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451
FXUS61 KRNK 240004
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
704 PM EST SUN NOV 23 2014

.SYNOPSIS...
A WARM FRONT WILL LIFT NORTH ACROSS THE REGION TONIGHT. THE RAIN
MAY BE HEAVY AT TIMES THIS EVENING AND EARLY TONIGHT...AND WINDS
WILL BECOME QUITE GUSTY ACROSS THE MOUNTAIN EMPIRE REGION AND
OTHER HIGH ELEVATIONS WEST OF THE BLUE RIDGE. UNSEASONABLY WARM
CONDITIONS ARE EXPECTED MONDAY IN THE WAKE OF THIS SYSTEM...BEFORE
A COLD FRONT MOVES THROUGH MONDAY NIGHT INTO TUESDAY...RETURNING
TEMPERATURES TO BELOW NORMAL FOR THE REST OF THE WEEK. THERE IS
THE POTENTIAL FOR A COASTAL STORM TO IMPACT PARTS OF THE MID
ATLANTIC FOR MID WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 630 PM EST SUNDAY...

WINDS HAVE BEEN GUSTING UP TO 35-40 KTS AT BLF AND WEST...AS CORE
OF LLJ MOVES ACROSS THE CENTRAL APPALACHIANS. A FEW MORE HOURS ARE
EXPECTED OF HIGHER WINDS IN THE FAVORED WRN SLOPES WITH A SE
COMPONENT TO THE WIND. NOT GOING TO ADD SUMMERS OR WESTERN
GREENBRIER TO AN ADVISORY BUT WE COULD SEE A SMALL WINDOW REST OF
THE EVENING WHERE HIGHER RIDGES COULD GUST TO 45 TO 50 MPH...BUT
BY MIDNIGHT FLOW TURNS MORE SOUTH TO SSW...WITH MAIN JET MOVING
OUT.

RADAR SHOWING MORE OF A SOLID AREA OF RAIN MOVING NWD ACROSS NC
INTO SW VA. THE 21Z HRRR SHOWING THIS FAIRLY WELL WITH THE LOCAL
WRF NOT TOO FAR OFF...AND ADJUSTED POPS THROUGH MIDNIGHT TO
ACCOUNT FOR BETTER THREAT IN THE WEST. REGIONAL RADAR SHOWS THE
DRY SLOT MOVING ACROSS ERN AL/WRN GA INTO SRN TN....WITH UPPER
SHORTWAVE PUSHING EAST OF MEMPHIS TN. SOLID SHIELD OF RAIN WILL BE
LIFTING ACROSS BETWEEN NOW AND 1 AM...AND SHOULD CLEAR OUR CWA
AFTER 1-2 AM.

ADJUSTED TEMPS DOWN ACROSS THE WEDGE AREAS THIS EVENING AS TEMPS
RUNNING COOLER THAN EARLIER FORECAST. STILL LOOKS LIKE WARM FRONT
LIFTING NORTH WITH WEDGE BREAKING UNDER THE MODERATE TO HEAVY RAIN
SHOULD CAUSE TEMPS TO STEADY OR SLIGHTLY RISE OVERNIGHT...PER
PREVIOUS FORECAST.

AS FAR AS SVR THREAT FORECAST EFFECTIVE SHEAR AND CAPE SUGGEST
THAT OUR CWA WILL BE OUTSIDE THE WIND THREAT...THOUGH SOME HIGHER
GUSTS COULD OCCUR AROUND MIDNIGHT SOUTH OF THE DAN/SOUTH BOSTON
AREA.

PREVIOUS VALID DISCUSSION...
WIND ADVISORY REMAINS IN EFFECT FOR THE COUNTIES OF TAZEWELL AND
SMYTH IN VIRGINIA AND MERCER IN WEST VIRGINIA.

BROAD UPPER LEVEL 500H TROUGH WILL ENCOMPASS MUCH OF THE CENTRAL
CONUS FOR MONDAY TO START THE WORKWEEK. A COLD FRONT WILL APPROACH
FROM THE WEST MONDAY. A WARM SECTOR SOUTHERLY WINDS WILL RESULT IN A
BREEZY MILD MONDAY. 1000-500MB THICKNESS VALUES OF 565-570DM AND
850H TEMPERATURES AROUND PLUS 10C SUPPORT SURFACE TEMPERATURES FROM
AROUND 60 DEGREES IN THE MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT.
THE SURFACE COLD FRONT CROSSES THE MOUNTAINS LATE IN THE DAY... WITH
GFS SOLUTION A LITTLE QUICKER THAN THE NAM/ECMWF.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 338 PM EST SUNDAY...

ON MONDAY NIGHT LOW LEVEL MOISTURE IS BANKED UP AGAINST THE WESTERN
SLOPES OF THE APPALACHIANS. MODELS ERODE LOW LEVEL MOISTURE ON
TUESDAY MORNING.

