Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 202347
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
747 PM EDT SUN APR 20 2014

.SYNOPSIS...
SLOW MOVING LOW PRESSURE OFF THE CAROLINAS WILL DRIFT EAST AND
OFFSHORE TONIGHT. STRONG HIGH PRESSURE WILL CONTINUE TO BUILD
INTO THE AREA FROM OFF THE MID ATLANTIC COAST OVERNIGHT AND
REMAIN IN PLACE INTO MONDAY. A COLD FRONT ARRIVES LATER TUESDAY
WITH THE NEXT CHANCE OF SHOWERS AND STORMS.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 711 PM EDT SUNDAY...

SMALL ADJUSTMENTS WERE MADE IN TEMPS IN THE NEW RIVER AND ROANOKE
VALLEYS... DROPPING THEM A COUPLE DEGREES. CLOUD COVER WAS
REDUCED FROM 22Z TO 06Z MONDAY TO FIT THE TRANSITION AS THE LOW
MOVES OUT TO SEA. DEWPOINT TEMPERATURES WERE MODIFIED ACCORDING TO
SURFACE OBSERVATION TREND.

AS OF 215 PM EDT SUNDAY...

LOW PRESSURE OFFSHORE THE CAROLINAS WILL FINALLY GET BUMPED EAST
OVERNIGHT ALLOWING STRONG SURFACE HIGH PRESSURE OFF NEW ENGLAND
TO BUILD SW AND BE PARTIALLY OVERHEAD BY MORNING. THIS ALONG WITH
ANOTHER FLUX OF DRY AIR UNDER INCREASING SHORTWAVE RIDGING
SUPPORTS GOING CLEAR OVERNIGHT WITH JUST SOME HIGH CLOUDS AROUND
MAINLY SE EARLY. GIVEN THE LOW DEWPOINT AIR IN PLACE AND
POTENTIAL FOR ALL EXCEPT THE RIDGES AND PIEDMONT TO DECOUPLE
UNDER CLEAR SKIES...SHOULD SEE QUITE A DIURNAL SWING WITH LOWS
GOING DOWN CLOSE TO IF NOT BELOW THE COOLER MAV MOS IN SPOTS.
LIKELY TO EVEN SEE A FEW 20S IN THE VALLEYS WHILE SOME CONCERN
FOR AT LEAST SCTD/PATCHY FROST IN THE EAST WHERE THE GROWING
SEASON HAS STARTED. HOWEVER APPEARS TEMPS THERE WONT FALL OFF TOO
FAST UNTIL LATE WHEN WINDS FADE...WHILE DRYNESS PER DEWPOINT
DEPRESSIONS...DOESNT SUPPORT MUCH FROST EVEN IF TEMPS DROP INTO
THE LOWER 30S IN THE BOTTOMS. THUS ONLY ADDING IN SOME PATCHY
FROST FOR AN HOUR OR TWO IN THE EAST LATE INCLUDING HWO MENTION
FOR THE OUTLYING AREAS TOWARD DAWN. OTRW CHILLY OVERNIGHT WITH
LOWS MOSTLY IN THE 30S EXCEPT 40S RIDGES SIMILAR TO THE PREVIOUS
EC MOS.

RIDGING BOTH SFC/ALOFT WILL GRADUALLY START TO WEAKEN MONDAY WITH
THE APPROACH OF THE UPSTREAM 5H TROF/COLD FRONT. HOWEVER DRY AIR
WILL STILL PREVAIL UNDER NORTH/NW TRAJECTORIES ALOFT AS THE FLOW
REMAINS MUCH WEAKER DESPITE A QUICK SURGE IN 85H WARMING. COULD SEE
SOME MID/HIGH CLOUDS INVADE THE WEST WELL AHEAD OF THE FRONT LATE
BUT NOT ENOUGH TO DETER A MAINLY SUNNY DAY. TEMPS SHOULD GET ANOTHER
BOOST WITH HEATING ALTHOUGH ONLY LIGHT MIXING MAY KEEP VALUES JUST
BELOW THE VERY WARM MAV MOS FOR NOW WITH 70S MOST SPOTS.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 245 PM EDT SUNDAY...

MONDAY NIGHT...MOISTURE WILL CONTINUE TO POOL INTO THE AREA IN
ADVANCE OF AN APPROACHING COLD FRONT. ANTICIPATE MILDER LOW
TEMPERATURES THAN THOSE OF SUNDAY NIGHT...WITH MID TO UPPER 40S
COMMON ACROSS MOST OF THE AREA. ISOLATED TO SCATTERED SHOWERS
IN ADVANCE OF THE FRONT ARE EXPECTED WEST OF THE BLUE RIDGE BY
SUNRISE TUESDAY. THE FRONT WILL CROSS THE AREA DURING THE DAY ON
TUESDAY WITH THE FOCUS FOR THE BEST COVERAGE BEING IN THE CENTRAL
AND WESTERN PARTS OF THE AREA DURING THE MORNING. BY THE
AFTERNOON... THE FOCUS JUMPS TO THE PIEDMONT. NORTHWEST WINDS
BEHIND THE FRONT WILL YIELD A QUICK CLEAR OUT OF THE PRECIPITATION
AND CLOUDS TUESDAY EVENING...WITH THE POTENTIAL FOR SOME ISOLATED
SE WV UPSLOPE SHOWERS THROUGH MIDNIGHT. WHILE INSTABILITY FACTORS
OFFER THE POTENTIAL FOR SOME ISOLATED THUNDERSTORMS ON
TUESDAY...CONFIDENCE ON SEVERE STORMS IS LOW. WINDS WILL BE GUSTY
IN THE WAKE OF THE DEPARTING COLD FRONT AND THE APPROACH OF HIGH
PRESSURE. ACROSS THE HIGHER TERRAIN...GUSTS OF 20 TO 30 MPH WILL
BE COMMON TUESDAY AFTERNOON AND NIGHT.

