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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
503 AM EDT MON AUG 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE AREA TODAY PROVIDING MAINLY
DRY WEATHER. A COLD FRONT DROPS SOUTHEAST INTO THE REGION BY
TUESDAY BEFORE STALLING OUT MIDWEEK. LOW PRESSURE WILL RIDE ALONG
THE FRONT BRINGING A BETTER CHANCE FOR MORE WIDESPREAD SHOWERS AND
STORMS THURSDAY INTO FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 430 AM EDT SUNDAY...

FORECAST AREA REMAINS UNDER INFLUENCE OF DRY AIR COURTESY OF HIGH
PRESSURE CENTERED OVER THE REGION. THIS DOME OF FAIR WEATHER IS
GRADUALLY FADING PER DEEPER MOISTURE OVER THE SOUTHEAST STATES
OOZING NORTH...AND A COLD FRONT DROPPING SOUTHEAST THROUGH THE
GREAT LAKES. SOUTHWEST FLOW AHEAD OF THE APPROACHING FRONT WILL
BEGIN TO DRAW HIGHER DEWPOINTS INTO THE REGION...BUT LACK OF
FORCING WILL KEEP POPS AT A MINIMUM. MAIN THREAT FOR
SHOWERS/STORMS WILL BE OVER THE OHIO VALLEY ALONG THE APPROACHING
FRONT. THIS ACTIVITY MAY REACH OUR FAR NORTHWESTERN CWA...WV
COUNTIES...TOWARD SUNSET. MODELS INSIST THAT ACTIVITY WILL DRY UP
AS IT TRIES TO CROSS THE MOUNTAINS LATE THIS EVENING AND
OVERNIGHT.

OTHER ISOLATED SHOWERS MAY DEVELOP WITHIN THE LEE TROF OVER THE
SOUTHEAST CWA...PIEDMONT COUNTIES...THIS AFTERNOON...BUT COVERAGE
LESS THAN 30 PERCENT. OVERALL IT LOOKS LIKE A MOSTLY SUNNY...VERY 
WARM AND MAINLY DRY AFTERNOON. 85H TEMPS OF +20 DEG C SHOULD
PROMOTE SURFACE TEMPERATURES WELL INTO THE 80S ACROSS THE
MOUNTAIN VALLEYS...AND INTO THE LOWER 90S ALONG AND EAST OF THE
BLUE RIDGE. ELEVATIONS ABOVE 3500 FEET SHOULD REMAIN MAINLY IN THE
70S.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
AS OF 430 AM EDT MONDAY...

UPPER LEVEL TROUGHING WILL GRADUALLY BECOME LESS PRONOUNCED OVER THE 
NORTHEAST THROUGH MID WEEK...ALLOWING WINDS ALOFT TO BECOME 
GENERALLY WEST TO EAST ACROSS THE MID ATLANTIC...THEREBY OPENING OUR 
AREA TO THE APPROACH OF DISTURBANCES FROM THE CENTRAL PLAINS AND 
MIDWEST.

ONE DISTURBANCE PASSING NEAR THE OHIO RIVER EARLY TUESDAY WILL HELP 
PUSH A COLD FRONT SOUTHWARD ACROSS OUR AREA DURING THE DAY. WITH 
ONLY MODEST MOISTURE RETURNING AHEAD OF THE BOUNDARY...BELIEVE THAT 
SHOWER AND THUNDERSTORM ACTIVITY DEVELOPING WITH AFTERNOON HEATING 
WILL BE WIDELY SCATTERED...WITH BETTER CHANCES FOUND SOUTH OF 
HIGHWAY 460. THE COLD FRONT WILL CLEAR OUR AREA TO THE SOUTH LATE 
TUESDAY NIGHT...WITH POST FRONTAL NORTHWESTERLY WINDFLOW HELPING TO 
DIMINISH ANY LINGERING SHOWER ACTIVITY.

