Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 252348
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
748 PM EDT SAT APR 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO SHIFT OFF THE COAST TODAY AS A LOW
PRESSURE SYSTEM PUSHES EAST FROM THE CENTRAL PLAINS...BRINGING RAIN
TO THE CENTRAL APPALACHIANS TODAY AND TONIGHT. THE SYSTEM WILL EXIT
TO THE EAST SUNDAY MORNING...WITH HIGH PRESSURE BUILDING IN FROM THE
WEST DURING THE AFTERNOON. ANOTHER LOW PRESSURE SYSTEM IS EXPECTED
TO AFFECT THE SOUTHEAST AND MID ATLANTIC REGION DURING THE MIDDLE OF
NEXT WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 345 PM EDT SATURDAY...

LATEST VISIBLE SATELLITE IMAGES SHOW CLEARING UPSTREAM ACROSS ERN
KY AND TN. THIS IS ALLOWING TEMPS TO SURGE AND LOW LEVEL
INSTABILITY IS INCREASING WITH CAPE VALUES NOW AOA 2000J/KG. THIS
IS SETTING THE STAGE FOR VIGOROUS CONVECTION TO OCCUR AND MOVE IN
OUR DIRECTION. COOL AND STABLE AIR ANCHORED IN A WEDGE SITUATION
WILL PROHIBIT ANY STORMS FROM MOVING INTO THE REGION...THOUGH
EXTREME WESTERN AND SOUTHERN AREAS MAY BE VULNERABLE IF THE EDGES
OF THE WEDGE ERODE MORE THAN ANTICIPATED. THE NAM AND ITS
ASSOCIATED MESO MODELS HAVE BEEN HINTING AT THIS CONVECTION FOR
THE LAST FEW RUNS AND BELIEVE THIS MAY BE THE SOLUTION OF CHOICE.
HIGHEST PRECIPITATION AMOUNTS WILL BE FOUND FROM THE MOUNTAIN
EMPIRE REGION THROUGH NORTHWEST NORTH CAROLINA BUT WILL TEMPER QPF
AMOUNTS DOWN FROM RAW MODEL OUTPUT IN ANTICIPATION OF CONVECTION
WEAKENING AS IT ENCOUNTERS LESS FAVORABLE CONDITIONS. WILL HAVE TO
KEEP AN EYE ON EXACTLY HOW THINGS UNFOLD TO SEE IF ANY SEVERE OR
HYDRO CONCERNS WILL AFFECT EXTREME SW PORTION OF OUR AREA BUT IT
CURRENTLY LOOKS LIKE WE WILL GET BY WITHOUT ANY SIGNIFICANT
PROBLEMS.

ALL OF THIS IS BEING DRIVEN BY A WARM FRONT DRAPED OVER THE REGION
EXTENDING FROM A LOW PRESSURE SYSTEM MOVING OUT OF THE MID
MISSISSIPPI VALLEY. THE LOW WILL CROSS OUR REGION TONIGHT INTO
SUNDAY AND BRING AN END TO THE BULK OF THE PRECIPITATION. TEMPS
SHOULD PUSH UPWARDS LATE TOMORROW IN ANTICIPATION OF SOME LATE
BREAKS OF SUN BUT FOR THE MOST PART WE ARE LOOKING AT COOL AND
DAMP CONDITIONS WITH TEMPS WELL BELOW NORMAL TO CLOSE OUT THE
WEEKEND.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 330 PM EDT SATURDAY...

DEEP UPPER LEVEL TROUGH IS FORECAST TO REMAIN POSITIONED OVER THE
WESTERN ATLANTIC THE FIRST HALF OF NEXT WEEK.  THIS WILL PROMOTE
COOL NORTHERLY FLOW ACROSS THE MID ATLANTIC YIELDING COOLER THAN
NORMAL TEMPERATURES.

A SHORT WAVE EMBEDDED WITHIN THE UPPER LOW WILL CROSS THE FORECAST
AREA FROM THE NORTHWEST ON MONDAY.  THIS FEATURE WILL RESULT IN
MAINLY CLOUD COVER...BUT SOME INSTABILITY PER LATE APRIL SUN...CAPE
OF 100-200 J/KG...MAY SPAWN A FEW SHOWERS...ESP ACROSS THE MTNS
OF WV AND VA HIGHLANDS. WITH 850MB TEMPS NEAR 0C...CAN NOT TOTALLY
RULE OUT A FEW FLAKES OF SNOW MIXING IN...ESPECIALLY AT ELEVATIONS
ABOVE 3500 FT...BUT CERTAINLY NOTHING OF ANY CONSEQUENCE.

FOR TUESDAY...THE UPPER TROUGH SHIFTS A BIT MORE OFFSHORE ALLOWING
FOR LESS CLOUDS...MORE SUN AND BETTER DRYING. TEMPERATURES ALOFT
WARM A FEW DEGREES WHICH SHOULD PROMOTE SLIGHTLY WARMER BOUNDARY
LAYER TEMPERATURES...HIGHS TESTING 60 IN THE MOUNTAINS AND NEAR 70
IN THE PIEDMONT.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 330 PM EDT SATURDAY...

