Area Forecast Discussion


005 
FXUS61 KLWX 010129
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
929 PM EDT FRI OCT 31 2014
.SYNOPSIS...
LOW PRESSURE OVER INDIANA THIS EVENING WILL CROSS SOUTH CAROLINA
SATURDAY BEFORE STRENGTHENING OFFSHORE WHILE HEADING TOWARDS CAPE
COD SATURDAY NIGHT INTO SUNDAY. HIGH PRESSURE WILL BUILD OVER THE
AREA INTO MONDAY WITH THE NEXT COLD FRONT ARRIVING LATE WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 01Z...UPR LOW CENTER IS APPROACHING LOUISVILLE PER WATER
VAPOR IMAGERY. THE UPR LOW WILL SHIFT SOUTHEAST OVERNIGHT AND CROSS
SOUTH CAROLINA SATURDAY MORNING. THE 1008MB SFC LOW IS CURRENTLY
OVER COLUMBIA SOUTH CAROLINA...CONFIRMING THE DIRECTION THE STORM
IS EXPECTED TO TAKE. THE LEADING LOBE OF THE UPR TROUGH IS OVER NC
(WHERE SOME TSTMS ARE) WITH THE SFC LOW WELL OFF THE NC/VA
BORDER...LIKELY AROUND 1004MB.
THE EASTERN FLANK OF THE TRAILING...MORE POTENT LOW IS PRODUCING
PRECIP OVER THE ALLEGHENY HIGHLANDS. OUR OBSERVER AT 3700FT IN
SWRN PENDLETON CO REPORTED SNOW STICKING TO CARS AT 8PM.
ELEVATIONS ABOVE 3000 FT WILL SEE A WET DUSTING TO AN INCH OR
POSSIBLY OVERNIGHT...NOT ENOUGH FOR AN ADVISORY.
OTHERWISE...CLOUDS THICKEN AND LOWER. RAIN FROM THE OFF SHORE LOW
WILL SPREAD IN FROM THE OCEAN LATE TONIGHT. THIS COVERAGE OF
PRECIP WILL SLOWLY CLOSE THROUGH SATURDAY MORNING.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
PREVIOUS DISCUSSION STILL VALID...
UPR VORT/SHORT WV OVR ERN TN SAT MRNG...MOVG E OF THE SC CST DURG
THE AFTN. THIS WL MAKE THE HIGHLANDS THE ONLY AREA IN THE FCST
AREA W/ THE PSBLTY OF SEEING SNOWFALL..BUT THE 1000-850MD TCHKNS'S
AREN'T THAT LOW: ~1320M. THIS MEANS THE ATMOSPHERIC COLUMN JUST
ISN'T THAT COLD...AND ANY PCPN THAT FALLS IN THE FRZN VARIETY WL
BE VERY DEPENDENT ON ELEVATION. DURG SAT ACCUMULATIONS WOULD BE
SLUSHY AND MINOR. BLV THAT THERE WL BE A PD OF RA E OF THE MTNS
JUST ABT EVERYWHERE SAT.
HIGHS RANGING FM THE L50S E OF I-95 TO THE U30S IN THE HIGHLANDS.
BY SAT NGT...S/WV ENERGY WUD HV SHIFTED OFF THE CST...INDUCING
CYCLOGENESIS NE OF CAPE HATTERAS. IN TERMS OF PCPN E OF THE
APLCHNS...THAT PRETTY MUCH WL MARK THE END...AS DRIER AIR WL WORK
IN ON THE NW SIDE OF THE CYCLONE. WINDS MAY BE THE BIGGEST
IMPACT...BUT THE NOCTURNAL TIMING MAY PREVENT THE FULL 30-40 KT
AVBL H9-8 FM MIXING DOWN. WL BE KEEPING GUSTS 25-30 MPH.
ACRS THE MTNS...THE AMS WL BE COOLING SUFFICIENTLY FOR SOME SNOW. 
HWVR...THE BEST DYNAMIC COOLING WL PASS S OF AREA. THIS LEAVES ONLY 
A MARGINALLY FVRBL AMS W/ WARM GRND. SNOW TOTALS 1-2" IN THE HIGHER
ELEVS. IT IS NOT OUT OF THE QSTN THAT ACCUMS COULD BE ENUF TO
REACH ADVSRY LVL...BUT THIS IS NOT A SLAM DUNK AND WL LV THIS TO
BE DECIDED LATER.
LOWS SAT NGT RANGE FM THE M20S IN THE MTNS TO THE L40S ALONG THE
BAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
BLV WINDS MAY END UP BEING THE BIGGEST STORY FM THE UPCOMING SYSTEM.
SOME SNOW FLAKES COULD CONTINUE TO FALL FOR A COUPLE OF HOURS AFTER 
SUNRISE ALONG THE ALLEGHENY FRONT...BUT ALL OF THE PRECIP WILL BE 
WRAPPED UP ACROSS THE AREA BY MID-MORNING SUNDAY. THE STORY WILL 
THEN BE THE COLD AND WIND. A 100+ KT JET CENTERED AROUND 20000 FT 
WILL PASS OVERHEAD SUNDAY. EXPECT A DECENT AMOUNT OF THESE WINDS TO 
MIX DOWN TO THE SURFACE...WITH FREQUENT GUSTS IN THE 30 TO 40 KT 
RANGE POSSIBLE FOR THE HIGHER ELEVATIONS AND OVER THE BAY...AND 
GUSTS OF 20 TO 30 KTS POSSIBLE ELSEWHERE...DURING THE DAY SUNDAY. 
