Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 021109
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
709 AM EDT THU OCT 2 2014

.SYNOPSIS...
HIGH PRESSURE BUILDS OVER THE MID ATLANTIC REGION THROUGH FRIDAY.
A STRONG COLD FRONT CROSSES THE AREA SATURDAY MORNING...USHERING
IN MUCH COOLER AND DRIER WEATHER FOR THE END OF THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATEST WX ANALYSIS CONTINUES TO FEATURE HIGH PRESSURE RIDGING SOUTH
INTO THE MID-ATLANTIC AND SOUTHEAST FROM NEW ENGLAND. TO THE WEST,
ALOFT, GOES WV SAT IMAGERY FEATURES CLOSED LOW SLOWLY DRIFTING EAST
ACROSS SE NEW ENGLAND, WITH SHORTWAVE RIDGING PUSHING ACROSS THE
MOUNTAINS THIS MORNING. A WEAK IMPULSE EMBEDDED IN NW FLOW ON THE
WESTERN PERIPHERY OF THE DEPARTING TROUGH HAS ALLOWED FOR SOME SCT
SHRAS TO PERSIST INTO THE OVERNIGHT. KAKQ RADAR SHOWING SOME
ISO-WIDELY SCT SHRAS DIVING E-SE ACROSS THE RIC METRO AREA AT 08Z.
HAVE ALLOWED FOR A BRIEF WINDOW OF SOME ISOLATED SHRAS/SPRINKLES
THROUGH THE NEXT FEW HOURS. HAVE ALSO ALLOWED FOR SOME ADDITIONAL
AREAS OF FOG, MAINLY OVER SOUTH CENTRAL/INTERIOR SE VA AND JUST
EAST OF THE I-95 CORRIDOR THROUGH MID-MORNING. SIMILAR TO THE PAST
FEW MORNINGS, STRATUS WILL SLOWLY DIMINISH THROUGH THE MORNING,
WITH SKY EVENTUALLY BECOMING PARTLY SUNNY BY AFTERNOON. FOR HIGHS,
LOOK FOR HIGHS IN THE MID 70S EASTERN SHORE AND ALONG THE
IMMEDIATE COASTAL LOCATIONS...W/ U70S TO AROUND 80 FARTHER INLAND.

HIGH PRESSURE AT THE SFC AND ALOFT WILL PIVOT OFFSHORE TONIGHT AND
EARLY FRIDAY, ALLOWING LIGHT LLVL FLOW TO SHIFT AROUND TO THE E-SE.
NAM FAMILY MODELS STILL KEYING IN ON SOME ADDITIONAL AREAS OF LIGHT
OVERRUNNING IN THE LATE NIGHT HOURS TNGT/ERY FRIDAY. WHILE THIS
COULD PORTEND TO ANOTHER ROUND OF ISO SHRAS/SPRINKLES...LIFT IS
SHALLOW ENOUGH THAT ACCUMULATING PCPN IS NOT ANTICIPATED. THUS, HV
HELD OUT OF FORECAST FOR NOW AND WILL CAP POP AT 14% ACROSS I-95
AND WEST. WENT WITH MILDER ENVELOPE OF MOS GUIDANCE WITH ONSHORE
FLOW. LOWS GENERALLY LOW 60S, WITH SOME U50S OVER THE FAR NORTH-
NORTHEASTERN ZONES.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
FORECAST MODELS CONTINUE TO SLOW THE APPROACH OF THE MID-UPPER
TROUGH DIVING SOUTHEAST ACROSS THE UPPER MIDWEST AND UPPER GREAT
LAKES ON FRIDAY, WITH ITS ASSOCIATED STRONG SFC COLD FRONTAL
PASSAGE PUSHING ACROSS THE OH/TN VLYS FRIDAY AND FRI NIGHT. EXPECT A
RATHER MILD AND PLEASANT DAY AHEAD OF THE FRONT WITH HIGHS IN THE
LOW 80S INLAND...MID TO UPPER 70S EASTERN SHORE AND COASTAL ZONES.
FRONT WILL SWEEP ACROSS THE AREA FRIDAY NIGHT...REACHING THE COASTAL
ZONES BY SUNRISE SAT MORNING. OVERNIGHT LOWS FRIDAY NIGHT IN THE 60S.

AS FAR AS TIMING POPS, ARW/NMM SEEM IN GOOD AGREEMENT WITH LATEST
00Z ECMWF IN BRINGING A DECAYING LINE OF SHRAS TOWARDS THE REGION
LATE FRIDAY AFTN INTO FRI NIGHT. PW VALUES QUICKLY RAMP UP INTO
1.50-1.75 RANGE, SO HIGH CHC TO LKLY POPS FRIDAY NIGHT LOOK GOOD.
HOWEVER, DYNAMICS/INSTABILITY PARAMETERS LOOK ANEMIC DUE TO LATE
NIGHT FROPA TIMING AND THE ORIENTATION OF THE TROUGH WELL TO OUR
N-NW. THUS, HAVE DECIDED TO HOLD THUNDER WORDING OUT OF THIS
PACKAGE. DID ALLOW FOR SOME SCT SHRAS LATE FRIDAY AFTERNOON ACROSS
OUR WESTERN TIER OF COUNTIES, WITH POPS RAMPING UP FRIDAY NIGHT OVER
THE I-95 CORRIDOR AND OVERNIGHT FRIDAY OVER THE EASTERN SHORE. TOTAL
QPF IS GENERALLY AROUND A QUARTER INCH ACROSS THE AREA, SLIGHTLY
MORE ACROSS THE NORTH.

