Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 070131
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
931 PM EDT FRI MAY 6 2016

.SYNOPSIS...
LOW PRESSURE WILL PULL AWAY FROM THE AREA TONIGHT INTO SATURDAY.
A COLD FRONT WILL PASS THROUGH THE REGION SUNDAY. HIGH PRESSURE
WILL BRIEFLY BUILD OVERHEAD SUNDAY NIGHT. THE BOUNDARY WILL RETURN
NORTH AS A WARM FRONT EARLY NEXT WEEK...REMAINING NEARBY THROUGH
MUCH OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
VERT STACKED LOPRES REMAINS NEAR METRO BALT THIS EVNG. SINCE ATLC
INFLOW HAS LARGELY BEEN CUT OFF...SHRA CVRG HAS BEEN GREATLY
REDUCED SINCE SUNSET. HV BEEN ABLE TO SPEED UP DRYING...THO WL
STILL HOLD ONTO CHC POPS PAST MIDNGT...AND KEEPING SCHC TWD DAWN.
OTHER CHGS HV BEEN MINIMAL. DO NOT XPCT MUCH OF A TEMP FALL DUE TO
AMPLE LLVL CLDCVR. WL BE CONSULTING LAMP SHORTLY.

IN LIGHT OF TRENDS TNGT...HV ACCELERATED THE BREAK IN PCPN...AND
TANGIBLY INSERTED THAT TIMEFRAME AS MIDDAY IN DATABASE. SHUD EVEN
HV A PD OF PTSUN SKIES. HWVR...AN APPROACHING CDFNT FM THE OHVLY
WL SUPPORT SHRA. UNCERTAIN WHETHER ANY WL REACH MTNS MID-LT AFTN.
AS A RESULT...POPS RETURN TO THE FCST FOR THA LATER HALF OF THE
AFTN.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
THE COLD FRONT WILL CROSS THE REGION SATURDAY NIGHT INTO SUNDAY
MORNING RESULTING IN MORE SHOWERS ACROSS THE REGION. RAINFALL AMTS
SHOULD STAY LIGHT. A BREAK IN UNSETTLED CONDITIONS IS EXPECTED
SUNDAY AS DRY AIR MOVES INTO THE REGION BEHIND THE COLD FRONT AND
SUNSHINE IS EXPECTED. HIGH TEMPS TO REACH THE 60S/L70S. CLOUDS
WILL MOVE BACK INTO THE REGION FROM SOUTH TO NORTH SUNDAY NIGHT AS
THE COLD FRONT RETURNS TO THE MID-ATLANTIC.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
WARM FRONT LIFTS NORTH FROM THE CAROLINAS MON INTO TUE BRINGING
BACK THE CHANCE OF SHOWERS TO OUR CWA. THE FRONTAL BOUNDARY STALLS
NEAR OUR AREA KEEPING UNSETTLED CONDITIONS THRU FRI. SOUTHERLY
FLOW WILL BRING WARM AND HUMID CONDITIONS... MAINLY ON WED...
WHICH COULD LEAD TO SOME TSTMS.

HIGH TEMPS WILL BE IN THE 70S AND LOW 80S THRU WED... IN THE 70S THU
AND FRI. LOW TEMPS WILL BE IN THE 50S AND LOW 60S.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
ALTHOUGH RAIN ENDING...THE LACK OF MIXING SHOULD ALLOW CIGS TO
DROP. THEREFORE...AM TAKING THE CURRENT VFR/MVFR AND FORECASTING
IFR CONDS AT BALT/DC TERMINALS. AM NOT AS PESSIMISTIC CHO/MRB
SINCE THEY ARE FURTHER REMOVED FROM DEPARTING UPR LOW.

FLGT CONDS SHOULD IMPROVE TO VFR SAT AS LOW CONTS TO HEAD NE. A
COLD FRONT WILL CROSS THE TERMINALS SATURDAY NIGHT. VFR CONDITIONS
EXPECTED SUNDAY.

SUB-VFR CONDITIONS EXPECTED MON THRU WED AS A FRONT KEEPS
UNSETTLED CONDITIONS OVER OUR REGION.

&&

.MARINE...
THERES NOT MUCH WIND ON THE WATER ATTM AS SFC/UPR LOW NEARLY OVHD.
NOT ONLY ARE WINDS LGT BUT DIRECTIONS VRBL. SHRA PROVIDING MUCH OF
THE FORCING...SO PTTN LOCALIZED. WHILE THAT WL GENERALLY PREVAIL
THRU THE NGT...IF THERE WERE ANY TRAJECTORY IT WOULD BE FROM THE
NW AS LOPRES DEPARTS.

SUB-SCA WINDS CONTINUE THROUGH SATURDAY NIGHT. NWLY WINDS BECOME
SWLY AHD OF CDFNT. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED
SUNDAY WITH GUSTS 20-25 KNOTS OUT OF THE NORTHWEST BEHIND FRONTAL
PASSAGE.

