Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 021528
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1128 AM EDT THU JUL 2 2015

.SYNOPSIS...
A FRONTAL BOUNDARY WILL REMAIN DRAPED ACROSS THE AREA FOR THE
NEXT SEVERAL DAYS. THERE WILL BE SEVERAL WAVES OF LOW PRESSURE
PASSING ACROSS THE BOUNDARY KEEPING THE THREAT OF SHOWERS AND
THUNDERSTORMS IN OUR FORECAST THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1100 AM EDT THURSDAY...

EXPECT ISOLATED SHOWER COVERAGE EAST OF INTERSTATE 81 TO THE
PIEDMONT FOR A FEW HOURS...WITH MORE ORGANIZED ACTIVITY MOVING
INTO THE WV/FAR SW VA/NC MTNS AROUND NOON...THEN MOVING EWD
THROUGH THE AFTERNOON. A SMALL WINDOW OF SUNSHINE IN THE PIEDMONT
OF VA/NC WILL ACT TO DESTABILIZE THE AIRMASS...BUT MORE CLOUDS
THAN SUN WILL HOLD INSTABILITY TO A MINIMUM IN THE WEST.

WITH THIS UPDATE...CUT BACK POPS EARLY IN THE EASTERN THREE-
FOURTHS OF THE CWA...AND CUT BACK THUNDERSTORM COVERAGE AS WELL.

THE 06Z LOCAL WRF SEEMS TO HANDLE THE OVERALL PRECIP FIELD WELL
THIS MORNING...BRINGING MORE ORGANIZED SHOWERS/STORMS INTO THE
MTNS BY 18Z...AND SHIFTING IT EAST BY 20Z. THE LATEST NAM SHOWS
TWO DISTINCT HEAVIER BANDS OF CONVECTION HOWEVER...RADAR IS NOT
VERIFYING THE NAMS SOLUTION WELL.

THE STORM PREDICTION CENTER CONTINUES TO HIGHLIGHT THE ENTIRE
FORECAST AREA IN A MARGINAL RISK. GIVEN LACK OF INSTABILITY THE
THREAT OF SVR IS LOW. WILL HAVE TO WATCH THE PIEDMONT WHERE THERE
IS SUNSHINE TO SEE HOW UNSTABLE THE AIRMASS GETS BEFORE MORE
CLOUDS MOVE IN.

WILL ALSO BE MONITORING INTO LATE TODAY...TRAINING OF HEAVIER
SHOWERS/STORMS FOR FLOODING CONCERNS. AT THIS TIME...RAINFALL HAS
NOT BEEN HEAVY OR WIDESPREAD ENOUGH FOR ANY WATCHES.

PREVIOUS VALID DISCUSSION...

WE CONTINUE TO BE LOCKED IN TO THE SAME PATTERN WITH A LONG SERIES OF
SHORT WAVES MOVING THROUGH AN UPPER TROF OVER THE EASTERN US...AS AN
EAST TO WEST FRONTAL BOUNDARY STRETCHES ACROSS THE AREA. THIS WILL KEEP
OUR WEATHER QUITE UNSETTLED AND SHOWERS/STORMS CAN NOT BE RULED OUT AT
ANY TIME...THOUGH DIURNAL HEATING WILL KEEP THE BULK OF ACTIVITY BIASED
TO THE AFTERNOON/EVENING HOURS. WILL CONTINUE TO HIGHLIGHT THE
POTENTIAL FOR HEAVY PRECIPITATION AND POSSIBLE FLOODING ISSUES IN
THE HWO AND WAIT TO SEE IF A THREAT AREA REVEALS ITSELF WITH TIME.
AFTER A DOWNTURN IN ACTIVITY EARLY TONIGHT INDICATIONS ARE THAT
ANOTHER WAVE WILL BE SET TO MOVE THROUGH THE REGION LATE
TONIGHT/TOWARD DAYBREAK FRIDAY.

EXTENSIVE CLOUD COVER WILL HELP KEEP TEMPERATURES A FEW DEGREES COOLER
TODAY THAN YESTERDAY WITH LOW TO MID 80S FOR THE PIEDMONT/SOUTHSIDE AND
LOW TO MID 70S WEST OF THE BLUE RIDGE. LOWS TONIGHT REMAIN MILD WITH
UPPER 60S EAST TO LOWER 60S WEST.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 420 AM EDT THURSDAY...

