Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 070458
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1258 AM EDT THU MAY 7 2015

.SYNOPSIS...
A BACKDOOR COLD FRONT WILL SLOWLY MAKE ITS WAY INTO AND THROUGH OUR
REGION THROUGH THURSDAY...ALL WHILE HIGH PRESSURE CONTINUES ITS
GRIP ON THE SOUTHEAST UNITED STATES. A SLOW MOVING AREA OF LOW
PRESSURE WILL MOVE NORTH ALONG THE COAST OF THE CAROLINAS THIS
WEEKEND. A COLD FRONT WILL MOVE ACROSS THE AREA ON MONDAY OR
TUESDAY OF NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
AS OF 1030 PM EDT WEDNESDAY...

KEEPING AN ISOLATED THREAT FOR SHOWERS OVER THE NRV INTO THE VA
FOOTHILLS THROUGH EARLY MORNING...AND ANOTHER AREA WHERE BETTER
INSTABILITY/MOISTURE CONVERGENCE RESIDES ATTM OVER AMHERST-
BUCKINGHAM COUNTY. THESE SHOWERS WILL FADE AFTER 2-3AM.

00Z RNK SOUNDING SHOWING WEAK STEERING WINDS IN THE LOWS 400
MB...MAINLY NE AT 10 KTS. PWATS OVER 1" NOW AND AIRMASS WILL STAY
MOIST OVERNIGHT...THOUGH WITH BACKDOOR FRONT SOME LOWER DEWPOINTS
IN THE 40S MAY CREEP INTO THE MTNS. EXPECT CLOUD COVER TO STICK
AROUND THROUGH THE OVERNIGHT WITH THE LOW LVL FLOW FROM THE
EAST/NE. THERE WILL BE PERIODS WHERE IT SCATTERS OUT BUT OVERALL
WILL SEE MORE CLOUDS THAN STARS ACROSS THE EASTERN 3/4THS OF THE
CWA. LOWS TEMPS WILL BE IN THE 50S...WITH SOME LOWER 60S IN THE
PIEDMONT/FOOTHILLS. THESE TEMPS ARE RUNNING BETWEEN 5 TO 15
DEGREES ABOVE NORMAL FOR EARLY MAY.



PREVIOUS VALID DISCUSSION...

ON THURSDAY...THE BACKDOOR FRONT IS EXPECTED TO TAKE UP RESIDENCY
OVER THE FAR WESTERN PORTION OF THE AREA. LOOK FOR THE FOCUS FOR
SHOWER AND THUNDERSTORM DEVELOP TO SHIFT WEST FROM THE BLUE
RIDGE...TO BE IN THE VICINITY OF THE FRONT. COVERAGE WILL BE
SCATTERED NEAR THE FRONT AND ISOLATED EAST TO THE CREST OF THE
BLUE RIDGE. HIGHS WILL ONLY BE SLIGHTLY COOLER THAN CONDITIONS OF
TODAY. HIGHS WILL RANGE FROM THE MID 70S TO THE UPPER 70S ACROSS
THE MOUNTAINS WITH UPPER 70S TO AROUND 80 ACROSS THE PIEDMONT.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 345 PM EDT WEDNESDAY...

SHORT AND LONG TERM FORECAST COMPLICATED BY MOVEMENT OF POTENTIAL
TROPICAL STORM ALONG THE SOUTHEAST U.S. COAST. LATEST NHC OUTLOOK
HAS A 60 PERCENT CHANCE OF THIS DEVELOPING INTO A
TROPICAL/SUBTROPICAL SYSTEM WITHIN THE NEXT 48 HOURS SOMEWHERE OFF
THE SC/GA COAST. AS WITH PREVIOUS MODEL RUNS...THE GFS REMAINS
THE MOST AGGRESSIVE IN BRINGING THIS SYSTEM INTO THE CENTRAL AND
EASTERN PORTIONS OF OUR CWA UNDERNEATH A BROAD UPPER RIDGE ACROSS
THE EASTERN U.S. AND WEAK STEERING CURRENTS. HOWEVER...ALL MODELS
INDICATE THAT WE WILL SEE AT LEAST SOME EFFECTS IN THE WAY OF
CLOUDS AND AT LEAST LIMITED MOISTURE INTO THE EASTERN SECTIONS
WITHIN THIS TIME FRAME AS A RESULT OF THIS SYSTEM. TO THE WEST...A
BROAD UPPER TROUGH PERSISTS IN THE WESTERN U.S. AND IS EXPECTED TO
REMAIN WELL WEST OF THE CWA THROUGH THIS TIME FRAME.
MEANWHILE...WHATEVER IS LEFT OF THE BACKDOOR FRONT WOULD APPEAR
TO BE ACROSS EITHER FAR SW VA INTO NW NC OR BACK IN EASTERN
TN...GENERALLY BEING ABSORBED INTO THE LARGE SCALE CIRCULATION
AROUND THE TROPICAL SYSTEM.

