-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 211136
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
736 AM EDT TUE MAY 21 2013

.SYNOPSIS...
LOW PRESSURE ALOFT WILL DRIFT EAST OF THE REGION THIS MORNING. A
LARGE LOW PRESSURE SYSTEM WILL TRACK FROM THE CENTRAL PLAINS INTO
THE GREAT LAKES BY THURSDAY. THIS SYSTEM WILL PUSH A COLD FRONT
THROUGH THE AREA THURSDAY...FOLLOWED BY HIGH PRESSURE ON FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 500 AM EDT TUESDAY...

MANY LOCATIONS REPORTING VISIBILITIES ONE QUARTER MILE OR LESS.
HAVE ISSUED A DENSE FOG ADVISORY. CONDITIONS WILL IMPROVE AFTER
8AM.

RADAR SHOWED ISOLATED SHOWERS IN NORTH CENTRAL NORTH CAROLINA THIS
MORNING...MOVING SOUTHEAST. HAVE KEPT CHANCE OF PRECIPITATION OUT
OF THE FORECAST FOR THIS MORNING. DID LEAVE IN AREAS OF FOG.

SHORT WAVE WAS OVER THE FORECAST AREA EARLY THIS MORNING. MOST
MODELS HAVE FEATURE MOVING INTO EASTERN VIRGINIA BY THIS
AFTERNOON. RUC AND WRF MODELS SUGGEST MOST LIKELY LOCATION FOR
THUNDERSTORM DEVELOPMENT WILL BE ALONG THE SOUTHERN BLUE RIDGE
THIS AFTERNOON. THEN IN EASTERN KENTUCKY AND WEST
VIRGINIA...MOVING INTO OUR SOUTHEAST WEST VIRGINIA COUNTIES AND
THROUGH THE NORTHERN COUNTY WARNING AREA THIS EVENING. DO NOT
ENVISION MORE THAN SCATTERED COVERAGE THIS AFTERNOON OR TONIGHT.

850 MB WINDS TURN TO THE NORTHWEST BRIEFLY AFTERNOON FOLLOWING THE
SHORT WAVE THEN BACK TO SOUTHWEST FOR TONIGHT. NORTHWEST FLOW AND
850 MB TEMPERATURES AROUND +16 WILL RESULT IN DECENT WARM UP FOR
THE FOOTHILLS AND PIEDMONT...ESPECIALLY IN AREAS THAT HAVE SUN
THIS MORNING. GUIDANCE LOOKED REASONABLE FOR AFTERNOON HIGHS.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 300 AM EDT TUESDAY...

CLOSED UPPER LOW AND SHARP TROUGH OVER THE MIDWEST WILL MAKE SLOW
EASTWARD PROGRESS AGAINST STRONG RIDGE OFF THE ATLANTIC COAST BUT
EVENTUALLY WILL SHOVE A SURFACE FRONT THROUGH THE CWA THURSDAY
AFTERNOON. UNTIL THEN AREA WILL REMAIN UNDER SOUTHERLY FLOW WITH
GENERALLY ABUNDANT MOISTURE BUT WEAK TO DISORGANIZED FORCING. MAY
SEE A PRE-FRONTAL SQUALL LINE ACRS THE OH VALLEY WED AFTERNOON
WHICH WILL LIKELY BE WEAKENING AS IT APPROACHES FAR WESTERN CWA
WED EVENING/NIGHT. STILL MAINTAINED AT LEAST HIGH CHC POPS IN THE
MOUNTAINS AHEAD OF ANY PSBL LINE WEDNESDAY AFTERNOON WHERE
DIFFERENTIAL DIURNAL HEATING AND UPSLOPE ENHANCMENT WILL BE FOCUS
FOR MOST LIKELY ACTIVITY WITH LOWER CHC POPS ACRS THE PIEDMONT.
SOME STORMS POTENTIALLY STRONG WITH CAPE APPROACHING 1000 J/KG BUT
LIMITED SHEAR SHOULD PRECLUDE MUCH IN THE WAY OF SEVERE STORMS.
AGAIN COULD BE WITH LOCALLY HEAVY RAINFALL AS PWATS REMAIN IN THE
1.2 TO 1.5 INCH RANGE AHEAD OF FRONT AND STORMS COULD BE SLOW-
MOVING.

