Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 300050
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
850 PM EDT FRI AUG 29 2014

.SYNOPSIS...
A STALLED FRONTAL BOUNDARY NEAR THE SOUTH CAROLINA...NORTH
CAROLINA BORDER WILL MOVE GRADUALLY NORTH TONIGHT THROUGH
SATURDAY...AND BE POSITIONED OVER NORTHERN VIRGINIA BY SATURDAY
AFTERNOON. A MORE SUBSTANTIAL COLD FRONT WILL APPROACH THE AREA
SATURDAY NIGHT AND MOVE THROUGH THE AREA SUNDAY AND SUNDAY NIGHT.
&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 820 PM EDT FRIDAY...

EVENING SOUNDINGS SHOW MOISTURE TRAPPED BENEATH THE INVERSION AT
85H AIDED BY SHALLOW SE FLOW NORTH OF THE RESIDUAL FRONT TO THE
SOUTH. MOST INSTABILITY THIS EVENING REMAINS OVER THE FAR SW WHERE
STILL HAVE A FEW SHOWERS ONGOING NEAR THE FRONT. THUS LEAVING IN
SOME CHANCE POPS THERE A WHILE LONGER AS THE HRRR SHOWS SOME OF
THIS COVERAGE SLIDING NORTH THROUGH MIDNIGHT. OTRW SATELLITE
DEPICTING LOW CLOUDS SPREADING BACK NORTH FROM SOUTHERN VIRGINIA
ATTM AHEAD OF THE BOUNDARY THAT WILL LIFT SLOWLY BACK NORTH
OVERNIGHT. MOST LATEST MODEL SOLUTIONS SHOW LOW CLOUDS REMAINING
ALONG/EAST OF THE BLUE RIDGE THROUGH MORNING WITH ONLY THE FAR
SOUTH AND WEST STAYING MORE PC ALONG THE PERIMETER OF THE WEAK
WEDGE. SHOWER CHANCES ELSW REMAIN IFFY GIVEN LOSS OF HEATING WITH
THE BOUNDARY ACROSS THE REGION LATE. LATEST NAM AND TO SOME DEGREE
THE HRRR WANT TO DEVELOP A FEW SHRA CLUSTERS ALONG AND JUST EAST
OF THE BLUE RIDGE AFTER MIDNIGHT...WHILE MOST OTHERS DRY OR
FARTHER SOUTH WITH ISOLATED COVERAGE. SINCE ALREADY HAVE SOME
ISOLATED POPS GOING AND SEEING SOME INSTABILITY ABOVE THE
INVERSION...WILL LEAVE IN AND EXTEND INTO SOUTHSIDE VIRGINIA
OVERNIGHT. OTRW FOG/LOW CLOUDS LOOK ON TRACK WITH JUST SOME UPWARD
ADJUSTS TO LOW TEMPS GIVEN THE CLOUD CANOPY AND MOIST DEWPOINTS
OVERNIGHT.

WE EXPECT A BREAK IN THE PRECIPITATION SATURDAY MORNING WITH THE
FORCING ASSOCIATED WITH THE FRONT NORTH OF THE REGION.
HOWEVER...BY THE AFTERNOON...ENOUGH DAYTIME HEATING IS EXPECTED TO
REFIRE SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE NORTHERN
PARTS OF THE REGION CLOSEST TO THE NEW LOCATION OF THE STALLED
FRONT. ALSO...INCREASING SOUTHERLY WINDS WILL FOCUS UPSLOPE
ISOLATED SHOWER AND THUNDERSTORM POTENTIAL ALONG THE CREST OF THE
BLUE RIDGE.

LOW TEMPERATURES TONIGHT WILL BE A MIX OF LOW TO MID 60S ACROSS THE
MOUNTAINS WITH MID TO UPPER 60S ACROSS THE PIEDMONT. ON
SATURDAY...HIGH TEMPERATURES IN THE LOW TO MID 80S WILL BE COMMON IN
THE MOUNTAINS WITH UPPER 80S TO NEAR 90 ACROSS THE PIEDMONT.
&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 330 PM EDT FRIDAY...

UPPER LEVEL RIDGE FORECAST OVER THE SOUTHEASTERN CONUS TO REMAIN IN
PLACE IN THE SHORT-TERM WITH THE MAIN WEATHER FEATURE A SERIES OF
SOUTHERN STREAM SHORT-WAVES EXPECTED TO TRACK FROM THE GULF COAST
NORTHEAST INTO THE OHIO VALLEY. 12Z MODEL RUNS OF GFS/NAM/EURO
SHOWING THIS FEATURE OR SERIES OF FEATURES TRACKING SOMEWHAT
FURTHER WEST THAN PREVIOUS RUNS DUE PARTLY TO THE STRONG RIDGE.
AXIS OF HEAVIEST RAINFALL SHOULD STAY WEST OF OUR CWA BUT STILL
HAVE LIKELY POPS IN THE FAR WEST ON SUNDAY TAPERING TO CHANCE
ACROSS THE PIEDMONT ON SUNDAY. RIDGE FLATTENS SOMEWHAT ON MONDAY
AS UPPER TROUGH ENERGY REMAINS WILL NORTH BUT WILL STILL BE
CHANCES FOR MAINLY AFTERNOON SHOWERS AND SCATTERED THUNDERSTORMS
MONDAY AFTERNOON. TEMPS WILL REMAIN WARM THROUGH THE PERIOD WITH
MAINLY 80S FOR HIGHS AND 60S FOR LOWS EVEN WITH CONSIDERABLE
CLOUDS ON SUNDAY.
&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 330 PM FRIDAY...

