Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 251755
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
155 PM EDT SAT APR 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO SHIFT OFF THE COAST TODAY AS A LOW
PRESSURE SYSTEM PUSHES EAST FROM THE CENTRAL PLAINS...BRINGING RAIN
TO THE CENTRAL APPALACHIANS TODAY AND TONIGHT. THE SYSTEM WILL EXIT
TO THE EAST SUNDAY MORNING...WITH HIGH PRESSURE BUILDING IN FROM THE
WEST DURING THE AFTERNOON. ANOTHER LOW PRESSURE SYSTEM IS EXPECTED
TO AFFECT THE SOUTHEAST AND MID ATLANTIC REGION DURING THE MIDDLE OF
NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM EDT SATURDAY...

NAM BUFKIT SOUNDING WAS IN GOOD AGREEMENT WITH 12Z RNK SOUNDING...
WHICH WAS IN THE SAME BALLPARK AS GFS SO HAVE GOOD CONFIDENCE IN
MODEL SOLUTIONS THROUGH THE NEAR TERM. ABUNDANT MOISTURE AND
ISENTROPIC LIFT RUNNING OVER THE SURFACE WEDGE OF COOL AIR WILL
KEEP PERIODS OF RAIN GOING THROUGHOUT THE AFTERNOON. INSTABILITY
AND DYNAMIC ENVIRONMENT BECOME FAVORABLE FOR SIGNIFICANT STORMS
TO OUR WEST AS INDICATED BY SPC PRODUCTS...BUT AS THE STORMS
DEVELOP AND MOVE IN OUR DIRECTION LATE THIS AFTERNOON THEN WILL
ENCOUNTER THE COOL STABLE AIR IN PLACE OVER OUR REGION AND WILL
NOT POSE A THREAT FOR SEVERE WEATHER...THOUGH EXTREME WEST AND
SOUTH MAY HEAR A RUMBLE OR TWO OF THUNDER. THE COOL WEDGE WILL
KEEP TEMPS 15 TO 20 DEGREES BELOW NORMAL TODAY. THIS IS ALL IN
GOOD AGREEMENT WITH THE CURRENT SET OF GRIDS SO ONLY SOME MINOR
ADJUSTMENTS TO FINE TUNE CURRENT CONDITIONS ARE NECESSARY.

APPLICABLE PORTION OF PREVIOUS AFD...

CANNOT RULE OUT LOCALLY HEAVY RAIN ACROSS THE MOUNTAINS DURING
LATE THIS AFTERNOON AND THE AFTERNOON AS A WAVE OF LOW PRESSURE
PASSES OVERHEAD...HOWEVER WITH DRY CONDITIONS OVER THE PAST FEW
DAYS...MOST LOCATIONS CAN HANDLE SOME RAINFALL AND THEREFORE
EXPECT ANY FLOODING TO BE MINOR AND ISOLATED.

A SECOND WAVE OF LOW PRESSURE WILL PASS ACROSS THE AREA LATE THIS
EVENING...TRIGGERING ANOTHER ROUND OF RAIN ACROSS THE AREA. THE LOW
WILL ALSO DRAG A COLD FRONT ACROSS THE CENTRAL APPALACHIANS WHICH
WILL SHIFT OUR WINDS MORE FROM THE NORTH BY SUNRISE SUNDAY.
WIDESPREAD LOW CLOUDS AND RAIN WILL KEEP TEMPERATURES ON THE MILD
SIDE FOR OVERNIGHT LOWS...RANGING FROM THE LOW 50S ACROSS NORTHERN
NORTH CAROLINA...TO THE UPPER 30S NEAR THE INTERSTATE 64 CORRIDOR.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
AS OF 400 AM EDT SATURDAY...

STRONG SHORT WAVE OF SATURDAY WILL SLIDE EAST-SOUTHEAST ACROSS THE
VA/NC PIEDMONT TOWARD THE VA/NC COASTLINE SUNDAY AS THE DEEP UPPER
LOW ACROSS THE CANADIAN MARITIMES SINKS SLOWLY SOUTHWARD. WEAK SFC
LOW PRESSURE WILL RIDE ALONG THE BOUNDARY AS HIGH PRESSURE BUILDS
SOUTHWARD FROM THE CENTRAL CANADIAN PROVINCES INTO THE REGION.
MOIST...COOL...NORTHEAST MARITIME FLOW WILL CONTINUE ACROSS THE
REGION...ESSENTIALLY CONTINUING THE COOL/WEDGE AIR MASS OF SAT.
THUS...SUNDAY SHOULD BE A DREARY...UNSEASONABLY COOL DAY YET AGAIN
WITH LIGHT RAIN THROUGHOUT THE DAY...BUT MOST LIKELY DURING THE
FIRST HALF AS BY EVENING DRIER AIR SHOULD BEGIN TO WORK INTO THE
REGION FROM THE NORTHWEST. RAINFALL AMOUNTS SUNDAY WILL GENERALLY
BE 1/4 INCH OR LESS...FOCUSED MAINLY ACROSS THE EASTERN AREAS.