POPS RAMP DOWN FROM WEST TO EAST QUICKLY SATURDAY MORNING, WITH A
CLEARING SKY FROM MID MORNING THROUGH AFTERNOON. USED THICKNESS
TOOLS FOR MAX T ON SATURDAY, BUT DO EXPECT WEST (DOWNSLOPING) WINDS
ALONG W/PLENTY OF AFTN SUNSHINE TO HELP BOOST TEMPS A DEGREE OR TWO
WARMER. HIGHS U60S/AROUND 70 IN THE PIEDMONT TO LOWER 70S ACROSS THE
COASTAL PLAIN.

COOLEST NIGHT OF THE YOUNG FALL SEASON IS EXPECTED SATURDAY NIGHT.
BEST COLD AIR ADVECTION WILL REMAIN NORTH AND WEST OF THE LOCAL
AREA, BUT H85 TEMPS DO DROP TO BETWEEN 0-2 DEG C SUNDAY MORNING.
EXPECT A PLEASANT, CHILLY NIGHT SAT NIGHT WITH LOWS IN THE LOWER TO
MIDDLE 40S...TO NEAR 50 ALONG THE COAST UNDER A MOSTLY CLEAR SKY.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
LONG TERM PERIOD WILL FEATURE MAINLY DRY AND SEASONABLE CONDITIONS.
MID-LEVEL TROF AXIS AND ASSOCIATED SFC COLD FRONT PUSHES FARTHER
OFFSHORE SUN. HI PRES THEN BLDS INTO THE SE U.S. SUN AFTN WITH SW
FLOW DEVELOPING ACROSS THE MID ATLANTIC. EXPECT A SUNNY SKY WITH
HI TEMPS IN THE MID TO UPR 60S. DRY CONDITIONS CONTINUE INTO MON
WITH A BROAD UPR-LEVEL TROF OVR THE E HALF OF THE CONUS AND SFC HI
PRES SLIDING OFFSHORE. HI TEMPS NEAR NORMAL...IN THE LO TO MID
70S.

FOR TUE/WED...A MID-LEVEL SHORTWAVE TROF AND WEAK SFC FRONTAL BOUNDARY
WILL CROSS THE MID ATLANTIC LEADING TO A SLGT CHANCE FOR A SHRA.
DIFFICULT TO TIME THIS FAR OUT BUT EITHER WAY NOT EXPECTING A LARGE
AMOUNT OF PRECIP WITH THIS SYSTEM. HI TEMPS BOTH DAYS STILL IN THE LO
TO MID 70S WITH LOWS RANGING THRU THE 50S.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
AREAS OF MVFR FOG/MIST HAVE DEVELOPED EARLY THIS MORNING WITH
VISIBILITIES PRIMARILY RANGING FROM 2-5SM. THERE ARE SOME ISOLATED
POCKETS OF IFR FOG/CIGS OBSERVED AT TIMES...THEREFORE OCCASIONALLY
RAPID BUT BRIEF REDUCTIONS IN FLIGHT CONDITIONS SHOULD ALSO BE
ANTICIPATED. AS WITH THE PAST FEW MORNINGS...FOG SHOULD
LIFT/DISSIPATE BTWN 02/1300-1400Z. THE COMBINATION OF LIGHT ONSHORE
FLOW AT THE SFC AND LIGHT NW WINDS ALOFT WILL ALLOW A MID LEVEL
CLOUD DECK TO PERSIST THROUGH TODAY...GENERALLY 4-9 KFT AGL. FOG
POTENTIAL SLOWLY WANES FOR TONIGHT AS UPPER RIDGING MOVES DIRECTLY
OVERHEAD. PATCHY FOG MAY DEVELOP ALONG/WEST OF INTERSTATE
95...OTHERWISE THE REST OF THE AREA SHOULD REMAIN FOG-FREE DUE TO
WEAK COLD AIR ADVECTION CLOSER TO THE COAST. A STRONG COLD FRONT
APPROACHES THE MID ATLANTIC REGION ON FRIDAY AND SE WINDS WILL
BECOME BREEZY BY FRIDAY AFTN WITH GUSTS AROUND 15 KT. THE SFC
PRESSURE GRADIENT TIGHTENS SIGNIFICANTLY WITH THE FROPA FRI NIGHT
INTO SAT. EXPECT S-SW WINDS TO STRENGTHEN AHEAD OF AND ALONG THE
FRONT...TURNING TO THE W-NW BEHIND THE FROPA WITH WIND SPEEDS
REMAINING ELEVATED THROUGH SATURDAY DUE TO NOTICEABLY COOLER TEMPS
AND STRONG COLD AIR ADVECTION. MODERATE TO HEAVY RAINFALL WILL ALSO
BE POSSIBLE AT TIMES DURING THE FROPA. HIGH PRESSURE AND DRY
CONDITIONS RETURN TO THE REGION LATE SATURDAY AFTN INTO EARLY NEXT
WEEK WITH PLEASANT FLYING CONDITIONS ANTICIPATED.

