411
FXUS61 KLWX 131611
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1111 AM EST SAT MAR 13 2010
SYNOPSIS
LOW PRESSURE WILL DRIFT ACROSS THE MID ATLANTIC REGION THROUGH
SUNDAY. IN ASSOCIATION WITH THIS LOW A ROUND OF MODERATE TO HEAVY
RAIN IS EXPECTED INTO THIS AFTERNOON. LOW PRESSURE WILL LINGER
ACROSS THE REGION THROUGH EARLY NEXT WEEK BEFORE HIGH PRESSURE
BUILDS INTO THE REGION LATER IN THE WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
SFC LOPRES LOCATED ACRS SWRN CWA AT 16Z WILL CONT PUSHING NEWD
ACRS CWA THRU THE AFTN. BAND OF RAIN PUSHING SLOWLY NWD THRU NERN
MD...WITH CELLS WITHIN THIS BAND TRAINING NWWD. ONE HALF INCH QPE
XPCD WITH THIS ACTIVITY THROUGH MID AFTERNOON. ELSEWHERE...DRY
SLOT GRADUALLY MAKING ITS WAY INTO THE AREA...THOUGH SATURATED LOW
LEVELS WILL SUPPORT WIDESPREAD DRIZZLE AND VERY LIGHT RAIN. LESS
OVERALL RAINFALL TOTALS FCST THIS AFTN...THOUGH HIGH POPS RMN.
WARMER AIR ACRS SRN VA MAY TRY TO PUSH TWD CWA THIS AFTN...AND
WITH A FEW BREAKS IN THE CLOUDS...ISOLATED ELEVATED CNVCTN CANT BE
RULED OUT. TEMPS XPCD TO RMN IN M/U50S THRU RMNDR OF TDA.
PLEASE REFER TO THE HYDROLOGY SECTION FOR FLOODING DETAILS.
SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/
COMPLICATED FORECAST FOR TONIGHT WITH THE LOW PRESSURE SYSTEM
BECOMING NEARLY VERTICALLY STACKED AS IT DRIFTS EAST OVER THE CWA.
HEAVY RAIN AND STRONG EASTERLY FLOW ARE EXPECTED TO BE NORTH OF THE
MASON-DIXON BY NIGHTFALL WITH ONLY LIGHT TO LOCALLY MODERATE RAIN
UNDER THE LOW /UP ONE TENTH OF AN INCH OF ADDITIONAL RAIN
EXPECTED...PERHAPS A QUARTER OF AN INCH ACROSS NORTHERN ZONES/.
PLEASE SEE HYDROLOGIC SECTION FOR FURTHER RIVER FLOODING DETAILS.
SUNDAY AND SUNDAY NIGHT...LLVL LOW CENTER EAST OF THE CWA WITH
MAINLY NLY FLOW AND SCATTERED LIGHT SHOWERS. WITH COOLER AIR AND
CONTINUED CLOUD COVER EXPECT TEMPERATURES TO BE A COUPLE DEGREES
BELOW NORMAL...SHOULD BE COLD ENOUGH FOR SNOW FLAKES TO MIX IN FOR
THE HIGHEST ELEVATIONS OUT WEST...THOUGH GIVEN THE RECENT WARM
TEMPERATURES NO ACCUMULATION IS EXPECTED.
LONG TERM /MONDAY THROUGH FRIDAY/
STARTING MONDAY...DRIER AIR WILL BEGIN TO WORK INTO THE AREA FROM
AS NLY WINDS PICK-UP DURING THE LATE MRNG/AFTN. ANOTHER SERIES OF
UPPER DISTURBANCES WILL GLIDE DOWN ACROSS THE GREAT LAKES REGION
AND MIDDLE-UPPER MISSISSIPPI VLY REGIONS. FOR THE MID ATLC
THO...LITTLE IF ANY OF THIS ACTIVITY WILL AFFECT THE REGION OTHER
THAN KEEPING TEMPS DOWN INTO SEASONAL AND SLIGHTLY LOWER THAN AVG
TEMPS FOR THE EARLY- MIDDLE PARTS OF NEXT WEEK.
AVIATION /16Z SATURDAY THROUGH WEDNESDAY/
MRNG VBSY/CIGS RMNG IFR...WITH IFR CONDS CONTG THRU TDA. RA/GUSTY
WINDS XPCD ACRS BWI THRU 18/19Z...OTHERWISE INTERMITTENT -RA/DZ.
