Area Forecast Discussion
Issued by NWS Blacksburg, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KRNK 051426
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1026 AM EDT SAT SEP 5 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO WEDGE SOUTH ALONG THE EASTERN
SLOPES OF THE APPALACHIANS THROUGH THE WEEKEND BRINGING SOMEWHAT
COOLER AND DRIER AIR INTO SUNDAY. WARMER AND MORE HUMID AIR ALONG
WITH A RETURN TO DIURNAL SHOWERS AND STORMS WILL RETURN MONDAY AND
LINGER FOR MUCH OF NEXT WEEK. A STRONGER COLD FRONT WILL ARRIVE
LATE NEXT WEEK WITH POTENTIAL FOR MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS BY THE WEEKEND.
&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 950 AM EDT SATURDAY...

SURFACE FRONT HAS BASICALLY WASHED OUT ACROSS THE EASTERN SLOPES
OF THE BLUE RIDGE THIS MORNING WITH ONGOING EASTERLY FLOW NOW IN
PLACE ACROSS MUCH OF THE AREA. THIS SEEN OFF EARLY MORNING
SOUNDINGS WITH A DEEP ONSHORE FETCH THROUGH THE COLUMN WHICH
REMAINS QUITE MOIST GIVEN ANY DRYING WELL TO THE NORTH PER MSAS
AND WATER VAPOR LOOPS. EARLIER LIGHT SHOWERS NEAR THE BLUE RIDGE
HAVE ALSO FADED WITH VIS PICS SHOWING BREAKS OVER THE WEST FILLING
IN WITH HEATING...WHILE THICKER CANOPY REMAINS OUT EAST WHERE THE
BEST LOW AXIS OF THETA-E PERSISTS.

LATEST MODELS CONTINUE TO SHOW A LOBE OF DRYING WORKING IN FROM
THE NE THIS AFTERNOON IN TURN PUSHING DEEPER MOISTURE AND INSTABILITY
BACK TO THE WESTERN FRINGE COUNTIES THAT WILL BE ON THE EDGE OF
THE LOW LEVEL WEDGE. THIS SUPPORTED BY THE HRRR/RAP AND MOST ENSEMBLE
SOLUTIONS WITH PERHAPS A BAND OR TWO OF SHRA/TSRA FAR WEST LATER.
HOWEVER DEPTH/STRENGTH OF ANY TSRA EXPECTED TO BE MUCH LESS THIS
AFTERNOON WITH DEEPER INSTABILITY LIKELY TO REMAIN SOUTH AND WEST
OF THE REGION CLOSER TO THE RESIDUAL OUTFLOW FROM LAST EVENING.
ALSO EXPECT MORE ISOLATED SHRA/TSRA POSSIBLE SOUTH/EAST WHERE A
FEW BREAKS...AND WEAK INSTABILITY WITHIN THE EASTERLY FLOW COULD
LEAD TO POP UP COVERAGE ON THE PERIMETER OF THE DEEPER WEDGE
ESPCLY SE PER THE 12Z NAM AND EARLIER SPC WRF.

THUS HAVE TRIMMED BACK GOING POPS FOR THE MORNING INTO EARLY
AFTERNOON GIVEN STABILITY AND CLOUD COVER WITH HIGHEST CHANCE
POPS FAR SW AND EAST NEAR THE VA/NC BORDER FOR THE AFTERNOON.
CLOUDS AND EASTERLY FLOW MAKING HIGH TEMPS TRICKY WITH PERHAPS
MOST STAYING IN THE 70S OVERALL EXCLUDING THE FAR WEST AND
SOUTHERN/SE SECTIONS WHERE SOME 80S COULD OCCUR. OTRW STAYING ON
THE COOL SIDE OF MOS OVERALL FOR NOW.

THE WEDGE WILL PEAK OVERNIGHT INTO EARLY SUNDAY. LOW CLOUDS ARE
EXPECTED TO PERSIST INTO SUNDAY MORNING...WHICH WILL HOLD MIN
TEMPS CLOSER TO NORMAL VALUES FOR EARLY SEPTEMBER. ONLY LIMITED
SHOWER ACTIVITY IS EXPECTED OVERNIGHT IN THE FAR SOUTHWEST. CANNOT
COMPLETELY RULE OUT SOME LIGHT DRIZZLE ON THE EAST SIDE OF THE
ALLEGHANY FRONT (BCB-LWB AREA) EARLY SUNDAY...BUT NOT ENOUGH
CONFIDENCE TO INCLUDE IN THE GRIDS AT THIS TIME. FOG DEVELOPMENT
SUN MORNING SHOULD BE LIMITED BECAUSE OF CLOUDS AND WIDESPREAD
EASTERLY LOW-LEVEL FLOW.
&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM EDT SATURDAY...