BROAD TROUGHING AND NORTHWEST FLOW ALOFT REMAINS IN PLACE AT THE
BEGINNING OF THE PERIOD. A REMNANT MCS...MOST LIKELY IN THE FORM
OF WIDESPREAD LIGHT TO MODERATE RAIN AND EMBEDDED THUNDER APPEARS
LIKELY AT THE START OF THE DAY FRI...ONE OF TWO POTENTIAL
CONVECTIVE COMPLEXES OR THE REMNANTS OF SUCH TO DRIFT INTO THE
AREA FROM THE TN VALLEY. GIVEN TIME OF DAY...THREAT OF SEVERE
SHOULD BE LITTLE TO NONE. MAIN CONCERN WOULD BE HEAVY RAINFALL ON
TOP OF RAINFALL EXPECTED THU. MODEL AND WPC QPC AMOUNTS OVER THE
24-48 HOUR PERIOD ARE MOSTLY IN THE 1.5 TO 2.0 INCH RANGE...WHICH
SHOULD BE HANDLED WITHOUT ANY SIGNIFICANT PROBLEMS. LOCALIZED
PROBLEMS ARE ENTIRELY POSSIBLE...BUT THIS SHOULD LARGELY BE THE
RESULT OF COMBINED RAINFALL FROM THU INTO FRI MORNING RATHER THAN
NEW EVENTS FRI MORNING...GIVEN THE EXPECTED LACK OF HEAVIER
CONVECTION DURING THE MORNING.

BY AFTERNOON...WEAK SFC LOW PRESSURE DRIFTS TOWARD THE VA/MD COAST
AND THE BETTER THREAT FOR DIURNAL CONVECTION SHIFTS EAST WITH THE
MORNING MCS. HOWEVER...AMPLE MOISTURE REMAINS IN PLACE AND BROAD
TROUGHING ALSO REMAINS IN PLACE...WITH THE AXIS STILL TO THE WEST
ACROSS THE TN/OH VALLEY. WILL NEED TO KEEP AT LEAST CHANCE POPS
ALL AREAS...KEEPING THE HIGHER POPS EAST AND SOUTH. ANOTHER MCS
APPEARS LIKELY TO DEVELOP UPSTREAM LATE SATURDAY AND TRANSLATE
ACROSS MUCH OF THE SOUTHERN PART OF THE CWA SATURDAY NIGHT/SUNDAY
MORNING BEFORE THE UPPER TROUGH FINALLY WEAKENS AND BEGINS TO
DRIFT ESE INTO THE CAROLINAS...WHILE A SHORT WAVE RIDGE RIDES OVER
THE TOP OF THE TROUGH INTO THE OH VALLEY/PA REGION. THE FOCUS FOR
CONVECTION SUNDAY SHOULD BE MAINLY EAST-SOUTH OF THE BLUE RIDGE
AS DEEPER MOISTURE IS SHOVED SLIGHTLY SOUTHWARD.

OVERALL...AS NOTED YESTERDAY...POPS CANNOT BE REDUCED BEYOND
MENTIONABLE 15 PERCENT VALUES ANYTIME DURING THIS PERIOD.
HOWEVER...THE EXACT TRACK AND TIMING OF CONVECTIVE COMPLEXES OR
THE REMNANTS OF SUCH WILL REMAIN DIFFICULT TO DETERMINE AND WILL
ONLY BE RESOLVED NEAR THE EVENT AND ON THE MESOSCALE...NOT THE
SYNOPTIC SCALE LEVEL.

ABUNDANT CLOUD COVER AND LIMITED DAYTIME HEATING WILL HOLD MAX
TEMPS BELOW NORMAL. HOWEVER...HIGH HUMIDITY LEVELS/DEWPOINTS WILL
RESULT IN WELL ABOVE NORMAL MAX TEMPS.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 430 AM EDT THURSDAY...

A SURFACE BOUNDARY WILL STALL ACROSS THE CAROLINAS OVER THE
WEEKEND. MEANWHILE...THE TAIL END OF THE LONGSTANDING EASTERN
UPPER TROUGH WILL BECOME CUTOFF ACROSS SOUTHEAST VA/NORTH NC AND
SLOWLY DRIFT SOUTH INTO SOUTH CAROLINA. THE GFS ADVERTISES THIS TO
A MUCH GREATER EXTENT THAN THE OTHER MODELS. MEANWHILE...A SHORT
WAVE RIDGE DRIFTS OVER THE TOP OF THIS WEAK CUTOFF UPPER
LOW/TROUGH. CONVECTION SHOULD BECOME MUCH MORE DIURNAL IN NATURE
AS THE FAVORABLE MCS PATTERN OF THE CURRENT WEEK FADES GIVEN THE
CHANGE IN THE SYNOPTIC PATTERN AND AN END TO THE STRONG WNW-NW
FLOW ALOFT. AREAS SOUTH AND EAST OF THE BLUE RIDGE SHOULD SEE THE
BEST CHANCE OF CONVECTION THROUGH THIS PERIOD CLOSER TO THE
SURFACE BOUNDARY...UPPER LOW...AND DEEPER MOISTURE. BEYOND
MON...THE MODELS TO VARYING DEGREES DEPICT A COLD FRONT
APPROACHING THE REGION FROM THE NORTHWEST...THEN LIKELY STALLING
IN/NEAR THE REGION BY WED AS BROAD UPPER RIDGING DEVELOPS ACROSS
THE SOUTHERN STATES. THUS...WE ARE LEFT IN A CONTINUAL UNSETTLED
PATTERN. ANY DECREASE IN CONVECTION ACROSS THE CWA IN THE MON/TUE
TIME FRAME WILL BE FOLLOWED BY AN UPTICK IN SUCH BY WED.