FOCUS FOR SHOWERS/THUNDERSTORMS SHOULD BE EITHER IN THE FAR
WEST...GENERALLY WEST OF I-77...OR PERHAPS NEAR OUTERBANDS OF THE
TROPICAL SYSTEM IN AREAS OF DIFFERENTIAL HEATING. CANNOT JUSTIFY
ANY MORE THAN CHANCE POPS AT THIS POINT. WITH RESPECT TO
THUNDER...INSTABILITY IS LIMITED AND GENERALLY WEST OF THE REGION
ACROSS THE OH/TN VALLEY. CLOUDS AND SHOWERS ASSOCIATED WITH THE
TROPICAL SYSTEM WILL MINIMIZE INSTABILITY ACROSS THE PIEDMONT...SO
OVERALL THUNDER THROUGH SATURDAY WILL BE LIMITED.

TEMPERATURES WILL BE QUITE WARM THROUGH THE PERIOD...BUT MAY BE
HELD DOWN SOMEWHAT ACROSS THE PIEDMONT PENDING CLOUD COVER
ASSOCIATED WITH THE TROPICAL SYSTEM. GENERALLY LOOK FOR LOWS IN
THE 50S AND 60S WITH HIGHS IN THE 70S TO LOWER 80S...OVERALL ABOUT
10 DEGREES ABOVE NORMAL.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 400 PM EDT WEDNESDAY...

SUNDAY APPEARS TO LARGELY BE A REPEAT OF SATURDAY...WITH EFFECTS
OF REMNANT TROPICAL SYSTEM ACROSS THE EAST...AND THE FRONTAL
SYSTEM STILL WELL AT BAY TO THE WEST. MONDAY APPEARS TO BE THE
BEST DAY FOR WIDESPREAD CONVECTION AND ANY THREAT OF
SEVERE...ALBEIT THAT REMAINS LOW...AS THE FRONTAL SYSTEM AND
ASSOCIATED UPPER TROUGH PUSH THROUGH THE AREA. GFS APPEARS TOO
QUICK WITH PUSHING THE FRONT SOUTH OF THE AREA AND BRINGING MUCH
COOLER/DRIER AIR INTO THE REGION FROM THE NORTH. HAVE LEANED MORE
TOWARD THE ECMWF SOLUTION OF SLOWING THIS DOWN...HOLDING ONTO LOW
CHANCES FOR CONVECTION ACROSS THE SOUTHERN COUNTIES INTO TUE. MUCH
OF THE UPPER SUPPORT ON MONDAY TRACKS EITHER NORTH OR SOUTH OF THE
REGION...AND THERE STILL REMAIN QUESTIONS AS TO HOW MUCH
SUBSIDENCE OR INTERACTION WITH THE FRONT THE REMNANT TROPICAL
SYSTEM WILL HAVE AT THAT POINT. HAVE NOT ADVERTISED ANY LIKELY
POPS AT THIS POINT...STICKING WITH MID TO HIGH RANGE CHANCE POPS.
TEMPERATURES SHOULD REMAIN WELL ABOVE NORMAL SUNDAY AND
MONDAY...TRENDING MORE TOWARD NORTH READINGS TUE-WED. ANOTHER
STRONGER SYSTEM APPEARS DESTINED TO APPROACH FROM THE SOUTHWEST
TOWARD THE VERY END OF THE PERIOD...BUT FOR NOW HAVE JUST
ADVERTISED SLIGHT CHC POPS NORTHWEST NC.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 1245 AM EDT THURSDAY...

CLUSTERS OF CONVECTION CONTINUE TO PERSIST MAINLY NORTH OF KLYH
ATTM BUT EXPECT A GRADUAL DECREASE IN COVERAGE/INTENSISTY OVER THE
NEXT COUPLE OF HOURS GIVEN DIURNAL COOLING. MAY NEED TO LEAVE IN A
VCSH AT KLYH GIVEN VICINITY OF SHRA OTRW MAIN CONCERN WITH CLOUDS
AND SUBSEQUENT FOG COVERAGE THROUGH DAYBREAK.

