY DURING PEAK HEATING. MVFR CIGS
MAY LINGER IN THESE AREAS...BUT VFR CIGS TO NO CIGS ARE EXPECTED
ACROSS THE PIEDMONT. WINDS WILL BE NORTHWEST 5-10KTS...WITH SOME
LOW END GUSTS POSSIBLE WEST OF THE BLUE RIDGE. VFR CONDITIONS ARE
EXPECTED TUE BEFORE CONDITIONS WORSEN ONCE AGAIN WED-THU AS A LOW
PRESSURE SYSTEM PASSES 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. AN
UPPER LOW WILL ALSO BUILD SOUTHWARD FROM THE GREAT LAKES AT THE
SAME TIME.

&&

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

&&

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


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