Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 291900
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
300 PM EDT SUN MAR 29 2015

.SYNOPSIS...
HIGH PRESSURE OVER THE AREA WILL MOVE OFFSHORE TONIGHT. A COLD
FRONT WILL CROSS THROUGH THE REGION ON MONDAY. A REINFORCING
CLIPPER LOW WILL PASS OVER THE REGION ON TUESDAY. THE HIGH
PRESSURE THAT FOLLOWS WILL SLIDE TO OUR SOUTHEAST THURSDAY AND
FRIDAY ALLOWING FOR WARM TEMPERATURES. ANOTHER COLD FRONT IS
EXPECTED AT THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...

SFC HIPRES OVER VA AND THE CAROLINAS TAFTN. THE NEXT CDFNT FOUND
ACRS THE WRN GRTLKS ATTM. EXCELLENT MDL AGREEMENT TIMING THE ADVC OF
THE FNT...REACHING THE MTNS BY 12Z MON. AHD OF THE FNT...STRONG WAA
AND A 40 KT LLJ WL BE PUMPING WARMER AIR NWD. THUS...DONT THINK
WE/LL SEE MUCH OF A TEMP DROP OFF TNGT. USED A NON-DIURNAL TEMP
TREND. FURTHER...THE ASSOCD LIFT WL RESULT IN RAPIDLY INCRSG CLDS
THIS EVNG AND LGT PCPN DVLPG BTWN MIDNGT-DAWN. HV PLACED HIEST POPS
/LKLY/ AT THE NOSE OF THE THTE RDG...WHICH PINPOINTS THE I-95 CRRDR.
FORTUNATELY...BELIEVE THAT TEMPS FM SFC THRU CLD LYR WL BE WARM ENUF
FOR JUST RA AT THAT TIME. AM NOT SO SURE ABT NRN MD...AND HV A RASN
MIX THERE W/ CHC POPS. HWVR THERES A PSBLTY THAT THIS SETUP CUD BE
RA/FZRA. WL ADVISE EVE SHIFT OF THAT POTL.

THE FNT ITSELF WL BE RATHER MSTR STARVED. THEREFORE XPCT MOST OF THE
PCPN AHD OF THE FNT. CFP WL OCCUR BY NOON AREAWIDE. CAA MAY RESULT
IN A QUICK CHGOVER TO SHSN ON THE WRN SLOPES OF THE MTNS PRIOR TO A
RAPID PCPN /AND CLDCVR/ DECREASE. AT THE SAME TIME...WINDS WL BE
INCREASING...AND THE COMPRESSIONAL WARMING MAY YIELD MAXT WARMER
THAN TDA. IT APPEARS AS THO THE CORE OF HIER WINDS WL BE AT THE TOP
/OR JUST ABV/ THE MIXED LYR...W/ CLDS PRESENT TO INTERFERE W/ DP LYR
MIXING. THEREFORE AM KEEPING GUSTS 20-25 KT.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...

IN A RELATIVELY SHORT AMOUNT OF TIME AFTER THE EXIT OF THE GUSTY
MONDAY SYSTEM...THE NEXT UPPER LEVEL DISTURBANCE WILL BE RIGHT ON
THE DOORSTEP TO OUR NW. THIS FEATURE WILL BE MUCH MORE COMPACT AND
THEREFORE AFFECTING MUCH LESS AREA...ALSO BEING DRIVEN BY A MORE
COMPACT ADVECTION PATTERN - TIGHTLY WOUND AROUND THE SYSTEM. AHEAD
OF AND BEHIND THIS NEXT UPPER WAVE SOME WIND...MAINLY AROUND 5-10KT
BUT GENERALLY THE SYSTEM WILL PASS W/O THE DAY-LONG PERIOD OF STRONG
WINDS BEHIND IT.

