000
FXUS61 KRNK 161824
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
224 PM EDT THU MAY 16 2013

.SYNOPSIS...
A COLD FRONT IN THE OHIO VALLEY WILL DRIFT SLOWLY SOUTH ACROSS THE
MID ATLANTIC REGION TODAY BEFORE REACHING THE BLUE RIDGE FRIDAY
INTO FRIDAY NIGHT. THIS FRONT WILL REMAIN IN THE AREA THROUGH THE
WEEKEND...PROVIDING THE FOCUS FOR SPOTTY SHOWER AND THUNDERSTORM
ACTIVITY...MAINLY DURING THE AFTERNOON AND EVENING HOURS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 252 AM EDT THURSDAY...

LOOKING AT SCATTERED MID AND HIGH CLOUDS MAKING THEIR WAY ACROSS
THE AREA THIS MORNING...WHILE SHOWER AND THUNDERSTORM ACTIVITY
ASSOCIATED WITH AN APPROACHING COLD FRONT CONTINUES TO PUSH SOUTH
FROM NEAR THE OHIO RIVER VALLEY. MAY SEE A FEW SPRINKLES REACH
INTO BATH...ROCKBRIDGE AND PERHAPS BUCKINGHAM COUNTIES THIS
MORNING AS A WAVE PASSES ALONG THE FRONT...BUT THE VAST MAJORITY
OF RAIN IS EXPECTED TO STAY TO THE NORTH THROUGH MID AFTERNOON PER
LATEST SET OF MODELS. EVEN AS CONVECTION ENTERS THE AREA...EXPECT
THE RAINFALL TO BE A LITTLE MORE ON THE SPOTTY SIDE AS DEEP
WESTERLY FLOW KEEPS THE MID LEVELS OF THE ATMOSPHERE DRY TO START.
THEREFORE ADJUSTED RAIN CHANCES IN THE FORECAST TO REFLECT THIS
THINKING. AT ANY RATE...HIGH CLOUDS ARE THIN ENOUGH TO ALLOW
ABUNDANT SUNSHINE TO REACH THE SURFACE ACROSS THE PIEDMONTS...WITH
TEMPERATURES ALREADY NEAR 80 DEGREES AND CLIMBING. CLOUD COVER IS
THICKER ACROSS THE MOUNTAINS...AND CURRENTLY OBSERVING UPPER 60S
TO MID 70S.

BETTER CONVECTIVE COVERAGE WILL COME SHORTLY BEFORE SUNSET ONCE
MIXING DECREASES...ALLOWING MORE CONVERGENCE TO DEVELOP AS
DEWPOINTS RISE. MAIN FOCUS WOULD AGAIN BE OVER THE NORTHWEST AND
FAR EAST...CLOSER TO THE FRONT...WITH MORE WIDELY SCATTERED
COVERAGE ELSEWHERE AS SUGGESTED BY THE RATHER WET LOCAL RNK-WRF
SOLUTION. INSTABILITY APPEARS TO QUICKLY WANE AFTER MIDNIGHT AS
THE WEAK UPPER IMPULSE EXITS...SO DECREASING RAIN CHANCES TO MORE
ISOLATED COVERAGE LATE TONIGHT. SHOULD BE A WARM/MUGGY NIGHT WITH
SOME PATCHY FOG AROUND AND TEMPERATURES MAINLY UPPER 50S TO LOWER
60S.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 400 AM EDT THURSDAY...

UNSETTLED WEATHER EXPECTED ALONG AND SOUTH OF A FRONTAL BOUNDARY
WHICH DROPS SOUTH ACROSS THE MID ATLANTIC REGION THROUGH SATURDAY
NIGHT. THIS FRONT ENTERS NORTHERN PORTIONS OF OUR AREA FRIDAY AND
PUSHES TO THE VIRGINIA/NORTH CAROLINA BORDER ON SATURDAY.

CUT BACK POPS INITIALLY FRIDAY MORNING USING A BLEND OF THE GFS/NAM
WITH SCATTERED CONVECTION MAINLY IN THE WEST WITH LIGHTER CHANCES IN
THE EAST. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS
THE ENTIRE REGION FRIDAY AFTERNOON INTO FRIDAY EVENING. MLCAPE
VALUES ON FRIDAY MAY CLIMB TO 500 TO 1000 J/KG...WITH 0-6KM SHEAR
WEAK AROUND 20 KTS. LOWERED HIGHS A FEW DEGREES FRIDAY WITH VALUES
FROM THE LOWER 70S IN THE WEST TO THE LOWER 80S IN THE EAST. ALLOWED
FOR SOME SHOWERS WITH SHORTWAVE MAINLY ACROSS THE NORTH FRIDAY
NIGHT. FRIDAY NIGHT WILL BE MILD WITH READINGS FROM THE LOWER 50S IN
THE MOUNTAINS TO THE LOWER 60S IN THE EAST. INCREASED POPS TO LIKELY
ON SATURDAY WITH NAM...GFS AND ECMWF ALL SUPPORTING THUNDERSTORMS.
ROBUST CAPES OFF THE GFS FROM 1 TO 3K J/KG LEAD TO POTENTIAL FOR
STRONGER STORMS IN SOUTHSIDE. A PULSE TYPE SEVERE STORM MAY BE
POSSIBLE WITH WIND AND RAIN. TRAINING OF ECHOES COULD RESULT IN
FLOODING PROBLEMS WITH HIGHER PWAT VALUES. WENT WITH COOLER HIGHS
FOR SATURDAY IN THE 70S WITH BETTER COVERAGE AND THICK CLOUDS. HELD
ON TO CHANCE OF SHOWERS SATURDAY NIGHT...WITH LOWS FROM THE MID 50S
IN THE MOUNTAINS TO THE LOWER 60S IN THE PIEDMONT.

