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000
FXUS61 KRNK 181522
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1122 AM EDT SAT MAY 18 2013

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM EDT SATURDAY...

WEAK HIGH PRESSURE REMAINS WEDGED AGAINST THE EASTERN FACE OF THE
APPALACHIANS THIS MORNING...WHILE AN UPPER LEVEL TROUGH APPROACHES
FROM THE WEST. ONE DISTURBANCE ROTATING AROUND THE BASE OF THE
TROUGH HAS TRIGGERED WIDESPREAD SHOWER ACTIVITY ACROSS THE
MOUNTAINS AND FOOTHILLS OF NORTH CAROLINA INTO THE MOUNTAIN
EMPIRE...AND EXPECT THIS ACTIVITY TO SPREAD ACROSS THE MOUNTAINS
THROUGH THE AFTERNOON. WILL BE MONITORING THIS ROUND OF RAIN FOR
ANY POTENTIAL FOR INTENSIFICATION OR TRAINING...BUT SO FAR THERE
HAVE BEEN NO PROBLEMS REPORTED. CLOUD COVER HAS REMAINED
WIDESPREAD THROUGH THE MORNING...WHICH HAS KEPT A LID ON
INSTABILITY...BUT WILL STILL BE LOOKING FOR AN INCREASE OF SHOWER
ACTIVITY BY EARLY AFTERNOON AS DAYTIME HEATING INCREASES.

STILL MAINTAINING EARLIER CONCERNS FOR THE POSSIBILITY OF HEAVY
RAIN...AND POTENTIAL FLOODING FOR TONIGHT THROUGH THE BEGINNING OF
THE WORKWEEK...AS ROUNDS OF RAINFALL ASSOCIATED WITH THE
APPROACHING UPPER LEVEL TROUGH PASS ACROSS THE AREA. CURRENTLY
OBSERVING A STALLED FRONT SITUATED ACROSS CENTRAL VIRGINIA. SURFACE
WINDS REMAIN FROM THE EAST...BUT WINDS A FEW THOUSAND FEET OFF THE
SURFACE ARE OUT OF THE SOUTH. THIS FRONT WILL SERVE AS LOW LEVEL
SUPPORT FOR RAINFALL AS UNSTABLE AND VERY MOIST AIR LIFTING OVER
THIS BOUNDARY WILL TRANSFORM INTO SHOWERS AND THUNDERSTORMS IN
THE EAST THROUGH SUNDAY MORNING.

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
REMAINS EXCEPTIONALLY HIGH BETWEEN 00Z/8PM TONIGHT AND 12Z/8AM
SUNDAY. ALREADY HAVE A FLASH FLOOD WATCH IN THE NORTH CAROLINA
MOUNTAINS INTO THE MOUNTAIN EMPIRE...AND AM STILL DEBATING THE
NEED AND THE LOCATION FOR A FLOOD WATCH FURTHER TO THE EAST.

CLOUDS WILL LIMIT WARM UP TODAY IN ALL BUT THE FAR SOUTHEAST PART
OF THE FORECAST AREA...WHERE VISIBLE SATELLITE IMAGERY INDICATES
THINNING IN THE CLOUD COVER. 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.

&&

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

SHORTWAVE 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 SHORTWAVE 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.

&&

.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 /15Z SATURDAY THROUGH WEDNESDAY/...
AS OF 745 AM EDT SATURDAY...

PATCHES OF IFR FOG AND IFR CEILINGS...MAINLY EAST OF THE BLUE
RIDGE WILL DISSIPATE BY MID MORNING.

A SHORT WAVE CROSSING SLOWLY OVER THE SOUTHERN APPALACHIANS TODAY
WILL TRIGGER WIDESPREAD SHOWERS AND THUNDERSTORMS THIS AFTERNOON
AND EVENING. HIGH CONFIDENCE 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...
VA...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR VAZ009-015.
NC...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR NCZ001-002-018.
WV...NONE.

&&

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