POPS DIMINISH OVERNIGHT WED WITH LOSS OF HEATING BUT RENEWED
CONVECTIVE ACTIVITY LIKELY ON THURSDAY WITH PASSAGE OF SURFACE
FRONT. NOT LOOKING FOR MUCH IN THE WAY OF SEVERE AS BEST SUPPORT
WELL TO NORTH OF CWA BUT A FEW STRONG STORMS AND MORE POCKETS OF
HEAVY RAINFALL POSSIBLE. POPS DECREASING THURS NIGHT AND FRI AS
DRIER NW FLOW TAKES OVER. LEFT CHC POPS FRI AS COOLER AIR ALOFT
ENHANCES INSTABILITY LESSENING TREND. MILD TEMPS WILL PREDOMINATE
AHEAD OF THE FRONT WITH 80S WED AND EVEN THUR BUT SUBSTANTIALLY
COOLER WEATHER EXPECTED BEHIND THE FRONT FOR FRIDAY AND BEYOND.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 345 PM EDT MONDAY...

BOTH THE GFS AND ECMWF ARE DELIVERING A GOOD INTRUSION COOLER AIR BY
12Z FRIDAY WITH H85 TEMPS SLIPPING TO +5C.  THE UPPER TROUGH IS FCST
TO SLIDE ACROSS NEW ENGLAND ON FRIDAY WITH COOL NORTHWEST FLOW
PROGGED FROM THE GREAT LAKES TO THE MID ATLANTIC.

COOLER NORTHWESTERLY FLOW ALSO SUGGESTS THE AIR WILL BE DRY...THUS
HAVE REMOVED ALL MENTION OF PRECIP FOR THE WEEKEND.  THAT SAID...AS
HIGH PRESSURE PASSES OVHD SATURDAY AND ROLLS OFF THE EAST COAST
SUNDAY...MOISTURE COULD SNEAK BACK IN THE PICTURE AS EARLY AS SUNDAY
AFTERNOON.  ATTM...WILL GO WITH AN OPTIMISTIC FCST AND JUST
ADVERTISE INCREASING CLOUDS FOR SUNDAY...AND HOLD OFF ON NEXT
OPPORTUNITY FOR SHOWERS UNTIL MONDAY.

BOTH SATURDAY AND SUNDAY MORNINGS LOOK COOL WITH EARLY MORNING LOWS
IN THE 40S IN THE MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT. IF
WINDS DECOUPLE AND SKIES REMAIN CLEAR...SOME OF THE SHELTERED
MOUNTAIN VALLEYS MAY SLIP INTO THE UPPER 30S.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 730 AM EDT TUESDAY...

WIDESPREAD FOG COVERED THE REGION THIS MORNING WITH IFR TO LIFR
VISIBILITIES. LOW CONFIDENCE AS TO HOW FAST VISIBILITIES WILL
IMPROVE TO MVFR THEN VFR. ONCE 12Z RNK AND GSO UPPER AIR SOUNDINGS
ARE AVAILABLE...DEPTH OF LOW CLOUDS AND FOG WILL BE DETERMINED AND
EROSION TIME MAY BE EASIER TO JUDGE.

A SHORT WAVE OVER THE AREA TONIGHT MOVES INTO EASTERN
VIRGINIA THIS MORNING. ISOLATED TO SCATTERED THUNDERSTORMS WILL
DEVELOP AGAIN THIS AFTERNOON. PROBABILITY AT ANY ONE AIRPORT IS
TOO LOW TO INCLUDE IN THE TAFS AT THIS TIME. FOG FORMATION
OVERNIGHT WILL BE DEPENDENT ON WHICH LOCATIONS GET RAIN THIS
AFTERNOON AND WHICH CLEAR OUT DURING THE EVENING.

THE REGION STAYS IN A WARM...MOIST AIRMASS THROUGH THURSDAY.
AREAS OF FOG WITH MVFR VISIBILITIES IS LIKELY EACH NIGHT AND EACH
AFTERNOON AND EVENING THERE WILL BE SCATTERED THUNDERSTORMS.

NEXT FRONT APPROACHES ON THURSDAY WITH MORE SHOWERS/STORMS
DEVELOPING. HIGH PRESSURE AND BETTER FLYING CONDITIONS ARE
EXPECTED ON FRIDAY BEHIND THE FRONT.
-- End Changed Discussion --

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR VAZ009-
     012>020-022>024.
NC...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR NCZ001-002-
     018.
WV...NONE.

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...PC
LONG TERM...PM
AVIATION...AMS