Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 231140
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
740 AM 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/...
THE BAROCLINIC ZONE...PARKED OVER THE REGION FOR THE PAST SEVERAL
DAYS...WILL BEGIN TO DRIFT WEST TODAY AS CONFLUENT FLOW ALOFT
DEVELOPS ACROSS THE NORTHEAST U.S. THINKS TO A STRONG MID- LEVEL
RIDGE BUILDING NORTHEASTWARD FROM THE MS VALLEY AND A BROAD AREA
OF LOW PRESSURE ACROSS THE NORTHERN. THIS WILL FINALLY PUSH THE
LONG STANDING BAROCLINIC ZONE WEST INTO THE TN VALLEY SUN-MON. IN
SO DOING...MORE STABLE MARITIME AIR WILL SPREAD INTO THE REGION
FROM THE EAST...BEGINNING LATE TODAY...THEN SPREADING WEST TOWARD
THE WESTERN BORDER OF THE CWA BY SUN.

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 /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 735 AM EDT SATURDAY...

FAIRLY POOR AVIATION CONDITIONS EXPECTED THROUGH THE TAF VALID
PERIOD AS BAROCLINIC ZONE...ORIENTED FROM NW-SE...SLOWLY DRIFTS
WESTWARD THROUGH THE WEEKEND AS HIGH PRESSURE MOVES TOWARD THE
NORTHERN MID-ATLANTIC REGION SETTING UP A FAIRLY CLASSIC WEDGE
PATTERN UNDERNEATH A BUILDING UPPER RIDGE. THIS PATTERN WILL
CONTINUE TO RESULT IN VARIABLE CLOUD CONDITIONS...ALONG WITH SCT
SHRA AND SOME TSRA...MAINLY WEST OF THE BLUE RIDGE...DURING THE
AFTERNOON. UNTIL THE BAROCLINIC ZONE DRIFTS FURTHER WEST...CANNOT
RULE OUT -SHRA FROM TIME TO TIME...SO HAVE RETAINED MENTION OF
VCSH MOST HOURS AT MOST SITES. TIMING OF INDIVIDUAL SHORT WAVES OR
IMPULSES RIDING DOWN THE BAROCLINIC ZONE WILL BE DIFFICULT. CIGS
WILL VARY FROM VFR AT TIMES...MAINLY LATE MORNING THROUGH LATE
AFTERNOON...TO MOSTLY MVFR OR WORSE AT NIGHT...LOCALLY IFR- LIFR
IN FOG/LOW CLOUDS. WEDGE DEVELOPMENT AND ATTENDANT MOIST EASTERLY
FLOW WILL PROMOTE MORE WIDESPREAD MVFR-IFR CIGS OVERNIGHT AND
EARLY SUN. VSBYS MVFR-VFR EARLY...LOCALLY IFR-LIFR IN DENSE GROUND
FOG...IMPROVING TO MAINLY VFR AFT 14Z. AGAIN...WEDGE DEVELOPMENT
WILL PROMOTE MORE WIDESPREAD MVFR VSBYS AFT 04Z SUN...BUT CURRENT
THINKING IS THAT LOW STRATUS WILL BE MORE PREVALENT THAN DENSE
FOG. AS THE BACKDOOR FRONT/WEDGE EVOLVES THROUGH THE
DAYTIME...EXPECT WINDS TO TRANSITION TO THE NE-ENE EAST OF THE
BLUE RIDGE...WITH WNW-NW WINDS CONTINUING TO THE WEST...BECOMING
VARIABLE WEST OF THE BLUE RIDGE AFT 00Z.

LOW TO MEDIUM CONFIDENCE IN CIGS/VSBYS THROUGH THE TAF VALID
PERIOD.
MEDIUM TO HIGH CONFIDENCE IN WIND/SPD THROUGH THE TAF VALID
PERIOD.
MEDIUM CONFIDENCE IN TSRA POTENTIAL WEST OF THE BLUE RIDGE AFT
18Z.

EXTENDED AVIATION...

EXPECT FLYING CONDITIONS TO SLOWLY IMPROVE SUNDAY AS HIGH PRESSURE
CONTINUES TO BUILD IN FROM THE NORTHEAST. WILL SEE A FEW SHOWERS
DEVELOP SUNDAY AFTERNOON...MAINLY WEST OF THE BLUE RIDGE...HOWEVER
THE MAIN CONCERN WILL BE EARLY MORNING FOG AND STRATUS. STRATUS
WILL BE SLOW TO BURN OFF THROUGH THE DAY...ALTHOUGH BREAKS WILL
DEVELOP DURING THE AFTERNOON. A BETTER PUNCH OF DRY AIR WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHEAST MAY BE ENOUGH WITH
MIXING/HEATING TO ALLOW FOR INCREASING VFR CONDITIONS MONDAY INTO
TUESDAY UNDER MAINLY DRY 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...RAB
SHORT TERM...DS
LONG TERM...AMS
AVIATION...RAB
EQUIPMENT...RAB/WP


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