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000
FXUS61 KAKQ 051405
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
905 AM EST THU DEC 5 2013

.SYNOPSIS...
TWO WARM FRONTS WILL LIFT NORTHWARD TODAY. THE FIRST WILL EXIT TO
THE NORTH THIS MORNING AND THE SECOND WILL LIFT THROUGH THE REGION
THIS AFTERNOON...SPREADING LIGHT RAIN SHOWERS ACROSS THE SOUTHERN
HALF OF THE FORECAST AREA. A SLOW MOVING COLD FRONT IS EXPECTED
TO MOVE INTO THE AREA BY MID DAY FRIDAY...FOLLOWED BY A PERIOD OF
UNSETTLED WEATHER THROUGH THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE AS OF 9AM EST...
PATCHY DENSE FOG CONTINUES TO DISSIPATE THIS MORNING AND HAVE
ALLOWED SPS TO EXPIRE PER LATEST SFC OBS AND WEB CAM IMAGES. STILL
SOME PATCHY FOG UNDER 1 NM ALONG THE COAST THAT MAY LINGER UNTIL
EARLY AFTERNOON AND HAVE ADJUSTED WX GRIDS TO ACCOUNT FOR THIS.
NEXT AREA OF CONCERN IS A BATCH OF SHOWERS CURRENTLY MOVING INTO
SW PORTIONS OF THE FA. INCREASED TO CHC POPS (30-40%) ACROSS THIS
AREA AND ALSO TO THE I-95 CORRIDOR THROUGH EARLY AFTERNOON AS THESE
SHOWERS CONTINUE TO SPREAD EAST. IF THE LOWER STRATUS ACROSS THE
AREA NOW IS UNABLE TO SHOW SIGNS OF LIFTING OVER THE NEXT HOUR OR
TWO...MAY ALSO HAVE TO ADJUST MAX TEMPS DOWN A BIT SO WILL
CONTINUE TO MONITOR THOSE TRENDS FOR ANOTHER POSSIBLE UPDATE LATER
THIS MORNING.

PREVIOUS DISCUSSION...
AREAS OF FOG CONTINUE TO PLAGUE AREAS THROUGHOUT NE NC AND
COASTAL VA/MD. DATA OBSERVATIONS WITHIN THESE AREAS HAVE SHOWN
SIGNS OF IMPROVEMENT...HOWEVER POCKETS OF LOCALLY DENSE FOG WITH
VISIBILITIES OF ONE QUARTER MILE OR LESS ARE STILL OCCURRING.
ELSEWHERE...VISIBILITIES ARE BOUNCING BETWEEN ONE HALF MILE TO
THREE MILES. AT THIS TIME THE COVERAGE OF DENSE FOG IS NOT
WIDESPREAD ENOUGH TO WARRANT A DENSE FOG ADVISORY...THEREFORE A
SPECIAL WEATHER STATEMENT HAS BEEN EXTENDED THROUGH 9 AM TO
ACCOUNT FOR LIMITED VISIBILITIES AND POOR DRIVING CONDITIONS. FOG
IS EXPECTED TO DISSIPATE BY MID MORNING...HOWEVER LOW CLOUDS WILL
LINGER THROUGHOUT THE DAY AS A WARM FRONT MOVES UP FROM THE SOUTH.

