Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 220814
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
414 AM EDT MON SEP 22 2014

.SYNOPSIS...
A LARGE HIGH PRESSURE SYSTEM OVER THE MID MISSISSIPPI VALLEY WILL
MOVE EAST TODAY AND TONIGHT AND WILL COVER MUCH OF THE EASTERN
UNITED STATES THROUGH WEDNESDAY. LOW PRESSURE WILL DEVELOP ALONG THE
SOUTHEAST COAST THURSDAY AND FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 400 AM EDT MONDAY...

DEEP UPPER TROF OVER THE GREAT LAKES AND OHIO VALLEY THIS MORNING.
SHORT WAVE OVER MISSOURI REACHES THE BASE OF THE TROF AND CLOSES OFF
AN UPPER LOW NEAR SOUTH CAROLINA TONIGHT. MODELS ALSO SHOWING COLDER
500 MB TEMPERATURES OVER THE FORECAST AREA THIS AFTERNOON AND
TONIGHT.

FRONT HAS CLEARED FORECAST AREA. 850 MB TEMPERATURES WILL DROP
TODAY AND TONIGHT AND WILL REACH +8 TO +10 BY 12Z/8AM TUESDAY. AN
EVEN BIGGER CHANGE IN THE DEW POINTS WAS ALREADY UNDERWAY. SURFACE
DEW POINTS HAVE LOWERED INTO THE UPPER 40S IN SOUTHEAST WEST
VIRGINIA. BY THIS AFTERNOON PRECIPITABLE WATER VALUES WILL BE LESS
THAN 0.50 INCHES.

SURFACE HIGH PRESSURE THE WAS CENTERED OVER THE MID MISSISSIPPI
VALLEY THIS MORNING WILL MOVE EAST INTO THE OHIO VALLEY TONIGHT.
WINDS WILL STILL BE GUSTY AT HIGHER ELEVATIONS THIS MORNING...BUT AS
THE HIGH GETS CLOSER...WINDS WILL DIMINISH. WINDS WILL DECOUPLE THIS
EVENING. WITH A MOSTLY CLEAR SKY AND THE LIGHT TO CALM WINDS
OVERNIGHT...EXPECT THE COOLER AIR OVER THE RELATIVELY WARMER AREA
RIVERS AND LAKES WILL RESULT IN FOG FORMATION.

BUFKIT SOUNDINGS SHOWED A SHALLOW LAYER OF MOISTURE AND INSTABILITY
FROM SOUTHEAST WEST VIRGINIA INTO THE ALLEGHANY HIGHLANDS THIS
MORNING. WILL KEEP A SIGHT CHANCE OF SHOWERS IN SOUTHEAST WEST
VIRGINIA THROUGH NOON. AS THE WINDS AND UPSLOPE FORCING
DIMINISHES...THE CLOUDS WILL DISSIPATE. THIS MAY TAKE MOST OF THE
DAY IN THE FAR NORTHWEST PART OF COUNTY WARNING AREA.

STAYED BELOW GUIDANCE FOR MINIMUM TEMPERATURES TONIGHT...ESPECIALLY
IN THE WESTERN VALLEYS BASED ON IDEAL RADIATIONAL COOLING CONDITIONS
AFTER MIDNIGHT AND SURFACE DEWPOINTS DIPPING INTO THE 30S.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 AM EDT MONDAY...

A STRONG DRY HIGH PRESSURE SYSTEM WILL BE CENTERED OVER NEW
ENGLAND...WEDGING DOWN THE MID ATLANTIC THROUGH THE PERIOD. FOR THE
MOST PART...THIS WEDGE WILL KEEP THE AREA COOL AND DRY. MODELS ARE
DEVELOPING A CUT-OFF LOW OVER THE CAROLINAS ON TUESDAY. THE STRENGTH
OF THIS LOW VARIES BETWEEN MODELS. IN RESPONSE TO THIS UPPER LOW...A
DISTURBANCE IS EXPECTED TO DEVELOP OFF THE SOUTHEAST COAST. THE NAM
KEEPS THIS DISTURBANCE AND ITS PRECIPITATION ALONG THE SOUTHEAST
COAST THROUGH WEDNESDAY...THEN SLOWLY PUSHES IT INLAND TOWARDS THE
THE NC/VA PIEDMONT WEDNESDAY NIGHT. THE GFS IS A LITTLE MORE
PROGRESSIVE...ADVANCING THIS PRECIPITATION NORTHWARD ALONG THE COAST
WEDNESDAY INTO WEDNESDAY NIGHT. LIGHT RAIN ENTERS THE PIEDMONT
WEDNESDAY EVENING. THE ECM IS SLOWER AND TRACKS THE UPPER LEVEL LOW
NORTHWARD OVER THE APPALACHIANS. THIS SCENARIO WOULD BRING
PRECIPITATION FURTHER WESTWARD/INLAND THAN THE GFS/NAM FOR WEDNESDAY
AND WEDNESDAY NIGHT. THE ECM HAS LIGHT PRECIPITATION TO THE BLUE
RIDGE WITH STRONGER CONVECTION OVER THE COASTAL PIEDMONT OF VA/NC
WEDNESDAY NIGHT. ANY ONE OR A COMBINATION OF THE MODELS COULD BE
RIGHT. IT DOES APPEAR THE LOW OVER THE SOUTHEAST WILL STRENGTHEN THE
WEDGE THROUGH THE PERIOD. A STRONGER WEDGE WOULD SUPPORT LIGHTER
PRECIPITATION AND MORE SO TOWARDS THE PIEDMONT. SINCE CONFIDENCE IS
LOW FOR MEASURABLE RAINFALL...WILL CONTINUE TO CARRY SLIGHT CHANCE
POPS FOR RAIN ALONG AND EAST OF THE BLUE RIDGE.

