Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 290846
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
346 AM EST SAT NOV 29 2014

.SYNOPSIS...
HIGH PRESSURE CENTERED ALONG THE EAST COAST WILL CONTINUE TO MOVE
EAST TODAY. A COLD FRONT OVER THE CENTRAL UNITED STATED TONIGHT
WILL MOVE SOUTHEAST....PASSING THROUGH THE MID ATLANTIC AREA ON
MONDAY AND MONDAY NIGHT. ARCTIC HIGH PRESSURE WILL WEDGE IN FROM
THE NORTH BEHIND THIS FRONT FOR TUESDAY AND TUESDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM EST SATURDAY...

UPPER RIDGE MOVES ACROSS SOUTHEAST UNITED STATES RESULTING IN HEIGHT
RISES ACROSS THE FORECAST AREA TODAY AND TONIGHT. GRADUAL WARM
ADVECTION AT 850 MB AS WINDS BACK FROM THE WEST TO THE SOUTHWEST
WILL BRING 850 MB TEMPERATURES TO ABOUT +5 BY THIS EVENING. WIND
SPEEDS ALSO INCREASE FROM THE SOUTHWEST AS THE HIGH MOVES FARTHER
OFFSHORE. HIGHEST ELEVATIONS WILL BE GUSTY AND STAYED MIXED TONIGHT.

LITTLE INDICATIONS OF ANY SHORT WAVES CROSSING THE REGION TODAY OR
TONIGHT. AFTER THIS MORNING....MID AND UPPER LEVEL MOISTURE
DIMINISHES. NOT EXPECTING MUCH CLOUD COVER THIS AFTERNOON OR
EVENING. LOW CLOUDS MOVE BACK INTO THE FAR WEST AFTER MIDNIGHT.

ACCORDING TO THE NATIONAL OPERATIONAL HYDROLOGIC REMOTE SENSING
CENTER...2-4 INCHES SNOW DEPTH LEFT WAS IN THE WESTERN COUNTY
WARNING AREA...SO HAVE GONE AT OR BELOW GUIDANCE FOR MAXIMUM
TEMPERATURES TODAY.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
AS OF 245 AM EST SATURDAY...

SUNDAY INTO MONDAY...THE AXIS OF THE UPPER RIDGE SHIFTS EAST TO OFF
THE EAST COAST...WHILE A COLD FRONT GRADUALLY MAKES ITS WAY INTO
FIRST THE WESTERN AND NORTHERN PARTS OF THE REGION. ANTICIPATE
TEMPERATURES TO REMAIN ON THE MILD SIDE DURING THIS PART OF THE
FORECAST WITH LIGHT RAIN CHANCES SLOWLY INCREASING FROM WEST TO
EAST...WITH A SLIGHT CHANCE NEAR THE CREST OF THE BLUE RIDGE BY
MONDAY AFTERNOON. THE PIEDMONT REGION IS EXPECTED TO REMAIN IN THE
RAIN-FREE AREA DURING THIS TIME.

MONDAY NIGHT INTO TUESDAY...THE FRONT FOLDS OVER ACROSS THE AREA
ALLOWING FOR A WEDGE OF HIGH PRESSURE TO START WORKING ITS WAY SOUTH
ALONG THE LEE OF THE BLUE RIDGE. ANTI-CYCLONIC FLOW AROUND THE RIDGE
WILL GRADUALLY YIELD A SOUTHEAST...UPSLOPE FLOW ACROSS THE
REGION...WITH FORCING MAXIMIZED ALONG THE BLUE RIDGE. MODEL GUIDANCE
HAS TRENDED COLD WITH THE MAGNITUDE OF THE LOW LEVEL THERMAL PROFILE
IN THE WAKE OF THE BACKDOOR COLD FRONT. NOW...ENOUGH OF THE PROFILE
OFFERS OF TEMPERATURES COLD ENOUGH TO SUPPORT A WINTRY MIX OF SNOW
AND/OR SLEET WITHIN A MIX OF PLAIN RAIN WITHIN A REGION CONFINED BY
ROUGHLY A LEWISBURG WV TO FLOYD VA TO BUCKINGHAM VA LINE. HAVE
ALLOWED FOR THIS MIX IN THE FORECAST MONDAY NIGHT. ON
TUESDAY...CHOSE A RAIN VERSUS SNOW FORECAST IN THE FORENOON TO
CONFORM TO LOCAL POLICY OF NO MORE THAN TWO WEATHER TYPES FROM DAY 4
AN ONWARD IN THE FORECAST. LIKEWISE...THE AFTERNOON WILL OFFER A
RAIN VERSUS FREEZING RAIN FORECAST AS THE LOW LEVEL THERMAL PROFILE
AGAIN WARMS TO ABOVE FREEZING ALOFT WITH ONLY A FEW LOCATIONS AT THE
SURFACE REMAINING AT OR BELOW FREEZING. TUESDAY
NIGHT...PRECIPITATION CHANCES DECREASE AS A DEVELOPING WARM
FRONT LIFTS NORTH OF THE REGION.

TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL REMAIN WELL
ABOVE NORMAL THROUGH MONDAY NIGHT. TUESDAY WILL BE NOTABLE
COLDER...AND BELOW NORMAL...AS A STRONG WEDGE DEVELOPS ACROSS THE
REGION.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 320 PM EST THURSDAY...

BY WEDNESDAY MORNING...THE WEDGE COULD BE AS FAR SOUTH AS THE
FLORIDA PANHANDLE. BULK OF THE MOISTURE WILL EXIT WITH THE
TROUGH...HOWEVER WARM MOIST AIR WILL BEGIN TO OVERRUN THE COOLER
LOW LEVELS TUESDAY NIGHT INTO WEDNESDAY. THICK LOW CLOUDS AND FOG
WILL LIKELY ENGULF THE FORECAST AREA TUESDAY NIGHT...LINGERING
INTO THURSDAY MORNING. WARM MOIST AIR ADVECTING IN ALOFT AND
INCREASING ISENTROPIC LIFT TUESDAY NIGHT INTO WEDNESDAY
MORNING...MAY BE ENOUGH TO PRODUCE LIGHT PRECIPITATION ALONG AND
EAST OF THE BLUE RIDGE. CONSIDERING HOW DRY THE PARENT HIGH IS
OVER NEW ENGLAND...MEASURABLE PRECIPITATION MAY BE LIMITED TO THE
EASTERN SLOPES OF THE BLUE RIDGE. CONFIDENCE IS NOT
HIGH...THEREFORE WILL KEEP POPS UNDER 30 PERCENT.

PRECIPITATION TYPE WILL BE THE CHALLENGE AS DRY COOLER LOW LEVEL AIR
WILL ADVANCE SOUTH WITH WARM MOIST AIR ALOFT ADVECTING NORTH. LOW
LEVEL THICKNESSES ARE AROUND 1300M OVER THE ALLEGHANY HIGHLANDS AND
SOUTHERN SHENANDOAH VALLEY TUESDAY NIGHT...THEN GRADUALLY INCREASE
GOING INTO WEDNESDAY MORNING. 85H TEMPERATURES AROUND 0C ALONG THE
SOUTHWEST VIRGINIA BLUE RIDGE...+2C ACROSS THE NORTH CAROLINA
HIGHLANDS. THESE 85H TEMPERATURES ALSO WARM GOING INTO WEDNESDAY
MORNING. VIEWING MODEL SOUNDINGS...THE COLD SUB-FREEZING AIR IS
AROUND 4000 FEET THICK. SOUNDING PROFILES ALSO SUGGESTING ANY
MEASURABLE P-TYPE WOULD BE SLEET OR FREEZING RAIN. LOOKING AT
SOUNDING PROFILES...I WOULD LEAN TOWARDS A FREEZING FOG/DRIZZLE
SCENARIO...A GLAZING OF ICE ALONG THE EASTERN SLOPES OF THE BLUE
RIDGE BETWEEN 2500-4000 FT.. WE ALSO NEED TO UNDERSTAND THAT THIS IS
A DAY 5-6 FORECAST AND MODELS MAY CHANGE OVER THE NEXT SEVERAL DAYS.
FOR NOW...WILL KEEP MAJORITY OF PRECIPITATION AS RAIN. WITH
CONFIDENCE BEING VERY LOW AT THIS TIME FOR A POSSIBLE TRACE
EVENT...WILL NOT ADD TO THE HAZARDOUS WEATHER OUTLOOK (HWO) AT THIS
TIME.

