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[Printable]
455
FXUS61 KRNK 201404
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1004 AM EDT SUN APR 20 2014

.SYNOPSIS...
SLOW MOVING LOW PRESSURE ALONG THE SOUTHEAST COAST WILL CONTINUE
TO DRIFT EAST AND OFFSHORE TODAY. STRONG HIGH PRESSURE WILL BUILD
INTO THE AREA FROM OFF THE MID ATLANTIC COAST TODAY PROVIDING A
RETURN OF DRIER AIR INTO EARLY NEXT WEEK. ANOTHER COLD FRONT
ARRIVES LATER TUESDAY WITH THE NEXT CHANCE OF SHOWERS AND STORMS.
&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 930 AM EDT SUNDAY...

LOW PRESSURE CONTINUES TO DRIFT EAST OFF S CAROLINA THIS MORNING
WITH A GOOD SURGE OF DRIER AIR FROM THE NE ACROSS THE REGION PER
MORNING RNK RAOB SHOWING A PWAT OF BELOW A QUARTER INCH. THIS DRY
AIR AND DEEP NE FLOW HAS ALREADY ACTED TO MIX OUT MOST CLOUD COVER
EXCEPT FOR SOME LINGERING CI NORTH AND OVER THE FAR SE WHERE
CLOSER TO THE DEEPER MOISTURE AXIS AROUND THE SYSTEM. MAY STILL
SEE SOME INTERVALS OF HIGH CLOUDS THROUGH THE AFTERNOON...OTRW
THINKING MAINLY SUNNY/COMFORTABLE UNDER LOWERING DEWPOINTS WITH A
GUSTY NE WIND LINGERING EASTERN SECTIONS AS THE GRADIENT PERSISTS
A BIT LONGER. MORNING THICKNESS GIVEN HEATING OF DRY AIR...AND
GRADUAL EROSION OF THE 85H COOL POCKET SUPPORTS UNIFORM HIGHS IN
THE 60S...WITH PERHAPS SOME SPOTS GETTING TO AROUND 70 LATE SO
BUMPED UP TEMPS A LITTLE IN SPOTS.

PREVIOUS DISCUSSION AS OF 345 AM EDT SUNDAY...

A FEW SPRINKLES/SPOTTY LIGHT RAIN WERE STILL OBSERVED ON RADAR
ACROSS THE NORTHERN PIEDMONT OF NORTH CAROLINA. THIS REGION REMAINS
UNDER THE INFLUENCE OF THE NORTHERN PERIPHERY OF THE DEPARTING UPPER
LOW OFF THE SOUTHEAST U.S. COAST.

GFS ILLUSTRATED THIS AREA OF PRECIP WELL IN ITS 700MB-300MB OMEGA
FORECAST WHICH IS PUSHED EAST BY 12Z. IN ADDITION...DRIER AIR
CONTINUES TO INFILTRATE OUR AREA UNDER A WEAK NORTHEAST FLOW WITH
DEW POINTS FALLING THROUGH THE EARLY MORNING HOURS. AS
RESULT...ANY LIGHT PRECIP ACROSS THE SOUTHEAST PORTION OF THE
FORECAST AREA EARLY THIS MORNING WILL CONTINUE TO WANE AND DRY
CONDITIONS ARE EXPECTED REGION-WIDE LATER THIS MORNING.

DISCOUNTED THE 00Z NAM SOLUTION WHICH TRIES TO SURGE 850MB THETA-E
AIR BACK INTO THE FORECAST AREA WITH A MORE EASTERLY COMPONENT TO
THE WIND.

AS AN UPPER RIDGE GRADUALLY BUILDS TODAY...CLOUDS WILL THIN FROM
WEST TO EAST ALLOWING SKIES TO BECOME MOSTLY SUNNY. CLEARING WILL BE
DELAYED IN THE FAR SOUTHEAST UNTIL AFTER 18Z WHEN LAST PIECE OF
UPPER LEVEL ENERGY FINALLY EXITS.

MOSTLY SUNNY SKIES WILL HELP MIX DOWN 15-25KT 850MB WINDS AND DRIER
AIR WHICH MAY RESULT IN SOME PERIODIC WIND GUSTS. ALSO LOWERED DEW
POINTS WITH THIS MIXING. BOTH THE GFS AND NAM MOS HAVE SHOWN A WARM
BIAS UNDER THIS MAINLY DRY WEDGE PATTERN. WITH MORE SUN EXPECTED
LATER TODAY...READINGS SHOULD BE A COUPLE OF DEGREES WARMER COMPARED
TO SATURDAY...BUT STILL UNDERCUT THE GFS/NAM MOS VALUES BY A COUPLE
OF DEGREES.

