Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 231831
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
231 PM EDT SAT AUG 23 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ALONG THE NORTHERN MID-ATLANTIC COAST
THROUGH THE WEEKEND PUSHING A BACKDOOR FRONT THROUGH THE REGION
FROM THE EAST. SHOWERS AND A FEW THUNDERSTORMS WILL ACCOMPANY THE
FRONT AGAIN TODAY WITH WARM...HUMID CONDITIONS CONTINUING. FOR
SUNDAY INTO EARLY NEXT WEEK...THE FRONT WILL CONTINUE TO PUSH WEST
INTO THE TENNESSEE VALLEY ALLOWING DRIER...COOLER AIR TO FILTER
INTO THE REGION FROM THE EAST. THIS AIR MASS WILL REMAIN IN PLACE
THROUGH THE MID PART OF NEXT WEEK RESULTING IN INCREASED
SUNSHINE...LESS HUMIDITY...COOL NIGHTS AND MILD TO SEASONABLY WARM
DAYS.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 1015 AM EDT SATURDAY...

ONLY MINOR ADJUSTMENTS NECESSARY FOR THE LATE MORNING FORECAST
UPDATE. RADAR IMAGERY INDICATES VERY LIGHT SHOWERS PASSING ACROSS
THE MOUNTAINS THIS MORNING...IN MOST INSTANCES THEY ARE JUST
HEAVY ENOUGH TO DAMPEN THE SURFACE. HEAVIER SHOWERS ARE LOCATED
EAST OF A LYNCHBURG TO DANVILLE LINE. PUT THE HIGHEST RAIN CHANCES
FURTHER EAST FOR THE REMAINDER OF THE MORNING...AND THEN WILL
SHIFT THE HIGHER RAIN CHANCES TOWARD THE BLUE RIDGE FOR THE
AFTERNOON AS INCREASING LOW LEVEL CONVERGENCE NEAR THE RIDGELINES
TRIGGERS SCATTERED SHOWERS LATER TODAY.

AS OF 415 AM EDT SATURDAY...

FOR TODAY...EXPECT MORE SHOWERS AND THUNDERSTORMS ACROSS THE
REGION. ACTIVITY HAS LINGERED IN VARIOUS AREAS OVERNIGHT...MOSTLY
JUST NORTH AND SOUTHWEST OF THE CWA...WHERE LOCALLY HEAVY RAINFALL
AND FLASH FLOODING HAS BEEN REPORTED. THIS WILL REMAIN A
POSSIBILITY THROUGHOUT THE DAY. THE FOCUS FOR HEAVIER RAIN WILL
FOCUS MAINLY WEST OF THE BLUE RIDGE BY AFTERNOON AS THE FRONT
DRIFTS WEST. WITH PWATS STILL IN THE 1.5-1.9 INCH RANGE FROM NE-
SW...LOCALLY HEAVY RAIN CAN STILL BE EXPECTED. HOWEVER...NONE OF
THE SHORT RANGE OR LONG RANGE MODELS INDICATE ANY EXCESSIVE
RAINFALL BY ANY MEANS OVERALL...WITH ONLY MODEST AMOUNTS ALL LESS
THAN 1 INCH FOR THE 24HR PERIOD ENDING 12Z SUN. EARLIER FFA WAS
CANCELLED AND FEEL ANY FLOODING ISSUES TODAY...AGAIN MAINLY WEST
OF THE BLUE RIDGE...CAN BE HANDLED WITH LOCAL FLOOD ADVISORIES OR
IN THE WORST CASE SCENARIOS FLASH FLOOD WARNINGS. WITH RESPECT TO
THUNDERSTORMS...HAVE INDICATED AT LEAST ISOLD TSRA ALL AREAS
TODAY...BUT THE MOST LIKELY AREA WILL BE WEST OF THE BLUE
RIDGE...AND ESPECIALLY FAR SW VA/NW NC/SE WV WEST OF THE FRONTAL
BOUNDARY WHERE AFTERNOON CAPES EXCEED 1000 J/KG. SPC DOES NOT HAVE
ANY AREA INDICATED FOR SEVERE...HOWEVER...AN ISOLD WET DOWNBURST
CANNOT BE RULED OUT...ESPECIALLY NEAR THE FRONTAL BOUNDARY.
AGAIN...THE MAIN CONCERN WOULD BE LOCALLY HEAVY RAIN WEST OF THE
BLUE RIDGE AND ESPECIALLY AREAS WEST OF I-77. OVERNIGHT INTO EARLY
SUN...WOULD EXPECT INCREASING LIKELIHOOD OF -DZ DEVELOPING EAST OF
THE ALLEGHANY FRONT AS THE MARITIME LAYER DEEPENS.

