Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 221443
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1043 AM EDT FRI AUG 22 2014

.SYNOPSIS...
A STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE IS CENTERED OVER THE
LOWER MISSISSIPPI RIVER VALLEY WITH A STATIONARY SURFACE FRONT
EXTENDING FROM THE UPPER MIDWEST...THROUGH THE OHIO VALLEY AND
INTO THE MID ATLANTIC STATES. THIS FRONT WILL BE THE FOCUS
FOR PERIODIC ROUNDS OF SHOWERS AND STORMS FROM THE OHIO VALLEY
INTO THE MID ATLANTIC TODAY AND TONIGHT. OVER THE WEEKEND THE
FRONT IS EXPECTED TO MOVE SOUTH ALONG THE EAST COAST...TURNING
INTO A BACKDOOR COLD FRONT WHICH WILL BRING COOLER AIR TO AREAS
EAST OF THE APPALACHIANS...WHILE VERY WARM SULTRY WEATHER
CONTINUES ACROSS THE MID SECTION OF THE UNITED STATES.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM EDT FRIDAY...

LITTLE CHANGE FROM THE EARLY MORNING FORECAST PHILOSOPHY DESCRIBED
BELOW. FOR THE 10 AM UPDATE...INCREASED RAIN CHANCES HEADING INTO
THE AFTERNOON FROM SOUTHEAST WEST VIRGINIA EASTWARD...BASICALLY
ALONG THE HIGHWAY 460 CORRIDOR...AS A SERIES OF DISTURBANCES PASS
ACROSS OUR AREA. RAINFALL APPEARS TO BE A GREATER CERTAINTY GIVEN
LATEST RADAR TRENDS...ALTHOUGH DO NOT ANTICIPATE HIGHER RAINFALL
AMOUNTS OVER WHAT WAS FORECAST EARLIER THIS MORNING.

ALSO...ADJUSTED HIGH TEMPERATURES FOR THIS AFTERNOON DOWNWARD A
COUPLE DEGREES FOR THE NORTHERN HALF OF THE AREA DUE TO THICK
CLOUD COVER AND SHOWER ACTIVITY. LEFT TEMPERATURES FOR THE
SOUTHSIDE AND NORTH CAROLINA PIEDMONT UNTOUCHED FOR THE MOST PART
AS A LACK OF CLOUD COVER IN THESE AREAS IS ALLOWING FOR STRONGER
HEATING.


AS OF 530 AM EDT FRIDAY...

FLASH FLOOD WATCH IN EFFECT TODAY AND TONIGHT FOR MUCH OF WEST
VIRGINIA AND PARTS OF SOUTHWESTERN VIRGINIA.

CLASSIC RING OF FIRE PATTERN SETTING UP AROUND THE PERIPHERY OF
THE STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE WHICH HAS NOW BECOME
CENTERED OVER THE MISSISSIPPI VALLEY. A VERY RICH...MOISTURE LADEN
AIRMASS...IS BEING PUMPED FROM THE GULF OF MEXICO NORTHWARD...AND
IS POOLING ALONG A STATIONARY FRONT WHICH ARCS AROUND THE NORTHERN
PERIPHERY OF THE RIDGE. THIS FRONT EXTENDS FROM THE UPPER MID
WEST ACROSS THE OHIO VALLEY AND INTO THE MID ATLANTIC...THE
NUMEROUS STORMS EVOLVING ALONG THIS BOUNDARY APPEARING AS A LARGE
RING LIKE FEATURE WHEN YOU LOOK AT REGIONAL SATELLITE AND RADARS.
IT ALSO GIVES THE IMPRESSION OF A TRAIN WITH STORMS APPEARING TO
TRAVERSE THE SAME AREAS...FOLLOWING A PROVERBIAL RAILROAD TRACK.
THIS OF COURSE IS PROBLEMATIC SINCE REPEATED DOWNPOURS OVER THE
SAME AREA WILL ULTIMATELY LEAD TO FLOODING.

MESOANALYSIS FROM THIS MORNING INDICATES THE MOST PRONOUNCED PART
OF THE RAILROAD TRACK...STRONGEST PART OF THE BAROCLINIC ZONE...
RUNS FROM NORTHERN IL/IN...THEN BENDS SOUTHEAST ACROSS OHIO AND
INTO WV...BECOMING DIFFUSE ONCE YOU GET EAST OF THE MTNS. IN
SPITE OF THE LARGER SCALE MODEL DIFFERENCES...WHICH UNDERPLAY THE
QPF FROM THE MESOSCALE FEATURES...I AM MODERATE TO HIGHLY
CONFIDENT STORMS WILL CONTINUE TO REGENERATE ALONG THE STRONGEST
PART OF THE BAROCLINIC ZONE...STORMS MOVING SOUTHEAST ALONG THIS
RAILROAD TRACK FEATURE AND INTO OUR CWA AND PRODUCING HIGHER QPF.
STRONG 85H MOISTURE TRANSPORT IS ONGOING ACROSS WV WITH PWATS
STEADILY CLIMBING TOWARD 2.0. THIS SUGGESTS STORMS THAT PASS
THROUGH THIS ENVIRONMENT WILL BE VERY RAIN EFFICIENT. GIVEN THE
POTENTIAL FOR THESE STORMS TO REPEATEDLY MOVE OVER THE SAME
AREA...A FLASH FLOOD WATCH SEEMS TO BE A GOOD HEADLINE FOR THE
DAY. ATTM WILL FOCUS THE ATTENTION ON OUR WV COUNTIES AND ACROSS
THE NEW RIVER VALLEY WHERE FLASH FLOOD GUIDANCE SUGGESTS ANY RAIN
THAT EXCEEDS 1.5 TO 2.0 INCHES IN AN HOUR WILL REQUIRE A FLASH
FLOOD WARNING. THESE NUMBERS ARE CERTAINLY ACHIEVABLE GIVEN THE
ENVIRONMENT.