WEAK SFC RIDGE BUILDS OVER THE AREA TONIGHT WHICH ALLOWS WINDS TO
DIMINISH. THIS...COMBINED WITH MOSTLY CLEAR SKIES SHOULD ALLOW TEMPS
TO FALL TO THE COOLER GFS MOS VALUES. CANNOT RULE OUT SOME PATCHY
FROST TONIGHT IN THE MOUNTAIN VALLEYS.
&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
AS OF 345 AM EDT SUNDAY...

RIDGING IN THE UPPER LEVELS OF THE ATMOSPHERE WILL BEGIN TO TAKE
SHAPE ON MONDAY...ALLOWING WINDS ALOFT TO SHIFT MORE SOUTHWESTERLY.
DESPITE SURFACE HIGH PRESSURE STILL WEDGED AGAINST THE EASTERN FACE
OF THE APPALACHIANS AND INCREASING MID AND HIGH CLOUDS THROUGH THE
DAY...THE UPPER RIDGING WILL ALLOW AFTERNOON TEMPERATURES TO WARM A
FEW DEGREES OVER THOSE FROM SUNDAY...WITH HIGHS CLIMBING INTO THE
LOW 70S. BY LATE EVENING...SURFACE WINDS WILL BEGIN TO SHIFT
SOUTHWESTERLY AHEAD OF AN APPROACHING COLD FRONT. EXPECT WARMER
RIDGELINES COMPARED TO THE VALLEY BOTTOMS...WITH OVERNIGHT LOWS
GENERALLY IN THE 40S AND THE LOW 50S.

FOR TUESDAY...A SURFACE TROUGH WILL DEVELOP ALONG THE LEE OF THE
BLUE RIDGE. THE LOW LEVEL CONVERGENCE OF THE TROUGH WILL COMBINE
WITH STRONG DAYTIME HEATING TO TRIGGER SCATTERED SHOWERS AND SOME
THUNDERSTORMS DURING THE AFTERNOON AND EVENING...WITH THE CHANCE
THAT ONE OR TWO STORMS MAY BECOME STRONG TO SEVERE DURING EARLY
EVENING. WITH ANY STRONG STORMS THAT DO DEVELOP...WOULD SAY THE MAIN
CONCERNS WOULD BE LOCALLY GUSTY WINDS DUE TO DRY LOW LEVELS OF THE
ATMOSPHERE...AND MODEST INSTABILITY THAT WILL ALSO SUPPORT SOME
HAIL. INSTABILITY WILL FALL OFF QUICKLY DURING THE EVENING AS WINDS
SHIFT INCREASINGLY WEST TO NORTHWESTERLY...AND SHOWERS AND
THUNDERSTORMS SHOULD FADE AROUND SUNSET. THE COLD FRONT WILL PASS
QUICKLY ACROSS THE AREA DURING THE EVENING...EXITING TO THE EAST
AFTER MIDNIGHT.

DRY CONDITIONS ARE EXPECTED FOR WEDNESDAY AS HIGH PRESSURE PASSES
ACROSS THE GREAT LAKES...MAINTAINING A COOLER NORTHERLY WIND FLOW.
REGARDLESS...WITH ABUNDANT SUNSHINE AND ANOTHER UPPER LEVEL RIDGE
APPROACHING FROM THE WEST...WILL SEE AFTERNOON HIGHS RANGE FROM
AROUND 60 ACROSS SOUTHEAST WEST VIRGINIA...TO AROUND 70 ACROSS THE
SOUTHSIDE. STRONG RADIATIONAL COOLING MAY ALLOW FOR SOME FROST TO
DEVELOP IN THE MOUNTAIN VALLEYS WEDNESDAY NIGHT.
&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 1245 PM EDT SATURDAY...

SURFACE HIGH PRESSURE WILL CONTINUE TO SHIFT EAST ON THURSDAY AND
BECOME SITUATED OFF THE EAST COAST BY FRIDAY. AN UPPER LEVEL RIDGE
WILL CONTINUE TO BUILD OVER THE APPALACHIANS WHILE STRENGTHENING
SOUTHWEST FLOW ALLOWS FOR GOOD WARM AIR ADVECTION. EXPECT THURSDAY
TO CONTINUE TO BE A PERIOD OF NO PRECIPITATION AND MODERATING
TEMPERATURES.