&&

.MARINE...
CONTINUED LIGHT N-NE WINDS AOB 10 KT WILL PERSIST ACROSS MOST
LOCATIONS THIS MORNING. N-NE WINDS OF 15-20KT WILL OCCUR OFF THE NRN
COASTAL WATERS (FROM 10-20NM) DUE TO THE PRESENCE OF A
QUASI-STATIONARY LOW PRESSURE SYSTEM THAT IS WELL EAST OF NEW
ENGLAND. THIS FEATURE WILL PROVIDE JUST ENOUGH OF A PRESSURE
GRADIENT TO KEEP WINDS ELEVATED HERE. OBSERVED SEAS AT BUOY 44009
KEEP FLUCTUATING BTWN 4.3-4.6FT NEAR 20NM AND EXPECT THIS TO
CONTINUE THROUGH TODAY...HOWEVER IT IS NOT WIDESPREAD ENOUGH TO
WARRANT SCA FLAGS ATTM. OTHERWISE...SEAS WILL AVERAGE 3-4FT ALL
WATERS TODAY/WAVES 1-2FT.

A STRONG COLD FRONT APPROACHES THE MID ATLANTIC REGION ON FRI AND
STARTS TO PUSH THE OFFSHORE NEW ENGLAND LOW EWD. THIS WILL CAUSE THE
PRESSURE GRADIENT TO RELAX OVER ALL WATERS ON FRI WITH NE-E WINDS
AOB 10KT FOR MOST OF THE DAY. THE COLD FRONT IS EXPECTED TO CROSS
THE WATERS LATE FRI NIGHT INTO SAT. WINDS VEER TO THE SE-S ON FRI
EVENING INTO EARLY SAT AHEAD OF/ALONG THE FRONT WITH SPEEDS
INCREASING TO 15-20KT AND GUSTS AROUND 25 KT. WINDS THEN SWING
AROUND TO THE W-NW BEHIND THE FRONT BY EARLY SAT AFTN. A PERIOD OF
SCA CONDITIONS MAY BE POSSIBLE LATE FRI THROUGH SAT NIGHT DUE TO
WINDS AND SEAS/WAVES. THE TIMING OF THE FRONTAL PASSAGE MAY SLOW
DOWN AS THE ASSOCIATED UPPER TROUGH DIGS INTO THE TN VALLEY FRI/FRI
NIGHT...THEREFORE HAVE DECIDED TO HOLD OFF ON ISSUING SCA FLAGS ATTM
SINCE THE START TIME IS HIGHLY DEPENDENT ON THE INCOMING/INCREASING
PRESSURE GRADIENT (I.E. SCA CONDITIONS COULD BEGIN EARLY FRI AFTN OR
LATE FRI EVENING). WINDS AND SEAS DIMINISH SUNDAY AS HIGH PRESSURE
BUILDS INTO THE AREA AND STRONG CAA SUBSIDES.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES ARE EXPECTED TO AVERAGE AROUND 1.0 FT ABOVE NORMAL
TODAY THROUGH FRIDAY DUE TO PERSISTENT ONSHORE/NE WINDS. THIS
HAS THE POTENTIAL TO PUSH PORTIONS OF THE MIDDLE BAY AND TIDAL
POTOMAC INTO MINOR FLOODING THRESHOLDS DURING HIGH TIDE THIS
EVENING/TONIGHT AT LEWISETTA AND BISHOPS HEAD. CAMBRIDGE SHOULD STAY
JUST BELOW MINOR FLOODING THRESHOLDS BUT WILL NEED TO MONITOR TRENDS
FOR THIS EVENING ONCE NEW 12Z MODEL RUNS COME IN. WATER LEVELS WILL
AGAIN APPROACH MINOR THRESHOLDS AT THE SAME LOCATIONS FRIDAY
EVENING/NIGHT AS THE WIND BECOMES SOUTHERLY AHEAD OF A STRONG COLD
FRONT. TIDAL ANOMALIES SHOULD BEGIN TO DECLINE SATURDAY AS THE WIND
SHIFTS OFFSHORE/NW BEHIND THE COLD FRONT.

&&

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

&&

$$
SYNOPSIS...MAM
NEAR TERM...MAM
SHORT TERM...MAM
LONG TERM...MAS
AVIATION...BMD
MARINE...BMD
TIDES/COASTAL FLOODING...AKQ






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