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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 152013 CCA
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
357 PM EDT WED MAY 15 2013

.SYNOPSIS...
A DEEP LOW PRESSURE SYSTEM PASSING NORTH OF THE GREAT LAKES WILL
DRAG A COLD FRONT SOUTHWARD TOWARDS THE OHIO RIVER VALLEY
TONIGHT...ON ITS WAY TO THE NORTHERN PORTION OF OUR FORECAST
REGION THURSDAY NIGHT AND FRIDAY. THIS FRONT WILL REMAIN IN THE
AREA THROUGH THE WEEKEND...PROVIDING THE FOCUS FOR SPOTTY SHOWER
AND THUNDERSTORM ACTIVITY...MAINLY EACH AFTERNOON AND EVENING.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 400 PM EDT WEDNESDAY...

LOOKING AT RELATIVELY CLEAR SKIES THROUGH THE REMAINDER OF THE
EVENING NOW THAT MID LEVEL CLOUDS ARE EXITING THE EAST. MAY SEE A
FEW CLOUDS POP UP ALONG THE RIDGELINES...HOWEVER THESE WILL
DIMINISH AT SUNSET AS DAYTIME HEATING ENDS. WEST WINDS REMAIN
GUSTY AND CHINOOK-LIKE THIS AFTERNOON...AND WHEN COMBINED WITH
UPPER LEVEL RIDGING ALONG THE APPALACHIAN CHAIN HAVE ALLOWED HIGHS
TODAY TO CLIMB FROM THE MID 80S TO NEAR 90 EAST...AND THE UPPER
70S TO LOW 80S ACROSS THE MOUNTAINS.

OVERNIGHT...SURFACE WINDS WILL DECREASE WITH THE LOSS OF DAYTIME
HEATING...BUT WILL AGAIN SEE WINDS BECOME SOMEWHAT GUSTY ALONG THE
RIDGES AS ANOTHER WEAK TROUGH PASSES ACROSS THE REGION...REACHING
35 TO 40 MPH AT TIMES AT THE HIGHEST PARTS OF THE NORTH CAROLINA
MOUNTAINS INTO GRAYSON COUNTY. WILL ALSO SEE HIGH CLOUDS INCREASE
THROUGH THE NIGHT AS A COLD FRONT SINKS FROM THE GREAT LAKES
TOWARD THE OHIO RIVER VALLEY...AND EXPECT TO SEE A CANOPY OF
CIRRUS ACROSS THE AREA AT SUNRISE. DESPITE UPPER LEVEL RIDGING
BREAKING DOWN OVERNIGHT...WILL STILL SEE WARM AIR BUILD IN AHEAD
OF THE APPROACHING COLD FRONT...WITH OVERNIGHT LOWS RANGING FROM
THE MID 50S TO LOW 60S MOST AREAS.

CLOUD COVER AND SHOWER ACTIVITY WILL INCREASE THROUGH THE DAY ON
THURSDAY AS THE COLD FRONT CONTINUES ITS SOUTHWARD PUSH. MAY SEE A
FEW THUNDERSTORMS DEVELOP ACROSS THE MOUNTAINS WITH AFTERNOON
HEATING...A FEW OF WHICH MAY BECOME STRONG FOR BRIEF PERIODS OF
TIME...HOWEVER BETTER INSTABILITY IS EXPECTED TO REMAIN TO THE
NORTH OF OUR AREA. INCREASED CLOUD COVER WILL HELP LIMIT
HEATING...ALTHOUGH AFTERNOON HIGHS WILL STILL BE WARM...RANGING
FROM THE UPPER 70S WEST TO THE MID/UPPER 80S EAST.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 400 PM EDT WEDNESDAY...

