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 300342
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1142 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 1135 PM EDT TUESDAY...

ENOUGH LOW LVL THETA-E INTO THE SOUTHERN VA PIEDMONT AS WELL AS
9.0C/KM LOW LVL LAPSE RATES EARLY THIS EVENING WERE ENOUGH TO
PROPEL SHOWERS INTO LATE EVENING. NOT EVERYONE IS SEEING RAIN BUT
THOSE THAT ARE...WERE GETTING UP TO ONE HALF INCH PER RADAR
ESTIMATES. THE MODELS ARE ALLOWING FOR THESE SHOWERS TO FADE
THROUGH 2 AM...SO KEEPING POPS ISOLATED AT BEST TOWARD SOUTH
BOSTON/YANCEYVILLE AND CHARLOTTE COURT HOUSE ANOTHER 1-2 HOURS.
APPEARS SKIES SHOULD CLEAR OUT SOME OVERNIGHT. NO OTHER CHANGES
NEEDED WITH THIS UPDATE.

PREVIOUS VALID DISCUSSION...

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. OVERNIGHT...DRIER AIR WILL
CONTINUE TO FILTER INTO THE REGION. THIS WILL HELP LIMIT 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 /04Z WEDNESDAY THROUGH SUNDAY/...
AS OF 735 PM EDT TUESDAY...

UPPER TROUGH AND CYCLONIC FLOW WILL CONTINUE ACROSS THE FORECAST
AREA THROUGH THE WEEK. WEAK SHORT WAVES WILL ROTATE THROUGH THE
BASE OF THE TROUGH AND BRING PERIODS OF CLOUDS AND ISOLD -SHRA TO
MAINLY AREAS WEST OF THE BLUE RIDGE AFTER THIS EVENING. THE CLOUD
COVER AND -SHRA WILL BE AMPLIFIED DURING THE NORMAL DIURNAL
HEATING CYCLE...PEAKING IN THE 18Z-22Z TIME FRAME. ISOLD -SHRA
EAST OF THE BLUE RIDGE THIS EVENING CURRENTLY SUPPORTED BY WEAK
UPPER SHORT WAVE MOVING THROUGH THAT REGION. THIS ACTIVITY WILL
DISSIPATE QUICKLY BY 01Z. MOST CLOUDS OF CONSEQUENCE OVERNIGHT
WILL BE WEST OF THE BLUE RIDGE...AND EVEN MORE SO WEST OF THE
ALLEGHANYS. CIGS MOSTLY LOW END VFR WEST OF THE BLUE
RIDGE...TRENDING TOWARD MVFR OVERNIGHT/EARLY THU. DID INCLUDE
-SHRA FOR LWB/BLF WED AFTERNOON WITH EVIDENCE OF A SLIGHTLY
STRONGER SHORT WAVE ROTATING THROUGH THAT REGION DURING PEAK
HEATING. NOT MUCH CONCERN WITH VSBYS...EXPECT POTENTIALLY AT LWB
IF CLOUDS CAN CLEAR ENOUGH AND WIND DECOUPLE. NOT EXPECTING ANY
VSBYS WORSE THAN MVFR AT THIS POINT. WINDS MOSTLY WNW 5-7KTS
THROUGH THE TAF VALID PERIOD...WITH MORE TENDENCY FOR VRB OR
LIGHT SW WINDS ACROSS THE PIEDMONT.

MEDIUM CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD.
MEDIUM TO HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD.
MEDIUM CONFIDENCE IN WIND DIR THROUGH THE TAF VALID PERIOD...HIGH
CONFIDENCE IN WIND SPD THROUGH THE TAF VALID PERIOD.

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/WP
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...DS/RAB
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.