THE NEXT QUESTION IS ABOUT PRECIP AND PTYPE. THE PAST FEW RUNS OF
ALL MAIN GUIDANCE SUITES HAVE BEEN WAVERING BACK/FORTH ABOUT THE SFC
LOW TREKKING DIRECTLY OVER THE CWA...A HUNDRED MILES TO THE
NORTH...OR SOMEWHERE IN BETWEEN. THE 12Z NAM IS GOING W/ THE MASON-
DIXON LINE SOLN...BUT IN TERMS OF PRECIP - THAT MEANS VERY LITTLE
FOR AREAS S OF THE SFC LOW. MUCH OF THE PRECIP IS CARRIED ALONG
NORTH OF THE LOW...AS IT IS FOR THE EURO AND GFS BUT THEIR
DETERMINISTIC 12Z RUNS HAVE THE LOW FURTHER SOUTH - BETWEEN THE I-70
AND I-66 CORRIDOR OF THE CWA. AHEAD OF THE FEATURE...SWLY LOW LEVEL
WINDS WILL INCREASE AND SO WILL SFC TEMPS - INTO 40S/50S FROM S TO
N. ALTHOUGH A RAIN/SNOW MIX IS POSSIBLE EARLY TUE MRNG OVER THE
EXTREME NW QUAD OF THE CWA AS PRECIP ARRIVES...PRECIP EXPECTED TO BE
ALL RAIN FOR THE DAYTIME HRS AND MUCH OF IT WILL SPREAD ACROSS THE
NRN HALF OF THE CWA. KEPT A HIGH CHANCE AND SOME LIKLIES IN FOR
THESE AREAS. ON THE IMMEDIATE BACK END OF THE LOW`S PASSAGE IS STILL
SOMEWHAT IN QUESTION. THE COLD AIR W/ THE FEATURE WILL AGAIN BE
COMPACT AND CLOSE INTO THE BACK END OF THE SYSTEM. THERE MAY BE
ENOUGH OVER NERN MD FOR A BRIEF PERIOD AND THE COLD FRONT SWINGS
THRU TO MIX IN SOME SNOW BUT ALSO THE PRECIP MAY BE WELL E OF THE
AREA BY THAT TIME.

AS W/ A TYPICAL UPPER WAVE PASSAGE...THE DAY AFTER WILL BE A
MODERATED VERSION OF THE PREV DAY IN TERMS OF TEMPS AND DRY. SFC
WINDS WILL BE A STEADY NW AND DRIER BREEZE BUT NOT ALL THAT STRONG
AND HIGHS WILL BE ALLOWED TO REACH THE 50S ACROSS MUCH OF THE
AREA...NEAR 60 ACROSS THE SOUTH.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
HIGH PRESSURE...MOVING OFFSHORE THE EAST COAST...WILL SPONSOR DRY
CONDITIONS AND NEAR NORMAL TEMPERATURES WEDNESDAY NIGHT. AN
INCREASED SOUTHERLY FLOW WILL DEVELOP WEDNESDAY NIGHT AND THURSDAY
AHEAD OF AN APPROACHING COLD FRONT. HIGHS ARE EXPECTED TO APPROACH
70 DEGREES ACROSS MUCH OF THE REGION THURSDAY WITH A CHANCE OF RAIN
SHOWERS ACROSS THE WESTERN HALF OF THE REGION.

THE COLD FRONT SHOULD PUSH ACROSS THE REGION THURSDAY NIGHT
INTO FRIDAY BEFORE STALLING TO THE SOUTH FRIDAY NIGHT.
ADDITIONAL RAIN SHOWERS AND PERHAPS A THUNDERSTORM OR TWO COULD
DEVELOP IN LIEU OF THE PASSING FRONT. TEMPERATURES SHOULD REMAIN
MILD THURSDAY NIGHT AND FRIDAY WITH HIGHS REACHING THE UPPER
60S TO NEAR 70 FRIDAY.

THE STALLED FRONT SHOULD MEANDER NORTH AND SOUTH FRIDAY NIGHT
AND SATURDAY...ONLY TO REMAIN THE FOCAL ZONE FOR ADDITIONAL
RAIN SHOWERS OR RUMBLES OF THUNDER AND COOLER TEMPERATURES. A
LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP ALONG THIS FRONT BEFORE
PUSHING TO THE EAST COAST LATER SATURDAY INTO SATURDAY NIGHT.

HIGH PRESSURE WILL BRING DRIER CONDITIONS AND REINFORCING COOLER AIR
INTO THE MID ATLANTIC FOR SUNDAY.
&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...