FLAT UPPER RIDGE IS EXPECTED TO DOMINATE OUR MID-WEEK WEATHER
PATTERN ACROSS THE CENTRAL APPALACHIAN AND MID-ATLANTIC REGION. THIS
SHOULD MAINTAIN SUMMER-LIKE TEMPERATURES THROUGH THE ENTIRE PERIOD
WITH HIGHS NEAR 90F IN THE PIEDMONT AND MID-80S IN THE MOUNTAINS
ALONG WITH NIGHT-TIME LOWS IN THE 60S TO LOW 70S. COULD END UP BEING
ONE OF THE WARMEST WEEKS OF THE SUMMER EVEN AS THE SO-CALLED
METEOROLOGICAL SUMMER ENDS ON AUGUST 31. PRECIPITATION WILL ALSO
GENERALLY BE OF SUMMER-LIKE CHARACTER WITH DIURNALLY DRIVEN
CONVECTION PROVIDING THE BEST CHANCES FOR RAINFALL. WEDNESDAY
AFTERNOON LOOKS LIKE THE MOST PROMISING DAY FOR STORMS AS WEAK
FRONTAL BOUNDARY PUSHES ACROSS THE CWA. THURSDAY AND FRIDAY LIKELY
TO BE DRIER ALTHOUGH WIDELY SCATTERED SHOWERS STILL POSSIBLE.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AS OF 645 PM EDT FRIDAY...

VISIBILITY SENSOR AT KDAN REMAINS INOPERABLE. PARTS ARE ON
ORDER. UNTIL REPAIRS COMPLETE...NO AMENDMENTS WILL BE SCHEDULED.

ISOLATED SHOWERS AND STORMS...MAINLY SW OF KBLF HAVE ALL BUT FADED
THIS EVENING WITH OUTFLOW DRIVEN ADDITIONAL SHRA HOW FARTHER WEST.
HOWEVER STILL SOME POTENTIAL TO SEE A FEW ADDED SHRA DEVELOP
MAINLY SW SO MAY LEAVE IN A VCSH MENTION AT KBLF OVER THE NEXT
HOUR OR TWO.

OTRW MAIN CONCERN OVERNIGHT WITH THE DEVELOPMENT OF LOW CIGS AND
FOG AS THE WEAK FRONT TO THE SOUTH SLIDES NORTH INTO THE AREA BY
MORNING. MODELS SHOW A FEW SHRA DEVELOPING ACROSS THE CENTRAL AND
NORTH LATE TONIGHT BUT IFFY GIVEN LACK OF INSTABILITY AND AFTER
LOSS OF HEATING. LOW LEVEL MOISTURE WILL INCREASE AND BECOME
TRAPPED UNDER THE INVERSION ALOFT. ANTICIPATE MOST OF THE REGION
TO DEVELOP MVFR CIGS WITH SOME REGIONS OF IFR PER LATEST NAM.
VSBYS WILL ALSO DECREASE WITH MOST AREAS HAVING MVFR WITH POCKETS
OF IFR NEAR THE BLUE RIDGE. HOWEVER GIVEN CURRENT TRENDS OFF
SATELLITE IN ALREADY SEEING CLOUDS PUSH NORTH ACROSS EASTERN
SECTIONS...WILL INTRODUCE MVFR CIGS A BIT SOONER THERE BUT DELAY
SOME FROM KBCB WESTWARD WHERE THINGS ARE MORE MIXED.

ANY SUB-VFR CONDITIONS WILL BE FAIRLY SLOW TO IMPROVE TO VFR AFTER
SUNRISE SATURDAY. 15Z/11AM IS THE MOST LIKELY TIME MOST OF THE
REGION WILL BE BACK TO VFR BUT MAY TAKE UNTIL MID AFTERNOON FOR
KROA/KLYH TO IMPROVE. THINK MOST SHOULD FINALLY GO TO A SCATTERED
CU FIELD ONCE LOW CIGS IMPROVE WITH ANY CONVECTION VERY ISOLATED
GIVEN THE FRONT TO THE NE.

EXTENDED DISCUSSION...

ANY ISOLATED OR SCATTERED SHOWERS AND STORMS WILL BE MAINLY
CONFINED TO AN AREA ALONG AND NORTH OF A KHSP-KFVX LINE SATURDAY
EVENING...JUST SOUTH OF THE AGAIN STALLED FRONTAL BOUNDARY.

LATE SATURDAY NIGHT THROUGH SUNDAY EVENING AN AREA OF LOW PRESSURE
WILL HEAD EASTWARD THROUGH THE GREAT LAKES REGION TOWARD NEW
ENGLAND. ITS ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE REGION
BRINGING A GENEROUS COVERAGE OF SHOWERS AND SOME STORMS. SUB-VFR
CONDITIONS ARE EXPECTED TO ACCOMPANY THE SYSTEM AND PRECIPITATION.

ANOTHER COLD FRONT IS EXPECTED TO PRODUCE SIMILAR CIRCUMSTANCES
TUESDAY INTO WEDNESDAY. HOWEVER...MODEL GUIDANCE FOR THIS ONE
OFFERS PRECIPITATION IN A MORE SCATTERED DISTRIBUTION. AS
SUCH...THE MAGNITUDE OF SUB-VFR CONDITIONS MAY BE LESS.

&&

.EQUIPMENT...
AS OF 730 AM EDT FRIDAY ...

THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL
BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED.

&&

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

&&

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


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