DEEP LAYER NORTHWESTERLY FLOW WITH A FETCH WELL UP INTO EASTERN 
CANADA WILL BRING SEASONABLY COOL AIR TO THE MID-ATLANTIC. HIGHS 
SUNDAY WILL BE AROUND 50...WHICH IS ABOUT 10 TO 15 DEGREES BELOW 
NORMAL...THOUGH STILL A COUPLE OF DEGREES ABOVE RECORD LOW MAXIMUM 
TEMPS.
SUNDAY NIGHT WILL SEE THE COLDEST TEMPS OF THE FALL SO FAR...WITH 
FREEZING AND SUBFREEZING TEMPERATURES EXPECTED FOR MOST OF THE CWA 
AS HIGH PRESSURE SETTLES INTO THE AREA. WIND SPEEDS WILL ALSO BE ON 
THE DECLINE SUNDAY NIGHT DUE TO THE DECREASING PRESSURE GRADIENT AS 
THE HIGH PRESSURE CENTER APPROACHES. 
HIGH PRESSURE WILL SETTLE ALONG THE SOUTHEAST COAST FOR THE FIRST 
PART OF THE WORKWEEK AND TEMPS WILL MODERATE TOWARD NORMAL AS LIGHT 
RETURN FLOW FILLS IN. HIGHS TUESDAY AND WEDNESDAY SHOULD BE WELL 
INTO THE 60S WITH PLENTY OF SUNSHINE. 
A COLD FRONT MAY APPROACH THE AREA WEDNESDAY NIGHT AND THURSDAY. 
THIS DOES NOT APPEAR TO BE A STRONG COLD FRONT...SO CONFIDENCE IS 
LOW IN PRECIPITATION COVERAGE AT THIS POINT. OPERATIONAL ECMWF 
ACTUALLY KEEPS US MOSTLY DRY WHILE GFS BRINGS IN SOME LIGHT RAIN. 
OVERALL HAVE LOW END CHANCE POPS IN THE FORECAST WITH RAIN AS THE 
ONLY EXPECTED P-TYPE DUE TO WARM LOW LEVEL TEMPS. HIGH PRESSURE 
SHOULD BUILD BACK IN BY THE END OF NEXT WORKWEEK.
&&
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
SKIES HV GONE OVC OVR MUCH OF THE AREA AS LOW PRES OVR MI ROTATES
MOISTURE INTO THE MID ATLC. CIGS ARE PRSNTLY VFR...BUT THESE ARE
XPCTD TO SLOWLY LWR OVRNGT. MVFR CONDS XPCTD SAT. PSBL IFR FOR
KBWI/KMTN WITH MORNING RAIN SHOWERS.
LOW PRESSURE STRENGTHENS OFF THE COAST SAT. NRLY WINDS WILL GUST
UP TO 20-25 KT.
WINDS WL PROVIDE PRIMARY IMPACT SAT NGT-SUN...AS AN ELEVATED CORE
OF 40+ KT WNDS CROSS TERMINALS. THE LLJ WL RESIDE ABT 2K FT ABV
SFC. SHUD HV 25-30KT GUSTS IN NW FLOW AT GRND LVL...MAYBE A LTL
HIER THAN THAT SUN MRNG-MIDDAY. ANY CIGS WUD BE MVFR-VFR SAT NGT
AND SHUD CLR BY/SOON AFTR SUNRISE SUN MRNG.
VFR SUN AFTN INTO TUE.
&&
.MARINE...
NLY FLOW INCREASES THROUGH THE NIGHT...SCA BEGINS AT 2AM...EXPANDS
TO ALL WATERS BY 8AM SATURDAY.
WITH THE STRENGTHENING LOW MOVING OFF THE COAST ON SATURDAY...SMALL
CRAFT CONDITIONS WILL BE MET WITH NORTHERLY WINDS GUSTING TO
AROUND 30 KT.
WE HV ISSUED A GALE WRNG FOR SAT NGT.
A GALE WARNING WILL LIKELY BE NEEDED FOR PORTIONS OF THE WATER 
DURING THE DAY SUNDAY AND POTENTIALLY INTO SUNDAY EVENING. A SMALL 
CRAFT ADVISORY MAY BE NEEDED INTO EARLY SUNDAY MORNING.
&&
.TIDES/COASTAL FLOODING...
BLOWOUT CONDITIONS ARE EXPECTED SATURDAY EVENING THROUGH SUNDAY.
IT IS UNCERTAIN AS TO HOW FAR BELOW MLLW THE WATER LEVELS WILL
DROP AT THIS TIME...BUT A NORTHWESTERLY GALE SHOULD DROP THEM TO
AT LEAST ONE FOOT BELOW MLLW.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TO 8 PM EDT SATURDAY FOR 
     ANZ531>534-537-539>541-543.
     GALE WARNING FROM 8 PM EDT SATURDAY TO 6 AM EST SUNDAY FOR 
     ANZ530>543.
     SMALL CRAFT ADVISORY FROM 6 AM TO 8 PM EDT SATURDAY FOR ANZ530-
     536-538-542.
     SMALL CRAFT ADVISORY FROM 8 AM TO 8 PM EDT SATURDAY FOR ANZ535.
&&
$$
UPDATE...JACKSON
PREVIOUS...WOODY!/CEB