Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 241417
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1017 AM EDT THU JUL 24 2014

.SYNOPSIS...
A COLD FRONT ACROSS THE AREA THIS MORNING WILL SHIFT SLOWLY SOUTHEAST
BY LATE TONIGHT. HIGH PRESSURE OVER THE MIDWEST WILL BUILD ACROSS
THE MID-ATLANTIC THROUGH FRIDAY. OVER THE WEEKEND THE PATTERN
SETS UP FOR POTENTIAL UPPER DISTURBANCES MOVING INTO THE REGION ON
A NORTHWEST FLOW. A STRONG FRONT IS EXPECTED TO CROSS THE AREA
MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 1000 AM EDT THURSDAY...

UPDATED GRIDS FOR CURRENT RADAR TRENDS AND INCORPORATING SHORT-
RANGE MODEL SOLUTIONS. HIGH-RES WRF HAD DECENT HANDLE ON
INITIALIZATION WITH BULK OF EARLY MORNING LOCATED ACTIVITY EAST
OF THE CWA AND SHOWING ADDITIONAL FAIRLY WIDESPREAD COVERAGE
BEGINNING AROUND 18Z. RAMPED UP POPS TO LIKELY MOST AREAS BY THEN
18-19Z BUT MODEL SHOWS PRECIP SHIFTING EAST FAIRLY RAPIDLY AS THE
FRONT SAGS FURTHER SOUTHEAST. HPC QPF GENERALLY 0.25 TO 0.50
INCHES BUT VERY UNEVEN AS USUAL WITH A FEW AREAS GETTING BRIEF
HEAVY DOWNPOURS AND OTHERS NONE AT ALL. SPC ALSO SHIFTED SLIGHT
RISK OF SVR BACK INTO PORTIONS OF SOUTHERN CWA...WHICH MIGHT
DEPEND ON GETTING SOME BREAKS IN OVERCAST TO HELP GENERATE MORE
INSTABILITY ALONG WITH WHATEVER THE FRONT CAN PROVIDE IN THE WAY
OF A TRIGGER.

FRONTAL BOUNDARY ANALYZED ACROSS THE NORTHERN CWA AT THIS MORNING
WITH 14Z OBS NORTH OF THE BOUNDARY SHOWING A SUBTLE WIND SHIFT TO
NORTHERLY BUT WITH DRIER AIR IS STILL WELL BACK TO THE WEST
ACROSS THE OH RIVER VALLEY WHERE MID-50S DEWPOINTS CAN BE FOUND.
STILL UPPER 60S TO LOWER 70S DEWPOINTS ACROSS THE CENTRAL AND
SOUTHERN CWA. THIS FRONT COULD BECOME THE FOCUS FOR STORM
DEVELOPMENT LATER TODAY...ALONG WITH RESIDUAL OUTLFOW BOUNDARIES
WHICH MAY EXIST.

FORECAST HIGHS TODAY BASICALLY UNCHANGED WITH READINGS RANGING
FROM THE MID 70S WEST TO MID 80S EAST.

PREVIOUS VALID DISCUSSION...
AS OF 330 AM THURSDAY...

TONIGHT...THE MAIN AXIS OF LIFT AND MOISTURE SHIFTS EAST OF AREA
WITH SKIES STARTING TO CLEAR IN THE WEST. WILL KEEP HIGH CHANCE
EARLY IN THE EAST THEN DRY IT OUT BY MIDNIGHT/EARLY OVERNIGHT...WHEN
MAIN TROUGH AXIS AT 5H SHIFTS ACROSS. LESS HUMID AIR WILL PUSH INTO
THE MOUNTAINS AT LEAST THOUGH PROXIMITY OF FRONT THAT STALLS OVER
ERN NC/SC MAY INHIBIT THE LOWER DEWPOINTS REACHING THE SE CWA
UNTIL FRIDAY. LOWS ARE GOING TO RANGE FROM THE MID 50S ACROSS THE
HIGHER MTNS TO MID 60S SOUTHEAST.

FRIDAY WILL BE DRY AND LESS HUMID WITH HIGH PRESSURE NOSING IN FROM
THE MID ATLANTIC TURNING WINDS AROUND MORE TO THE NE-E. HIGHS
RANGING FROM THE UPPER 70S MTNS TO LOWER 80S ROANOKE TO MID 80S EAST
CAN BE EXPECTED.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
AS OF 350 AM EDT THURSDAY...