WITH RESPECT TO TEMPERATURES TODAY...A TRANSITION IN THE AIR MASS
FROM WARM/HUMID/SUMMERLIKE TO ATLANTIC MARITIME WILL BE TAKING
PLACE EAST OF THE BLUE RIDGE...WITH WESTERN AREAS REMAINING VERY
WARM AND HUMID UNDER THE INFLUENCE OF THE UPPER RIDGE. USED A
MODEL BLEND FOR TODAY...BUT AFTER TODAY THE GFS MOS JUST LOOKS WAY
TO WARM FOR THE SYNOPTIC SITUATION DEVELOPING. MIN TEMPS SUN
MORNING SHOULD REMAIN QUITE MILD WITH DEWPOINTS STILL 65-70 IN
MANY AREAS. ECMWF MOS SEEMS TO HAVE THE BEST HANDLE ON TEMPS
THROUGH SUN.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 300 AM EDT SATURDAY...

THIS PERIOD OF THE FORECAST WILL OFFER A TREND TOWARDS DRIER
CONDITIONS. A BACKDOOR COLD FRONT WILL BE WELL TO THE WEST AND SOUTH
OF THE AREA BY SUNDAY EVENING. BEHIND IT...HIGH PRESSURE WILL START
TO NOSE SOUTH ALONG THE SPINE OF THE APPALACHIANS. THE FORECAST WILL
REFLECT A TYPICAL COLD AIR DAMMING WEDGE PATTERN WITH MOST AREAS OF
THE FORECAST AREA SOCKED IN WITH CLOUDS...PATCHY DRIZZLE...AND
SLIGHTLY BETTER ORGANIZED LIGHT RAIN GIVEN THE EASTERLY UPSLOPE
COMPONENT OF RESIDUAL LOW LEVEL MOISTURE. MODEL GUIDANCE WANTS TO
BRING DRIER AIR INTO THE REGION AS EARLY AS MID-DAY SUNDAY. WHILE IT
IS STILL AUGUST...GUIDANCE TENDS TO BE A BIT TOO PROMPT IN CLEARING
OUT THE IMPACTS OF THE WEDGE. AS SUCH...THE FORECAST WILL CONTINUE
TO HOLD THE WEDGE FAST THROUGH THE DAY SUNDAY...ALL WHILE MAKING
ADJUSTMENTS ALONG THE BORDERS WITH OTHER OFFICE TO BETTER BLEND WITH
THEIR DRIER AND MILDER FORECASTS.

SUNDAY NIGHT INTO MONDAY...WE ARE EXPECTING THE WEDGE AND ASSOCIATED
CLOUDS AND DRIZZLE TO GRADUALLY ERODE...BUT LINGER THE LONGEST ALONG
THE CREST OF THE BLUE RIDGE FROM ROUGHLY FLOYD VA SOUTHWEST INTO THE
NORTHERN MOUNTAINS OF NORTH CAROLINA.

BY MONDAY NIGHT...THE FORECAST WILL REFLECT DRY HIGH PRESSURE
WINNING OUT ACROSS THE ENTIRE REGION WITH LITTLE IN THE WAY OF CLOUD
COVER REMAINING. THIS REGIME IS EXPECTED TO CONTINUE THROUGH AT LEAST
TUESDAY NIGHT.

HIGH TEMPERATURES WILL GRADUALLY MODERATE AS MORE AND MORE OF THE
REGION EXPERIENCES SUNNY SKIES OVER CLOUDY ONES. NIGHTTIME LOWS
THOUGH WILL TREND LOWER AS LESS CLOUD COVER...LOWER DEW POINTS...AND
LIGHT WINDS YIELD COOLER TEMPERATURES.

BY MONDAY AND TUESDAY NIGHTS...LOWS IN THE MID TO UPPER 50S WILL BE
COMMON ACROSS THE MOUNTAINS WITH READINGS AROUND 60 ACROSS THE
PIEDMONT. HIGH TEMPERATURES BY TUESDAY WILL MODERATE INTO THE UPPER
70S TO AROUND 80 ACROSS MUCH OF THE AREA.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 1145 AM EDT FRIDAY...

DEEP UPPER TROF CROSSING THROUGH THE CENTRAL UNITED STATES
COMPLETELY FLATTENS THE SOUTHEAST RIDGE ON WEDNESDAY AND THURSDAY.
SPREAD OF SOLUTIONS ON MODELS BECOMES QUITE LARGE BY WEDNESDAY.
WPC WAS LEANING TOWARD THE LESS AMPLIFIED...MORE PROGRESSIVE
ECMWF.

