-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 180606
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
206 AM EDT SAT MAY 18 2013

.SYNOPSIS...
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A COLD FRONT WILL CONTINUE TO MOVE SOUTH TONIGHT ACROSS THE
EASTERN HALF OF THE FORECAST REGION...ALLOWING WEAK HIGH PRESSURE
TO WEDGE AGAINST THE MOUNTAINS. AN UPPER LEVEL DISTURBANCE WILL
ADVANCE TOWARD THE CENTRAL APPALACHIAN CHAIN ON SATURDAY...
INCREASING THE CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE
AREA. A DEEP UPPER LEVEL LOW PRESSURE SYSTEM WILL APPROACH THE
AREA TOWARD THE END OF THE COMING WEEK...WHICH MAY BRING A RETURN
OF COOLER WEATHER.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TODAY/...
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AS OF 1030 PM EDT FRIDAY...

SCATTERED SHOWERS WITH EMBEDDED THUNDERSTORMS CONTINUE ACROSS THE
FORECAST AREA. SURFACE FRONT IS GRADUALLY BACKDOORING IN FROM THE
NORTHEAST...BOUNDARY LAYER WINDS GRADUALLY SHIFTING AROUND AND
COMING FROM AN EASTERLY DIRECTION. ALOFT HOWEVER...WINDS IN BOTH
THE GSO/RNK SOUNDINGS WERE FROM THE SOUTH. WITH THIS WARM MOIST
AIR RIDING UP AND OVER THE FRONT...EXPECT SHOWER THREAT TO
CONTINUE THROUGH THE OVERNIGHT. CAN`T RULE OUT A RUMBLE OF THUNDER
AS THERE IS SOME ELEVATED CAPE...BOTH THE GSO/RNK SOUNDINGS
SHOWING CAPE OF ABOUT 1000-1500 J/KG. WINDS ALOFT ARE RELATIVELY
WEAK...MEAN WIND OF ABOUT 10KTS/12MPH. AS SUCH STORM MOVEMENT IS
SLOW...THUS RESULTING IN PERSISTENCE OF HEAVY RAIN WHERE IT
HAPPENS TO OCCUR...SOME CASES RESULTING IN AN INCH OF RAIN IN LESS
THAN AN HOUR.

THROUGH THE OVERNIGHT...WILL SEE GREATEST CONCENTRATION OF
SHOWERS AND A FEW THUNDERSTORMS OVER THE PIEDMONT AS THE FRONT
ENTERS THE AREA AND WIND SPEEDS ALOFT DIMINISH. EXPECT THAT THE
ACTIVITY WILL REMAIN PULSY IN NATURE...ALTHOUGH WOULD NOT BE
SURPRISED TO SEE CLUSTERS OF SEMI-ORGANIZED CELLS WHERE OUTFLOW
BOUNDARIES MERGE. RAINFALL SHOULD DECREASE IN COVERAGE HEADING
INTO THE EARLY HOURS OF SATURDAY...THEN INCREASE AGAIN BY SATURDAY
AFTERNOON.

SHOWER AND THUNDERSTORM ACTIVITY WILL BECOME MORE WIDESPREAD
GOING INTO SATURDAY AFTERNOON AS THE UPPER LEVEL TROUGH MOVES
CLOSER. INCREASED CLOUD COVER AND SCATTERED RAINFALL WILL LIMIT
SURFACED BASED INSTABILITY...WITH AFTERNOON HIGHS HOLDING MAINLY
IN THE UPPER 60S TO MID 70S...SO DO NOT FORESEE A LARGE THREAT OF
SEVERE THUNDERSTORM ACTIVITY DURING THE AFTERNOON. HOWEVER...WEAK
UPPER LEVEL WINDS WILL RESULT IN SLOW MOVEMENT OF ANY STRONGER
SHOWERS AND STORMS...WHICH MAY LEAD TO LOCALLY HEAVY RAIN. BELIEVE
WE WILL HAVE A FEW AREAS OF LOCALIZED NUISANCE FLOODING WHERE
HEAVY RAIN DEVELOPS...BUT DO NOT FORESEE THE THREAT TO BE
WIDESPREAD ENOUGH AT THIS TIME TO GO WITH ANY SORT OF FLOOD WATCH.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
AS OF 330 PM EDT FRIDAY...

SLOW MOVING UPPER LOW/TROUGH WILL MAKE ITS WAY EASTWARD ALONG A
STALLED FRONTAL BOUNDARY. ITS PASSAGE WILL ALLOW FOR DAILY ORGANIZED
SHOWERS AND STORMS TO OCCUR ACROSS THE AREA. SOME WILL BE DRIVEN BY
THE DYNAMICS OF THE SYSTEM...THOSE OCCURRING DURING THE DAY WILL
BENEFIT FROM DAYTIME INSTABILITY AS WELL. THE AXIS OF THE SYSTEM IS
PROGGED TO LIFT NORTHEAST OF THE AREA LATE IN THE DAY MONDAY. WE
EXPECTED A GRADUAL DECREASE IN COVERAGE DURING THIS TIME
PERIOD...WITH THE GREATEST COVERAGE ACROSS THE EASTERN PART OF THE
FORECAST AREA.

