Area Forecast Discussion
Issued by NWS Blacksburg, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KRNK 291932
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
332 PM EDT TUE JUL 29 2014

.SYNOPSIS...
AN UPPER LEVEL TROUGH OF LOW PRESSURE AND A DRY...COOL AREA OF
SURFACE HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH
WEDNESDAY. FROM THURSDAY INTO THE WEEKEND...THE UPPER TROUGH WILL
RETROGRADE WEST TOWARD THE MISSISSIPPI RIVER VALLEY. THIS WILL
ALLOW FOR ATLANTIC MOISTURE TO MAKE ITS WAY BACK INTO THE AREA AND
BRING AN INCREASE OF SHOWERS AND STORMS.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 245 PM EDT TUESDAY...

AN UPPER LEVEL LONGWAVE TROUGH WAS STILL CENTERED OVER THE REGION.
SURFACE HIGH PRESSURE WAS ALSO CENTERED OVER THE AREA AND IS
EXPECTED TO STRENGTHEN OVERNIGHT. A SHORTWAVE IS PROGRESSING THROUGH
THE MAIN LONGWAVE PATTERN AND IS CURRENTLY CROSSING THE AREA OF
OH/PA/MD/WV. THIS FEATURE ALONG WITH DAYTIME HEATING MAY STILL HELP
PRODUCE SOME ADDITIONAL ISOLATED SHOWERS THE REMAINDER OF THIS
AFTERNOON THAT WILL LAST TO JUST PRIOR TO SUNSET. MOST AREAS WILL BE
PRECIPITATION-FREE. OVERNIGHT...DRIER AIR WILL CONTINUE TO FILTER
INTO THE REGION. THIS WILL HELP LIMITED OVERNIGHT FOG DEVELOPMENT TO
A SHORT PERIOD TOWARDS DAYBREAK...MAINLY IN SOME OF THE DEEPER
MOUNTAIN VALLEY AND SOME OF THE RIVER VALLEY. ANY FOG THAT DEVELOPS
LATE TONIGHT SHOULD BURN OFF QUICKLY WEDNESDAY MORNING. LOW
TEMPERATURES TONIGHT WILL RANGE FROM THE UPPER 40S TO LOWER 50S
ACROSS THE MOUNTAINS TO THE MID 50S ACROSS THE PIEDMONT. SOME AREAS
ARE EXPECTED TO REACH OR BE NEAR RECORD LOW READINGS. SEE THE
CLIMATE SECTION OF THIS DISCUSSION FOR DETAILS.

FOR WEDNESDAY...WE EXPECT A SIMILAR DAY BUT WITH TEMPERATURES
RECOVERING A BIT HIGHER. LOWER 80S FOR HIGHS WILL BE COMMON ACROSS
THE PIEDMONT...WITH A MIX OF MID TO UPPER 70S ACROSS THE MOUNTAINS.
THE NEXT SHORTWAVE TROUGH TO ROUND THE BASE OF THE LONGWAVE TROUGH
LOOKS TO HAVE A TRACK A BIT FARTHER NORTH...AND THUS THE FOCUS FOR
ISOLATED SHOWERS WILL ALSO BE FARTHER NORTH. THE FORECAST WILL
REFLECT THE POTENTIAL ACROSS THE SOUTHERN ALLEGHANY HIGHLANDS AND
NEAR THE CREST OF THE BLUE RIDGE.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 325 PM EDT TUESDAY...

500 MB HEIGHTS GRADUALLY RISE THROUGH THURSDAY AS UPPER TROF
RETROGRADES. THIS LEAVES FORECAST AREA IN BROAD SOUTHWEST FLOW ON
THURSDAY NIGHT AND FRIDAY. AT THE SURFACE A WEAK COASTAL FRONT
WILL BE STATIONARY FROM THE DELMARVA TO FLORIDA PANHANDLE. LITTLE
IN THE WAY OF LIFT OR FORCING FOR THE COUNTY WARNING AREA UNTIL A
SHORT WAVE COMES THROUGH THE SOUTHWEST FLOW ON FRIDAY.

BUFKIT FORECAST SOUNDINGS FOR 00Z THURSDAY/8PM WEDNESDAY AND AGAIN
THURSDAY AFTERNOON SHOWED A RELATIVELY HIGH BASED STRATOCUMULUS WITH
A SMALL LAYER OF INSTABILITY...THEN DRIER AIR ABOVE AT MID LEVEL AND
BELOW NEAR THE SURFACE.

DEEPER MOISTURE RETURNS BE FRIDAY. A SHORT WAVE TRACKING FROM
SOUTHWEST TO NORTHEAST WILL PROVIDE SOME LIFT SO THIS WILL BE MOST
THE DAY WITH A BETTER PROBABILITY OF SHOWERS AND THUNDERSTORMS IN
THE AFTERNOON.