OVERALL PATTERN THIS TIME FRAME IS FOR SPLIT FLOW WITH AN ACTIVE
NORTHERN STREAM ALONG THE CANADIAN/NORTHERN U.S. BORDER AND SOUTHERN
STREAM THAT HAS A STRONG SHORT WAVE AT THE BASE OF THE TROF OVER THE
LOWER MISSISSIPPI VALLEY BY LATE TUESDAY. EVOLUTION AND TIMING OF
LONG WAVE TROF FROM POSITIVE TILT TO NEGATIVE TILT AND AMOUNT OF
PHASING BETWEEN THE TWO JET STREAMS WILL IMPACT THE RESULTING TRACK
OF THE GULF TO EAST COAST SURFACE LOW AND LOCATION OF THE HEAVIEST
PRECIPITATION. AT THIS TIME SPREAD IN DIFFERENT MODELS IS LARGE.
HIGHEST CONFIDENCE IS WITH THE TIMING BUT MUCH LOWER WITH THE
LOCATION AND TYPE OF PRECIPITATION. WILL BE LEANING TOWARD BLEND OF
THE ECMWF AND GFS AS SUGGESTED BY WPC.

MODELS SHOW MID ATLANTIC REGION IN THE RIGHT REAR QUADRANT OF A 170
KNOT UPPER JET BY LATE TUESDAY NIGHT. AT THE SURFACE THE COLD FRONT
MOVES OFF THE EAST COAST MONDAY NIGHT THEN HIGH PRESSURE BUILDS FROM
THE TENNESSEE VALLEY INTO THE MID ATLANTIC STATES ON TUESDAY. LOW
PRESSURE DEVELOPS IN THE GULF OF MEXICO ON TUESDAY...THEN TRACKS
ACROSS FLORIDA TUESDAY NIGHT. THE LOW SHOULD BE OFF THE SOUTH
CAROLINA COAST ON WEDNESDAY MORNING AS IT MOVES NORTHEAST AND BEGINS
TO DEEPEN.

ONCE THE LOCATION OF THE PRECIPITATION IS DETERMINED...TEMPERATURES
WILL INFLUENCE WHAT TYPE OF PRECIPITATION WILL OCCUR. EVEN TAKING THE
COOLER MET/SREF GUIDANCE FOR TEMPERATURES ON TUESDAY NIGHT AND
WEDNESDAY...SURFACE VALUES MAY STILL BE TOO WARM EAST OF THE BLUE
RIDGE TO SUPPORT ANYTHING BUT RAIN. HAVE USED PARTIAL THICKNESS
VALUES...MAINLY FROM THE GFS/ECMWF TO PLACE RAIN/SNOW LINE. THIS
WILL CHANGE AS THE EVENT DRAWS CLOSER.

LOOKED AT PROBABILITY FOR SNOW AND CORRELATION WITH PAST ANALOG
EVENTS. APPEARS THERE IS AT LEAST THE POTENTIAL FOR SOME WINTER
PRECIPITATION. SINCE WEDNESDAY IS A MAJOR TRAVEL DAY WILL MENTION
POTENTIAL FOR WINTER PRECIPITATION IN THE HAZARDOUS WEATHER
OUTLOOK.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 130 PM EST SUNDAY...

THIS PORTION OF THE FORECAST STARTS WITH THE AFTERMATH OF WHAT
UNFOLDS TUESDAY NIGHT INTO WEDNESDAY EVENING. GIVEN THERE STILL IS
GENEROUS UNCERTAINTY IN THOSE EVENTS...THE EVENTS AFTERWARDS ARE
EQUALLY CHALLENGING. THE GENERAL CONSENSUS IS FOR A LOW/TROUGH TO
DEEPEN ACROSS THE GREAT LAKES/OHIO VALLEY AS THE SYSTEM ALONG THE
COAST HEADS NORTHEAST...AND MAKES WAY FOR THE UPSTREAM SYSTEM TO
ENTER OUR REGION. THE PAST FEW DAYS...GUIDANCE HAS TRANSITIONED THIS
SYSTEM FROM A SLOWER...MORE AMPLIFIED SYSTEM INTO ONE THAT IS MORE
PROGRESSIVE AND THE BULK OF ITS ENERGY REMAINS NORTH OF THE REGION
AS IT MOVES EASTWARD. THAT TREND CONTINUES TODAY. OUR FORECAST WILL
REFLECT LITTLE CHANGE FROM THE PRIOR DURING THE THURSDAY THROUGH
FRIDAY TIMEFRAME. THE HIGHLIGHTS HERE ARE UPSLOPE RAIN/SNOW SHOWERS
ACROSS SOUTHEAST WEST VIRGINIA AND NEIGHBORING COUNTIES OF SOUTHWEST
VIRGINIA. A DECENT NORTHWEST FLOW WILL HELP CLOUDS TO A MINIMUM EAST
OF THE CREST OF THE BLUE RIDGE AND ADD A TOUCH OF A WARMING
INFLUENCE. PARTLY TO MOSTLY CLOUDY SKIES AND COOLER TEMPERATURES
WILL BE THE RULE FOR THE MOUNTAINS.