CURRENTLY TWO WARM FRONTS ARE WITHIN THE MID ATLANTIC REGION. THE
FIRST IS DRAPED ACROSS NRN VA AND THE MD/VA EASTERN SHORE AND WILL
EXIT THE REGION THIS MORNING. THE SECOND WARM FRONT EXTENDS FROM
THE NRN OUTER BANKS DOWN THE CAROLINA COAST INTO SRN SC. THIS
BOUNDARY WILL LIFT NORTH INTO THE REGION THIS AFTN...WARMING
TEMPERATURES IN ITS PATH. EXPECT HIGHS IN THE LOWER 70S SW TO
MID/UPPER 60S NE. SHORT RANGE MODELS SHOW A BRIEF PERIOD OF LIFT
IN OMEGA FIELDS AND ISENTROPIC SFCS WITH THIS BOUNDARY...HOWEVER
TIME HEIGHTS/CROSS SECTIONS/SOUNDINGS INDICATE THAT THE LOW LEVELS
ARE SOMEWHAT DRY WHICH IS CONTRADICTED BY THE PRESENCE OF FOG
EARLY THIS MORNING. TAKING THESE FACTORS INTO CONSIDERATION...LIGHT
RAIN SHOWERS WILL BE POSSIBLE THIS AFTN/EARLY EVENING IN THE
VICINITY OF THE SRN WARM FRONT AS IT LIFTS THROUGH THE REGION.
WILL ONLY CARRY A SLIGHT CHANCE FOR PRECIP ACROSS THE SRN HALF OF
THE FA.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
LITTLE CHANGE TO THE OVERALL FORECAST AND PROGRESSION OF THE COLD
FRONT INTO THE MID ATLANTIC REGION OVER THE NEXT FEW DAYS.

TONIGHT THROUGH FRIDAY NIGHT...
A COLD FRONT CROSSES THE OH VALLEY TODAY AND GETS HUNG UP ALONG
THE SPINE OF THE APPALACHIANS TONIGHT INTO FRI MORNING. THIS IS
DUE TO A BLOCKING PATTERN DEVELOPING...WHERE A STRONG ARCTIC HIGH
IS DIGGING INTO THE NCTRL U.S. AND ANOTHER HIGH IN THE WRN ATLANTIC
IS PREVENTING THE COLD FRONT FROM PROGRESSING EWD. ONCE LIGHT
SHOWERS END THIS EVENING...A BRIEF DRY PERIOD IS ANTICIPATED LATE
THIS EVENING. MOISTURE AND WEAK SHORTWAVE ENERGY THEN RIDES ALONG
THE FRONT FROM SW TO NE AND SHIFTS PRECIP BACK INTO FAR NW PORTIONS
OF THE FA AFTER MIDNIGHT. THE PRESSURE GRADIENT BEGINS TO TIGHTEN
AND S-SW WINDS WILL STAY BREEZY OVERNIGHT. THE WELL-MIXED CONDITIONS
IN ADDITION TO CONTINUED WAA WILL KEEP TEMPERATURES IN THE LOWER 60S
OVERNIGHT (UPPER 50S MD/VA EASTERN SHORE)...WHICH IS WELL ABOVE
NORMAL.

AS THE COLD ARCTIC AIRMASS FINALLY TAKES OVER THE WARMER AIR TO
ITS SOUTH...THE FRONT WILL FINALLY START TO PUSH ACROSS THE AREA
FROM THE NORTHWEST BY FRI AFTN. SHARP TEMPERATURE AND PRESSURE
CONTRASTS BETWEEN THE WARMER AIRMASS OVER THE REGION VERSUS THE
COLD ARCTIC AIRMASS TO THE NORTHWEST WILL CAUSE SW WINDS TO BECOME
BREEZY...WITH GUSTS UP TO 25 MPH AHEAD OF THE FRONTAL BOUNDARY.
CONTINUED WAA ADVECTION SOUTHEAST OF THE FRONT AND FAVORABLE MIXING
WILL HELP BOOST HIGH TEMPS WELL ABOVE NORMAL ON FRI...ESPECIALLY
OVER SRN AREAS WHERE TEMPS COULD REACH THE MID-UPPER 70S. FOR NW
AREAS...TEMPS MAY ONLY BE IN THE LOW-MID 60S DEPENDING ON WHERE LOW
CLOUDS AND PRECIP OCCUR. THE COLD FRONT CROSSES THE REST OF THE FA
FRI NIGHT AND MOVES JUST OFF THE COAST BY SAT MORNING. PRECIPITATION
IS EXPECTED TO BECOME MORE WIDESPREAD AND STEADY OVERNIGHT FRI. LOW
TEMPS WILL BE TRICKY DEPENDING ON HOW FAST THE POST-FRONTAL ARCTIC
AIR CAN MOVE INTO THE REGION AND WHEN WINDS TURN TO THE
NORTHWEST/NORTH. AM CURRENTLY ANTICIPATING A CONTRAST WITH LOWS IN
THE UPPER 30S/LOWER 40S NW TO LOWER 50S FAR SE.