AN AREA OF LOW PRESSURE WILL BE TRACKING ACROSS THE SOUTHERN PART OF
THE CONUS FOR MID WEEK. MODELS HAVE BEEN IN DISAGREEMENT AS TO HOW
THIS SYSTEM WILL TRACK ONCE IT REACHES OUR PART OF THE COUNTRY...
SOLUTIONS RANGING FROM A WELL DEVELOPED CYCLONE TO AN OPEN WAVE.
LATEST GUIDANCE SUGGESTS THE BULK OF THE UPPER LEVEL SUPPORT WILL
PASS SOUTH OF OUR REGION...HOWEVER...OPPORTUNITY STILL EXISTS FOR
NORTHWARD JOG OF STORM TRACK...SO WILL MAINTAIN AT LEAST A CHANCE
THREAT FOR WETTING RAIN IN THE WEDNESDAY-THURSDAY TIME FRAME.

IN ADDITION TO THE SOUTHERN STREAM SYSTEM...THERE IS ENERGY THAT IS
FORECAST TO DIVE SOUTHEAST FROM THE GREAT LAKES PROVIDING ANOTHER
OPPORTUNITY FOR COOL AIR TO INFILTRATE THE REGION FOR WEDNESDAY AND
THURSDAY.  RESIDENCE TIME OF THE COOL AIRMASS WILL BE DEPENDENT ON
WHETHER ANY PHASING TAKES PLACE BETWEEN THE SOUTHERN/NORTHERN STREAM
SHORT WAVES.  IF THE ENERGY PHASES AND A FULL BLOWN CYCLONE WRAPS UP
ALONG THE EAST COAST ON THURSDAY...THEN COOL NORTHERLY FLOW WILL
PERSIST INTO FRIDAY AND SATURDAY.  IF THE STREAMS DO NOT PHASE THEN
THE WAVE WILL BE MORE PROGRESSIVE AND PASS OFF THE COAST QUICKER
ALLOWING FOR CONDITIONS TO MODERATE AND DRY OUT FOR FRIDAY AND
SATURDAY.

FOR THIS FORECAST PACKAGE HAVE LEANED MORE TOWARD THE LESS AMPLIFIED
SOLUTION CONFINING PRECIP THREAT AND COOL AIRMASS TO THE WEDNESDAY-
THURSDAY PERIODS FOLLOWED BY A WARMUP FOR THE WEEKEND.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
AS OF 735 PM EDT SATURDAY...

IN-SITU WEDGE WILL REMAIN OVER THE AREA THROUGH MIDNIGHT. HIGH
CONFIDENCE OF WIDESPREAD LIFR STATUS...FOG AND DRIZZLE IN ALL BUT
KBLF.

CLUSTER OF THUNDERSTORMS WAS APPROACHING KLWB AT THE 00Z START OF
THE TAF FORECAST PERIOD SO HAVE ADDED T AND CB INTO THE FORECAST.

LARGER AREA OF THUNDERSTORMS IN WESTERN KENTUCKY IS EXPECTED TO
TRACK EAST AND REACH SOUTHWEST VIRGINIA MAINLY AFTER 03Z/11PM.
THE STORMS WILL WEAKEN AS THEY ENCOUNTER THE WEDGE AND STABLE AIR
OVER THE REGION BUT PRECIPITATION WILL STILL MOVE ACROSS THE AREA
BEFORE 12Z/8AM. OTHERWISE STRATUS AND DENSE FOG WILL PERSIST
OVERNIGHT.

LOWER CONFIDENCE ON THE WINDS TONIGHT AND SUNDAY. LOW PRESSURE
OVER KENTUCKY WILL MOVE EAST TONIGHT AND A LOW WILL DEVELOP OFF
THE CAROLINA COAST EARLY SUNDAY AND BECOME THE DOMINANT LOW. AS
THE LOW DEEPENS OFF THE COAST...WINDS WILL BECOME NORTH THEN
NORTHWEST. DO NOT ANTICIPATE MUCH IMPROVEMENT IN CEILINGS EAST OF
THE BLUE RIDGE ON SUNDAY UNTIL WINDS BECOME NORTHWEST. THIS MAY
NOT BE UNTIL LATE IN THE DAY...MAINLY AFTER 21Z/5PM.

EXTENDED AVIATION DISCUSSION...

FLYING CONDITIONS WILL CONTINUE TO IMPROVE SUNDAY EVENING AS THE
LOW PULLS FARTHER OFFSHORE AND WEAK HIGH PRESSURE BUILDS IN FROM
THE NORTHWEST...WITH MOST LOCATIONS BACK TO VFR BEFORE MIDNIGHT
MONDAY.

BREEZY NORTHWEST FLOW IS EXPECTED FOR MONDAY AND EARLY TUESDAY
WITH HIGH PRESSURE BUILDING IN FROM THE NORTHWEST...VFR
CONTINUES.

BY WEDNESDAY A SOUTHERN STREAM SYSTEM APPEARS TO MAINLY
AFFECT THE GULF COAST REGION TO THE CAROLINAS...BUT COULD SEE RAIN
AND/OR SUB VFR CEILINGS INTO THE DAN-BCB-BLF AREA...BUT CONFIDENCE
IS LOW AT THIS TIME.

&&

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

&&

$$
SYNOPSIS...MBS
NEAR TERM...MBS
SHORT TERM...PM
LONG TERM...PM
AVIATION...AMS/MBS


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