FOR MONDAY...THE AFOREMENTIONED DEEP LOW WILL CONTINUE TO SAG
SLOWLY SOUTHWARD TO OFF THE NEW ENGLAND COAST . DEEP NORTHERLY
FLOW ALOFT WILL EVOLVE ACROSS THE REGION...ALLOWING COOL AIR TO
CONTINUE TO FILTER INTO THE REGION FROM THE NORTH. A SHORT WAVE
EMBEDDED WITHIN THE UPPER LOW ACROSS THE GREAT LAKES WILL MOVE
TOWARD THE REGION DURING THE DAY. THIS WILL PROMOTE AN INCREASE IN
-SHRA ACTIVITY...ESPECIALLY IN THE WEST AND NORTH. ACROSS THE
HIGHER ELEVATIONS OF THE WESTERN MOUNTAINS...WITH 850MB TEMPS
NEAR 0C...COULD NOT TOTALLY RULE OUT A FEW -SHSN...ESPECIALLY AT
ELEVATIONS ABOVE 3500 FT...BUT NOT ENOUGH CONFIDENCE TO ADVERTISE
IN THE GRIDS AT THIS POINT AND AT ANY RATE IT WOULD NOT CAUSE ANY
PROBLEMS.  THE ASSOCIATED CLOUD COVER AND PRECIPITATION WILL
CONTINUE TO HOLD TEMPERATURES WELL BELOW NORMAL ONCE AGAIN
MONDAY...ALTHOUGH PIEDMONT AREAS SHOULD BE SOMEWHAT WARMER THAN
OVER THE WEEKEND WITH INCREASINGLY DOWNSLOPE NORTHWEST FLOW AND AS
A RESULT FEWER CLOUDS.

FOR TUESDAY...THE UPPER LOW SHIFTS FURTHER SOUTHEAST LEAVING THE
AREA IN A WEAK COL AREA ON THE BACK SIDE OF THE DEPARTING LOW AND
A CLOSED LOW IN THE SOUTHERN STREAM TRACKING EASTWARD FROM THE
CENTRAL PLAINS. AT THIS POINT...TUESDAY APPEARS TO BE THE BEST DAY
OF THE PERIOD WITH DRIER NORTHWEST FLOW AND LARGE SCALE SUBSIDENCE
ON THE BACK SIDE OF THE NORTHERN ATLANTIC UPPER LOW.

TEMPERATURES WILL AVERAGE A GOOD 10 DEGREES BELOW NORMAL
THROUGHOUT THE PERIOD...WITH CLOUDS AND PRECIPITATION SUN-
MON...AND A LARGE POCKET OF 850MB TEMPS HOVERING NEAR 0C
THROUGHOUT THE PERIOD ON THE BACK SIDE OF THE NORTHERN ATLANTIC
UPPER LOW. EXPECT HIGHS 50S MOUNTAINS TO 60S PIEDMONT AND LOWS 30S
MOUNTAINS TO 40S PIEDMONT.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 415 AM EDT SATURDAY...

