Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 220241
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
941 PM EST FRI NOV 21 2014

.SYNOPSIS...
ARCTIC HIGH PRESSURE WILL REMAIN ACROSS MUCH OF THE REGION TONIGHT
BEFORE SLIDING OFFSHORE SATURDAY INTO SATURDAY NIGHT. A COMPLEX
STORM SYSTEM WILL APPROACH THE REGION FROM THE SOUTHWEST
SUNDAY...MOVING THROUGH THE REGION SUNDAY NIGHT AND EARLY MONDAY
BRINGING WIDESPREAD RAINFALL. UNSEASONABLY WARM CONDITIONS ARE
EXPECTED MONDAY IN THE WAKE OF THIS SYSTEM BEFORE A COLD FRONT
MOVES THROUGH TUESDAY...RETURNING TEMPERATURES TO BELOW NORMAL
FOR THE REST OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS 940 PM EST FRIDAY...

NO ADJUSTMENTS NEEDED TO TONIGHTS FORECAST AT THIS TIME.

HIGH PRESSURE WILL DRIFT EAST TONIGHT INTO SATURDAY. RADIATIONAL
COOLING CONDITIONS EXPECTED OVERNIGHT UNDER THE ARCTIC HIGH WITH
CLEAR SKIES AND CALM WINDS. WHILE IN THE WEST ACROSS THE HIGHER
ELEVATIONS...850 MB WARM ADVECTION IS EXPECTED WITH TEMPERATURES
CLIMBING TO AROUND PLUS 5C BY 12Z SATURDAY. HIGH PRESSURE SLIDES
OFF TO OUR EAST ON SATURDAY.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
AS OF 145 PM EST FRIDAY...

RIDGING BOTH SURFACE AND ALOFT EXTENDING INLAND ACROSS THE SE STATES
WILL WEAKEN SATURDAY NIGHT AHEAD OF THE COMPLEX/LARGE STORM SYSTEM THAT
WILL TAKE SHAPE FROM TX EAST ALONG THE GULF COAST STATES. NEW MODELS
CONTINUE TO SLOW DOWN THE NORTHWARD ADVANCE OF DEEPER MOISTURE WITH
THIS SYSTEM SATURDAY NIGHT AS PIECES OF CONVECTION FROM THE UPPER LOW
WELL TO THE SW AND OVER THE SE WITH THE COASTAL FRONT TEND TO INHIBIT
TRANSPORT. HOWEVER FORECAST SOUNDINGS DO INDICATE PERHAPS ENOUGH
ISENTROPIC LIFT/UPSLOPE AND LOW LEVEL MOISTURE TO POSSIBLY DEVELOP SOME
LIGHT RAIN ALONG THE NW N CAROLINA MOUNTAINS SO KEPT A VERY LOW
POP LATE ALTHOUGH APPEARS LITTLE MORE THAN DRIZZLE AT THIS POINT.
DO EXPECT TEMPS TO RISE GIVEN THE STRONG WARM ADVECTION SETUP SO
REMOVED ALL FROZEN PRECIP MENTION AT THE ONSET DESPITE SOME COLD
AIR LIKELY TRAPPED IN THE DEEPER VALLEYS. ELSW INCREASING CLOUDS
BUT STILL DRY OVERNIGHT WITH LOWS MAINLY 30S BEFORE EDGING UP
LATE.

