FXUS61 KLWX 042018
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
318 PM EST FRI DEC 4 2009
.SYNOPSIS...
LOW PRESSURE OVER THE NORTHERN GULF OF MEXICO WILL MOVE
NORTHEASTWARD UP THE EASTERN SEABOARD ON SATURDAY...AS COLDER AIR
FILTERS INTO THE MID ATLANTIC. HIGH PRESSURE WILL MOVE INTO THE
AREA SUNDAY AND MONDAY. A COMPLEX LOW PRESSURE SYSTEM WILL TRACK
NORTH OF THE AREA WEDNESDAY.
&&
.NEAR TERM /TONIGHT/...
OVC SKIES THIS AFTN AS ISENTROPIC LIFT CONTS TO INCRS. LGT WINDS AND
TEMPS IN THE U40S/L50S WILL BE SLOW TO FALL THROUGH THE 40S TONIGHT
DUE TO LITTLE RADIATIONAL COOLING AND NLY FLOW INCRS...KEEPING
BOUNDARY LAYER SOMEWHAT MIXED. LGT RADAR ECHOS OVER POTOMAC
HIGHLANDS IS VIRGA AS LOW LEVELS REMAIN RELATIVELY DRY.
LOW PRESSURE PUSHES EWD ALONG NRN GULF COAST THIS EVE...THEN SFC LOW
BEINGS TO MOVE N OFF GA COAST. UPPER VORT MAX ROTATED AROUND BASE OF
TROF THRU PLAINS STATES EARLIER...WILL MOVE INTO TENNESSEE VALLEY
OVNGT. AFTER MIDNIGHT...OROGRAPHIC LIFT COMBINED WITH MOISTENING ELY
FLOW ACROSS W/SW ZONES MAY ALLOW FOR LGT RN/SN TO BEGIN...THOUGH
MAJORITY OF PRECIP SHUD RMN OUT OF CWA. STAYED ON WARM SIDE OF
MODELS...WITH MOST WEIGHT GIVEN TO MOS GUIDANCE. LOWS IN U30S MOST
AREAS.
&&
.SHORT TERM /SATURDAY/...
COASTAL LOW INTENSIFIES OFF NC COAST THEN MOVES JUST EAST OF MD
EASTERN SHORE SAT AFTN. UPR SHRTWV PASSES W OF APPALACHIANS...WITH
850MB LOW CENTER PASSING ACRS SE VA. PLENTY OF LIFT ON NW SIDE OF
SYSTEM...THUS QPF RATHER IMPRESSIVE 0.25-0.50". TEMPS XPCD NEAR 40F
IN THE MRNG...THEREFORE PRECIP SHUD BEING AS RAIN...AROUND 12Z W OF
BLUE RIDGE...SPREADING NEWD TO BALTIMORE METRO AND POINTS NE BY 16Z.
AFTER RAIN BEGINS...EVAPORATIVE COOLING WILL ALLOW TEMPS TO FALL TO
NEAR FREEZING...AND WITH VERTICAL THERMAL PROFILE IN
SUPPORT...PRECIP WILL CHANGE TO SNOW. WITH STRONG VERTICAL
MOTION...XPCT DECENT SNOWFALL RATES. HOWEVER...WITH RELATIVELY WARM
TEMPS...ACCUMULATIONS WILL BE HINDERED...PARTICULAR SE HALF OF
CWA...WHERE HIGHEST PRECIP AMOUNTS ARE FCST. SNOW ACCUMULATIONS SHUD
RANGE FROM 2 TO 4 INCHES ACRS MUCH OF THE CWA W OF INTERSTATE
95...WITH 1 TO 2 INCHES XPCD ALONG THE URBAN CORRIDOR. WITH WARMER
SFC TEMPS ACRS LOWER SOUTHERN MARYLAND...SNOWFALL ACCUMULATION LOOK TO
RMN MINIMAL.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
SYSTEM WL EXIT TO THE NE OF THE CWA QUICKLY SAT NGT. XPCT SKIES TO
GO FM CLDY AT THE START OF SAT EVE TO CLR WHEN THE SUN RISES ON
SUNDAY. ALONG W/ 1ST SNOW COVER OF THE SEASON CLR SKIES WL AID IN
PRODUCING THE COLDEST NGT OF THE AUTUMN SO FAR - W/ TEMPS RANGING FM
THE L30S ALONG THE BAY TO THE MID TEENS IN THE HIGHLANDS. SAT NGT
SHOULD BE BRZY AS WELL...CREATING WINDS CHILLS RANGING FM M20S IN
THE E...TEENS W OF I-81...TO SINGLE DIGITS IN THE HIGHLANDS.
