Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 252334
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
734 PM EDT FRI JUL 25 2014

.SYNOPSIS...
WEAK HIGH PRESSURE WILL REMAIN OVER THE AREA TONIGHT BEFORE
SLIDING OFFSHORE THE SOUTHEAST COAST ON SATURDAY. A STRONG COLD
FRONT WILL APPROACH FROM THE NORTHWEST SUNDAY AND PASS ACROSS THE
REGION SUNDAY NIGHT INTO MONDAY. COOL HIGH PRESSURE SETTLES IN
BEHIND THE FRONT LATER MONDAY RESULTING IN COOLER AND DRIER
WEATHER INTO THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 730 PM EDT FRIDAY...

ISOLATED -SHRA POPPED ALONG THE EAST FACING SLOPES OF THE BLUE RIDGE
FROM WATAUGA NORTHEASTWARD TO FLOYD. DEWPOINT DISCONTINUITY AND
DIFFERENTIAL HEATING ALONG WITH CONTINUED CYCLONIC FLOW ALOFT ENOUGH
TO SUPPORT SUCH. SINCE THIS ACTIVITY IS THRIVING ALMOST ENTIRELY ON
DAYTIME HEATING AND THERE IS LITTLE AMBIENT INSTABILITY...EXPECT
THIS ACTIVITY TO DISSIPATE QUICKLY WITHIN AN HOUR OF SUNSET.
OTHERWISE...WILL MAINTAIN NON-MENTIONABLE POPS ELSEWHERE AND ACROSS
THE ENTIRE CWA AFT 03Z. ONLY MINOR CHANGES TO TEMPS/DEWPOINTS TO
BRING INTO LINE WITH CURRENT OBSERVATIONS.


AS OF 330 PM EDT FRIDAY...
TRANQUIL AND DRY CONDITIONS EXPECTED THE NEXT 24 HOURS AS HIGH
PRESSURE REMAINS IN CONTROL OVERNIGHT AND INTO SATURDAY. OVERNIGHT
TEMPS WILL BE CLOSE TO LATE JULY NORMALS WITH UPPER 50S FAR NW TO
MID-60S SE AND GENERALLY CLEAR SKIES. PATCHY FOG POSSIBLE IN SOME
OF THE WETTER LOCATIONS BUT NOT EXPECTING WIDESPREAD EARLY MORNING
FOG WITH SOME MID-LEVEL CLOUDS POSSIBLY INHIBITING FORMATION.

THE HIGH QUICKLY SHIFTS EAST ON SATURDAY WITH A WARM FRONT SURGING
NORTH OF THE AREA AND A BROAD WEST TO SOUTHWEST FLOW DEVELOPING AT
LOW TO MID-LEVELS ALONG WITH INCREASING HUMIDITY. DEWPOINTS WILL
RISE INTO L/M 60S BY AFTERNOON ACROSS MUCH OF THE AREA AND TEMPS
ALSO WARM BY ABOUT 5F OR SO FROM TODAYS HIGHS...RANGING FROM NEAR 80
NW TO NEAR 90 SE. SUPPORT FOR AFTERNOON CONVECTION APPEARS WEAK
AS FAIRLY STRONG CAP EXPECTED TO BE IN PLACE BETWEEN 850-800 MB
AND NO TRIGGER ACROSS THE REGION...KEPT POPS OUT THROUGH THE
PERIOD.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 215 PM EDT FRIDAY...

WEAK RIDGING WILL CONTINUE TO BREAK DOWN SATURDAY NIGHT IN ADVANCE
OF HEIGHT FALLS TO THE NW IN ASSOCIATION WITH THE DEVELOPING
UPSTREAM TROUGH AND COLD FRONT. MOISTURE APPEARS LACKING SATURDAY
EVENING EXCEPT ACROSS THE FAR NORTH WITH ANY UPSTREAM SHRA/TSRA
LIKELY NOT MAKING A RUN AT THE FAR NW UNTIL LATE AT NIGHT. THUS
REMOVED POPS SATURDAY EVENING AND THEN KEPT A SHARP GRADIENT TO
LIKELY POPS EXTREME NW AS A PROBABLE COMPLEX OF STORMS MOVES IN
FROM THE OHIO RIVER. WITH GUIDANCE SHOWING THE BEST JET ALOFT AND
THETA-E STILL WELL WEST DID SLOW DOWN ARRIVAL OF POPS UNTIL
AROUND DAYBREAK ALTHOUGH MAY BE MORE LIKE A SURGING OUTFLOW OF
WIND GIVEN TIMING PER LACK OF FORECAST INSTABILITY.