TONIGHT...EXPECT SOME LIGHT TO LOCALLY MODERATE RAIN WITH NELY
FLOW 15 KT TO CONTINUE FOR KBWI/KMTN WITH WLY FLOW 5 TO 10 KT FOR
KCHO WITH VARIABLE WINDS IN BETWEEN.
LOW PRESSURE MOVES EAST OF THE TERMINALS ON SUNDAY WITH SOME LIGHT
SHOWERS AND NLY-NWLY FLOW 10 TO 15 KT.
MARINE
GALE WRNG RMNS IN EFFECT TDA FOR UPPER CHESAPEAKE BAY ZONES...WITH
SCA UP FOR RMNDR OF MD CHESAPEAKE AND TIDAL POTOMAC. WINDS NOT
GUSTING MUCH ABOVE 20 KT ACR SRN ZONES OF CHESAPEAKE AND LOWER
TIDAL POTOMAC...BUT STILL WARRANT ADZY ATTM.
LOW PRESSURE MOVES ACROSS THE WATERS TONIGHT AND INTO SUNDAY. ANY
LINGERING STRONG WINDS ACROSS NORTHERN PARTS OF THE BAY TO BE
BELOW SCA CRITERIA AROUND MIDNIGHT. RAIN TAPERS OFF TO LIGHT AREAS
TONIGHT...THEN SOME LIGHT SHOWERS ON SUNDAY. NWLY WINDS ON SUNDAY
AROUND 15 KT WITH SCA CRITERIA GUSTS POSSIBLE BY LATE SUNDAY
NIGHT.
HYDROLOGY
FLOOD WATCH IS IN EFFECT FOR ENTIRE CWA THROUGH SUNDAY EVENING.
FOCUS OF HVY RN XPCD TO MV N OF MASON DIXON LINE THIS AFTERNOON.
STILL...SCATTERED HEAVIER SHOWERS WILL PRODUCE ONE HALF TO LOCALLY
ONE INCH OF RAINFALL. CREEKS AND STREAMS ACRS MUCH OF CWA RMN NEAR
BANKFUL...SO ADDITIONAL RAIN MAY LEAD TO FLOODING.
THEN...RIVER FLOODING IS EXPECTED TO BECOME THE BIGGER FOCUS TONIGHT
INTO SUNDAY...WITH POINTS SUCH AS PAW PAW...HARPERS FERRY...POINT OF
ROCKS AND LITTLE FALLS REACHING AT LEAST MODERATE FLOOD. RIVER
FLOODING MAY LAST INTO MONDAY.
TIDES/COASTAL FLOODING
MODERATE COASTAL FLOODING OCCURRED ALONG TIDAL POTOMAC WITH MRNG
HIGH TIDES.
WITH STIFF EASTERLY FLOW CONTINUING TODAY...THESE POSITIVE
ANOMALIES WILL CONTINUE TO INCREASE TO 2 TO 3 FEET ABOVE
ASTRONOMICAL PREDICTIONS...THUS COASTAL FLOOD WARNING IN EFFECT.
SIMILAR CONDS XPCD THRU TMRW MRNG...SO WRNG XPNDD TEMPORIALLY TO
16Z SUN.
WITH ADDITIONAL FRESHWATER RUNOFF THROUGH SUNDAY...MINOR TO
MODERATE TIDAL FLOODING CONCERNS WILL CONTINUE ON THE UPPER
POTOMAC THROUGH THE REST OF THE WEEKEND.
LWX WATCHES/WARNINGS/ADVISORIES
DC...COASTAL FLOOD WARNING UNTIL 11 AM EDT SUNDAY FOR DCZ001.
FLOOD WATCH THROUGH SUNDAY EVENING FOR DCZ001.
MD...COASTAL FLOOD WARNING UNTIL 11 AM EDT SUNDAY FOR MDZ007-011-
013-014-016>018.
FLOOD WATCH THROUGH SUNDAY EVENING FOR MDZ003>007-009>011-013-
014-016>018-501-502.
VA...COASTAL FLOOD WARNING UNTIL 11 AM EDT SUNDAY FOR VAZ052>055-
057.
FLOOD WATCH THROUGH SUNDAY EVENING FOR VAZ021-025>031-036>040-
042-050>057-501-502.
WV...FLOOD WATCH THROUGH SUNDAY EVENING FOR WVZ050>055-501>504.
MARINE...GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ530>532-
538>540.
SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR
ANZ533>537-541>543.
SYNOPSIS...BAJ/BPP
NEAR TERM...SBK
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BAJ/SBK/BPP
MARINE...BAJ/SBK/BPP
HYDROLOGY...SBK/BPP
TIDES/COASTAL FLOODING...SBK/BPP
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