W/ HIGH PRES OVR THE RGN SUNDAY THERE SHOULD BE ABUNDANT SUNSHINE.
AFTN TEMPS SHOULD REACH THE LM40S W/ XCPTN OF HIGHER ELEVS. BLV AREA
WL BE DRY TO START THE NEW WK W/ HIGHS IN THE 40S...LOWS SUN NGT
PRIMARILY IN 20S THEN A FEW DEGS WARMER MON NGT. NEXT WX SYSTEM
(WED) LOOKS TO BE FAIRLY COMPLICATED - A DEEP LOW OVR MI W/ AN
OCCLUSION/PTNL TRIPLE PT XTNDG INTO THE MID ATLC. IT'S TOO ERLY
TO TRY TO NAIL DOWN P-TYPES...BUT I WOULDN'T BE SURPRISED IF THERE
WERE A PD OF FRZN PCPN (IP) DURG THE OVRNGT HRS TUE NGT AHD OF THE
WRM FNT. BUT FOR NOW WL WORD IT AS "CHC R-S" IN THE FCST.
ON WED WARM WRM FNT WL PUSH TO THE N AND PCPN WL BECOME MORE
INTERMITTENT. AFTR CD FNT MOVES THRU WINDS TURN TO THE
W...BRINGING THE PTNL FOR UPSLOPE SNSH IN THE HIGHLANDS WED NGT.
AFTR THE MIDWEEK STORM IT LOOKS LK AREA WL GET ANOTHER RESPITE AS
HIGH PRES RETURNS FOR THU AND FRI. END OF WK HIGHS IN MU40S MAJORITY
OF THE CWA. THU NGT THE COOLEST W/ LOWS IN THE 20S.
&&
.AVIATION /TONIGHT THROUGH WEDNESDAY/...
LGT WINDS OVNGT WITH CIGS REMAINING AOA 3-4 KFT THRU 8Z. PRECIP
SHIELD THEN WORKS NEWD INTO THE AREA...BEGINNING AT KCHO BY
9Z...THEN REMAINDER OF CWA AROUND 12Z. XPCT 2-4 HR PERIOD OF RN OR
RN/SN MIX...WITH MVFR CIG/VSBY RAPIDLY BCMG IFR AS PRECIP BECOMES
ALL SNOW. SNOW SHUD CONT THRU SAT AFTN.
PCPN SHOULD END AT ALL TAF SITES DURG THE SAT EVE HRS...THEN VFR
CONDS W/ GUSTY NW WINDS...BCMG LGT SUN MRNG. VFR CONDS THRU THE 1ST
PART OF THE WORKWEEK...B4 NEXT SYSTEM CAUSES PROBS TUE NGT AND WED.
&&
.MARINE...
NLY FLOW GRADUALLY INCRS TNGT AS LOW PRESSURE STRENGTHS TO THE
SOUTH. BY SAT MRNG...WINDS REACH SCA CRITERIA...AND SPEEDS WILL
GRADUALLY INCR TO 20 TO 25 KT. ATTM GALE CONDS NOT XPCD THRU SAT
NGT...THO DEPENDING ON TRACK OF SFC LOW OFF THE MD EASTERN
SHORE...HIGHER WINDS ARE PSBL LATE SATURDAY.
WIDESPREAD PRECIPITATION BY SAT AFTN...WITH SIGNIFICANT VISIBILITY
RESTRICTIONS.
WINDS WL BE IN SMALL CRAFT CONDITIONS SAT NGT B4 DIMINISHING
LATE..AND THEN NO PROBS XPCTD ON WATERS SUN OR MON.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER WEATHER ADVISORY FROM 7 AM TO 9 PM EST SATURDAY FOR
DCZ001.
MD...WINTER WEATHER ADVISORY FROM 7 AM TO 9 PM EST SATURDAY FOR
MDZ003>007-009>011-013-014-501-502.
VA...WINTER WEATHER ADVISORY FROM 7 AM TO 9 PM EST SATURDAY FOR
VAZ028-031-041-042-050>056.
WINTER WEATHER ADVISORY FROM 5 AM TO 7 PM EST SATURDAY FOR
VAZ021-025>027-029-030-036>040.
WV...WINTER WEATHER ADVISORY FROM 7 AM TO 9 PM EST SATURDAY FOR
WVZ050>053-503-504.
WINTER WEATHER ADVISORY FROM 5 AM TO 7 PM EST SATURDAY FOR
WVZ054-055-501-502.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM SATURDAY TO 1 AM EST SUNDAY FOR
ANZ530>543.
&&
$$
PRODUCTS...SBK/WOODY!