A PRETTY IMPRESSIVE HYBRID WEDGE FOR AUGUST WILL REMAIN OVER THE
EAST COAST SUNDAY...STRETCHING FROM NEW ENGLAND SOUTH INTO GEORGIA.
MODELS ARE USHERING IN MORE DRIER AIR WITH THE 00Z RUN...PLACING
HIGHER RAINFALL AMOUNTS OF A TENTH OF AN INCH /0.10/ OR MORE OVER
NORTH CAROLINA AND SOUTH. THE INTERACTION OF THE WEDGE BOUNDARY AND
A BROAD BUT WEAK UPPER LEVEL LOW OVER THE SOUTHEASTERN USA WILL KEEP
THE STRONGER CONVECTION OUT OF THE AREA. WE STILL CAN NOT RULE OUT
SOME SHOWERS AND THUNDERSTORMS AS WEAK IMPULSES TRACK AROUND THIS
LOW AND OVER THE AREA. THE COMBINATION OF EASTERLY FLOW AND A
STRONGER WEDGE WILL KEEP TEMPERATURES COOLER THAN NORMAL ALONG AND
EAST OF THE BLUE RIDGE SUNDAY AFTERNOON. DOWNSLOPE FLOW WILL HELP
WARM THE WEST WITH TEMPERATURES RUNNING ABOVE NORMAL. THE OVERALL
TEMPERATURE PICTURE FOR THE AREA WILL BE UNIFORM WITH SUNDAY`S
AFTERNOON HIGHS RANGING FROM THE UPPER 70S TO LOWER 80S.

ON MONDAY...THE PARENT HIGH OVER NEW ENGLAND WILL DRIFT
EAST...LEAVING A RESIDUAL BAGGY HIGH OVER THE MID ATLANTIC REGION.
MEANWHILE...THE UPPER LEVEL LOW RETROGRADES WEST ACROSS THE GULF
STATES. WITH THE DEPARTURE OF THE TWO MAIN WEATHER
FEATURES...AFTERNOON HEATING WILL GENERATE SCATTERED SHOWERS AND
THUNDERSTORMS OVER THE MOUNTAINS DURING THE AFTERNOON. THESE SLOW
MOVING STORMS COULD PRODUCE LOCALIZED HEAVY DOWNPOURS. THESE SHOWERS
WILL FADE WITH LOSE OF HEATING. MORE SUN IS EXPECTED MONDAY WHICH
WILL LEAD TO TEMPERATURES RETURNING TO NORMAL...ESPECIALLY ACROSS
THE PIEDMONT. HOWEVER...WITH LIGHT SOUTHEASTERLY FLOW...WE STILL
EXPECT UNIFORM TEMPERATURES IN THE LOW TO MID 80S ACROSS THE
AREA...UPPER 70S ALONG HIGHER RIDGES.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 330 PM EDT FRIDAY...

A GENERAL SUMMERTIME WEATHER PATTERN WILL RETURN FOR THE MIDDLE OF
NEXT WEEK...WITH SPOTTY SHOWERS AND THUNDERSTORMS DEVELOPING EARLY
EACH AFTERNOON WITH DAYTIME HEATING...AND DIMINISHING TOWARD SUNSET
AS HEATING ENDS. EXPECT ONLY SPOTTY COVERAGE OF RAINFALL ON TUESDAY
DUE TO WEAK SUPPORTING DYNAMICS...HOWEVER COVERAGE WILL INCREASE
EACH DAY FOR WEDNESDAY AND THURSDAY AS A COLD FRONT APPROACHES FROM
THE NORTHWEST.

BY NEXT THURSDAY...LONG RANGE WEATHER FORECAST MODELS DIFFER AS TO
WHERE THE COLD FRONT WILL BE LOCATED...WITH THE ECMWF MODEL BRINGING
THE FRONT ACROSS OUR AREA...WHILE THE GFS MODEL KEEPS THE FRONT WELL
TO OUR NORTH. GIVEN WHAT APPEARS TO BE WEAK UPPER LEVEL SUPPORT TO
GIVE THE FRONT A SOUTHWARD PUSH...HAVE TRENDED TOWARD THE GFS MODEL
AND TRIMMED BACK RAIN CHANCES FOR THAT DAY.

