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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 171807
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
207 PM EDT FRI MAY 17 2013

.SYNOPSIS...
A COLD FRONT WILL CONTINUE TO SINK SOUTH TOWARD THE REGION
TODAY BEFORE SETTLING ACROSS THE EASTERN HALF OF THE FORECAST
AREA BY THIS EVENING. THE FRONT WILL STALL OVER NORTH CAROLINA
OVERNIGHT INTO SATURDAY NIGHT BEFORE LIFTING BACK NORTHEAST AS A
WARM FRONT BY EARLY NEXT WEEK. A WEAK UPPER LEVEL DISTURBANCE
WILL RIDE EAST ALONG THE FRONT ENHANCING THE THREAT FOR SHOWERS
AND THUNDERSTORMS ESPECIALLY OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM EDT FRIDAY...

PLENTY OF SUNSHINE REACHING THE SURFACE THIS MORNING FOR MUCH OF
THE AREA OUTSIDE OF PORTIONS OF THE ALLEGHANY HIGHLANDS AND THE
SHENANDOAH VALLEY. THE INCREASED HEATING IS ALREADY LEADING TO A
FEW CU POPPING UP ALONG THE RIDGELINES...AND WILL HAVE TO MONITOR
THROUGH THE MORNING FOR THE DEVELOPMENT OF SHOWER ACTIVITY...AND
THUNDERSTORMS LATER IN THE DAY. MAINTAINING THE PREVIOUS FORECAST
PHILOSOPHY FOR TODAY...WHICH IS FOR SPOTTY SHOWERS AND
THUNDERSTORMS TO DEVELOP BY EARLY AFTERNOON ALONG THE RIDGES AS
SOUTHEASTERLY WINDS LEAD TO STRONGER LOW LEVEL CONVERGENCE...AND
THEN THUNDERSTORM ACTIVITY WILL BECOME MORE WIDESPREAD ACROSS THE
PIEDMONTS DURING THE EVENING AHEAD OF A FRONT THAT WILL BE SINKING
ACROSS THE AREA. BELIEVE THAT THUNDERSTORM ACTIVITY WILL BE MORE
PULSE LIKE IN NATURE...AND MAY BE SLOW MOVING DUE TO WEAK WINDS
ALOFT. AS SUCH...MAY SEE LOCALLY HEAVY RAIN IN A FEW AREAS IF
CELLS LINGER LONG ENOUGH OR IF THEY BEGIN TO TRAIN.

LINGERING INSTABILITY WILL GET SHOVED BACK TO ALONG AND WEST OF
THE BLUE RIDGE OVERNIGHT AS THE FRONT PASSES INTO THE FAR SOUTHERN
AREAS BY DAYBREAK. WILL HAVE CONTINUED HIGH POPS DURING THE
EVENING PENDING WHERE MORE ORGANIZED THUNDERSTORM ACTIVITY TAKES
SHAPE...THEN DECREASING BY MIDNIGHT ESPECIALLY EAST IN THE WAKE
OF THE BOUNDARY. WESTERN AREAS MAY SEE SHOWERS INCREASE AGAIN
LATE AHEAD OF THE APPROACHING UPPER LOW BUT IFFY...SO ONLY KEEPING
CHANCE POPS GOING THERE. OTHERWISE MOSTLY CLOUDY AND MUGGY WITH
LOWS IN THE 50S TO LOWER 60S FOR OVERNIGHT LOWS.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
AS OF 349 AM EDT FRIDAY...

BOUNDARY JUST TO OUR NORTH WILL SINK SOUTH OVER THE WEEKEND...IN A
BACKDOOR FASHION AS HIGH PRESSURE SLIPS OVER NEW ENGLAND. THIS
BOUNDARY IN COMBINATION WITH SOUTHEAST UPSLOPE WINDS AGAINST THE
BLUE RIDGE...AND AN UPPER WAVE MOVING ACROSS TN...SHOULD PRODUCE A
SOMEWHAT COOL AND DAMP WEEKEND. SUNDAY APPEARS TO BE THE WETTEST DAY
WITH THE UPPER DISTURBANCE RIGHT ON OUR DOORSTEP THEN MOVING INTO
VIRGINIA DURING THE DAY. PWATS START OUT FAIR SATURDAY BUT REALLY
INCREASE SUNDAY TO 1.5" THROUGH THE PIEDMONT. WITH DEAD FLOW
ALOFT AND WEAK MBE VELOCITIES...STORMS MAY BE SLOW MOVING AND
LATCHED ONTO THE BLUE RIDGE...POSSIBLY LEADING TO SOME WATER
PROBLEMS. INSTABILITY ISN`T THE STRONGEST...AS SUNSHINE WILL BE
LIMITED BY ABUNDANT CLOUDS...BUT COOLING ALOFT THANKS TO THE UPPER
WAVE COULD LEAD TO A MINIMAL STRONG STORM THREAT...ALTHOUGH NOT
TOO THRILLED ABOUT SEVERE WEATHER. SURFACE WINDS VEER ON
MONDAY...MORE OF A S TO SSW WIND AS THE SHORTWAVE MOVES
EAST...THUS ONLY CHC POPS AND WARMER AFTERNOON TEMPS...ESPECIALLY
WEST OF THE BLUE RIDGE WITH LESS CLOUDS.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 315 AM EDT FRIDAY...