A COLD FRONT WILL APPROACH THE AREA THURSDAY NIGHT AND CROSS THE
REGION FRIDAY INTO FRIDAY NIGHT. ANTICIPATE TEMPERATURES TO REMAIN
MILD IN ADVANCE OF THE FRONT THURSDAY NIGHT INTO FRIDAY...BUT WITH
INCREASING CLOUD COVER AND CHANCES OF SHOWERS. MODEL GUIDANCE
CURRENTLY OFFERS THE POTENTIAL FOR SOME CONVECTIVE WEATHER WITH THE
PASSAGE OF THE FRONT. HAVE INCLUDED A SLIGHT CHANCE OF THUNDERSTORMS
ACCORDINGLY ON FRIDAY.

COOLER AIR ARRIVES FRIDAY NIGHT INTO SATURDAY...WHILE LINGERING RAIN
SHOWERS DECREASE IN COVERAGE...ENDING LAST ACROSS SOUTHEAST WEST
VIRGINIA WHERE UPSLOPE CONDITIONS WILL MAINTAIN THE PRECIPITATION
THE LONGEST.
&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
AS OF 720 AM EDT SUNDAY...

IR SATELLITE SHOWS HIGH AND MID LEVEL CLOUDS THINNING ACROSS THE
REGION...WITH ALL TAF SITES REPORTING VFR CONDITIONS THIS MORNING.
THESE VFR CONDITIONS WILL PREVAIL THROUGH 12Z MONDAY.

A LOW LEVEL NORTHEAST FLOW HAS ALLOWED DRIER AIR
TO INFILTRATE THE FORECAST AREA...WHICH WILL KEEP THE AREA DRY.
AN UPPER LEVEL LOW OFF THE SOUTHEAST U.S. COAST THIS MORNING
WILL CONTINUE TO PUSH EAST AND AN UPPER LEVEL RIDGE BUILDS. THIS
WILL CONTINUE THE TREND OF CLEARING SKIES THROUGH THE MORNING.

DRY AIR ALOFT MIXING DOWN TO THE SURFACE WITH CLEARING SKIES MAY
BRING SOME LOCALIZED WIND GUSTS TO 15-20KTS BETWEEN 15-23Z SUNDAY.

EXTENDED AVIATION DISCUSSION... WITH HIGH PRESSURE IN PLACE
THROUGH MONDAY...VFR CONDITIONS ARE EXPECTED.

THE NEXT COLD FRONT APPROACHES MONDAY NIGHT WITH MORE SHOWERS AND
POSSIBLE THUNDERSTORMS...WITH LOCALIZED MVFR FLIGHT RESTRICTIONS
ON TUESDAY. THE FRONT EXITS TUESDAY NIGHT...RESULTING IN A RETURN
TO VFR WEATHER WEDNESDAY...EXCEPT FOR THE POTENTIAL OF SOME MVFR
CIGS OVER THE FAR WESTERN UPSLOPE SITES IN SE WEST VA. HIGH
PRESSURE BUILDS IN FOR THURSDAY...WITH WIDESPREAD VFR LIKELY.

&&

.FIRE WEATHER...
AS OF 945 AM EDT SUNDAY...

THE COMBINATION OF DRY/GUSTY EASTERLY FLOW AND HEATING WILL CAUSE
AFTERNOON HUMIDITY LEVELS TO FALL BELOW 30 PERCENT MAINLY OVER
THE MOUNTAINS. THIS DRYING AND STRONG HEATING WILL ALSO ALLOW FUEL
MOISTURE LEVELS TO QUICKLY DECREASE ESPCLY IN AREAS THAT DID NOT
SEE ANY RAINFALL ON SATURDAY. HOWEVER WIND SPEEDS ARE EXPECTED TO
SLOWLY DIMINISH THIS AFTERNOON OVER THE WESTERN MOUNTAINS IN SE
WVA WHERE PARAMETERS ARE MORE CRITICAL...WITH SUSTAINED VALUES
DROPPING BELOW 10-15 MPH. THUS WILL HEADLINE THE FIRE WEATHER
FORECAST FOR LOWERING HUMIDITY AND GUSTY WINDS THIS AFTERNOON BUT
HOLD OFF ON ANY STATEMENTS PENDING CONDITIONS OVER FAR WESTERN
SECTIONS EARLY THIS AFTERNOON.

&&

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

&&

$$
SYNOPSIS...PH
NEAR TERM...JH/PH
SHORT TERM...NF
LONG TERM...NF
AVIATION...PH/WERT
FIRE WEATHER...JH




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