Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 262353
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
753 PM EDT WED AUG 26 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTROL OUR WEATHER TONIGHT INTO THURSDAY. AS
THE HIGH SHIFTS TO THE MID ATLANTIC...THE FLOW WILL TURN MORE
EASTERLY INCREASING MOISTURE OVER TIME INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 640 PM EDT WEDNESDAY...

THE CONVECTION EARLY THIS AFTERNOON ACROSS THE FAR SOUTHEAST
PORTION OF THE FORECAST AREA HAS DISSIPATED...STABILITY IS
INCREASING...AND SATELLITE SHOWS LESS ORGANIZED CUMULUS CLOUDS IN
THIS AREA. GIVEN THESE TRENDS...THE SLIGHT CHANCE OF SHOWERS AND
STORMS FOR THIS PART OF THE REGION HAS BEEN REMOVED FROM THE
FORECAST. THE REMAINDER OF THE FORECAST HAS BEEN LEFT UNCHANGED
EXCEPT FOR SOME MINOR ADJUSTMENTS TO THE TEMPERATURE AND DEW POINT
TRENDS BASED UPON THE LATEST OBSERVATIONS AROUND THE AREA.

AS OF 249 PM EDT WEDNESDAY...

18Z WSR-88D IMAGE SHOWED SOME ISOLATED STORMS FORMING IN THE THETA-E
RIDGE WITH CAPES FROM 500 TO 1000 J/KG. THE SPC MESOSCALE ANALYSIS
INDICATED LIS AROUND MINUS 1 ACROSS THE SOUTHEAST PORTIONS OF
FORECAST AREA. AN UPPER AIR DISTURBANCE ROTATING AROUND THE UPPER
TROF TRIGGERING SOME SHOWERS ACROSS NORTH CAROLINA THIS AFTERNOON
INTO TONIGHT. DECIDED TO ADD SOME ISOLATED POPS FOR CONVECTION IN
THE SOUTHEAST CORNER OF FORECAST AREA. ANY DIURNAL SHOWERS AND
THUNDERSTORMS WILL DIMINISH QUICKLY THIS EVENING.

A WEAK SHORTWAVE WILL PIVOT EAST ALONG THE UPPER TROUGH TONIGHT INTO
THURSDAY MORNING. AN AREA OF LOW PRESSURE OVER SOUTH CAROLINA WILL
RIDE NORTHWARD ALONG THE SOUTHEAST FRONTAL BOUNDARY TONIGHT INTO
THURSDAY. MEANWHILE...HIGH PRESSURE WILL BUILD INTO OUR REGION
TONIGHT INTO THURSDAY. LOW TEMPERATURES TONIGHT WILL BE COMFORTABLE
WITH READINGS FROM THE UPPER 40S IN THE COLDER MOUNTAIN VALLEYS TO
THE LOWER 60S IN THE PIEDMONT.

THE UPPER TROUGH WILL REMAIN ACROSS THE EAST COAST THURSDAY. A WEAK
SHORTWAVE WILL TRAVEL EAST ACROSS OUR REGION. ISOLATED SHOWERS AND
THUNDERSTORMS WILL DEVELOP ACROSS THE HIGH TERRAIN THURSDAY
AFTERNOON. HIGH TEMPERATURES THURSDAY WILL RANGE FROM THE UPPER 60S
IN THE MOUNTAINS TO THE MID 80S IN THE PIEDMONT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 230 PM EDT WEDNESDAY...

WEAK MID LEVEL TROUGH WILL LIFT OUT OF THE AREA THURSDAY NIGHT ALLOWING
BROAD RIDGING TO TAKE SHAPE FOLLOWED BY INCREASING 5H HEIGHTS TO START
THE WEEKEND. THIS MAY ALLOW FOR SOME ISOLATED CONVECTION TO PERSIST
INTO THURSDAY EVENING MAINLY MOUNTAINS BEFORE CUTTING TO PC OVERNIGHT.
MOISTURE REMAINS RATHER LIMITED ON FRIDAY AS GUIDANCE SHOWS A BUBBLE
HIGH JUST EAST OF THE MOUNTAINS AND VERY LITTLE INSTABILITY DESPITE
SOME INCREASE IN DEWPOINTS. SINCE LIFT IS QUITE LIMITED AND SEEING SOME
CAPPING ALOFT...GOING WITH ONLY ANOTHER ROUND OF ISOLATED MOUNTAIN
CONVECTION WHILE KEEPING THINGS DRY ELSEWHERE INTO FRIDAY EVENING.