FRONT LIFTS TO OUR NORTH TUESDAY WHICH SHOULD BE OUR BEST BET TO
AVOID PCPN GIVEN SOME SHORT WAVE RIDGING...THOUGH LOCAL MOUNTAIN
EFFECTS MAY STILL COOK UP SOME ISOLATED CONVECTION. NEXT FRONT
WILL BE APPROACHING FROM THE WEST ON WEDNESDAY SO EXPECT
INCREASING CHC OF THUNDER AS WE GET INTO WEDNESDAY AFTERNOON. THE
FRONT WANTS TO PUSH THROUGH AND CLEAR THE AREA FOR
THURSDAY...THOUGH WAVE DEVELOPMENT ON THE FRONT MAY SLOW IT DOWN
AND DO NOT HAVE A GREAT DEAL OF CONFIDENCE WITH FRONTAL POSITION
THIS FAR OUT WITH MODELS STILL SORTING THINGS OUT.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 615 AM EDT FRIDAY...

HIGH PRESSURE WILL BE WEDGING DOWN THE EAST COAST THROUGH THE
PERIOD...PUSHING A WAVY FRONT INTO THE AREA AND LEAVING IT HERE
THROUGH THE WEEKEND. SAT LOOP SHOWED MAINLY MID LEVEL CLOUDS
ACROSS NORTHERN AND WESTERN PORTION OF THE REGION WITH A GOOD
DEAL OF CLEAR SKIES AND HEATING THROUGHOUT THE MORNING. BELIEVE
THERE IS ENOUGH MOISTURE IN PLACE FOR CONVECTION TO DEVELOP WITH
MTNS AND DIFFUSE FRONTAL BOUNDARY SERVING AS A LOW LEVEL FOCUS AND
A WEAK 500MB VORT LOBE AND SOME UL JET DYNAMICS AIDING FROM ABOVE.
BUFKIT SOUNDINGS SHOW LONG AND SKINNY CAPE WHICH IS NOT FAVORABLE
FOR SVR BUT INVERTED V SOUNDING INDICATES STORMS SHOULD BE
EFFICIENT PRODUCERS OF GUSTY WINDS.

EXPECTING A TYPICAL DIURNAL TIMING FOR BEST SHOT AT CONVECTION
FROM ABOUT 18Z TO ABOUT 02Z. WILL USE VCTS DURING THIS PERIOD AND
ATTEMPT TO CONFINE PREDOMINANT TS TO A MOST FAVORABLE HOUR OR TWO.
WRF MODEL SEEMED TO DO WELL WITH CONVECTION YESTERDAY AND WILL
LEAN ON IT FOR ANTICIPATED EVOLUTION TODAY.

DO NOT EXPECT WINDS TO BE PROBLEMATIC OUTSIDE OF CONVECTIVE
AREAS. MOS GUIDANCE IS SHOWING DEVELOPMENT OF LOW CLOUDS/FOG
OVERNIGHT AND BASED ON TREND FROM LWB LAST NIGHT THIS SEEMS
REASONABLE...ESPECIALLY FOR AREAS THAT RECEIVE DIRECT PCPN THIS
AFTERNOON.

BELIEVE WAVY NATURE OF FRONT MAY KEEP SHOWERS LINGERING THROUGH
THE OVERNIGHT BUT BEST CHANCE OF PCPN WILL WAIT UNTIL SATURDAY AS
THE BULK OF UPPER SHORT WAVE APPROACHES THE AREA...THOUGH TIMING
ON THIS WILL BE LATE IN THE PERIOD.

.AVIATION EXTENDED...
WEDGIE SITUATION WILL BRING ELY FLOW TO THE AREA SATURDAY
AFTERNOON THROUGH SUNDAY NIGHT. THIS WILL KEEP SITES IN A GOOD
CHANCE OF PCPN...ALONG WITH LOW CIGS/VSBYS AT NIGHT. CONDITIONS
LOOK TO IMPROVE AS THE HIGH NUDGES EAST AND SHOULD LET THE FRONTAL
BOUNDARY PUSH OFF TO OUR NORTH ON MONDAY. EXPECT TUESDAY TO BE THE
BEST BET FOR DECENT FLYING CONDITIONS THOUGH MOUNTAINS MAY HELP
FIRE SOME ISOLATED AFTERNOON SHOWERS/STORMS. NEXT LAZY FRONT
APPROACHES ON WEDNESDAY WITH MORE SHOWERS/STORMS DEVELOPING. THIS
FRONT DOES NOT APPEAR TO BE IN A BIG HURRY AND LOOKS TO BRING MVRF
CONDITIONS...POSSIBLY IFR AT NIGHT...TO TAF SITES FOR THE END OF
THE WEEK.
-- End Changed Discussion --

&&

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

&&

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