FOLLOWING P-TYPE CONCERNS INTO WEDNESDAY...THE NEXT QUESTION TO
ANSWER IS...HOW LONG WILL THE WEDGE REMAIN OVER THE AREA.
SURPRISING...THE USUALLY PROGRESSIVE GFS LINGERS A PIECE OF THE
WEDGE OVER THE REGION INTO THURSDAY MORNING. DESPITE THE LINGERING
WEDGE...12Z GFS STILL HAS THE WINDS TURNING TO THE SOUTH BY
WEDNESDAY AFTERNOON. WE WILL CONTINUE TO KEEP THE WEDGE AND CLOUDS
IN THE AREA INTO THURSDAY MORNING WITH THE PIEDMONT BEING THE LAST
TO CLEAR. THE WEDGE WILL ERODE EACH PERIOD...FROM THE SOUTHWEST TO
NORTHEAST AND FROM TOP-DOWN. BY THURSDAY AFTERNOON...A WARM FRONT
AND PRESSURE FALLS OVER THE OHIO VALLEY WILL BREAK THE WEDGE.
TEMPERATURES COULD POSSIBLY WARM 10F OR SO IN JUST A FEW HOURS.
ONCE THE WEDGE BREAKS...WE COULD SEE A DAY OR SO OF WARM
TEMPERATURES...THEN A WEAK COLD FRONT WILL BRING LIGHT RAIN
SHOWERS TO THE REGION THURSDAY NIGHT AND FRIDAY. THIS FRONT COULD
STALL OVER THE REGION FRIDAY.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
AS OF 1150 PM EST FRIDAY...

VFR CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD. A NORTHERN
STREAM SHORT WAVE ALONG WITH WAA WILL RESULT IN A PERIOD OF
MID/HIGH CLOUDS SKIRTING THE NORTHERN PARTS OF THE CWA OVERNIGHT
AND ESPECIALLY FIRST HALF OF THE DAY SAT. AS THE DISTURBANCE MOVES
NE OF THE REGION BY AFTERNOON...MID/HIGH CLOUDS WILL DECREASE
LEAVING EITHER SKC OR SCT250. OTHERWISE...NO CIGS BELOW 10KFT THROUGH
THE TAF VALID PERIOD. NO VISIBILITY ISSUES THROUGH THE TAF VALID
PERIOD. WINDS BECOMING SW-S OVERNIGHT/EARLY SAT...INCREASING IN
SPEED 8-10KTS AFT 14Z SAT WITH LOW END GUSTS AT BLF/BCB/ROA/DAN AS
GRADIENT TIGHTENS BETWEEN DEPARTING ARCTIC HIGH AND LOW PRESSURE
CENTRAL U.S.

HIGH CONFIDENCE IN VFR CIGS/VSBYS THROUGH THE TAF VALID PERIOD.
MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID
PERIOD.

EXTENDED DISCUSSION...
VFR CONDITIONS ARE EXPECTED TO LINGER SATURDAY NIGHT AND MUCH OF
SUNDAY AHEAD OF A COLD FRONT THAT MAY BRING MVFR CIGS TO AREAS
FROM KBCB WESTWARD. THIS COLD FRONT WILL REACH THE REGION MON-TUE
WITH A CHANCE OF -SHRA BR AND ASSOCIATED MVFR TO LOCALLY IFR
CIGS/VSBYS ALONG THE FRONT. A WEDGE PATTERN EXPECTED TO SET UP BY
MON NIGHT/TUE WITH WIDESPREAD MVFR-IFR CIGS AND -RA. SOME -FZRA
APPEARS POSSIBLE TUE MORNING THROUGH THE NEW RIVER VALLEY INTO THE
SHENANDOAH VALLEY.

&&

.EQUIPMENT...
AS OF 1030 AM EST WEDNESDAY...

VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WAS MALFUNCTIONING
AGAIN. PARTS HAVE BEEN ORDER BUT THE REPAIR MAY NOT BE UNTIL
MONDAY. THE VISIBILITY AT KLYH WILL BE AUGMENTED BY STAFF WHEN THE
CONTROL TOWER IS OPEN...OTHERWISE THE VISIBILITY WILL BE MISSING.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...DS
LONG TERM...RCS
AVIATION...PC/RAB
EQUIPMENT...AMS


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