HIGH PRESSURE BUILDING IN BEHIND THE FRONT WILL MAKE FOR DRY 
CONDITIONS MOST AREAS FOR WEDNESDAY...WITH PERHAPS A FEW PULSE 
VARIETY SHOWERS/ISOLATED STORMS DEVELOPING DURING THE AFTERNOON AND 
EVENING. AGAIN...BETTER RAIN CHANCES WILL BE FOUND SOUTH OF HIGHWAY 
460...ESPECIALLY IN THE HIGHLANDS OF NORTH CAROLINA WHERE 
CONVERGENCE ALONG THE RIDGETOPS MAY TRIGGER BETTER SLIGHTLY COVERAGE 
OF CONVECTION IN THE DEEPER MOISTURE.

A LOW PRESSURE SYSTEM WILL APPROACH FROM THE PLAINS WEDNESDAY NIGHT. 
MODELS ARE IN DECENT AGREEMENT THAT WAVES OF ENERGY RIDING AHEAD OF 
THE LOW WILL PASS ACROSS OUR AREA...AND SUPPORT SCATTERED SHOWERS 
THROUGH THE NIGHT AS THE FRONTAL BOUNDARY BEGINS TO LIFT BACK TO THE 
NORTH AS A WARM FRONT TOWARD DAYBREAK THURSDAY. 

THE LOW WILL PUSH UP THE OHIO RIVER VALLEY ON THURSDAY. EXPECT TO 
START THE DAY WITH ONLY SPOTTY RAIN ACTIVITY...HOWEVER SHOWER AND 
THUNDERSTORM CHANCES WILL INCREASE DURING THE EVENING AS THE LOW 
APPROACHES THE APPALACHIAN CHAIN. THE LOW WILL PASS JUST NORTH OF 
OUR AREA THURSDAY NIGHT...DRAGGING ANOTHER COLD FRONT INTO THE 
MOUNTAINS BEFORE DAWN. OF NOTE IS THE SIGNIFICANT DIFFERENCE BETWEEN 
MODELS IN THE INTENSITY OF THE LOW AS IT PASSES OUR AREA. THE GFS 
MODEL IS FAR WEAKER THAN THE ECMWF/CANADIAN MODELS IN ITS DEPICTION 
OF THE LOW...WITH THE STRONGER SOLUTIONS INDICATING A THREAT FOR 
SEVERE WEATHER DURING THE NIGHT. RIGHT NOW...BELIEVE THE ECMWF/ 
CANADIAN SOLUTIONS ARE A LITTLE TOO STRONG GIVEN THE TIME OF YEAR 
AND LACK OF UPPER LEVEL SUPPORT...SO FOR NOW WILL STICK CLOSER TO 
THE WEAKER GFS SOLUTION AND SIMPLY CONTINUE TO WATCH THE EVOLUTION 
OF THIS SYSTEM IN FUTURE MODEL RUNS.


&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 1245 PM EDT SUNDAY...

TRANSITION TO MORE ZONAL FLOW ALOFT WILL OCCUR EARLY IN THE PERIOD 
AS THE REGION GETS CAUGHT UNDER THE SURFACE-850 MB BAROCLINIC ZONE 
AND WITHIN A NEARBY FRONTAL ZONE STRETCHED BACK INTO THE MIDWEST. 
STRONGER ENERGY ALOFT DROPPING OVER THE CENTRAL STATES UPPER RIDGE 
WILL THEN START TO DIG OUT ANOTHER RATHER STRONG 5H TROUGH TO THE NW 
FRIDAY...WITH AN ASSOCIATED SURFACE WAVE HELPING TO DRIVE THE NEXT 
COLD FRONT THROUGH THE REGION BY FRIDAY EVENING. 

