Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 231133
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
733 AM EDT TUE SEP 23 2014

.SYNOPSIS...
HIGH PRESSURE STRETCHED FROM ILLINOIS TO NEW YORK THIS MORNING.
THIS HIGH WILL REMAIN OVER THE MID ATLANTIC REGION THROUGH
WEDNESDAY. MEANWHILE LOW PRESSURE WILL DEVELOP ALONG THE
SOUTHEAST COAST TODAY...AND DRIFT SLOWLY TOWARD THE CAROLINA COAST
BY FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 345 AM EDT TUESDAY...

WATER VAPOR LOOP SHOWED AN UPPER LOW OVER NORTHEAST GEORGIA. MODELS
INDICATED THIS LOW WILL FILL SLIGHTLY AND DRIFT NORTHEAST BY
WEDNESDAY MORNING. SURFACE HIGH PRESSURE WILL MOVE FROM THE OHIO
VALLEY INTO NEW ENGLAND BY WEDNESDAY MORNING. THE HIGH WILL WEDGE
DOWN THE EAST SLOPS OF THE APPALACHIANS TODAY THEN WINDS WILL BEGIN
TO RESPOND MORE TO THE DEVELOPING LOW OFF THE SOUTHEAST COAST
TONIGHT.

EXPANSIVE SHIELD OF CIRRUS OVER THE MID ATLANTIC REGION THIS MORNING
WITH THE WESTERN EDGE CLOSE TO THE VIRGINIA/WEST VIRGINIA BORDER.
DEEPEST MOISTURE WILL REMAIN JUST TO THE SOUTHEAST OF THE FORECAST
AREA...BUT NET RESULT OF UPPER AND SURFACE PATTERN WILL BE EXTENSIVE
CLOUD COVER AND GRADUALLY INCREASING PRECIPITABLE WATER VALUES
THROUGH TONIGHT.

WILL BE GREATLY INCREASING CLOUD COVER TODAY AND TONIGHT. BASED ON
THE EXPECTED CLOUD COVER TODAY...HAVE LOWERED MAXIMUM TEMPERATURES
IN THE EASTERN HALF OF THE FORECAST AREA. THE WESTERN EXTENT OF THE
CLOUDS TONIGHT WILL IMPACT HOW MUCH TEMPERATURES DROP IN THE
MOUNTAINS. STAYED CLOSER TO BIAS CORRECTED MET GUIDANCE FOR
OVERNIGHT LOWS.

&&

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

WEDNESDAY STARTS OUT WITH SURFACE HIGH PRESSURE OVER NEW ENGLAND
WEDGING SOUTH INTO THE CAROLINAS. OVER THE SOUTHEASTERN USA...AN
UPPER LEVEL LOW WILL HELP SPAWN A DISTURBANCE OFF THE SOUTHEAST
COAST. THESE THREE SYSTEMS WILL INTERACT WITH EACH TO BRING AN
INCREASE IN CLOUDS OVER THE ENTIRE AREA WITH LIGHT RAIN/DRIZZLE
ALONG AND EAST OF THE BLUE RIDGE FROM WEDNESDAY AFTERNOON INTO
THURSDAY MORNING. COMPLICATING THE ISSUE IS AN UPPER LEVEL BLOCKING
RIDGE IN THE WESTERN ATLANTIC. THIS RIDGE WILL SLOWLY DIRECT THE
UPPER LEVEL AND THE SURFACE LOW NORTHWARD IN TANDEM. BY THURSDAY
AFTERNOON...THESE LOWS WILL BE NORTH OF THE AREA WITH DRY NORTHWEST
FLOW CLEARING THE AREA OUT OF RAIN. THE DEFORMATION ZONE BETWEEN
THESE LOWS SHOULD KEEP THE HEAVIEST RAIN ALONG THE COAST...WITH A
POSSIBLE QUARTER OF AN INCH /0.25/ OF RAIN OVER THE PIEDMONT.
LATEST MODELS ARE NOW BRING MORE RAIN INLAND WEDNESDAY AFTERNOON AND
NIGHT...THEREFORE INCREASED POPS IN THE EAST. MODELS ARE ALSO DRYING
THE REGION OUT ON THURSDAY WITH THE LOW TRACKING INTO THE NORTHERN
MID ATLANTIC REGION. CLOUDS LIKELY TO LINGER THROUGH MUCH OF THE DAY
THURSDAY BUT HAVE LOWERED POPS TO AROUND 10 PERCENT.

