National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 171958
AFDRNK

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

.SYNOPSIS...
-- Changed Discussion --
A COLD FRONT WILL CONTINUE TO MOVE SOUTH THIS EVENING AND
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 SATURDAY/...
-- Changed Discussion --
AS OF 400 PM EDT FRIDAY...

LATEST RADAR IMAGERY INDICATES SPOTTY SHOWER ACTIVITY THIS
AFTERNOON...MAINLY ACROSS THE MOUNTAINS...WITH ONLY A THUNDERSTORM
OR TWO IN THE MIX. WHERE WE HAVE BEEN OBSERVING THUNDERSTORMS
HOWEVER...A FEW HAVE BECOME STRONG ENOUGH TO PRODUCE SMALL
HAIL...SO WILL HAVE TO MONITOR THE INTENSITY OF ANY NEW STORMS
THROUGH THE EVENING NOW THAT WE ARE IN MAXIMUM DAYTIME HEATING.
JUST TO THE NORTH OF THE AREA...KEEPING AN EYE ON A COLD FRONT
WHICH HAS BEEN SINKING SLOWLY SOUTHWARD THROUGH THE DAY...AND IS
GETTING READY TO ENTER OUR NORTHERN TIER OF COUNTIES.

THROUGH THIS EVENING AND TONIGHT...WILL SEE SHOWERS AND A FEW
THUNDERSTORMS SPREAD TO THE PIEDMONTS AS THE FRONT ENTERS THE AREA
AND WINDSPEEDS ALOFT DIMINISH. EXPECT THAT THE ACTIVITY WILL
REMAIN PULSY IN NATURE...ALTHOUGH WOULD NOT BE SURPRISED TO SEE
MORE ORGANIZED DEVELOPMENT AHEAD OF THE FRONT FOR A FEW HOURS. NOT
THAT MUCH INSTABILITY FOR THESE STORMS TO WORK WITH...SO NOT
EXPECTING MUCH SEVERE ACTIVITY...ALTHOUGH CANNOT RULE OUT AT LEAST
ONE STRONG STORM. RAINFALL WILL DIMINISH IN COVERAGE HEADING INTO
THE EARLY HOURS OF SATURDAY...AND EXPECT TO SEE A FEW SHOWERS
LINGER THROUGH THE NIGHT AS AN UPPER TROUGH APPROACHES FROM THE
WEST...BUT COVERAGE WILL OVERALL DIMINISH. WITH THE SLIGHTLY
COOLER AND MORE STABLE AIR ENTERING THE PIEDMONTS BEHIND THE
FRONT...BELIEVE WE WILL SEE PATCHY FOG DEVELOP OVERNIGHT...
ESPECIALLY IN AREAS THAT RECEIVE RAINFALL THIS EVENING.

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 /SATURDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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.

&&

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

&&

$$
SYNOPSIS...NF
NEAR TERM...NF
SHORT TERM...DS
LONG TERM...DS
AVIATION...MBS