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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 180927
AFDRNK

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

.SYNOPSIS...
-- Changed Discussion --
A FRONT EXTENDED FROM CENTRAL OHIO INTO NORTHEAST NORTH CAROLINA
THIS MORNING. THIS FRONT WILL DRIFT SOUTHEAST AND REMAIN ACROSS
THE MID ATLANTIC REGION THROUGH SUNDAY NIGHT. BY TUESDAY LOW
PRESSURE OVER THE MISSISSIPPI VALLEY WILL PUSH THE FRONT NORTH
OUT OF THE REGION.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 445 AM EDT SATURDAY...

SEVERAL FACTORS INDICATE AN INCREASED RISK OF FLOODING TODAY AND
TONIGHT. FLASH FLOOD GUIDANCE EAST OF THE BLUE RIDGE IS STILL
ABOVE 2.00 INCHES PER 3 HOURS. HOWEVER...SOME LOCATIONS FROM
CENTRAL PITTSYLVANIA COUNTY INTO EASTERN APPOMATTOX AND SOUTHERN
BUCKINGHAM COUNTY HAD MORE 1.5 TO 2.5 INCHES OF RAIN ON FRIDAY AND
FRIDAY NIGHT. IN THE MOUNTAINS FLASH FLOOD GUIDANCE RANGES FROM
1.5 TO 2.5 INCHES IN THREE HOURS.

SCATTERED SHOWERS REMAINED OVER AMHERST...APPOMATTOX AND
BUCKINGHAM COUNTIES EARLY THIS MORNING. ASIDE FROM THIS AREA AND A
ISOLATED SHOWERS IN SUMMERS AND GREENBRIER COUNTY WEST
VIRGINIA...MUCH OF THE FORECAST AREA WILL HAVE A BREAK IN THE RAIN
THIS MORNING.

A SURFACE FRONT WAS OVER THE EASTERN COUNTY WARNING AREA. BOUNDARY
SHOWED UP BEST IN THE LIFTED INDEX AND DEW POINT ANALYSIS.SURFACE
WINDS ARE OUT OF THE EAST...BUT JUST ABOVE THE SURFACE WINDS ARE
OUT OF THE SOUTH. UNSTABLE AND VERY MOIST AIR LIFTING OVER THIS
BOUNDARY WILL MAINTAIN A CHANCE OF SHOWERS AND THUNDERSTORMS IN
THE EASTERN COUNTY WARNING AREA THROUGH SUNDAY MORNING.

A SHORT WAVE OVER CENTRAL TENNESSEE WILL MOVE SLOWLY EAST TODAY.
SHOWERS AND THUNDERSTORMS WILL FILL IN OVER THE CENTRAL
APPALACHIANS IN RESPONSE TO THIS FEATURE BY THIS AFTERNOON AND
WILL CONTINUE FOR MUCH OF TONIGHT.

PLUS SATELLITE PICTURES SHOWED A BREAK IN THE CLOUD COVER OVER
CENTRAL AND EASTERN NORTH CAROLINA. EXPECT THE SOUTHERN COUNTY
WARNING AREA TO GET SOME SUN THIS MORNING. THIS WILL INCREASE THE
INSTABILITY BY THE TIME SHOWERS AN THUNDERSTORMS FORM THIS
AFTERNOON.

PRECIPITABLE WATER VALUES IN THE EASTERN FORECAST AREA WILL REACH
AROUND 1.75 INCHES WHICH IS 2 STANDARD DEVIATIONS...WELL
ABOVE...NORMAL. PRECIPITATION POTENTIAL PLACEMENT ON BOTH THE NAM
AND GFS IS EXCEPTIONALLY HIGH BETWEEN 00Z/8PM TONIGHT AND 12Z/8AM
SUNDAY. SO IN MOUNTAINS AREAS THAT HAD HIGHER RAINFALL AMOUNTS ON
FRIDAY HAVE ISSUED A FLASH FLOOD WATCH.

CLOUDS WILL LIMIT WARM UP TODAY IN ALL BUT THE FAR SOUTHEAST PART
OF THE FORECAST AREA. USE BIAS CORRECTED MET GUIDANCE AND LATEST
GRIDDED LAMP GUIDANCE FOR HIGHS TODAY. DEW POINTS INTO THE LOWER
60S WILL KEEP MINIMUM TEMPERATURES MILD TONIGHT.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
AS OF 319 AM EDT SATURDAY...

SHRTWV THAT CAUSED SO MUCH TROUBLE ACROSS TEXAS ARRIVES IN A
WEAKENED FORM ON SUNDAY...SLOWLY MOVING ACROSS THE REGION.
CONSIDERING THE RAIN THAT FELL OVER THE PAST 24 HOURS...AND
ADDITIONAL RAINFALL ON SATURDAY...A FLASH FLOOD WATCH MAY BE NEEDED
FOR THE VIRGINIA PIEDMONT AND ALSO NW NC FOR SUNDAY. MODELS ARE
SIMILAR TO YESTERDAY`S RUNS WHICH ELEVATED PWATS ABOVE 1.5" ACROSS
THE VIRGINIA PIEDMONT. PATTERN RECOGNITION WOULD SUGGEST AT LEAST
SOME WATER PROBLEMS DEVELOP...AS UPSLOPE FLOW...NEARBY BACKDOOR
BOUNDARY AND ARRIVING SHRTWV HAVE LED TO ISSUES IN THE PAST. WEAK
MBE VELOCITIES SUGGEST SLOW MOVERS AND/OR BACKBUILDERS. WITH THE
WAVE MOVING EAST WITH SOME SINKING MOTION/SOME DRIER AIR AT
H7...EXPECTING LESS COVERAGE ON MONDAY...BUT THERE WILL REMAIN THE
CHANCE FOR ELEVATED CONVECTION ALONG THE BLUE RIDGE DURING PEAK
HEATING. HIGHEST POPS WILL BE ALONG AND EAST OF THE BLUE RIDGE
MONDAY. RELATIVE POP MINIMUM FOR EXTREME WESTERN VA AND SE WEST VA.
TUESDAY LOOKS TO BE THE WARMEST AND DRIEST DAY OF THE SHORT TERM
FORECAST WITH H5 HEIGHTS RISING THANKS TO A DIGGING MIDWEST TROUGH.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY 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 /09Z SATURDAY THROUGH WEDNESDAY/...
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.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
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VA...FLASH FLOOD WATCH FROM NOON EDT TODAY THROUGH SUNDAY MORNING
     FOR VAZ009-015.
NC...FLASH FLOOD WATCH FROM NOON EDT TODAY THROUGH SUNDAY MORNING
     FOR NCZ001-002-018.
WV...NONE.
-- End Changed Discussion --

&&

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