CLOUD COVER ON THURSDAY NIGHT WILL LIMIT DROP IN TEMPERATURES. AIR
MASS GRADUALLY WARMS THROUGH THE PERIOD. BY FRIDAY 850 MB
TEMPERATURES WILL BE BACK UP TO ABOUT +14. DEPENDING ON THE AMOUNT
OF CLOUDS AND PRECIPITATION. FRIDAY WILL BE THE WARMEST DAY AS FAR
AS MAXIMUM TEMPERATURES SO FAR THIS WEEK.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 325 PM EDT TUESDAY...

UPPER LOW OVER THE NORTHEAST FLATTENS BY SUNDAY WITH A SHORT WAVE
PASSING NORTH OF THE FORECAST AREA ON SUNDAY. ECMWF SUGGESTS
ANOTHER COLD FRONT WILL APPROACH THE AREA FROM THE NORTH ON TUESDAY
AND POSSIBLY MOVE ALL THE WAY THROUGH THE MID ATLANTIC REGION ON
WEDNESDAY. NOT ALL THE EXTENDED GUIDANCE SUPPORTS A TROF AS
AMPLIFIED AS THE ECMWF SO STILL QUESTIONABLE HOW FAR SOUTH FRONT
WILL ADVANCE.

AHEAD OF THAT FRONT FORECAST AREA STAYS IN TYPICAL AIR MASS FOR
SUMMER WITH NEAR NORMAL TEMPERATURES AND ENOUGH MOISTURE AND
INSTABILITY FOR A DAILY THREAT OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
AS OF 130 PM EDT TUESDAY...

VFR CONDITIONS PREVAIL ACROSS THE AREA WITH A MIX OF PARTLY TO
MOSTLY CLOUDY CUMULUS CLOUDS ACROSS THE REGION. THERE HAS BEEN
LESS SHOWER ACTIVITY AS COMPARED TO THIS TIME YESTERDAY. MOST OF
THE ACTIVITY HAS BEEN NEAR OR WEST OF KLWB WITH DONE ELSEWHERE.
CANNOT RULE OUT ISOLATED DEVELOPMENT THE REMAINDER OF THE
AFTERNOON NEAR THE CREST OF THE BLUE RIDGE AND OVER PARTS OF THE
MOUNTAIN EMPIRE OF SOUTHWEST VIRGINIA AND THE NORTHERN MOUNTAINS
OF NORTH CAROLINA.

OVERNIGHT...THE CENTER OF SURFACE HIGH PRESSURE MOVES OVERHEAD.
EXPECT VERY LIGHT IF NOT CALM WINDS...AND CUMULUS CLOUDS
DISSIPATING AT OR AROUND SUNSET. WITH DRIER AIR ARRIVING...ANY
SUB-VFR CONDITIONS SHOULD BE EVEN MORE LIMITED AS COMPARED TO
REALITY FROM THIS MORNING. BEST CHANCES WILL BE AT KLWB.

ON WEDNESDAY...ANY SUB-VFR CONDITIONS SHOULD IMPROVE RAPIDLY TO
VFR BY MID-MORNING.

EXTENDED AVIATION DISCUSSION...

A BROAD TROUGH OF LOW PRESSURE WILL BE ACROSS THE EASTERN UNITED
STATES THROUGH SUNDAY. HOWEVER...IT WILL START CENTERED OVER THE
REGION...AND THEN RETROGRADE WEST TO NEAR THE MISSISSIPPI RIVER BY
SUNDAY. THIS TRANSITION WILL ALLOW FOR BETTER CHANCES OF
SHOWERS...AND PERHAPS A FEW THUNDERSTORMS...TO OCCUR ACROSS THE
REGION AS ATLANTIC MOISTURE WILL BE ABLE TO WORK ITS WAY INTO THE
AREA. ALONG WITH THIS MOISTURE WILL COME BETTER CHANCES FOR SUB-
VFR CONDITIONS...ESPECIALLY UNDER ANY HEAVIER SHOWER OR STORM THAT
FORMS...BUT ALSO DURING THE OVERNIGHT HOURS AS BOUNDARY LAYER
MOISTURE GETS TRAPPED UNDER THE NOCTURNAL INVERSION.

&&

.CLIMATE...
JULY 30TH RECORD LOWS:

ROANOKE......54...1997
BLUEFIELD....50...1981
DANVILLE.....60...1972/81/83/2013
LEWISBURG....46...2013
LYNCHBURG....52...1997
BLACKSBURG...50...1973/81


JULY 31ST RECORD LOWS:

ROANOKE......49...1914
BLUEFIELD....49...1997
DANVILLE.....55...1966
LEWISBURG....48...1997
LYNCHBURG....49...1997
BLACKSBURG...44...1997

&&

.EQUIPMENT...
THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING
ON A FREQUENCY OF 162.450 MHZ...IS OFF THE AIR...DUE TO PHONE LINE
ISSUES. PHONE COMPANY IS WORKING ON IT. THE RADIO IS NOT EXPECTED
TO BE BACK IN SERVICE ANY SOONER THAN WEDNESDAY MORNING.

&&

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

&&

$$
SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...DS
CLIMATE...PH
EQUIPMENT...DS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.