TEMPERATURES WILL AVERAGE NEAR NORMAL...IF NOT A SLIGHTLY ABOVE
NORMAL ON AVERAGE GIVEN ELEVATED DEW POINT VALUES OVERNIGHT.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 330 PM EDT FRIDAY...

MONDAY NIGHT...THE PROCESS OF DECREASING COVER THAT BEGAN ON MONDAY
WILL CONTINUE MONDAY NIGHT AS THE TROUGH CONTINUES HEADING OUT OF
THE REGION. ON TUESDAY...WE WILL BE BETWEEN SYSTEMS...WITH THE
POTENTIAL FOR A BRIEF PERIOD OF UPPER LEVEL RIDGING ACROSS THE
REGION. HOWEVER...LOW LEVELS WILL REMAIN ON THE ACTIVE SIDE AHEAD OF
THE NEXT APPROACHING SYSTEM.

THIS NEXT SYSTEM WILL BE AN UPPER LOW THAT WILL HAVE A MORE
NORTHERLY TRACK AS COMPARED TO THE ONE OVER THE WEEKEND.
HOWEVER...ITS PATH WILL ALLOW FOR A SOUTHERLY FETCH OF GULF OF
MEXICO MOISTURE TO STREAM INTO THE REGION WITH INCREASING CHANCE OF
SHOWERS AND STORMS THROUGH THE START OF FRIDAY. MODEL GUIDANCE
VARIES AS TO HOW QUICKLY THE ASSOCIATED COLD FRONT CROSSES THE
AREA...BUT CONSENSUS IS FAIRLY GOOD THAT LINGERING MOISTURE WILL
REMAIN OVER THE AREA ON THE BACKSIDE OF THE FRONT REGARDLESS OF THE
MODEL OF CHOICE. THIS EQUATES TO SHOWERS IN THE FORECAST THROUGH AT
LEAST FRIDAY.

TEMPERATURES WILL TREND MILDER THROUGH THE PERIOD THROUGH AT LEAST
WEDNESDAY...THEN START TO BE COOLER AS CLOUDS AND PRECIPITATION
BECOME MORE ABUNDANT.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 200 AM EDT SATURDAY...

A CLUSTER OF SHOWERS AND THUNDERSTORMS WAS MOVING NORTHEAST AND
AWAY FROM SOUTHWEST VIRGINIA EARLY THIS MORNING. A FEW LIGHT
SHOWERS ARE STILL POSSIBLE AT BCB AND ROA THROUGH 12Z. WEAK EAST
SURFACE WINDS MAY LEAD TO LOW CLOUDS AND IFR CEILINGS DEVELOPING
ALONG THE EAST SLOPE OF THE BLUE RIDGE THIS MORNING. CONFIDENCE IS
LOW SO FOR NOW HAVE FORECAST MVFR CEILINGS AT ALL TAF SITES. IN
ADDITION...RAIN FROM FRIDAY ALONG WITH LIGHT WINDS AND SURFACE DEW
POINTS IN THE 60S WILL RESULT IN FOG OVERNIGHT. MOST LIKELY TAF
SITES WHERE LIFR FOG MAY DEVELOP BEFORE 12Z WERE BCB...LWB AND
BLF.

A SHORT WAVE CROSSING SLOWLY OVER THE SOUTHERN APPALACHIANS TODAY
WILL TRIGGER WIDESPREAD SHOWERS AND THUNDERSTORMS MAINLY THIS
AFTERNOON AND EVENING. THIS WILL PRODUCE MVFR CEILINGS AND
VISIBILITIES ALONG WITH HEAVY RAIN. LITTLE CHANGE IN THE WEATHER
PATTERN IS EXPECTED ON SUNDAY. MORE SHOWERS AND THUNDERSTORMS
ALONG WITH MVFR TO IFR FLYING CONDITIONS WILL CONTINUE.

CONDITIONS LOOK TO IMPROVE MONDAY AS THE UPPER TROUGH MOVES
TO THE MID ATLANTIC COAST. EXPECT TUESDAY TO BE THE BEST BET FOR
DECENT FLYING CONDITIONS ALTHOUGH AN ISOLATED AFTERNOON AIRMASS
SHOWER OR THUNDERSTORM IS STILL POSSIBLE. NEXT FRONT APPROACHES
ON WEDNESDAY WITH MORE SHOWERS/STORMS DEVELOPING. THIS FRONT DOES
NOT APPEAR TO BE IN A BIG HURRY AND LOOKS TO BRING MVFR
CONDITIONS...POSSIBLY IFR AT NIGHT...TO TAF SITES FOR THE LATTER
HALF OF THE WEEK.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...NF
NEAR TERM...NF/PM
SHORT TERM...DS
LONG TERM...DS
AVIATION...AMS/PM