FXUS61 KLWX 261947
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
247 PM EST SAT DEC 26 2009

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE REGION TONIGHT INTO SUNDAY. AN 
UPPER-LEVEL LOW AND ITS ASSOCIATED COLD FRONT WILL PASS THROUGH 
SUNDAY NIGHT. HIGH PRESSURE WILL RETURN FOR MONDAY THROUGH 
WEDNESDAY. LOW PRESSURE MAY IMPACT THE AREA TOWARD THE END OF THE 
WEEK. 
&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
LOW PRESSURE OVER THE NORTHERN CHESAPEAKE BAY LATE THIS AFTERNOON 
WILL CONTINUE TO MOVE AWAY FROM THE REGION TONIGHT. HIGH PRESSURE 
CURRENTLY LOCATED OVER WEST VIRGINIA WILL BUILD OVERHEAD LATER 
TONIGHT. A NORTHWEST FLOW BETWEEN THESE TWO SYSTEMS WILL SLOWLY 
CLEAR THE LOW CLOUDS OUT THROUGH EARLY THIS EVENING. HOWEVER...HIGH 
CLOUDS WILL OVERSPREAD THE CWA FROM THE SOUTH AHEAD OF AN 
UPPER-LEVEL LOW. 

MIN TEMPERATURES WILL BE NEAR OR BELOW FREEZING ACROSS MANY 
LOCATIONS OVERNIGHT. THIS MAY CAUSE SLICK SPOTS ON WET ROADWAYS 
TOWARDS EARLY SUNDAY MORNING. AM CONCERNED ABOUT AREAS OF FOG 
TONIGHT AS WELL. PLENTY OF MOISTURE FROM RAIN AND MELTING SNOW WILL 
LINGER OVERNIGHT...BUT DRIER AIR WILL BE FILTERING IN FROM THE 
NORTHWEST. CURRENT FEELING IS THAT THERE WILL BE PATCHY 
FOG...ESPECIALLY IN SHELTERED VALLEYS AND RURAL LOCATIONS.  
&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
SFC HIPRES RDG OHD SUN. BUT...H5 CLSD LOW OVR WRN GRTLKS FILLS AND 
WOBBLES EWD. THAT/LL SEND SOME MID-UPR LVL MSTR EWD ALNG W/ DROPPING 
H8 TEMPS...PARTICULARLY IN THE AFTN HRS. 12Z GDNC SOLNS DIFFER ON 
TIMING...BUT OVRALL TREND A LTL SLOER. FOR THE MOST PART...THAT/LL 
KEEP SUN DRY ENTIRE CWFA. IF THERE IS A FLURRY...ITLL BE IN THE 
APPLCHNS.

SUN NGT WL BE A DIFF STORY...AS THAT WL BE WHEN THE TROF AXIS/SFC 
REFLECTION PIVOTS THRU. THE PATH OF THE UPR LOW ITSELF WL BE ACRS 
PA...SO WL BE DIFFICULT TO GET WDSPD SHSN S/E OF DC/BALT...BUT SCT 
SHSN WL BE FVRBL IN THE WRN BURBS...AND SHSN WL BE LKLY IN THE MTNS.

THAT NW FLOW UPSLP PTTN CONTS MON AND INTO ELY TUE...WHICH MAKE 
ACCUM SNW ALNG FVRD MTN TRRN. ENUF WK PVA ARND MON TO SUPPORT 
FLURRIES E TO THE BLURDG...AND E OF THERE ACRS NRN MD. BUT...NW 
DWNSLPG WL SCOUR OUT MOST OF THE CLDS BY MON NGT...SO TUE SHUD BE A 
MOSUN DAY E OF THE MTNS.

TEMP-WISE...ATYPICAL COLD RTNS AFTR SUN...AS CAA WL BE IN PLACE 
THRUT PD. LEANED ON COLD END OF GDNC MON...AND UNDER THAT FOR TUE. 
SINCE CAA WL BE QUITE STRONG...XPCTG BLUSTERY CONDS TO BOOT.
&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
HIPRES BLDS OVR CWFA TUE NGT-WED. THAT WL PROVIDE TRANQUIL ALBEIT 
COLD CONDS. HWVR...THAT TRANQUILITY APPRS TO BE SHORT LIVED ATTM. 
SIGNALS LOOKING SIMLR TWD NYE ON ANTHR SFC LOPRES DVLPG IN ACTV SRN 
STREAM ALNG GLFMEX CST...EJECTING INTO THE WRN ATLC...W/ 
CYCLOGENESIS EVOLVING OFF DELMARVA. PLENTY OF TIME FOR THINGS TO 
CHG...BUT AN INCR IN SNW POPS THU-FRI WELL W/IN REASON. AN AMPLE 
SUPPLY OF COLD AIR AVBL. OBVIOUSLY THERE ARE MANY THINGS YET TO NAIL 
DOWN. STAY TUNED.
&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
CIGS AND VSBYS SHOULD GRADUALLY IMPROVE LATE THIS AFTERNOON INTO 
THIS EVENING. AS LOW CLOUDS DISSIPATE...THIS MAY SET UP RADIATIONAL 
COOLING OVERNIGHT FOR AREAS OF MORE FOG. THE UNCERTAINTY ON HOW MUCH 
FOG CAN DEVELOP OVERNIGHT REMAINS HIGH. GUIDANCE SHOWS DRIER AIR 
MOVING IN...BUT THE GROUND REMAINS SATURATED FROM RAIN AND MELTING 
SNOW. HAVE INCLUDED IFR/SUBIFR VSBYS OVERNIGHT FOR FOG.