TEMPERATURES SHOULD BE SLIGHTLY WARMER MON/TUE WITH DECREASED
CLOUD COVER AND HENCE GREATER INSOLATION. OVERALL...TEMPERATURES
SHOULD AVERAGE NEAR NORMAL FOR HIGHS...BUT CONTINUE TO BE QUITE A
BIT ABOVE NORMAL FOR MIN TEMPS GIVEN CONTINUED HIGH MOISTURE
CONTENT.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
AS OF 730 AM EDT THURSDAY...

DUE TO AN FAA RELATED OUTAGE...THE TAFS FOR LWB WILL NOT BE
AMENDED DUE TO MISSING OBSERVATIONS.

THE FIRST ROUND OF CLOUDS AND RAIN FROM AN UPSTREAM MCS DRIFTING
INTO THE REGION NOW. MOST SITES REPORTING -RA NOW AND CIGS
LOWERING INTO THE MVFR RANGE AT SEVERAL SITES...WITH VISIBILITIES
DROPPING INTO THE MVFR RANGE AT BCB/BLF/LWB. EXPECT -SHRA TO
CONTINUE TO INCREASE ACROSS THE REGION THROUGH THE EARLY
AFTERNOON. BY MID-AFTERNOON...THE NEXT CONVECTIVE COMPLEX OR
ASSOCIATED OUTFLOW/REMNANTS ARRIVE INTO THE CWA WITH AN INCREASING
THREAT FOR WIDESPREAD -SHRA...EMBEDDED TSRA...AND ASSOCIATED
MVFR-IFR CIGS/VSBYS. THUNDERSTORMS SHOULD DIMINISH AFTER 04Z-
06Z...BUT -SHRA WILL CONTINUE ALONG WITH PREVAILING MVFR
CIGS/VSBYS AND POCKETS OF IFR-LIFR CIGS/VSBYS BCB/LWB/BLF.
OVERALL...POOR AVIATION CONDITIONS EXPECTED THROUGH THE TAF VALID
PERIOD.

WINDS...LIGHT WSW-WNW THROUGH THE TAF VALID PERIOD AT SPEEDS OF
3-7KTS...OF COURSE VARIABLE AND POTENTIALLY GUSTY IN/NEAR
THUNDERSTORMS.

EXTENDED AVIATION DISCUSSION...

THE REGION WILL BE IN A GENERAL NORTHWEST FLOW PATTERN THROUGH
SATURDAY. WILL AGAIN SEE SHOWERS AND THUNDERSTORMS DEVELOP ON
FRIDAY AND SATURDAY AS SEPARATE SHORTWAVE TROUGHS PROGRESS ACROSS
THE FORECAST AREA WITHIN THE NORTHWEST FLOW.

VFR CONDITIONS ARE EXPECTED FOR MOST OF THE AREA MUCH OF THE
TIME. THE EXCEPTIONS WILL COME AS TEMPORARY DECREASES WITHIN ANY
HEAVIER RAIN SHOWERS OR THUNDERSTORMS...AND THEN LATE AT NIGHT AND
EARLY MORNING DUE TO RIVER OR MOUNTAIN VALLEY FOG...ESPECIALLY IN
AREAS THAT RECEIVED PRECIPITATION THE DAY BEFORE.

SUNDAY INTO MONDAY...WHILE UPPER LEVEL HEIGHTS RISE DURING THE
PERIOD...THERE REMAINS AN UPPER TROUGH MOVING OVER THE MID
ATLANTIC DURING THIS TIME...SO STORMS ARE NEVER OUT OF THE
FORECAST.

&&

.EQUIPMENT...
AN OUTAGE EXISTS WITH SOME FAA AUTOMATED OBSERVATIONS IN THE
AREA. THERE IS NO ESTIMATED TIME FOR RESTORATION.

&&

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

&&

$$
SYNOPSIS...MBS
NEAR TERM...MBS/WP
SHORT TERM...RAB
LONG TERM...RAB/RCS
AVIATION...MBS/NF/RAB/WP
EQUIPMENT...



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