ON WEDNESDAY...DRIER AND COOLER HIGH PRESSURE WILL STARTING
BUILDING INTO THE AREA FROM THE NORTHWEST. WHILE NOT AS STRONG AS
TUESDAY NIGHT...ENOUGH OF A PRESSURE GRADIENT WILL STILL BE IN
PLACE TO WARRANT GUSTS IN THE MOUNTAINS APPROACHING 20 MPH. AREAS
EAST OF THE BLUE RIDGE WILL BE NOTABLY WEAKER. WEDNESDAY
NIGHT...THE CENTER OF THE SURFACE HIGHS MOVES OVER...AND THEN EAST
OF THE REGION BY THURSDAY MORNING. EXPECT A RETURN OF LOW TO MID
30S FOR LOWS ACROSS THE MOUNTAINS WITH UPPER 30S TO LOWER 40S EAST
OF THE BLUE RIDGE.

&&

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

A RIDGE OF HIGH PRESSURE WILL BECOME CENTERED OVER THE REGION ON
THURSDAY...AND START TO SHIFT TO THE COAST BY FRIDAY MORNING. THE
RESULT WILL BE PROGRESSIVE MODERATING TEMPERATURES AS LOW LEVEL
WINDS STRENGTHEN FROM THE SOUTHWEST AND WARM AIR ADVECTION
PREDOMINATES. AS THE RIDGE MOVES EAST...A COLD FRONT WILL APPROACH
THE AREA FRIDAY MORNING AND BE EAST OF THE AREA BY FRIDAY EVENING.
SCATTERED SHOWERS AND SOME ISOLATED THUNDERSTORMS WILL ACCOMPANY
THE FRONT.

BEHIND THE FRONT...MODEL GUIDANCE DEVIATES ENOUGH TO PROVIDE
UNIQUELY DIFFERENT WEATHER PATTERN SOLUTIONS FOR OUR REGION OF
THE COUNTRY. THE GFS SOLUTION DEEPENS THE PARENT LOW OF THE COLD
FRONT AND BRINGS IT SOUTH TO CAPE COD BY SUNDAY MORNING. THIS
KEEPS A PREVAILING NORTHWEST FLOW WHICH IS DRY AND PROGRESSIVELY
COOLER ACROSS THE AREA. THE ECMWF DOES NOT DEEPEN THE COLD FRONT/S
PARENT LOW...AND EJECTS ITS QUICKLY EASTWARD MORE AS AN OPEN WAVE.
THIS ALLOWS FOR A QUICKER RETURN OF ZONAL FLOW TO THE AREA THAT
HAVE THE POTENTIAL TO BRING CENTRAL U.S. SYSTEMS INTO OR TOWARD
THE AREA BY THE END OF THE WEEKEND...ALONG WITH HAVING A MILDER
PATTERN. OUR FORECAST WILL REFLECT THE GUIDANCE PROVIDED BY WPC
WHICH LEANS MORE CLOSELY TO THE ECWMF SOLUTION.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 745 PM EDT SUNDAY...

VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THE TAF VALID PERIOD.
SLOW MOVING CLOSED UPPER LOW OFF THE SC/NC COAST WILL CONTINUE TO
DRIFT SLOWLY EAST THROUGH THE PERIOD. NEXT UPSTREAM SYSTEM
DEVELOPING THROUGH THE MID-SECTION OF THE U.S. IN BETWEEN...RIDGE
OF HIGH PRESSURE FROM THE MID-SOUTH INTO THE MID-ATLANTIC REGION
WILL DOMINATE THE WEATHER THROUGH THE TAF VALID PERIOD. HIGH
CLOUDS WILL BE ON THE INCREASE AFTER DAYBREAK MON AS MID-U.S.
SYSTEM MOVES TOWARD THE REGION...BUT CIGS WILL REMAIN VFR THROUGH
THE TAF VALID PERIOD. NO ISSUES WITH VSBYS THROUGH THE TAF VALID
PERIOD EITHER. WINDS...TO START...NE ACROSS THE PIEDMONT...E-SE
WEST OF THE BLUE RIDGE. AS LOW PRESSURE MOVES AWAY TO THE EAST AND
HIGH PRESSURE DRIFTS OVER THE REGION...EXPECT WINDS TO BECOME
VARIABLE OVERNIGHT/EARLY MON...THEN TRANSITION TO THE SW BY MON
AFTERNOON. SPEEDS WILL REMAIN AOB 10KTS THROUGH THE TAF VALID
PERIOD...BUT SOME LOW END GUSTS ARE POSSIBLE THROUGH THE EVENING
ACROSS THE PIEDMONT.

HIGH CONFIDENCE IN VFR CIGS/VSBYS THROUGH THE TAF VALID PERIOD.
MEDIUM CONFIDENCE IN WIND SPD/DIR THROUGH 12Z...THEN LOW
CONFIDENCE IN WIND DIR...MEDIUM TO HIGH CONFIDENCE IN WIND SPD.

EXTENDED AVIATION DISCUSSION...

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 AND GUSTY NW WINDS ON 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. ANOTHER FAST MOVING COLD FRONT ARRIVES FOR FRIDAY WITH
A PERIOD OF MVFR POSSIBLE IN SHOWERS/ISOLATED STORMS INTO FRIDAY
EVENING.

&&

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

&&

$$
SYNOPSIS...JH/PH
NEAR TERM...JH/KK
SHORT TERM...DS
LONG TERM...DS
AVIATION...JH/RAB



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