MAIN CONCERN REMAINS ON SUNDAY WITH THIS AFOREMENTIONED MCS
POTENTIAL EARLY AND THEN ADDED DEVELOPMENT OF AT LEAST STORM
CLUSTERS ESPCLY NORTH AND WEST UNDER A PASSING STRONG WAVE TO THE
NORTH. HOWEVER MODELS REMAIN RELUCTANT TO BRING ORGANIZED
CONVECTION OVER THE WESTERN MOUNTAINS AND INTO DEEP WESTERLY FLOW
WELL AHEAD OF THE COLD FRONT TO THE NW. BEST INSTABILITY ALSO
STAYS OFF TO THE NORTH/WEST AND THEN DEVELOPS TO THE SW WHERE MAY
SEE THE INITIAL MCS MOVE TOWARD...OR ANOTHER DEVELOP SUNDAY
AFTERNOON/EVENING BEHIND THE INITIAL IMPULSE PER LATEST 12Z ECMWF.
DOES APPEAR GIVEN THE STRONG FLOW ALOFT THAT SOME OF THE
CONVECTION COULD MOVE FASTER THAN EXPECTED INTO THE WEST SUNDAY
MORNING AND THEN REDEVELOP WITH HEATING UNDER THE PASSING TAIL OF
THE VERY STRONG MID LEVEL JET JUST NORTH SUNDAY AFTERNOON. SINCE
THINK GUIDANCE TOO DRY...STAYED WITH LIKELY/CAT POPS NW THIRD
SUNDAY AND INCLUDED CHANCE COVERAGE ELSW WITH INCLUSION OF GUSTY
WINDS NW. TEMPS WILL SURGE SUNDAY PROVIDED CAN BURN OFF EARLY
DEBRIS CLOUDS WITH HIGHS LIKELY LOW/MID 90S EAST AND 80S WEST AS
DEEP WEST/SW FLOW PUNCHES 85H TEMPS TO AROUND +25C.

UNCERTAINTY CONTINUES SUNDAY NIGHT INTO MONDAY WITH LATEST MODEL
TRENDS TO LINGER CONVECTION WESTERN SLOPES SUNDAY EVENING BEFORE
JUMPING TO THE EASTERN LEE TROUGH OVERNIGHT BEFORE COVERAGE FADES.
ONCE THIS HAPPENS THE ACTUAL FRONT MAY BLEND INTO THE LEE
TROUGH...AND CAUSE A SURGE IN DRIER AIR ALOFT ON MORE OF A NW
TRAJECTORY...IN TURN LIMITING POPS TO MORE OF THE FAR WEST AND SE
INTO MONDAY AFTERNOON. SINCE THIS SCENARIO SIMILAR TO THE LATEST
ECMWF...ADJUSTED POPS DOWN SOME ON MONDAY WITH A SPLIT IN
COVERAGE ALONG THE BLUE RIDGE WHERE COULD GO MOSTLY DRY AFTER
SUNDAY NIGHT. ENOUGH COOL ADVECTION TO KEEP HIGHS IN THE 70S WEST
OF THE BLUE RIDGE MONDAY WITH STILL 80S TO NEAR 90 EAST.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 1245 PM EDT FRIDAY...

COLD FRONT ALONG THE LEADING EDGE OF THE LARGE 5H TROUGH FOR LATE
JULY WILL BE WELL TO THE EAST BY MONDAY NIGHT ALLOWING STRONG
COOL ADVECTION TO CONTINUE AS HIGH PRESSURE BUILDS IN FROM THE NW.
MAY SEE SOME UPSLOPE SHOWERS PERSIST MONDAY EVENING AT THE ONSET
OF THE BETTER COOLING ALOFT AND NW FLOW SO WILL KEEP SOME LOW POPS
FAR WEST EARLY. OTRW SHOULD BE DRYING OUT WITH A SIGNIFICANT COOL
SHOT THAT WILL PERSIST FOR MUCH OF THE WEEK.

MODELS DO BRING A COUPLE RE-ENFORCING SHORTWAVES AROUND THE UPPER
TROUGH LATE IN THE PERIOD WITH THESE PIVOTING THROUGH THE REGION
THURSDAY INTO FRIDAY. HOWEVER MOISTURE LIMITED UNDER THE CONTINUED
WEAK RIDGING WITH POPS MAINLY DRIVEN BY COLD AIR ALOFT AND WEAK
LOCAL CONVERGENCE MAINLY MOUNTAINS. THUS INCLUDING SOME SLIGHT
POPS LATER THURSDAY AND A BIT MORE CHANCE COVERAGE FRIDAY WITH A
SECOND STRONGER MID LEVEL WAVE THAT LOOKS TO SHARPEN UP THE TROUGH
A LITTLE MORE.