ANY MORNING FOG WILL DISSIPATE SATURDAY AND VFR CONDITIONS ARE 
EXPECTED LATER SATURDAY MORNING AND AFTERNOON. 

CIGS/VSBYS LWR SUN NGT-MON MRNG AS SCT SHSN CROSS BHD A REINFORCING 
CDFNT. RESTRICTIONS SHUDNT BE BLO MVFR. WNDS MAY BE THE BIGGEST 
FACTOR FOR AIRFIELDS THRU TUE IN WNW FLOW. VFR THRAFR.
&&

.MARINE...
LOW PRESSURE OVER THE NORTHERN CHESAPEAKE BAY LATE THIS AFTERNOON 
WILL MOVE OFF TO THE NORTHEAST TONIGHT. HIGH PRESSURE WILL APPROACH 
FROM THE WEST OVERNIGHT INTO SUNDAY. WIND SPEEDS WILL REMAIN BELOW 
SCA CRITERIA.

HIPRES TEMPORARILY BLDS ACRS WATERS TMRW BEFORE AN UPR LVL 
DISTURBANCE AND ITS SFC ARCTIC REFLECTION PIVOT ACRS WATERS LT TMRW 
NGT/ELY MON. WNDS WL SWING ARND TO THE W/NW AND PICK UP STEAM AFTR 
THAT. SOLID SCA SEEMS APPARENT MON-TUE...AND MAY BE CLOSE TO GLW AT 
TIMES. HIPRES ARRIVES TUE NGT-WED.
&&

.HYDROLOGY...
SMALL STREAM OVERFLOWS BECOMING MINOR RIVER FLOODING AT A FEW SPOTS 
NOW. SENECA CREEK NEAR DAWSONVILLE IN MONTCO MD HAS CRESTED ABOVE 
BANKFULL. SHOULD RETURN BELOW BANKS BY SUNSET. MONOCACY AT FREDERICK 
MD STILL RISING. EXPECTING A PEAK ABOVE FS MAYBE ARND MDNT. 
RAPPAHANNOCK AT REMINGTON VA WILL BE CLOSE. CONTG TO WATCH. 
STATEMENT OUT...WILL UPGRADE TO WARNING IF 15 FEET APPEARS IMMINENT. 
ONCE THESE WATERS RECEDE...NO POTENTIAL TROUBLES ANTICIPATED UNTIL 
THE NEXT SNOWPACK SHOWS UP AND MELTS WITH SOME RAIN MIXED IN. 
&&

.TIDES/COASTAL FLOODING...
LOW PRESSURE CURRENTLY LOCATED OVER THE NORTHERN CHESAPEAKE BAY WILL 
SLOWLY MOVE NORTHEAST LATE THIS AFTERNOON INTO TONIGHT. WINDS WILL 
TURN AROUND TOWARD THE WEST-NORTHWEST BEHIND THIS LOW. TIDAL 
ANOMALIES REMAIN ABOUT 2 TO 3 FEET ABOVE NORMAL. WATER LEVELS HAVE 
APPROACHED THRESHOLDS FOR MODERATE COASTAL FLOODING AROUND TIMES OF 
HIGH TIDE. THIS WILL CONTINUE LATE THIS AFTERNOON...BUT WATER LEVELS 
WILL RECEDE TONIGHT DUE TO THE WEST-NORTHWEST FLOW. 
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD WARNING UNTIL 6 PM EST THIS EVENING FOR DCZ001.
MD...COASTAL FLOOD WARNING UNTIL 6 PM EST THIS EVENING FOR MDZ007-
     011-013-014-016>018.
VA...COASTAL FLOOD WARNING UNTIL 6 PM EST THIS EVENING FOR 
     VAZ052>055-057.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...HTS
LONG TERM...HTS
AVIATION...BJL/HTS
MARINE...BJL/HTS
HYDROLOGY...RDH
TIDES/COASTAL FLOODING...BJL