SHOWERS AND STORMS ARE CERTAINLY POSSIBLE ELSEWHERE ACROSS THE
CWA. SIMILAR TO YESTERDAY...NORTHWEST FLOW WILL RESULT IN A
WEAKENING OF THE ACTIVITY AS IT CROSSES THE MOUNTAINS...THE STORMS
BREAKING UP INTO CLUSTERS OR SHORT LINE SEGMENTS AS THEY QUICKLY
TRAVERSE THE CWA. THESE STORMS WILL ALSO PRODUCE HEAVY RAIN...BUT
I AM LESS CONFIDENT EAST OF THE MOUNTAINS THAT STORMS WILL EXHIBIT
THE SAME SORT OF TRAIN EFFECTS AS AREAS TO THE WEST.

WENT BLO GFS MOS GUIDANCE AND CLOSER TO THE MET GUIDANCE FOR
TEMPERATURES TODAY AND TONIGHT. THE GFS SEEMED 3 TO 5 DEGREES TOO
WARM GIVEN THE MOSTLY CLOUDY MOIST SHOWERY FORECAST.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
AS OF 400 AM EDT FRIDAY...

DURING THIS PORTION OF THE FORECAST...THE MAIN ITEM OF FOCUS WILL BE
A BACKDOOR COLD FRONT THAT ENTERS THE REGION SATURDAY NIGHT INTO
SUNDAY AS HIGH PRESSURE BUILDS SOUTH OFF THE NEW ENGLAND COAST.
PRIOR TO ITS ARRIVAL...THE WEATHER ON SATURDAY WILL BE COMPARABLE
WITH THAT EXPECTED TODAY. THE AREA WILL BE WITHIN AN UNSTABLE
ENVIRONMENT WITH UPPER LEVEL DISTURBANCES TRAVERSING THE
REGION...PROVIDING ADDITIONAL SUPPORT FOR CONVECTION. HOWEVER...THE
FOCUS FOR ANY OF THESE WILL BE SHIFTED ACROSS MORE OF THE SOUTHWEST
PARTS OF THE REGION AS THE UPPER BAROCLINIC ZONE SHIFTS IN THAT
DIRECTION AS WELL.

SATURDAY NIGHT INTO SUNDAY...THE PASSAGE OF THE BACKDOOR COLD FRONT
WILL ITSELF BE A FOCUS FOR SHOWER ACTIVITY. HOWEVER...ONCE IT HAS
MOVED WEST OF A PARTICULAR AREA...LOW LEVEL WILL BECOME
EASTERLY...AND THE ONSET OF A LEE SIDE DAMMING WEDGE WILL ENSUE.
EXPECT AREAS ALONG AND WEST OF A LINE FROM ROUGHLY BLUEFIELD WV TO
MARION VIRGINIA WILL REMAIN SOMEWHAT UNSTABLE WITH THE FRONT TAKING
UP POSITION EITHER OVER...OR VERY CLOSE TO THAT AREA. IT WILL BE
HERE WHERE ANY ADDITIONAL SHOWERS OR STORMS MAY DEVELOP ON SUNDAY.
TEMPERATURES WITHIN THE AREA OF THE WEDGE WILL EXPERIENCE LITTLE
RISE FROM SATURDAY NIGHT OVERNIGHT LOWS. WE STILL ANTICIPATE A COOL
DAY SUNDAY WITHIN THE WEDGE WITH UPPER 60S TO AROUND 70 COMMON FOR
HIGH TEMPERATURES. THE FAR WESTERN PARTS OF THE AREA ARE MORE LIKELY
TO EXPERIENCE UPPER 70S TO LOWER 80S FOR HIGHS. PRECIPITATION WITHIN
THE WEDGE WILL TRANSITION FROM SHOWERS TO MORE A LIGHT RAIN OR
DRIZZLE SCENARIO.