FOR SATURDAY...MOISTURE WILL BEGIN TO RETURN TO THE FORECAST AREA
FROM THE SOUTH AND SOUTHWEST. CAN`T RULE OUT A LATE AFTERNOON
POPUP SHOWER OVER THE MOUNTAINS...BUT THINK MOST AREAS WILL REMAIN
DRY UNTIL THE ARRIVAL OF A FRONT MONDAY. WILL HAVE TO MONITOR
THIS UPSTREAM FRONT CLOSELY AS IT MAY CAST SOME PREFRONTAL SHOWERS
AND STORMS OUR WAY AS EARLY AS SATURDAY NIGHT.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 515 PM EDT WEDNESDAY...

STRONG COLD FRONT IS SLATED TO CROSS THE FORECAST AREA LATE SUNDAY
INTO MONDAY...ASSOCIATED WITH A VIGOROUS SHORT WAVE TROUGH THAT
WILL BE MOVING ACROSS THE GREAT LAKES AND OHIO VALLEY. THIS
PARTICULARLY STRONG DISTURBANCE...NOTED BY ALL THE
MODELS...PROMISES TO AMPLIFY THE EASTERN LONG WAVE TROUGH...A
PATTERN THAT WILL NET COOLER THAN NORMAL TEMPERATURES FOR SEVERAL
DAYS NEXT WEEK.

DURING THE TRANSITION SUNDAY INTO MONDAY...INCREASED INSTABILITY
AHEAD OF THE FRONT ALONG WITH STRONG DYNAMIC FORCING WILL RESULT
IN POTENTIAL FOR STRONG TO SEVERE STORMS. THE OPPORTUNITY WILL
EXIST FOR ORGANIZED DEEP CONVECTION WITH POTENTIAL FOR A MESOSCALE
CONVECTIVE SYSTEM (MCS) TO CROSS THE FORECAST AREA FROM THE WEST.

ATTM WILL MAINTAIN THE BEST CHANCE FOR SHOWERS/STORMS SUNDAY...WITH
THE THREAT LINGERING INTO MONDAY UNTIL THE SURFACE FRONT CAN
COMPLETELY CLEAR THE FORECAST AREA. GENERALLY FOLLOWED HPC
GUIDANCE THROUGH THE PERIOD TRENDING POPS DOWNWARD AFTER THE EARLY
WEEK FROPA.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
AS OF 735 AM EDT THURSDAY...

MOISTURE IN THE LOW LVLS PLUS ADDED RAINFALL HAS ALLOWED FOR FOG
AT A FEW LOCATIONS THIS MORNING. HOWEVER EXPECT THIS TO BE SHORT
LIVED. SHOWERS ARE GOING TO BRING TEMP MVFR VSBYS TO DAN TO START
THE TERMINALS.

HIGH-RES MODELS FAVOR MORE CONVECTION MOVING OUT OF WV INTO VA
AREA BY MIDDAY...WITH BEST CHANCE IN THE ROA/LYH/DAN CORRIDOR.
THIS AFTERNOON. KEPT VCTS IN BUT HAVE ENOUGH CONFIDENCE IN THE
HIGH RES MODELS OVERALL TO ADD TEMPO THUNDER IN AT LYH/DAN LATER
THIS AFTERNOON. LOOK FOR CIGS TO BE MVFR IN THE MTNS EARLY BEFORE
BECOMING VFR BY MIDDAY/18Z.

CONVECTION WILL EXIT THE MOUNTAINS BY 21-22Z AND DAN/LYH BY 00Z.

TONIGHT WILL BE TRICKY AS DRY AIR MAY BE SLOW TO ARRIVE IN
EARNEST. DEPENDING ON HOW MUCH RAIN OCCURS AND WITH CLEARING THINK
FOG WILL BECOME AN ISSUE AT MOST SITES. THINK LWB/BCB WILL HAVE
DENSE FOG AT LEAST BEFORE THE DRY AIR ARRIVES.

EXTENDED AVIATION DISCUSSION...

AIRMASS WILL DRY OUT BEHIND THE FRONT GOING INTO FRIDAY-
SATURDAY. VFR FRI- SAT OUTSIDE OF ANY VALLEY FOG AT KLWB/KBCB
EACH MORNING. ANOTHER FRONT AND ASSOCIATED UPPER IMPULSES COULD
BRING A GOOD THREAT OF STORMS IN THE SUN-MON TIME FRAME. DURING
THIS TIME MAINLY VFR...EXCEPT IN TSRA AND FOR ANY LATE NIGHT FOG.

&&

.HYDROLOGY...
U.S. DROUGHT MONITOR ISSUED THIS MORNING AND VALID THROUGH 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 JULY RAINFALL...WHICH IS CLIMATOLOGICALLY THE
WETTEST MONTH IN OUR CWA.

&&

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

&&

$$
SYNOPSIS...WP
NEAR TERM...PC/WP
SHORT TERM...PM/WP
LONG TERM...PM
AVIATION...WP
HYDROLOGY...PC



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