VFR THRU VALID TAF PD IN SPITE OF A CPL OF OBSTACLES. SLY FLOW TNGT
/SFC WINDS AOB 10 KT/ WL BRING AN INCREASE IN CLDS THIS EVNG...W/
CIGS 050 OVNGT. THERE SHUD BE ENUF LIFT FOR A LTL LGT RA ACRS
IAD/DCA/BWI/MTN. TEMPS AT THAT TIME SHUD BE ABV FRZG. PCPN POTL TOO
LMTD AT CHO/MRB TO INCL IN TAF...AND TOO LGT ELSW TO JUSTIFY TAKING
RESTRICTIONS. WNDS 2500-3000 FT ALOFT 30-40 KT. EQUATIONS DO NOT
QUALIFY FOR LLWS...BUT STILL NOTEWORTHY ENUF FOR A MENTION HERE.

CFP BTWN 12-16 UTC. WNDS POST-FROPA NW G20-25 KT. HIER WNDS AVBL ABV
LCL...BUT ONCE MIXING IMPROVES...THOSE HIER WINDS GONE.

YET ANOTHER QUICK-MOVING UPPER LEVEL LOW WILL SWING BY THE AREA ON
TUE...MAINLY DURING THE DAYTIME HRS. ANY PRECIP IS EXPECTED TO BE
RAIN...W/ WARMER TEMPS WORKING INTO THE SRN END OF THE SYSTEM AS IT
PASSES BY. BRIEF MVFR CIGS COULD RESULT FROM THIS SYSTEM DURING THE
DAYTIME HRS...BUT QUICKLY IMPROVING TUE NIGHT INTO WED AS SKIES
CLEAR OUT.

VFR CONDITIONS WEDNESDAY NIGHT. LIGHT SOUTHEAST WINDS WILL BECOME
SOUTHERLY. VFR CONDITIONS AT ALL TERMINALS THU NGT INTO FRI...EXCEPT
FOR MRB AND PERHAPS IAD WHERE MVFR COULD EVOLVE DUE TO SPOTTY RAIN
SHOWERS IN THE AREA. SOUTH WINDS BECOMING SOUTHWEST AND GUSTING
AROUND 15 KNOTS.

&&

.MARINE...

WINDS HV FINALLY RELAXED ENUF TO DROP ALL SCA...FOR NOW. XPCT
BACKING FLOW REST OF AFTN INTO THE EVNG...W/ AN INCRSD GRADIENT
TNGT. WHILE WINDS AOA 2000 FT 40 KT...VERT MOMENTUM TRANSFER VERY
POOR. WL MAINTAIN SCA AFTR MIDNGT FOR BAY/LWR PTMC FOR LOW END
SCA...AND THEN WIDEN TO ALL WATERS AFTR 9AM. WL STILL HV 35-40 KT
WINDS ABV INVERSION INTO THE MIDDAY. BY THE TIME THAT THE MIXED LYR
DEEPENS AND CFP OCCURS...THAT PACKET OF WINDS GONE. THEREFORE...WL
NOT BE GOING W/ ANYTHING HIER THAN SCA ATTM.

A COLD FRONT WILL CROSS THE REGION LATE TUE...W/ A PERIOD OF LOW-END
SCA GUSTS POSSIBLE FROM SW WINDS AHEAD OF THE FRONT. HIGH PRES WILL
CLEAR OUT THE CLOUDS/PRECIP TUE NIGHT. LOW-END SCA WINDS BEHIND THIS
FEATURE WILL PICK UP AGAIN OVER THE WATERS DURING THE DAYTIME HRS
WED.

NO MARINE HAZARDS EXPECTED WEDNESDAY NIGHT AND THURSDAY. WINDS
GENERALLY AROUND 5 KNOTS WEDNESDAY NIGHT...BECOMING SOUTH TO
SOUTHWEST AT 10 KNOTS WITH OCCASIONAL GUSTS AROUND 15 KNOTS.

&&

.TIDES/COASTAL FLOODING...
WATER LEVELS RUNNING A FOOT TO A FOOT AND A HALF BELOW ASTRO
PREDICTIONS DUE TO RECENT BLOWOUT WINDS. LEVELS SHOULD NORMALIZE
SOMEWHAT TONIGHT IN SLY FLOW. BLOWOUT TIDES WILL RETURN MON AFTN
AS NW WINDS RESUME.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT MONDAY
     FOR ANZ530>534-537>543.
     SMALL CRAFT ADVISORY FROM 9 AM TO 8 PM EDT MONDAY FOR ANZ535-
     536.

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS
SHORT TERM...GMS
LONG TERM...KLW
AVIATION...HTS/GMS/KLW
MARINE...HTS/GMS/KLW
TIDES/COASTAL FLOODING...HTS


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