UPPER RIDGING OFFSHORE WILL START TO DOMINATE BY SATURDAY WITH A BETTER
TAP OF MORE TROPICAL TYPE MOISTURE ADVECTION FROM THE SOUTH ESPECIALLY
ALONG THE MOUNTAIN CHAIN WHERE LOW LEVEL SE FLOW WILL PREVAIL. THIS
ALONG WITH HEATING SHOULD HELP DEVELOP A LITTLE MORE INSTABILITY WHICH
AIDED BY LIKELY DIFFERENTIAL HEATING FROM OVERNIGHT CLOUDS MAY RESULT
IN A BIT BETTER COVERAGE OF AT LEAST SHALLOW SHRA/TSRA SATURDAY
AFTERNOON. THEREFORE RUNNING WITH SLIGHTLY HIGHER CHANCE/SLIGHT POPS
LATE SATURDAY ESPECIALLY BLUE RIDGE AND POINTS WEST.

TEMPS TO MAKE A SLOW RECOVERY TO MORE SEASONAL LEVELS THROUGH THE
PERIOD WITH HIGHS MOSTLY UPPER 70S WEST TO MID 80S EAST.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1240 PM EDT WEDNESDAY...

UPPER LEVEL RIDGING ACROSS THE EAST WILL GET SPLIT OVER THE WEEKEND
INTO EARLY NEXT WEEK AS MIDWEST SHORTWAVE ENERGY DROPS SE CREATING A
WEAKNESS/SHEAR AXIS OVER AND JUST WEST OF THE MOUNTAINS THROUGH MONDAY.
THIS WILL ALLOW A GRADUAL TURN TO MORE SOUTHERLY FLOW INTO NEXT WEEK
WITH HIGHER PWATS RETURNING NORTH. HOWEVER THIS WILL OCCUR WITHIN BROAD
SURFACE RIDGING WITH THE CENTER OF THE HIGH CENTERED ABOUT OVERHEAD
THROUGH MOST OF THE PERIOD. SOME SOLUTIONS ALSO CONTINUE TO ENTERTAIN A
PLUME OF DEEPER MOISTURE GETTING ADVECTED BACK INLAND FROM THE RESIDUAL
FRONT NEAR THE COAST AND UNDER THIS COOL POCKET ALOFT BY SUNDAY. THIS
ALSO PERHAPS IN AN AXIS OF CONVERGENCE WELL NORTH OF ERIKA OFF THE
FLORIDA COAST SO KEEPING BEST CHANCE POPS SUNDAY AFTERNOON INTO MONDAY.
THIS MAINLY FOR DIURNAL OROGRAPHIC DRIVEN CONVECTION BUT GIVEN PROGGED
WEAK INSTABILITY AND WEAK UPPER DIFFLUENCE AHEAD OF THE UPPER LOW TO
THE WEST...COULD BE MORE WIDESPREAD IF A WEAK WAVE DOES SLIDE UP FROM
THE SOUTHEAST. UPPER RIDGING TO STRENGTHEN AGAIN BY MID WEEK AIDED BY
SUBSIDENCE TO THE NORTH PER THE PROBABLE ARRIVAL OF ERIKA OVER FLORIDA.
THUS WILL KEEP MORE ISOLATED MOUNTAIN CONVECTION FOR TUESDAY INTO
WEDNESDAY WITH HIGHER HEIGHTS IN PLACE. OTHERWISE WILL BE RETURNING TO
QUITE A WARM/MUGGY SCENARIO THROUGH THE PERIOD WITH HIGHS MOSTLY 80S
AND POSSIBLY NEAR 90 SE...AND LOWS MOSTLY IN THE 60S.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 745 PM EDT WEDNESDAY...