SIMILAR TO THE LAST WEEK OR TWO...APPEARS ANOTHER SURGE OF MUCH 
DRIER/COOLER AIR LIKELY BEHIND THE FRONT NEXT WEEKEND AS YET ANOTHER 
5H TROUGH CARVES ITSELF OUT ACROSS THE EAST. GUIDANCE EVEN COOLER 
ALOFT WITH THIS SYSTEM GIVEN PROGGED 850 MB TEMPS AS COOL AS +12C 
MOUNTAINS BUT MAY BE TOO COOL THAT FAR OUT. HOWEVER STILL ENOUGH TO 
DROP HIGHS BACK IN THE 70S MOUNTAINS AND ONLY LOW/MID 80S OUT EAST 
AS HIGH PRESSURE BUILDS/WEDGES IN FROM THE NORTH. RESIDUAL POPS A 
BIT TRICKY TOWARD DAYS 6/7 BUT SHOULD BE DRIER WITH PERHAPS SOME 
LEFTOVER UPSLOPE SHOWERS WEST SATURDAY AND ONLY ISOLATED FAR 
SOUTHWEST ON SUNDAY.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
AS OF 430 AM EDT MONDAY...

GENERALLY VFR CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD AS
A RELATIVELY DRY AIR MASS REMAINS OVER THE REGION. LOW-LEVEL
MOISTURE WILL SLOWLY BE INCREASING THROUGH THE PERIOD AS A COLD
FRONT APPROACHES THE REGION FROM THE NORTHWEST. MAIN CONCERN FOR
THUNDERSTORMS TODAY WILL BE ACROSS THE OHIO VALLEY FROM NORTHERN
KY UP THROUGH EASTERN OHIO ALONG THE OHIO RIVER INTO PENNSYLVANIA.
STORMS THAT FORM ALONG THIS FRONT TODAY MAY APPROACH KBLF/KLWB
LATE IN THE DAY...BUT CONFIDENCE LOW AS TO WHETHER THIS ACTIVITY
WILL BE ABLE TO CROSS THE MOUNTAINS...THUS OMITTING FROM THE
KBLF/KLWB TAFS ATTM. OVER AND EAST OF THE MOUNTAINS...CAN'T RULE
OUT A LATE AFTERNOON AIRMASS THUNDERSHOWER...BUT COVERAGE IS
EXPECTED TO BE ISOLATED.

FOG CONCERNS REMAIN MINIMAL AS AIR MASS IS VERY DRY. HOWEVER...AS
IS OFTEN THE CASE FOR LWB IN THE GREENBRIER VALLEY...RADIATIONAL
COOLING MAY PERMIT A BRIEF PERIOD OF IFR/LIFR EARLY THIS
MORNING...AND AGAIN TUESDAY MORNING. ELSEWHERE...CONFIDENCE IN ANY
FOG IS LOW...AND WILL KEEP IT OUT OF THE TAFS ATTM.

WINDS TODAY BECOMING SOUTHWEST MONDAY MID-MORNING AND INCREASING
INTO THE 6-9KT RANGE MOST SITES BY LATE MORNING. SOME LOW END
GUSTS POSSIBLE AT BLF JUST AHEAD OF THE APPROACHING FRONT THIS
AFTERNOON.

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

EXTENDED AVIATION FORECAST...
MOSTLY VFR OUTSIDE OF ANY DEEP CONVECTION THROUGH THE PERIOD. A
FRONT WILL STALL ACROSS THE MID ATLANTIC FOR MID WEEK WHICH COULD
BRING A FEW SHRA/TSRA BY TUESDAY...WITH A BIT MORE COVERAGE LATER
WEDNESDAY AND A BETTER CHANCE THURSDAY. THE THREAT OF SUB-VFR
REMAINS LOW UNTIL THURSDAY...EXCEPT FOR THE TYPICAL FOG POTENTIAL
AT KLWB/KBCB EACH MORNING BETWEEN 09-13Z.

&&

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

&&

$$
SYNOPSIS...JH
NEAR TERM...PM
SHORT TERM...NF
LONG TERM...JH
AVIATION...PM

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