&&

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

LARGE SCALE UPPER RIDGE OVER THE FORECAST AREA SUNDAY...BIT WITH A
SHORT WAVE OVER THE SOUTHERN APPALACHIANS. MODELS DIFFER IN THE
SURFACE REFLECTION OF THE SOUTHERN WAVE. MAIN FRONT WILL BE TO THE
NORTH OF THE FORECAST AREA BUT INFLUENCE OF THE SOUTHERN
APPALACHIANS FEATURE MAY BE ENOUGH TO RESULT IN BETTER AREAL
COVERAGE OF SHOWERS AND THUNDERSTORMS ON SUNDAY.

UPPER LOW CUTS OFF OVER THE DAKOTAS ON MONDAY. THE LOW MOVES EAST
THROUGH WEDNESDAY AND WILL PUSH A COLD FRONT INTO THE AREA BY
WEDNESDAY OR THURSDAY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 200 PM EDT THURSDAY...

CONDITIONS STILL VFR THIS AFTERNOON...ALTHOUGH CLOUDS CONTINUE TO
LOWER AS A COLD FRONT AND ASSOCIATED CONVECTION SINKS IN FROM THE
NORTH. BEST CHANCES FOR SHOWER AND THUNDERSTORM ACTIVITY THIS
EVENING WILL BE AT LWB...WITH SLIGHT CHANCE FOR BLF...BCB...ROA
AND LYH. STILL LOOKING FOR WESTERLY DOWNSLOPE WINDFLOW TO KEEP
CONVECTION CAPPED THROUGH SUNSET UNTIL WINDS DIE DOWN...AT WHICH
POINT EXPECT TO SEE SHOWERS AND A FEW THUNDERSTORMS BECOME MORE
SPREAD ACROSS THE FORECAST AREA. THAT SAID...CONVECTION SHOULD BE
SHORTLIVED WITH THE LOSS OF DAYTIME HEATING...WITH ONLY SPOTTY
SHOWER ACTIVITY LINGERING AFTER MIDNIGHT. ANY LOCATIONS WHERE
THUNDERSTORM ACTIVITY DOES PASS CAN EXPECT BRIEF PERIODS OF
IFR CONDITIONS...WITH VISIBILITIES DROPPING TO 1/4SM OR LESS IN
HEAVY RAIN.

OVERNIGHT...THE COLD FRONT WILL PUSH SOUTHWARD EAST OF THE BLUE
RIDGE...PASSING ACROSS LYH AND DAN...AND ADVANCING CLOSE TO ROA.
WITH THE WEAKLY STABLE AIRMASS IN PLACE...EXPECT A LIGHT
NORTHEASTERLY FLOW...WITH PATCHY FOG DEVELOPING ACROSS THE AREA.
WITH DAYTIME HEATING...THE FRONTAL BOUNDARY DRAPED ACROSS OUR AREA
WILL PROVIDE THE FOCUS FOR SCATTERED SHOWERS DURING THE
MORNING...WITH SOME INTENSIFYING INTO THUNDERSTORMS BY EARLY
AFTERNOON. MAIN AREAS TO WATCH WILL BE WHERE SUNSHINE BREAKS DOWN
TO THE SURFACE. WHILE SKIES WILL BE MOSTLY CLOUDY TO START THE
DAY...EXPECT TO SEE A FEW LOCATIONS BREAK OUT DURING THE
MORNING...ALLOWING SURFACE TEMPERATURES TO SPIKE UP QUICKLY.

THE FRONT WILL LINGER ACROSS THE AREA INTO EARLY NEXT WEEK...
RESULTING IN A PERSISTENT PATTERN OF SCATTERED AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS AS WEAK IMPULSES PASS
ACROSS...OFFERING UPPER LEVEL SUPPORT. PERIODS OF MVFR/IFR ARE
EXPECTED DURING ANY SHOWERS AND THUNDERSTORMS. PATCHY EARLY
MORNING FOG CAN ALSO BE EXPECTED.

&&

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

&&

$$
SYNOPSIS...JH/NF
NEAR TERM...JH/NF
SHORT TERM...KK
LONG TERM...AMS
AVIATION...JH/NF