HEADING INTO MONDAY...AM RELUCTANT TO REMOVE THE INFLUENCE OF THE
WEDGE TOO QUICKLY. HAVE CONTINUED WITH A MORE CLOUDY THAN CLEAR DAY
WITH RESIDUAL...BUT REDUCED IN COVERAGE...LIGHT RAIN OR DRIZZLE
WITHIN THE AREA OF THE WEDGE. BY MONDAY NIGHT...THE FORECAST WILL
REFLECT DRIER AIR WORKING ITS WAY INTO THE AREA AS THE CENTER OF THE
HIGH MOVES ONSHORE TO CENTRAL PENNSYLVANIA. STEERING ONSHORE FLOW
AROUND THE HIGH WILL START ADVECTING LOW LEVEL MOISTURE SOUTH OF OUR
REGION. LOW WILL RANGE FROM THE UPPER 50S ACROSS THE MOUNTAINS TO
LOWER 60S ACROSS THE PIEDMONT.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 1130 AM EDT THURSDAY...

SURFACE HIGH PRESSURE WILL BE IN A FAVORABLE LOCATION OVER NEW
ENGLAND TO WEDGE WELL DOWN THE EAST SLOPES OF THE APPALACHIANS
SUNDAY NIGHT AND MONDAY. SUPPORT FOR THE WEDGE WEAKENS BY TUESDAY.
HIGH PRESSURE WILL REMAIN OVER THE FORECAST AREA THROUGH WEDNESDAY.
WEDNESDAY NIGHT AND THURSDAY A COLD FRONT WILL APPROACH THE AREA.
LARGE 500 MB RIDGE ALOFT WILL COVER MUCH OF THE LOWER MISSISSIPPI
VALLEY ACROSS THE EASTERN UNITED STATES THROUGH THE PERIOD.

THE DEEPEST MOISTURE SHIFTS SOUTHWEST OUT OF THE FORECAST AREA ON
MONDAY AND TUESDAY. WILL HAVE THESE DAYS DRY IN THE FORECAST. THE
CHANCE OF PRECIPITATION RETURNS TO THE AREA ON WEDNESDAY AND
THURSDAY AHEAD OF THE FRONT. EXPECT MAXIMUM TEMPERATURES TO BE
WARMEST ON WEDNESDAY AND THURSDAY WITH THE WEDGE GONE AND MORE
POTENTIAL TO MIX DOWN WARM 850 MB TEMPERATURES.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AS OF 800 AM EDT FRIDAY...

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS CAN BE EXPECTED
TODAY AND TONIGHT...WITH THE GREATEST COVERAGE OVER THE MOUNTAINS.
FLYING CONDITIONS WILL BE HIGHLY VARIABLE WITH PRIMARILY MVFR/IFR
CONDITIONS OVER THE MTNS...AND A MIX OF VFR/MVFR EAST OF THE MTNS
THROUGH THE 24 HOUR TAF PERIOD.

EXTENDED AVIATION...

WEATHER CONDITIONS WILL REMAIN UNSETTLED THROUGH THE WEEKEND.
UPPER LEVEL DISTURBANCES WILL BE MOVING THROUGH PERIODICALLY AND
INTERACTING WITH A STATIONARY FRONT OVER THE AREA FOR THE NEXT FEW
DAYS...RESULTING IN PERIODS OF SHOWERS AND THUNDERSTORMS. DUE TO
THE HIGH MOISTURE CONTENT OF THE AIR...EXPECT STRATUS AND FOG
DURING THE OVERNIGHT PERIODS WITH AREAS OF MVFR/IFR MOST
PRONOUNCED BETWEEN MIDNIGHT AND 9AM EACH DAY. MODELS ARE
INDICATING THAT A DEEPER EASTERLY SORT OF WIND FLOW WILL SETUP FOR
THIS UPCOMING WEEKEND. THIS SUGGESTS THAT LOW CIGS MAY PERSIST
EVEN DURING THE DAYTIME PERIODS...SATURDAY AND SUNDAY...WITH
WIDESPREAD MVFR CONDITIONS ACROSS THE AREA THIS WEEKEND DUE TO
MOISTURE BANKING UP AGAINST THE EAST SIDE OF THE APPALACHIANS.
A BETTER PUNCH OF DRY AIR WITH HIGH PRESSURE BUILDING IN FROM THE
NE MAY BE ENOUGH WITH MIXING/HEATING TO ALLOW FOR INCREASING VFR
MONDAY INTO TUESDAY UNDER MAINLY DRY CONDITIONS.

&&

.EQUIPMENT...
THE ASOS AT LYNCHBURG (LYH) VA REMAINS PARTIALLY INOP DUE TO A
BOARD FAILURE. PARTS HAVE BEEN ORDERED WITH THE RETURN OF
COMPLETE SERVICE UNKNOWN AT THIS TIME.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR VAZ007-009>014.
NC...NONE.
WV...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR WVZ042>045.

&&

$$
SYNOPSIS...PM
NEAR TERM...PM/NF
SHORT TERM...DS
LONG TERM...AMS
AVIATION...PM
EQUIPMENT...


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