BELOW NORMAL TEMPS THE MAIN ASPECT OF NEXT WEEK WITH HIGHS LIKELY A
GOOD 5-10 DEGREES BELOW AVERAGE MUCH OF THE PERIOD AND LOWS DIPPING
INTO THE 40S AND 50S. COLDEST MORNINGS LOOK TO BE WEDNESDAY AND
THURSDAY WHEN THE SURFACE RIDGE WILL BE NEARBY AND 85H TEMPS REMAIN
AROUND +10C OVER THE WEST. THIS COULD PRODUCE SOME RECORD LOWS WITH
COOP MOS DATA GIVING DEEP VALLEY READINGS WELL DOWN INTO THE 40S.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AS OF 730 PM EDT FRIDAY...

MAINLY VFR CONDITIONS PREVAILING ACROSS THE REGION THIS EVENING WITH
SCATTERED TO BROKEN FAIR WEATHER CUMULUS CLOUDS...GENERALLY 3 TO
6KFT. SOME INSTABILITY UPSLOPE MVFR CLOUDS AND LIGHT SHOWERS ARE
OVER THE NORTH CAROLINA HIGH COUNTY BUT WILL FADE THROUGH THE
EVENING WITH LOSE OF HEATING. LINGERING MOISTURE WILL LIKELY GET
TRAPPED UNDER A SUBSIDENCE INVERSION OVERNIGHT WITH CEILINGS IN
THE 2-4KFT RANGE FOR AREAS ALONG AND EAST OF THE BLUE RIDGE.
DOWNSLOPE EASTERLY FLOW WILL KEEP WESTERN SLOPES CLEAR MOST OF THE
NIGHT...WITH IFR FOG POSSIBLE BY SUNRISE...LIFR IN MOUNTAIN
VALLEYS.

EXTENDED AVIATION DISCUSSION...

EXPECT MAINLY VFR THROUGH SUNDAY EXCEPT FOR OVERNIGHT FOG IN THE
VLYS OF LWB/BCB. ANOTHER FRONT IS GOING TO ARRIVE BY MONDAY.
BEFORE THIS SEVERAL DISTURBANCES IN NW FLOW ALOFT MAY BRING
SHRA/TSRA TO THE BLF/LWB CORRIDOR. SATURDAY IS LESS LIKELY AS
MODELS FAVOR A NWD TREND IN CONVECTION TOWARD PA/NRN VA. SUNDAY
COULD BE MORE FAVORABLE...BUT STILL LOOKS LIKE A NWD TRACK. WILL
HAVE TO WATCH HOW THIS DEVELOPS...BUT POTENTIAL FOR SUB VFR
SHRA/TSRA IN THE MTNS IS POSSIBLE LATE THIS WEEKEND. BETTER THREAT
WILL BE WITH THE FRONT MONDAY WITH UPPER TROUGH MOVING ACROSS BY
TUESDAY DRYING THINGS OUT.

&&

.HYDROLOGY...
AS OF 330 PM EDT THURSDAY...

RAINFALL YESTERDAY FELL MAINLY EAST OF THE INCREASINGLY DRY AREAS
OF THE NEW RIVER VALLEY INTO THE UPPER JAMES BASINS. U.S. DROUGHT
MONITOR ISSUED YESTERDAY AND VALID AS OF 12Z TUESDAY JULY 22
SHOWED EXPANSION OF THE EXISTING ABNORMALLY DRY CONDITIONS INTO
MOST OF OUR SE WV COUNTIES AND FAR WESTERN VA...MAINLY THE UPPER
JAMES RIVER BASIN. 30-DAY RAINFALL DEFICITS IN MUCH OF THIS AREA
ARE RUNNING 2 TO 3 INCHES OR ONLY 25 TO 50 PERCENT OF NORMAL AND
60-DAY RAINFALL NUMBERS NOT MUCH BETTER. JULY IS CLIMATOLOGICALLY
THE WETTEST MONTH IN OUR CWA WITH AN AVERAGE RANGING FROM 4 TO 5
INCHES.

&&

.CLIMATE...
RAINFALL YESTERDAY (7/24) AT LYNCHBURG AIRPORT OF 3.88 INCHES WAS
2ND HIGHEST ON RECORD AFTER JULY 24 1916 WHEN 4.03 INCHES FELL.
IT WAS ALSO THE 2ND HIGHEST FOR ANY JULY DAY. WILL ISSUE PNS
(WBCPNSRNK) WITH A FEW MORE DETAILS ON THIS UNUSUAL EVENT.

&&

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

&&

$$
SYNOPSIS...JH/WP
NEAR TERM...PC/RAB
SHORT TERM...JH
LONG TERM...JH
AVIATION...PC/RCS
HYDROLOGY...PC
CLIMATE...PC


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