SIMILAR TO PREVIOUS...GUIDANCE QUICKLY EJECTS THE PARENT LOW WITH THE
SOUTHERN STREAM SHORTWAVE TROUGH WELL TO THE WEST SUNDAY...WITH A
JET DRIVEN BAND OF DEEPER LIFT SWINGING TOWARD THE REGION FROM THE
SW ESPCLY DURING THE AFTERNOON...AND ACROSS MOST SPOTS BY
MIDNIGHT. THIS AHEAD OF A SURFACE WARM FRONT THAT WILL GET SLOWED
UP BY PRECIP INTO A VERY DRY BOUNDARY LAYER...WHICH SHOULD LIKELY
DELAY THE ONSET FARTHER NORTH...BUT ALSO CREATE A WEAK INSITU
WEDGE LATER IN THE DAY. HOWEVER TIMING REMAINS IFFY GIVEN
CONSENSUS OF GOING EVEN SLOWER AND POTENTIAL FOR SOME SPLITTING OF
THE HEAVIER RAIN PER STRONG DYNAMICS WELL TO THE NW AND CONVECTION
ALONG THE COASTAL FRONT OVER THE EASTERN CAROLINAS. FOR NOW
APPEARS EVEN WITH THAT SCENARIO THAT THE DEEP SOUTH/SE FLOW WILL
BE ENOUGH TO OVERCOME TO SOME DEGREE SO CONTINUING THE TREND OF
LIKELY/CAT POPS SLIDING NE SUNDAY AFTERNOON...JUST A COUPLE HOURS
SLOWER SIMILAR TO THE GFS. BRIEF PERIOD OF 50 KNOT WINDS AT 85H
CROSSING THE MTN EMPIRE REGION SUNDAY AFTERNOON REMAINS A CONCERN
FOR AT LEAST ADVISORY WINDS ON THE RIDGES SO KEEPING MENTION IN
THE HWO FOR A FEW COUNTIES OUT WEST. KEPT HIGHS A BIT BELOW THE
MAV MOS AS THE COOL MET MOS VALUES LOOK TOO COOL GIVEN THE SLOWER
NATURE TO PRECIP ARRIVAL INTO THE DRY AIR...AND THE DEGREE OF
WARMING ABOVE.

BEST UPWARD MOTION AS SEEN VIA MODEL DIFFLUENCE FIELDS LIKELY TO OCCUR
SUNDAY EVENING AS THE AXIS OF DEEP MOISTURE ACCELERATES A BIT WITH A
BAND OF HEAVIER RAIN POSSIBLY SWEEPING ACROSS ESPCLY
SOUTHERN/EASTERN SECTIONS. HOWEVER DESPITE STRONG WINDS ALOFT AND
FORECAST HIGH HELICITY...MOST OF THIS TO STAY ABOVE THE LOW LEVEL
INVERSION...AND GIVEN LACK OF MUCH INSTABILITY WILL TAKE A FASTER
SURFACE WARM FRONTAL PASSAGE OVER THE SE TO COINCIDE WITH THE
BETTER SHEAR WHICH DOESNT LOOK TO HAPPEN AT THIS POINT. OTRW
RUNNING WITH OVERALL CAT POPS DURING THE EVENING...THEN QUICKLY
CUTTING BACK TO CHANCE OR LESS OVERNIGHT AS THE UPPER JET RIDES A
VERY PRONOUNCED DRY SLOT ALOFT INTO THE AREA LATE. LOW TEMPS
SHOULD REMAIN MILD AND COULD RISE SOME LATE AS THE FLOW TURNS MORE
SW FROM ABOVE.

ASSOCIATED COLD FRONT TRAILING THE PARENT LOW TO THE NORTH WILL SLIDE
TOWARD THE REGION A BIT FASTER FROM THE WEST MONDAY...WITH THE LAGGING
COLD ADVECTION SPILLING IN MONDAY NIGHT. MOISTURE AHEAD OF THE FRONT
WILL REMAIN VERY SHALLOW BUT MAY BE ENOUGH TO KEEP TEMPS FROM
ZOOMING MONDAY AFTERNOON ESPCLY EAST...AND OVER THE FAR WEST WHERE
MORE OF A SHOWER THREAT COULD OCCUR. LATEST MOS REMAINS VERY WARM
PER SUCH MILD 85H TEMPS THAT LOOK TO PUNCH TO THE SURFACE ON GOOD
MIXING BEFORE THINGS COOL ALOFT LATER ON. SINCE TREND IN THIS
SETUP IS USUALLY FOR THE FRONT TO BE SLOWER CROSSING THE RIDGES
AND IN LINE WITH THE 12Z ECMWF...STAYED ON THE WARM SIDE WITH 60S
WEST AND SOME LOW 70S EAST. POPS IFFY BUT INCLUDED A 20/30 POPS
MOST SPOTS WITH SKIES BECOMING PC MONDAY...THEN MOSTLY ISOLATED
RAIN/SNOW SHOWERS WESTERN SLOPES MONDAY NIGHT AS COLDER AIR OOZES
IN.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 130 PM EST FRIDAY...