TEMPERATURES WILL BE TRICKY FOR EACH AFTERNOON THROUGH THE PERIOD.
ON WEDNESDAY...THE WEDGE AND EASTERLY FLOW WILL KEEP THE EAST COOL
BUT COULD BE SIGNIFICANTLY COOLER IF RAIN FALLS EARLY IN THE DAY.
TIMING THE DEPARTURE OF THE WEDGE AND LOW PRESSURE SYSTEMS TO THE
NORTH THURSDAY WILL BE DIFFICULT. GUIDANCE IS WARMING THE AREA WITH
ABOVE NORMAL TEMPERATURES. SINCE THE WEATHER PATTERN IS NOT
CONDUCIVE TO A SIGNIFICANT WARMUP...WILL LEAVE TEMPERATURES CLOSE TO
PREVIOUS FORECAST AND IN LINE WITH SURROUNDING OFFICES.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 300 PM EDT MONDAY...

CONSIDERABLE UNCERTAINTY EXISTS IN THE EXTENDED PERIOD AS A
FAIRLY COMPLEX UPPER LEVEL PATTERN DEVELOPS BY THE WEEKEND WITH
HIGHLY AMPLIFIED UPPER RIDGE OVER THE NORTH CENTRAL U.S. EXTENDING
INTO CANADA WITH TROUGHING OVER THE WESTERN ATLANTIC AND ACROSS
THE WESTERN STATES.

THE 12Z EURO IS MUCH FURTHER WEST WITH ATLANTIC TROUGH WITH
RESULTANT SURFACE LOW MEANDERING ALONG THE MID- ATLANTIC COAST
FRI-SAT BUT NOT FAR ENOUGH WEST FOR PRECIP THIS FAR INLAND. BUT
WOULD LIKELY SEE SUBSTANTIAL CLOUDINESS FROM THIS ALONG WITH THE
CAD-LIKE EFFECTS FROM A VERY SLOW-MOVING SURFACE HIGH OVER THE
NORTHEAST. IN FACT THE UPPER RIDGE TO THE NORTH RETARDS THE
NORTHWARD MOVEMENT OF THIS COASTAL SYSTEM WELL INTO SUNDAY.
GFS IS MUCH LESS DEVELOPED WITH ANY COASTAL SYSTEM WITH DRY HIGH
PRESSURE IN CONTROL THROUGH WEEKEND. ELECTED TO REFLECT MORE
OPTIMISTIC GFS SOLUTION AT THIS POINT WITH MORE SUN.

TEMPS NEAR TO ABOVE NORMAL WITH MAINLY 70S AND 50S FOR
HIGHS/LOWS. BOTH GFS/EURO SHOW SURFACE LOW OR INVERTED TROUGH
DEVELOPING OVER THE LOWER MISSISSIPPI VALLEY BY EARLY NEXT WEEK
WITH GRIDS SHOWING CLOUDS SPREADING IN FROM SW TO NE AS EARLY AS
SUNDAY NIGHT.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 730 AM EDT TUESDAY...

DENSE FOG ALONG THE RIVER VALLEYS IN SOUTHEAST WEST VIRGINIA THIS
MORNING WHERE IT STAYED CLEAR OVERNIGHT SO IFR FOG AT KLWB AND
KBLF. EXPECT FOG TO MIX OUT BY 14Z/10AM. OTHERWISE MUCH OF THE
REGION WAS UNDER A COVER OF HIGH CLOUDS. AFTER THE FOG MIXES
OUT...LITTLE CHANGE IN CONDITIONS IS EXPECTED FOR THE REST OF THE
DAY.

LOW PRESSURE WILL DEVELOP ALONG THE SOUTHEAST COAST TODAY AND
TONIGHT AND WILL BRING INCREASING MOISTURE AND GRADUALLY LOWERING
CEILINGS TO THE AREA. BUT EVEN BY 12Z/8AM ON WEDNESDAY HIGH
CONFIDENCE THAT CEILINGS EAST OF THE BLUE RIDGE WILL STILL BE VFR.

EDGE OF THE CLOUD COVER WILL BE FATHER WEST TONIGHT. MEDIUM
CONFIDENCE THAT CLOUD COVER WILL REACH KBLF THIS EVENING AND
PREVENT FOG FORMATION AT KBLF. EXPECT KLWB TO REMAIN CLOUD FREE
LONG ENOUGH THAT ONCE AGAIN LIFR FOG WILL FORM AFTER MIDNIGHT.

EXTENDED AVIATION DISCUSSION...

HIGH PRESSURE AND DRIER AIR IN THE REGION 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. SEVERAL
MODELS SHOW MOISTURE INCREASING OVERNIGHT WEDNESDAY THROUGH
THURSDAY EVENING WHICH MAY RESULT IN PERIODS OF IFR/MVFR CEILINGS
AND VSBYS. APPEARS HIGH PRESSURE WILL AGAIN RE-ESTABLISH OVER THE
REGION LATE IN THE WEEK RESULTING IN RETURN TO WIDESPREAD VFR BY
THE WEEKEND.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...RCS
LONG TERM...PC
AVIATION...AMS/JH



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