SIMILAR TO PAST FEW DAYS HIGHEST PROBABILITY OF PRECIPITATION WILL
LINE UP ALONG AND JUST SOUTH OF THE FRONT ACROSS THE OHIO VALLEY AND
MID ATLANTIC STATES WITH THE BEST AREAL COVERAGE IN THE AFTERNOON
AND EVENING. GFS AND NAM BROUGHT FRONT AND HIGHER CONVECTIVE
AVAILABLE POTENTIAL ENERGY INTO THE NORTHERN COUNTY WARNING AREA ON
FRIDAY THEN CLOSER TO THE VIRGINIA/NORTH CAROLINA BORDER ON
SATURDAY. 850MB BOUNDARY DOES NOT ADVANCE AS FAR SOUTH SO IT SEEMS
FORECAST AREA WILL BE IN THE BAROCLINIC ZONE. SHORT WAVE COMING OUT
OF THE SOUTHERN PLAINS AND MCS ACTIVITY MAY ALSO INFLUENCE POSITION
OF THE FRONT AND THEREFORE THE MOST LIKELY LOCATION FOR
PRECIPITATION.

LITTLE CHANGE IN AIR MASS THIS TIME FRAME. OF COURSE VARIATION IN
DAYTIME HIGH TEMPERATURES WILL BE DEPENDENT ON CLOUD COVER AND
LOCATION OF RAINFALL.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 100 PM EDT WEDNESDAY...

LARGE SCALE UPPER RIDGE OVER THE FORECAST AREA SATURDAY NIGHT AND
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.
-- End Changed Discussion --

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
AS OF 200 PM EDT WEDNESDAY...

EXPECT VFR CONDITIONS FOR ALL AIRPORTS THROUGH THE 15/18Z TAF
PERIOD.

THROUGH THE REMAINDER OF WEDNESDAY...SCT MID LEVEL CLOUDS IN THE
VICINITY OF DAN AND LYH WILL CONTINUE EAST...MAKING FOR CLEAR TO
MOSTLY CLEAR SKIES...POSSIBLY WITH A FEW AFTERNOON CU. WINDS WILL
REMAIN GUSTY FROM THE WEST...OCCASIONALLY REACHING 25KTS FOR ROA
AND POINTS WESTWARD...AND 20KTS AT DAN AND LYH. WIND SPEEDS WILL
DIMINISH WITH SUNSET.

A WEAK COLD FRONT WILL APPROACH FROM THE NORTH LATE TONIGHT WITH
A RIBBON OF LOWER CEILINGS LIKELY PRECEDING THE BOUNDARY ACROSS
THE FAR NORTH AROUND 16/12Z. MID AND HIGH CLOUDS WILL THICKEN
AFTER SUNRISE THURSDAY...AND LOW CLOUDS MAY APPROACH CLOSE ENOUGH
TO LWB FOR A LOW END VFR STRATO-CU DECK TO SETTLE ACROSS THE
FIELD.

SHOWER ACTIVITY WILL INCREASE FROM THE NORTH ON THURSDAY AS THE
FRONT SINKS FURTHER TO THE SOUTH...WITH SOME SHOWERS DEVELOPING
INTO THUNDERSTORMS DURING LATE MORNING WITH DAYTIME HEATING. AT
THIS TIME...BELIEVE BEST COVERAGE OF CONVECTION WILL BE DURING MID
AFTERNOON AND EVENING...WITH BETTER CHANCES ACROSS THE MOUNTAINS.

THURSDAY BEGINS A PERIOD OF SCATTERED SHOWER AND THUNDERSTORM
ACTIVITY THAT WILL LAST THROUGH THE WEEKEND AS THE FRONT STALLS
JUST NORTH OF THE FORECAST AREA...WITH WEAK IMPULSES PASSING ALOFT
TO OFFER UPPER LEVEL SUPPORT. APPEARS THE AFTERNOON AND EARLY
EVENING HOURS WOULD HAVE THE BEST CHANCE OF SEEING PERIODS OF
MVFR/IFR IN SHRA/TSRA...ESPECIALLY FRIDAY INTO SUNDAY AFTERNOON
PENDING WHERE THE FRONT ENDS UP. WILL ALSO SEE PATCHY FOG DURING
THE OVERNIGHTS.

&&

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

&&

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