THE WEDGE WILL KEEP TEMPERATURES COOLER THAN NORMAL ON TUESDAY. KEPT
TUESDAY TEMPERATURES NEAR GUIDANCE SINCE THE MODELS ARE ADVERTISING
A MOSTLY CLEAR DAY AND A DRY EASTERLY FLOW. DESPITE THE STRENGTH OF
THE WEDGE ON WEDNESDAY...EASTERLY FLOW AND A FETCH OFF THE ATLANTIC
WOULD INCREASE THE CHANCE FOR STRATUS CLOUDS TO OVERSPREAD THE AREA
LATE IN THE DAY WEDNESDAY AND WEDNESDAY NIGHT. FOR NOW...WILL LEAN
TEMPERATURES TOWARDS THE COOLEST GUIDANCE (NAM). IF THE CHANCES FOR
RAIN LOOKS MORE LIKELY...WEDNESDAY TEMPERATURES ALONG AND EAST OF
THE BLUE RIDGE WILL BE LUCKY TO HIT THE UPPER 60S. THIS FORECAST
PACKAGE HAS UNIFORM TEMPERATURES IN THE LOWER TO MID 70S WEDNESDAY.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 100 PM EDT SUNDAY...

A STRONG SURFACE HIGH OVER THE NE STATES ON THURSDAY WILL SLOWLY
DRIFT WESTWARD TO THE GREAT LAKES BY THE WEEKEND. THIS WILL LEAD TO
A PROLONGED EASTERLY FLOW ACROSS THE REGION. HIGH TEMPERATURES WILL
BE 5-10 DEGREES BELOW NORMAL RANGING FROM THE MID TO UPPER 60S
ACROSS THE MOUNTAINS TO LOWER 70S EAST OF THE BLUE RIDGE.

MODELS ARE STARTING TO AGREE ON A WEAK UPPER LEVEL DISTURBANCE
FORMING ACROSS THE SE STATES LATE IN THE WEEK...HOWEVER THERE IS
STILL MAJOR DIFFERENCES ON PLACEMENT WHICH WILL AFFECT HOW MUCH
MOISTURE CAN GET PULLED UP INTO THE REGION. THE GFS CONTINUES TO BE
MUCH DRIER THAN THE ECMWF. DUE TO THE MODEL DIFFERENCES...ONLY
SLIGHT CHANCE POPS IN FROM THE BLUE RIDGE EASTWARD.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AS OF 135 AM EDT MONDAY...

COLD FRONT EXTENDED FROM VERMONT TO EASTERN VIRGINIA TO NORTHERN
LOUISIANA AT 05Z/1AM. SURFACE WIND WERE FROM THE WEST TO
NORTHWEST BEHIND THE FRONT WITH GUSTS UP TO 25 KNOTS AT HIGHER
ELEVATIONS. ENOUGH PRESSURE GRADIENT TO SUPPORT GUSTY WINDS IN THE
MOUNTAINS THROUGH EARLY AFTERNOON.

MVFR CEILINGS ARE EXPECTED TO DEVELOP ALONG THE WESTERN SLOPES
EARLY THIS MORNING. ONLY MEDIUM CONFIDENCE ON THE TIMING OF WHEN
KLWB AND KBLF WILL DROP TO MVFR. BCB WILL BE ON THE EDGE OF VFR
TO MVFR CLOUDS EARLY THIS MORNING.

KLWB...AND ESPECIALLY KBLF WILL SEE THE MVFR CIGS HANG IN MUCH OF
THE DAY WITH UPSLOPE NORTHWEST FLOW. VFR CONDITIONS WILL PREVAIL
TO THE EAST. BCB SHOULD SEE CIGS IMPROVE TO VFR IN THE 15Z/11AM-
17Z/1PM TIME FRAME. AS HIGH PRESSURE BUILDS IN AND THE NORTHWEST
UPSLOPE FLOW WEAKENS...THE CLOUDS WILL ERODE. HIGH CONFIDENCE THAT KLWB
AND KBLF WILL IMPROVE TO VFR BY 00Z.

EAST OF THE BLUE RIDGE...VFR CONDITIONS SHOULD PREVAIL THROUGH
THE TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...

HIGH PRESSURE AND DRIER AIR IN THE REGION TONIGHT THROUGH
WEDNESDAY WILL RESULT IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG
WILL STILL BE POSSIBLE AT NIGHT AS WINDS DIMINISH AND COOL AIR
MASS DECOUPLES. A LOW PRESSURE SYSTEM COMING OUT OF THE GULF COAST
MAY BRING IFR CONDITIONS TO THE REGION AS EARLY AS WEDNESDAY
NIGHT.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...RCS
LONG TERM...CF
AVIATION...AMS/RAB



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