MORE WET COOL WEATHER APPEARS LIKELY THROUGH THE PERIOD. MODELS
CONTINUE TO DISAGREE ON THE DETAILS REGARDING THE ABSORPTION OF A
SOUTHERN STREAM LOW TRACKING EASTWARD FROM THE CENTRAL PLAINS INTO
THE PREDOMINANT NORTHERN STREAM/NW FLOW ACROSS THE EASTERN U.S.
HOWEVER...GENERAL CONSENSUS IS THAT WE ARE IN FOR MORE RAIN AND
BELOW NORMAL TEMPERATURES AS THE FAVORED TRACK OF THIS SYSTEM BY
MOST MODELS IS NEAR OR JUST TO THE SOUTH OF OUR CWA. THE ECMWF
REMAINS THE STRONGEST FOR THE SECOND CONSECUTIVE DAY WITH
DEVELOPMENT OF A COASTAL LOW. ALL MODELS KEEP SFC LOW PRESSURE
S-SE OF THE REGION...PUTTING US ON THE COLD SIDE OF THIS
SYSTEM...WITH MODEST INFLUX OF ATLANTIC MOISTURE. HOWEVER...PWATS
REMAIN MOSTLY LESS THAN 1 INCH WITH NO SIGNIFICANT INFLUX OF GULF
MOISTURE UNDER THE PREVAILING NW FLOW ALOFT. THIS SHOULD KEEP RAIN
AMOUNTS MODEST AND REDUCE FLOODING CONCERNS. THE HEAVIER RAINFALL
SHOULD REMAIN WELL S-SE OF THE CWA DURING THE TIME FRAME. DRIER
CONDITIONS SHOULD FINALLY RETURN BY FRIDAY AND MAY FINALLY
CONTINUE FOR SOMETIME THEREAFTER AS AN UPPER RIDGE BUILDS EASTWARD
FROM THE CENTRAL U.S. TEMPERATURES ARE EXPECTED TO CONTINUE BELOW
NORMAL THROUGH THURSDAY...CREEPING A LITTLE CLOSER TO NORMAL
FRIDAY.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 1215 PM EDT SATURDAY...

WARM FRONT REMAINS DRAPED ACROSS THE AREA EXTENDING FROM A LOW
PRESSURE SYSTEM OVER THE MID MISSISSIPPI VALLEY...WITH SHOWERS
FLOWING EASTWARD ALONG THE FRONT. LOW LEVELS OF THE ATMOSPHERE
HAVE BEEN SLOWER TO SATURATE THAN GUIDANCE WOULD INDICATE AND
BELIEVE THIS TREND WILL CONTINUE...ESPECIALLY WITH PRECIPITATION A
BIT MORE SPARSE THAN EXPECTED. HOWEVER...STILL EXPECT IFR CIGS TO
BECOME ESTABLISHED ALONG WITH SOME DRIZZLE THIS EVENING AND THEN
PERSIST INTO SUNDAY. GUIDANCE IS STILL LIKING THE IDEA OF
DEVELOPING CONVECTIVE ACTIVITY UPSTREAM AND MOVING IT INTO THE
AREA EARLY TONIGHT AND BELIEVE THIS IS A PLAUSIBLE SCENARIO WITH
THE ACTIVITY WEAKENING AS IT ENCOUNTERS THE MORE STABLE AIR
ENTRENCHED ACROSS THE AREA. TRACK OF EXPECTED PRECIPITATION WILL
MAINLY AFFECT KBLF/KBCB/KDAN AND WILL MENTION THUNDER AT KDAN DUE
TO CLOSER PROXIMITY TO UNSTABLE AIR TO THE SOUTH. THE LOW WILL BE
PULLING AWAY FROM THE REGION ON SUNDAY AND THIS SHOULD ALLOW FOR A
GRADUAL IMPROVEMENT LATER IN THE TAF PERIOD. DO NOT EXPECT A LOT
OF WIND THROUGH THE TAF PERIOD IN E/NE FLOW. KBLF MAY SEE A LOW
GUST OR TWO AND THERE WINDS WILL BECOME SWLY OVERNIGHT. THEN
EXPECT A TREND TO A NORTHERLY TO NWLY COMPONENT LATER IN THE TAF
PERIOD ON THE BACKSIDE OF THE DEPARTING LOW.

EXTENDED AVIATION DISCUSSION...

FLYING CONDITIONS WILL CONTINUE TO IMPROVE SUNDAY EVENING AS THE
LOW PULLS FARTHER OFFSHORE AND WEAK HIGH PRESSURE BUILDS IN FROM
THE NORTHWEST...WITH MOST LOCATIONS BACK TO VFR BEFORE MIDNIGHT
MONDAY. BREEZY NORTHWEST FLOW IS EXPECTED FOR MONDAY AND EARLY TUESDAY
WITH HIGH PRESSURE BUILDING IN FROM THE NORTHWEST...SO VFR
CONTINUES. BY WEDNESDAY A SOUTHERN STREAM SYSTEM APPEARS TO MAINLY
AFFECT THE GULF COAST REGION TO THE CAROLINAS...BUT COULD SEE
RAIN AND/OR SUB VFR CEILINGS INTO THE DAN-BCB-BLF AREA...BUT
CONFIDENCE IS LOW AT THIS TIME.

&&

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

&&

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


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