TUESDAY INTO WEDNESDAY...AN UPPER LOW IS PROGGED TO PROGRESS FROM
NEAR JAMES BAY NORTHEAST TOWARDS GREENLAND. THE SYSTEMS TRAILING
COLD FRONT IS EXPECTED TO PROGRESS EASTWARD TO NEAR THE EAST COAT OF
THE U.S.  MODEL GUIDANCE OFFERS VARIOUS SOLUTIONS REGARDING A WAVE
OF LOW PRESSURE THAT IS PROGGED TO HEAD NORTH ALONG THIS
FRONT...FROM THE GULF COAST STATES TO THE MID-ATLANTIC SEABOARD BY
MIDDAY WEDNESDAY. ENOUGH SOLUTIONS OFFER THE POTENTIAL THAT THIS WAVE
WILL HELP BUCKLE THE FRONT AND ITS ASSOCIATED MOISTURE WESTWARD...SO
THAT PRECIPITATION RETURNS TO AT LEAST THE EASTERN PARTS OF THE
REGION...IF NOT ALSO CENTRAL PORTIONS. OUR LATEST FORECAST FOR
WEDNESDAY WILL REFLECT THIS POTENTIAL...WITH THE GREATEST CHANCE FOR
PRECIPITATION OVER THE EASTERN PARTS OF THE REGION ON WEDNESDAY.
ENOUGH COLDER AIR WILL HAVE MADE ITS WAY INTO THE REGION FOR SOME
TYPE OF WINTRY PRECIPITATION. GIVEN THE MODEL VARIATIONS...FOR
SIMPLICITY SAKE...WILL ONLY OFFER A RAIN VERSUS SNOW FORECAST AT
THIS TIME. BY WEDNESDAY NIGHT INTO THURSDAY...THIS COASTAL WAVE WILL
BE NEAR THE CANADIAN MARITIMES AND NO LONGER BE A FACTOR IN OUR
FORECAST.

WHAT WILL BECOME A FACTOR IS YET ANOTHER DEEPENING UPPER LOW
THURSDAY INTO FRIDAY. GUIDANCE IS OFFERING THIS ONE TO TAKE A
FARTHER SOUTH TRACK THAN ITS PREDECESSOR...DEEPEN MORE...AND FUNNEL
A STRONGER SURGE OF COLDER AIR INTO OUR REGION. AFTER AN INITIAL
ROUND OF ISENTROPIC LIFT ASSOCIATED PRECIPITATION ON
THURSDAY...ITS ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE AREA
THURSDAY NIGHT. IN ITS WAKE...UPSLOPE SNOW SHOWERS AND GUSTY
NORTHWEST WINDS ARE ANTICIPATED IN THE PREFERRED AREAS OF
SOUTHEAST WEST VIRGINIA THURSDAY NIGHT INTO FRIDAY.

TEMPERATURES THROUGH THE PERIOD WILL TREND LOWER EACH DAY...WITH THE
BIGGEST DROP BEING THURSDAY INTO FRIDAY. TUESDAY IS EXPECTED TO BE
THE ONLY DAY ABOVE NORMAL WITH THE REST OF THE PERIOD BELOW NORMAL.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
AS OF 650 PM EST FRIDAY...

HIGH PRESSURE WILL PROVIDE OUR REGION WITH VFR CONDITIONS TONIGHT
AND SATURDAY. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT AS THE
HIGH PASSES ACROSS THE MID ATLANTIC STATES. THE HIGH CENTER WILL
PUSH OFF THE COAST SATURDAY NIGHT INTO SUNDAY WHICH WILL BRING
SURFACE WINDS AROUND TO THE SOUTHWEST.

HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS THROUGH THE
TAF PERIOD.

EXTENDED DISCUSSION...

THE NEXT SIGNIFICANT WEATHER WILL ARRIVE ON SUNDAY WITH RAIN AND
MVFR OR LOWER CIGS...ESPECIALLY SUNDAY AFTERNOON/NIGHT.
ALSO...STRENGTHENING LOW LEVEL WINDS LATER ON SUNDAY MAY LEAD TO
LLWS...ESPECIALLY THE BLF AREA. A BRIEF RETURN TO VFR DURING
MONDAY OUTSIDE OF THE MOUNTAINS AS A DRY SLOT DEVELOPS BETWEEN THE
EXITING FRONT FROM SUNDAY AND THE NEXT UPSTREAM COLD FRONT. FOR
THE REMAINDER OF NEXT WEEK...EXPECT PERIODS OF MVFR CIGS ACROSS
EASTERN WV/FAR SW VA...BUT MOSTLY VFR ELSEWHERE WITH A COLDER NW
FLOW.

&&

.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...NONE.
NC...NONE.
WV...NONE.

&&

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


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