GENERALLY VFR CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD.
THE ONLY EXCEPTION WILL BE LATE NIGHT/EARLY MORNING FOG POTENTIAL.

SYNOPTIC SCENARIO FEATURES A STALLED FRONTAL BOUNDARY/TROUGH ALONG
THE SC/NC COAST WITH AN UPPER TROUGH LINGERING ACROSS THE
NORTHEAST U.S. SURFACE HIGH PRESSURE WAS DRIFTING SLOWLY EAST
ACROSS THE OH VALLEY...PROVIDING A LIGHT NW-NNW FLOW ACROSS THE
REGION THIS AFTERNOON. MOISTURE TRAPPED IN THE 050-060 FT RANGE
REMAINS IN PLACE...WHICH GIVEN DIURNAL HEATING...RESULTS IN
SCATTERED CUMULUS DEVELOPMENT. SURFACE HIGH WILL DRIFT TO CENTRAL
PA BY THU EVENING...ALLOWING WINDS TO BEGIN TO COME AROUND TO THE
NE-E INTO THU AFTERNOON. THE COASTAL TROUGH WILL EDGE VERY SLOWLY
INLAND LATE IN THE WEEK AS HIGH PRESSURE ALOFT BUILDS ACROSS THE
WESTERN ATLANTIC. THE UPPER TROUGH ACROSS THE NORTHEAST WILL
DISSIPATE AND LIFT NORTHEAST OF THE REGION. EXPECT MAINLY A DRY
AIR MASS TO REMAIN ACROSS OUR REGION UNTIL THE WEEKEND...WHEN THE
COASTAL TROUGH DRIFTS BACK INLAND AND TROPICAL MOISTURE...POSSIBLY
IN THE FORM OF REMNANTS FROM DANNY...ARE DRAWN NORTHWARD FROM THE EASTERN
GULF REGION.

CUMULUS WILL DISSIPATE AFTER SUNSET EAST OF THE ALLEGHANY FRONT.
LINGERING UPSLOPE STRATOCUMULUS ACROSS EASTERN WV WILL ALSO
DIMINISH AFTER SUNSET AS SURFACE WINDS BECOME LESS ORTHOGONAL.
DEWPOINTS HAVE CREPT UPWARD SEVERAL DEGREES TODAY...ESPECIALLY
EAST OF THE BLUE RIDGE. THIS COMBINED WITH RADIATIONAL COOLING
WILL LIKELY PROMOTE GREATER FOG DEVELOPMENT LATE TONIGHT/EARLY
THU. HAVE INCLUDED POTENTIAL FOR LIFR AT LWB AND IFR AT BCB. FEEL
RELATIVELY DRY NE FLOW WILL PREVENT FOG DEVELOPMENT AT LYH/DAN.
WITH INCREASING MARITIME FLOW AND ASSOCIATED INVERSION...GREATER
POTENTIAL FOR BKN040-060 CIGS THU AFTERNOON...ESPECIALLY EAST OF
THE ALLEGHANYS.

WINDS NW-NNW 5KTS OR LESS THIS EVENING...BECOMING NE 6-9KTS THU
MORNING.

MEDIUM TO HIGH CONFIDENCE IN CEILINGS THROUGH THE TAF VALID
PERIOD.
HIGH CONFIDENCE IN VISIBILITIES...EXCEPT MEDIUM CONFIDENCE IN THE
08Z-13Z TIME FRAME THU MORNING.
MEDIUM TO HIGH CONFIDENCE IN WIND SPEED AND DIRECTION THROUGH THE
TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...

EXPECT A MAINLY VFR FORECAST INTO SUNDAY. MOISTURE GRADUALLY
INCREASES BY THE WEEKEND WITH ISOLATED TO SCATTERED CONVECTION
POSSIBLE...WITH BRIEF PERIODS OF MVFR CIGS/VSBYS POSSIBLE.
TYPICAL LATE NIGHT/EARLY MORNING FOG THREAT AT LWB/BCB/LYH THROUGH
THE PERIOD.

&&

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

&&

$$
SYNOPSIS...KK/WP
NEAR TERM...DS/KK
SHORT TERM...JH
LONG TERM...JH
AVIATION...KK/RAB/WP


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