THE SURFACE HIGH THAT WEDGES DOWN THE APPALACHIANS STARTS OUT
OVER NEW ENGLAND...THEN BY WEDNESDAY THE PARENT HIGH MOVES
OFFSHORE. BY THAT TIME THE AMOUNT OF EASTERLY FLOW AND RIDGING
WILL BE INFLUENCED BY WHATEVER TROPICAL SYSTEM WILL BE FATHER EAST
IN THE ATLANTIC.

A COLD FRONT OVER THE GREAT LAKES ON WEDNESDAY WILL APPROACH THE
FORECAST AREA LATE ON THURSDAY. MODELS SUGGEST NOT A LOT OF
SOUTHWARD PUSH OF THIS FRONT. BOUNDARY MAY STILL BE IN THE AREA ON
FRIDAY. AS THE SURFACE WEDGE BREAK DOWN AND THE FRONT
APPROACHES...850 MB TEMPERATURES WILL RISE.

FORECAST AREA WILL BE DRY AT MID AND UPPER LEVELS MONDAY NIGHT
THROUGH WEDNESDAY NIGHT. THEN BY THURSDAY DEEPER MOISTURE COMES
BACK INTO THE AREA ALONG THE FRONT. ECMWF EVEN SHOWED DRYING WELL
BELOW 850 MB ON TUESDAY.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 200 PM EDT SATURDAY...

SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS
AFTERNOON AND EVENING THANKS TO DAYTIME HEATING COMBINED WITH
STRONG LOW LEVEL CONVERGE AS NORTHWESTERLY FLOW COMING OFF THE
MOUNTAINS BUTTS UP AGAINST INCREASINGLY NORTHEASTERLY FLOW ACROSS
THE PIEDMONT AS HIGH PRESSURE BUILDS SOUTH FROM THE GREAT LAKES.
CEILINGS AND VISIBILITIES WILL REMAIN PREDOMINANTLY VFR FOR MOST
LOCATIONS...HOWEVER ATMOSPHERIC MOISTURE REMAINS HIGH...AND
CONDITIONS MAY TEMPORARILY DETERIORATE TO IFR IN THE HEAVIER RAIN
SHAFTS. WITH NO MAJOR DISTURBANCE PASSING OVERHEAD...EXPECT THE
SHOWER ACTIVITY TO BE VERY SPOTTY HIT AND MISS. HAVE ENTERED
MENTION OF SHOWERS INTO THE TAFS...BUT THUNDERSTORMS ARE EXPECTED
TO BE SO ISOLATED THAT DO NOT HAVE ENOUGH CONFIDENCE TO ENTER INTO
THE TAFS AT THIS TIME.

LOW LEVEL CONVERGENCE WILL REMAIN OVERNIGHT...EVEN AS FLOW BEGINS
TO TRANSITION MORE EASTERLY...DRAWING MARITIME AIR INTO THE AREA.
AS SUCH...CEILINGS WILL LOWER TO IFR FOR MUCH OF THE AREA BY
AROUND MIDNIGHT SUNDAY...HOLDING THERE UNTIL LATE SUNDAY MORNING
BEFORE BEGINNING TO IMPROVE. SHOWER ACTIVITY AND DRIZZLE CAN ALSO
BE EXPECTED...WHICH WILL LOWER VISIBILITIES AT TIMES.

SHOWERS WILL BEGIN TO WANE SUNDAY AFTERNOON AS HIGH PRESSURE
CONTINUES TO WEDGE INTO THE REGION...BECOMING THE DOMINANT WEATHER
FEATURE.

EXTENDED AVIATION...

HIGH PRESSURE STRETCHING FROM NEW ENGLAND SOUTHWARD ALONG THE
EASTERN FACE OF THE APPALACHIANS WILL MAINTAIN DRY CONDITIONS
THROUGH THE EARLY HALF OF THE WORKWEEK. LONG RANGE MODELS INDICATE
THAT A POTENTIAL TROPICAL CYCLONE DEVELOPING NEAR THE BAHAMAS
SHOULD REMAIN OFF THE EAST COAST AND NOT IMPACT THE LOCAL WEATHER.
A COLD FRONT WILL SINK SOUTHWARD FROM THE GREAT LAKES ON
THURSDAY...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS AS WELL
AS MVFR/IFR CONDITIONS.

&&

.EQUIPMENT...
THE ASOS TEMPERATURE AT LYNCHBURG (LYH) VA REMAINS INOP DUE TO A
BOARD FAILURE. PARTS HAVE BEEN ORDERED WITH THE RETURN OF COMPLETE
SERVICE UNKNOWN AT THIS TIME. TOWER OBSERVER AUGMENTING DURING
NORMAL SERVICE HOURS.

THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING
ON A FREQUENCY OF 162.450 MHZ IS OFF THE AIR. VERIZON HAS BEEN
CONTACTED. ELECTRONIC TECHNICIANS WILL ADDRESS THE PROBLEM TODAY.

&&

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

&&

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



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