EXPECT WARM AND MUGGY CONDITIONS FOR THE PERIOD...WITH HIGHS RANGING
FROM THE UPPER 70S/LOW 80S ACROSS THE MOUNTAINS...TO THE UPPER 80S
FOR THE PIEDMONT. LOWS WILL HOLD GENERALLY IN THE LOW TO MID
60S...PERHAPS WITH A FEW UPPER 50S ACROSS THE MOUNTAINS.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
AS OF 740 AM EDT SATURDAY...

TRUE BACKDOOR COLD FRONT LOCATED NEAR AN MRB-LYH-RDU LINE...WITH
MARITIME AIR NOW SURGING INTO THE EASTERN PART OF THE STATE. THIS
UPSLOPE MARITIME EASTERLY FLOW IS QUICKLY BEING REALIZED IN MVFR
CIGS AND MVFR VSBYS IN LOW CLOUDS AND FOG. ALSO...AS WELL DEPICTED
BY THE HRRR...PATCHES OF -SHRA/-DZ ALSO BEGINNING TO DEVELOP ALONG
THE LEADING EDGE OF THIS BOUNDARY...AND THIS ACTIVITY WILL
TRANSLATE WEST TOWARD THE ALLEGHANYS WITH THE BACKDOOR FRONT
THROUGH EARLY AFTERNOON. EXPECT WIDESPREAD MVFR...SOME IFR CIGS
ROA/LYH/DAN THROUGH 15Z...THROUGHOUT THE DAY. ANY IMPROVEMENT
DURING LATE AFTERNOON/EARLY EVENING...WILL QUICKLY DETERIORATEAGAIN
AFT 00Z. VSBYS ARE NOT EXPECTED TO GO BELOW MVFR CONDITIONS IN
THESE AREAS. PRECIPITATION EAST OF THE BLUE RIDGE WILL BE LIMITED
MOSTLY TO THIS MORNING.

TO THE WEST...LOW CLOUDS WERE ALSO ADVECTING/DEVELOPING INTO THE
REGION...BUT WILL LIKELY NOT PERSIST ALL DAY WEST OF THE BLUE
RIDGE. HOWEVER...NEAR THE ALLEGHANY FRONT AND I-77
CORRIDOR...GREATER POTENTIAL FOR SHOWERS/THUNDERSTORMS DURING THE
AFTERNOON...SO HAVE CONTINUED TO INCLUDE A VCTS AT BLF...BUT FEEL
THAT LWB/BCB WILL ESCAPE THIS. BETTER CHANCE FOR CONVECTION WILL
BE NEAR THE VA/NC/TN BORDER. CIGS MOSTLY MVFR IN THESE
AREAS...WITH SOME PERIOD OF VFR CIGS POSSIBLE DURING THE LATE
AFTERNOON/EARLY EVENING. THESE AREAS WILL SEE MVFR-IFR CIGS BY SUN
MORNING...HOWEVER WITH MVFR BR. EXCEPTION IS LWB...WHICH HAD
ENOUGH CLEARING FRI EVENING TO ALLOW LIFR FG TO DEVELOP AGAIN THIS
MORNING. THIS COULD PERSIST UNTIL AROUND 15

WINDS NE 6-9KTS WITH LOW END GUSTS...ESPECIALLY EAST OF THE BLUE
RIDGE LATE MORNING INTO MID-AFTERNOON.

MEDIUM CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD.
MEDIUM CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD.
MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID
PERIOD.
MEDIUM CONFIDENCE IN TSRA POTENTIAL WEST THIS AFTERNOON.

EXTENDED AVIATION DISCUSSION...

HIGH PRESSURE WILL GRADUALLY WORK INTO THE REGION BY THE END OF
THE WEEKEND...AND REMAIN OVER THE AREA INTO THE EARLY PART OF
NEXT WEEK. LINGERING MOISTURE AND AN EASTERLY FETCH WILL HELP
MAINTAIN SOME ISOLATED TO SCATTERED SHOWERS ACROSS MAINLY WESTERN
PARTS OF THE AREA. THIS MOISTURE WILL BEGIN TO RETURN NORTH AND
EAST BY MONDAY WITH CHANCES FOR SHOWERS AND THUNDERSTORMS
INCREASING THROUGH MID-WEEK AS INSTABILITY INCREASES AND A COLD
FRONT APPROACHES FROM THE WEST.

PAST SATURDAY...CEILINGS AND VISIBILITIES WILL PRIMARILY BE
VFR OUTSIDE EARLY MORNING PATCHY DENSE FOG AND AFTERNOON
SHOWERS/THUNDERSTORMS.

&&

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

&&

$$
SYNOPSIS...JH/RAB
NEAR TERM...JH/RAB
SHORT TERM...RCS
LONG TERM...NF
AVIATION...DS/RAB/WP



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.