SATURDAY...
THE AFOREMENTIONED COLD FRONT STALLS OUT ACROSS THE SERN U.S. AS
ARCTIC HIGH PRESSURE EXPANDS EWD FROM THE OHIO VALLEY AND INTO THE
NORTHEAST. N-NE SFC WINDS WILL CONTINUE TO FUNNEL COLDER AIR INTO
THE MID ATLANTIC REGION THROUGH SAT WITH HIGHS EITHER HOLDING
STEADY OR ONLY RISING A COUPLE OF DEGREES FROM THEIR MORNING LOWS.
HIGHS AROUND 40 NW TO THE LOW/MID 50S FAR SE. THE QUESTION THAT
STILL REMAINS IS JUST HOW MUCH PRECIP LINGERS ACROSS THE LOCAL
AREA ON SATURDAY. ATTM...THE ECMWF AND GFS MODELS STILL FAVOR
LIGHT RAIN LINGERING ALONG AND SOUTH OF A SOUTH HILL-RICHMOND-
SALISBURY LINE DURING THE DAY. THE NAM/SREF SOLUTIONS NOT ONLY
DRIVE THE SFC COLD FRONT A LITTLE FARTHER SOUTH BUT THEY FLATTEN
THE FRONT INTO A MORE WEST TO EAST ORIENTATION...WHICH SUPPORTS
LESS PRECIPITATION SAT AFTN. CONTINUE TO FAVOR THE PRECIP GETTING
HUNG UP NEAR SE COASTAL AREAS AND BEING SLOWER TO EXIT THE REGION
CONSIDERING THE GIVEN POSITION/STRENGTH OF THE WRN ATLANTIC RIDGE.
WILL KEEP BEST PRECIP CHANCES ACROSS THE SERN HALF OF THE FA
THROUGHOUT THE DAY.