SATURDAY INTO SUNDAY THE REGION TRANSITIONS INTO MORE OF A ZONAL
PATTERN. THERE IS CONSISTENCY IN EACH MODEL CONCERNING THAT FEATURE.
WHAT VARIES SIGNIFICANTLY IS THE TIMING...TRACK AND SPEED OF A
DISTURBANCE MOVING WITHIN THIS ZONAL FLOW THAT MAY OR MAY NOT IMPACT
OUR REGION. AT THIS TIME...HAVE PLACED THE GREATEST FORECAST WEIGHT
ON A MODEL CONSENSUS THAT OFFERS A SMALL CHANCE OF LIGHT RAIN/SNOW
MAINLY IN THE WESTERN PARTS OF THE AREA SATURDAY NIGHT INTO EARLY
SUNDAY WITH TEMPERATURES TRENDING MILDER OVER THE WEEKEND.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 650 PM EST SUNDAY...

WINDS...RAIN AND CLOUDS WILL HINDER AVIATION OPERATIONS
THROUGH THE MORNING MONDAY.

CIGS WILL BE VARIABLE IN THE IFR/MVFR RANGE WITH LIGHT TO MODERATE
RAIN EXPECTED THIS EVENING INTO EARLY OVERNIGHT. THINK THE DECENT
RAIN WILL BE EXITING AFTER MIDNIGHT IN THE WESTERN TAF
SITES/BLF/LWB...AND LYH/DAN AFTER 07Z. WITH IN SITU WEDGE IN PLACE
EARLY THIS EVENING AND STRONG LLJ...WILL SEE A PERIOD OF LOW LVL
WIND SHEAR WHICH ENDS AFTER MIDNIGHT...AT ALL SITES.

OVERNIGHT...MAIN ISSUE WILL BE WHETHER LEFTOVER MOISTURE CAN LEAD
TO FOG...BUT THINK WITH SOUTH TO SSW WINDS APPEARING TO STAY UP
WILL BE LIMITED IN FOG DEVELOPMENT. WILL KEEP CIGS MVFR THOUGH
OVER MUCH OF THE NIGHT THOUGH SEEING DRY SLOT INTO AL/GA MAY BRING
VFR CIGS OR EVEN SCATTERING THEM OUT IN BLF BY DAWN.

SW WINDS AHEAD OF THE COLD FRONT TO KEEP VFR AT ALL TAF SITES BY
LATE MONDAY MORNING. THE ISSUE WILL BE THE WINDS WITH 10-15 KT
SUSTAINED GUSTING TO 20-30 KNOTS AT TIMES.

WIND WILL TURN MORE WESTERLY LATE IN THE TAF PERIOD BUT LEFT THAT
OUT FOR NOW IN THE TAFS GIVEN SUCH AN ACTIVE FIRST 12-18 HOURS.

CONFIDENCE FOR SUB VFR THROUGH TONIGHT IS HIGH...BUT LOW ON TIMING
OF IFR VS MVFR WITH RESPECT TO CIG/VSBY...AGAIN FLUCTUATIONS WILL
OCCUR BASED ON RAINFALL INTENSITY.

CONFIDENCE IS HIGHER MONDAY WITH RETURN TO VFR MOST
LOCATIONS...WITH A SMALL WINDOW IN THE MORNING OF MVFR.


EXTENDED DISCUSSION...

WINDS WILL STAY GUSTY MONDAY NIGHT BEHIND COLD FRONT....WITH
POTENTIAL FOR SUB VFR CIGS IN THE MTNS...WHILE VFR IS EXPECTED TO
THE EAST. ANOTHER STORM SYSTEM IS EXPECTED TO MOVE UP THE
SOUTHEAST COAST BY EARLY WEDNESDAY WHICH MAY BRING WINTRY PRECIP
TO THE AREA ALONG WITH SUB VFR AT ALL SITES. LOOKS LIKE FLIGHTS
WILL BE IMPACTED GREATLY ACROSS THE MID ATLANTIC INTO THE
NORTHEAST WITH THIS SYSTEM WITH STRONG WINDS EXPECTED ALONG WITH
WIDESPREAD PRECIPITATION. AROUND HERE LOOKS LIKE WE WILL
EXPERIENCE SUB VFR AT LEAST WED INTO EARLY THANKSGIVING BEFORE
HIGH PRESSURE WORKS IN FROM THE WEST...THOUGH WINDS MAY STAY UP
THROUGH THU NIGHT...WITH UPSLOPE LOWER CIGS AT BLF/LWB.

&&

.EQUIPMENT...
AS OF 215 PM EST FRIDAY...

THE VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WILL BE OUT
OF SERVICE UNTIL PARTS ARRIVE TO REPLACE THE SENSOR. UNTIL THEN
THE VISIBILITY WILL ONLY BE REPORTED WHEN THE CONTROL TOWER IS
STAFFED.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND ADVISORY UNTIL 1 AM EST MONDAY FOR VAZ007-009.
NC...NONE.
WV...WIND ADVISORY UNTIL 1 AM EST MONDAY FOR WVZ042.

&&

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




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