SUB-SCA CONDITIONS MON THRU WED AS WINDS WILL BE BELOW CRITERIA.
SHOWERS OVER THE WATERS PSBL DUE TO A FRONTAL BOUNDARY NEAR OUR
REGION.

&&

.TIDES/COASTAL FLOODING...
THE CURRENT TIDE CYCLE IS AT THE UPPER REACHES OF THE CHESAPEAKE
BAYA ND TIDAL POTOMAC RIVER. DEPARTURES ARE RUNNING AROUND 1.5 OR
1.6 FT ON THE BAY...AND 1.7 OR 1.8 FT ON THE POTOMAC. THE RESULT
HAS BEEN THRESHOLD-HUGGERS AT MANY SITES-- WARNING IN DC...AND
ADVY IN BALTIMORE. ITS CLOSE ENOUGH THAT GIVEN THE DEGREE OF
UNCERTAINTY HAVE OPTED TO ADD HARFORD CO INTO THE ADVY. ALEXANDRIA
ISNT NEARLY AS CLOSE...SOLID ADVY AS FORECAST.

AM NOT SEEING A CATALYST TO ALLOW MUCH WATER TO DRAIN OVERNIGHT.
EVIDENTLY NEITHER IS THE LATEST BATCH OF MODEL GUIDANCE. FORECASTS
WENT UP FROM THE PREVIOUS CYCLE. IN ADDITION THIS IS THE HIGHER
TIDE CYCLE ASTRONOMICALLY. AFTER SOME CONSIDERATION...HAVE OPTED
TO ACCEPT THIS MODEL SOLUTION...LEANING A BIT MORE ON ESTOFS
WHICH IS A COUPLE INCHES HIGHER. /WITH THE LAST TIDE CYCLE...ETSS
WAS TOO LOW./

THE RESULT OF THESE ADJUSTMENTS WAS TO UPGRADE ST MARYS AND ANNE
ARUNDEL COUNTIES TO WARNING FOR THE SAT AM TIDE CYCLE. DO NOT HAVE
THE STRONGEST OF CONFIDENCE BECAUSE...ONCE AGAIN...THESE FORECASTS
ARE ON THE CUSP OF WARNING CRITERIA. WOULD RATHER MAKE THE
DECISION NOW RATHER THAN OVERNIGHT WHEN PLANS CANNOT BE MADE.
CALVERT...BALTIMORE...AND HARFORD COUNTIES WILL BE IN MINOR
INUNDATION...A LITTLE MORE CLEAR-CUT THAN THIS EVENING. THESE
ADVISORIES HAVE BEEN ISSUED AS WELL.

ON THE UPPER TIDAL POTOMAC...ADVISORIES ALREADY IN EFFECT FOR
TOMORROW MORNING. THERE ISNT THE ASTRONOMICAL DIFFERENCE BETWEEN
CYCLES...SO RESULTS SHOULD BE A FEW INCHES LOWER THAN TONIGHT.
THAT MEANS THAT CERTAINTY PRECLUDES MAKING DECISION BEYOND
TOMORROW MORNING ATTM.

AS THE UPPER LOW PULLS AWAY SAT/SAT NIGHT...SOME OF THIS EXCESS
WATER WILL OOZE OUT OF THE ESTUARY. HOWEVER...POSITIVE DEPARTURES
WILL LIKELY BE AN ISSUE THROUGH SUNDAY. HAVE THE CONFIDENCE TO
EXTEND AN ADVISORY FOR SAT PM IN ST MARYS COUNTY. ELSEWHERE WILL
NEED TO MONITOR TRENDS. ITS PLAUSIBLE THAT THE FAVORED CYCLE WILL
REACH MINOR FLOOD WHILE THE OTHER ONE DOESNT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD WARNING UNTIL MIDNIGHT EDT TONIGHT FOR DCZ001.
     COASTAL FLOOD ADVISORY UNTIL NOON EDT SATURDAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 6 AM EDT SATURDAY FOR MDZ018.
     COASTAL FLOOD ADVISORY UNTIL 2 PM EDT SATURDAY FOR MDZ011-508.
     COASTAL FLOOD WARNING FROM 2 AM TO 11 AM EDT SATURDAY FOR
     MDZ014.
     COASTAL FLOOD WARNING UNTIL 6 AM EDT SATURDAY FOR MDZ017.
     COASTAL FLOOD ADVISORY FROM 6 AM TO 8 PM EDT SATURDAY FOR
     MDZ017.
VA...COASTAL FLOOD ADVISORY UNTIL NOON EDT SATURDAY FOR VAZ054.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...HTS/HAS
NEAR TERM...HTS
SHORT TERM...HAS
LONG TERM...IMR
AVIATION...HTS/HAS/IMR
MARINE...HTS/HAS/IMR
TIDES/COASTAL FLOODING...HTS


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