SATURDAY NIGHT...
MODELS ARE IN GENERAL AGREEMENT WITH LAYING THE FRONTAL BOUNDARY
INTO A MORE FLAT W-E ORIENTATION SAT NIGHT...THEN PULLING IT BACK
UP THE APPALACHIANS ALMOST LIKE A RETROGRADING LEE TROUGH.
SHORTWAVE ENERGY MOVING UP THIS BOUNDARY FROM THE TN VALLEY IS
EXPECTED TO ENHANCE AND SPREAD PRECIPITATION BACK INTO THE REGION
FROM THE SOUTH/SOUTHWEST. MEANWHILE...A COLD AIR WEDGE IS
BEGINNING TO TAKE FORM AS COLD ARCTIC AIR FILTERS INTO THE REGION
FROM THE N/NE. THE COMBINATION OF WARMER AIR IN THE SOUTHEAST
VERSUS THE COLDER AIR TO THE NORTH WILL MAKE FOR A TRICKY
PRECIP-TYPE FORECAST. MODEL DISCREPANCIES REGARDING PRECIP
PLACEMENT AND TIMING ARE JUST DIFFERENT ENOUGH TO MAKE IT
DIFFICULT TO DETERMINE WHERE RAINFALL WILL TRANSITION TO SLEET
AND/OR FREEZING RAIN. AT THIS TIME...THE GFS/ECMWF ARE THE MOST
PROGRESSIVE IN PUSHING THE PRECIP NWD. THE NAM HAS MORE OF A DRY
BIAS...NOT BRINGING PRECIP BACK INTO SW PORTIONS OF THE FA UNTIL
AROUND 12Z SUN. THIS DELAY IS ALSO RESULTING IN A COLDER
TEMPERATURE BIAS OVER NWRN AREAS. THE SREF SPLITS THE DIFFERENCE
BTWN THE FAST GFS/ECMWF AND THE SLOWER/COLDER NAM. USING THICKNESS
HEIGHTS AND WET BULB ZERO TEMPS TO DETERMINE A GENERAL P-TYPE...
HAVE INTRODUCED A RAIN/SLEET MIX INTO LOUISA/FLUVANNA COUNTIES SAT
EVENING...THEN TRANSITIONING THE NW HALF OF THE FA INTO A FREEZING
RAIN/SLEET MIX DUE TO THE CLASHING AIRMASSES NW AND SE. OTHERWISE...
P-TYPE SHOULD BE A COLD RAIN. LOW TEMPS ARE EXPECTED TO BE BELOW
FREEZING NW OF A LINE FROM EMPORIA- WILLIAMSBURG- SALISBURY AND IN
THE MID 30S TO NEAR 40 SE OF THIS LINE.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
RATHER CHALLENGING FORECAST SUNDAY AS LATEST RUNS OF THE GFS AND
ECMWF ARE A BIT COLDER AT THE SFC DUE TO THE APPARENT RIDGE BEING
A BIT SLOWER TO MOVE OUT OF EASTERN NY. THIS WILL BE CRITICAL AS
TO WHERE SFC TEMPS FALL TO OR STAY BELOW 32 LEADING TO A FREEZING
RAIN VS SLEET VS A COLD RAIN SCENARIO AS THE NEXT IN A SERIES OF
SHORTWAVES RIDES NE WITH OVERRUNNING MOISTURE. LEANED TOWARD THE
ECMWF SOLUTION AS IT SEEMS TO HANDLE THE COLD WEDGE BETTER THAN
THE GFS. THE GFS HAS THE STRONGEST RIDGING EAST OF THE PIEDMONT
WHILE THE ECMWF HAS THE STRONGEST RIDGING ALONG AND JUST EAST OF
THE MOUNTAINS...WHICH IS KEY TO HOLDING THE COLDER AIR IN LONGER.
IN ADDITION...BUFKIT SOUNDINGS SHOW THE POTENTIAL FOR SEVERAL
HOURS OF ICE (ALONG AND NW OF A FVX-RIC-XSA LINE). SUNDAY WILL
HAVE ITS CHALLENGES AS THE COLD AIR GETS LOCKED IN ACROSS THE
PIEDMONT WITH STEADY OR SLOWLY RISING TEMPS TO JUST ABOVE FREEZING
IN THE AFTERNOON WHILE E-SE WINDS BRING MILDER AIR IN FROM THE
OCEAN. EXPECT COASTAL TEMPS TO RISE WELL INTO THE 50S...POSSIBLY
NEAR 60. HAVE EXTENDED THE FREEZING RAIN THROUGH THE AFTN ACROSS
LOUISA/FLUVANNA/WRN GOOCHLAND/CUMBERLAND COUNTIES...WHERE THE BEST
CHCS FOR ACCUMULATING ICE MAY SET UP. OTHERWISE...LIKELY POPS FOR
RAIN INTO SUNDAY NIGHT WITH STEADY OR SLOWLY RISING TEMPS SUNDAY
NIGHT.

DRIER AND COOLER CONDITIONS RETURN BY MID WEEK BEHIND A COLD
FRONTAL PASSAGE TUE. HIGHS TUE IN THE 40S/50S (FALLING TEMPS IN
THE AFTERNOON). LOWS TUE NIGHT IN THE 20S. COLD WED WITH HIGHS IN
THE M30S-L40S.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
LIGHT FLOW AND NEARLY SATURATED AIRMASS CONTINUES TO LEAD TO
WIDESPREAD IFR/LIFR CONDITIONS ACRS THE AREA. STILL SOME
VARIABILITY FROM SITE TO SITE...AND CONDITIONS APPEAR TO BE
IMPROVING ACRS FAR SE VA/NE NC AS WINDS ARE INCREASING ABOVE 5 KT.
STILL SHOULD SEE IFR CIGS AND/OR FOG AT KRIC/SBY/KPHF THROUGH
14-17Z. BY LATE MORNING/EARLY AFTN CIGS SHOULD GENLY RISE TO VFR
OR HIGH END MVFR CONDITIONS IN SSW FLOW OF 10 KT. SHOULD BE LESS
POTENTIAL FOR FOG LATE TONIGHT/FRI MORNING AS WARM SW FLOW
PERSISTS OVERNIGHT...ALTHOUGH THERE COULD BE MVFR/IFR CIGS FROM
ABOUT 04Z-12Z.