THE BACKDOOR COLD FRONT TO THE NORTH WILL MAKE SLOW PROGRESS
TOWARD THE REGION BY DAWN AS THE OVERALL FLOW TURNS MORE EASTERLY
IN RESPONSE TO THIS FEATURE AND LOW PRESSURE WELL TO THE SE.  SOME
GUIDANCE IS ALLOWING FOR THE POTENTIAL FOR MVFR CIGS TO ARRIVE IN
MAINLY NORTHERN/EASTERN PARTS OF THE AREA...THOUGH CONFIDENCE IS
LOW AT THIS OCCURRING SO KEPT CIGS MORE OF THE VFR VARIETY WITH
STRATO-CU UNDER MID DECK. PATCHY FOG WILL ALSO BE
POSSIBLE...ESPECIALLY IN AREAS THAT RECEIVED RAIN WEDNESDAY...AND
ALSO IN SOME OF THE MOUNTAIN AND RIVER VALLEYS...WITH LOCALLY
DENSE FOG TOWARD MORNING AT KLWB PENDING HOW FAST ANY CLEARING
DEVELOPS. GIVEN CURRENT SLOWER TRENDS IN EXODUS OF MID DECK ACROSS
THE REGION...SLOWING DOWN FOG DEVELOPMENT OVERNIGHT AND USING MORE
TEMPO NATURE COVERAGE OF THE MVFR TO IFR VSBYS/CIGS BY DAWN.

ON THURSDAY...ISOLATED TO SCATTERED SHOWER AND STORM DEVELOPMENT
WILL AGAIN BE POSSIBLE ALONG THE LEADING EDGE OF THE BACKDOOR
FRONT AND DURING THE PEAK HEATING OF THE DAY. THIS WOULD PLACE THE
GREATEST COVERAGE ACROSS SOUTHEAST WEST VIRGINIA...SOUTH INTO THE
NORTHERN MOUNTAINS OF NORTH CAROLINA. FOR NOW WILL HAVE VCSH IN
AT KBLF/KBCB WITH VCTS AT KLWB WHERE FORECAST INSTABILITY LOOKS
GREATER. OTRW OVERALL VFR CIGS EXCEPT LOCALLY MVFR OR WORSE NEAR
CONVECTION OVER THE MOUNTAINS. EXPECT MOSTLY VFR OUT EAST WHERE
ONSHORE FLOW SHOULD LIMIT CONVECTION AND KEEP CIGS MOSTLY OF THE
MID/HIGH VARIETY EXCEPT FOR PERIODS OF 4-6K FT STRATO-CU AROUND
KLYH ESPCLY THURSDAY MORNING.

FORECAST CONFIDENCE THURSDAY NIGHT THROUGH SATURDAY IS MEDIUM.

AFTERNOON AND EARLY EVENING SHOWERS AND STORMS WILL BE COMMON
THROUGH SATURDAY...BUT THE TREND FOR THE AXIS OF BEST COVERAGE
WILL SLOWLY WORK ITS WAY WEST OF THE REGION. CONDITIONS WILL
MAINLY BE VFR EXCEPT FOR SOME LATE NIGHT AND EARLY MORNING PATCHY
LIGHT FOG AND SUB-VERSION PATCHY MVFR CLOUDS.

FORECAST CONFIDENCE SATURDAY NIGHT INTO MONDAY IS LOW.

MODEL GUIDANCE IS STILL SHOWING A DECENT AMOUNT OF VARIABILITY IN
THEIR SOLUTIONS REGARDING THE ROUTE A SLOW MOVING UPPER LOW ALONG
THE COAST OF THE CAROLINAS WILL TAKE LATE THIS WEEKEND INTO EARLY
NEXT WEEK. ACCORDINGLY...THE TIMING AND APPROACH OF A COLD FRONT
FROM THE MID-MISSISSIPPI VALLEY WILL BE IMPACTED BY THE POSITION
OF THE LOW AS WELL. A CONSENSUS FORECAST PLACES INCREASING
COVERAGE OF SHOWERS AND STORMS OVER THE AREA DURING THIS PERIOD
WITH A MIX OF MVFR AND VFR CONDITIONS WITH THE BEST COVERAGE ON
MONDAY.

&&

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

&&

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


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