A COLD FRONT WILL BE SLOW TO PROGRESS INTO THE AREA FRI/FRI NIGHT...WITH
JUST A SMALL CHANCE FOR SHOWERS DURING THE DAY FRI (HIGHEST CHANCE
AT KSBY). BEST POTENTIAL FOR SIGNIFICANT REDUCTIONS IN CIGS/VSBYS
LOOKS TO ARRIVE LATER FRI NIGHT THROUGH SAT/SUN. GENLY APPEARS TO
BE A RAIN EVENT FOR KORF/KPHF/KECG/KSBY...WITH A GREATER PROBABILITY
FOR MIXED PRECIP AT KRIC SUNDAY MORNING.

&&

.MARINE...
LIGHT FLOW EARLY THIS MORNING WILL INCREASE FROM THE SSW LATER
TODAY AS PRESSURE GRADIENT TIGHTENS W/ APPROACH OF A COLD FRONT
FROM THE NW. HOWEVER...WARM AIRMASS WILL NOT MIX WELL OVER THE
COLD WATERS...SO WINDS WILL STILL ONLY AVG 10-15 KT ACRS THE
WATERS (A LITTLE HIGHER ACRS NORTHERN COASTAL WATERS). LATER
TONIGHT AS THE GRADIENT TIGHTENS A LITTLE MORE...COULD SEE
MARGINAL SCA CONDITIONS IN THE BAY (GUSTS TO 20 KT) AND NORTHERN
COASTAL WATERS (MAINLY FOR 5 FT SEAS WELL OFFSHORE). EITHER WAY...
IT WILL BE MARGINAL AND FAIRLY SHORT-LIVED AT BEST SO DECIDED NOT
TO ISSUE SCA HEADLINES AND ALLOW DAY-SHIFT TO MONITOR TRENDS LATER
TODAY AND ISSUE IF NECESSARY. ON FRI...AS A WAVE OF LOW PRESSURE
FORMS ALONG THE FRONT AND MOVES ENE...WILL LIKELY SEE MODERATE SW
FLOW ACRS SOUTHERN/CENTRAL ZONES...AND LIGHT E/NE FLOW ACRS THE
NORTHERN ZONES.

A CONSENSUS BETWEEN THE MODELS WOULD BRING THE FRONT THROUGH THE
AREA LATER FRI NIGHT/EARLY SAT MORNING. SCA CONDITIONS APPEAR
LIKELY FOR ALL ZONES BY SAT MORNING AS STRONG HIGH PRESSURE BUILDS
TO THE NORTH OF THE AREA AND MUCH COLDER AIR ALOFT BEGINS TO MIX
DOWN OVER THE WATERS. BOUNDARY STALLS TO THE SOUTH AS STRONG HIGH
PRESSURE BUILDS FROM THE GREAT LAKES TO NEW ENGLAND ON SUNDAY...WITH
SCA CONDITIONS LIKELY TO PERSIST INTO SUNDAY FOR MUCH OF THE AREA.
WINDS SHIFT TO THE SW AND CONDITIONS IMPROVE SUN NIGHT/MON ALTHOUGH
SEAS MAY STAY AT OR ABOVE 5 FT ON THE COASTAL WATERS.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BMD
NEAR TERM...BMD/JDM
SHORT TERM...BMD/JDM
LONG TERM...BMD/MPR
AVIATION...LKB
MARINE...LKB