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Area Forecast Discussion

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FXUS61 KLWX 171935 CCA
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
301 PM EDT THU APR 17 2014

.SYNOPSIS...
HIGH PRESSURE OVER NEW ENGLAND WILL STRETCH SOUTHWARD TOWARD THE
MID-ATLANTIC COAST THROUGH THE REMAINDER OF THE WEEK. AN AREA OF
LOW PRESSURE AND COLD FRONT MAY AFFECT THE AREA SATURDAY. A SECOND
COLD FRONT LOOKS TO MOVE THROUGH THE REGION TUESDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
HIGH PRESSURE OVER MAINE CONTINUES TO EXTEND SOUTHWARD THROUGH THE 
MID-ATLANTIC STATES THIS AFTERNOON. THERE HAVE BEEN SOME HIGH CLOUDS 
STREAMING ACROSS THE CWA...AND ALSO A FEW STRATOCU ADVECTING 
WESTWARD INTO N/C MARYLAND. OTHERWISE...MOSTLY SUNNY SKIES HAVE 
PREVAILED UNDER A MODIFIED COOL AIR MASS.

TONIGHT WILL BE DRY AND COOL AGAIN...ALTHOUGH PERHAPS NOT QUITE AS 
COOL AS LAST NIGHT UNDER A LIGHT EASTERLY FLOW REGIME. IT IS 
SOMEWHAT UNCERTAIN HOW MUCH LOW CLOUD COVER MAY PUSH WESTWARD FROM 
THE OCEAN. BEST CHANCE FOR STRATUS APPEARS TO BE IN SOUTHERN 
MARYLAND INTO THE NORTHERN VA PIEDMONT. THIS WOULD ALSO TEND TO KEEP 
TEMPERATURES A LITTLE HIGHER. BUT FURTHER NORTHWEST...MID 30S/LIGHT 
WINDS SUPPORTS A FROST ADVISORY IN THOSE COUNTIES EAST OF THE BLUE 
RIDGE THAT ARE IN THE OFFICIAL GROWING SEASON. THIS LASTS TIL 8 AM 
FRIDAY MORNING. 

HIGH PRESSURE BEGINS TO NUDGE A LITTLE EAST ON FRIDAY AS A WEAK COLD 
FRONT APPROACHES FROM THE WEST. WE/LL LIKELY HAVE MORE CLOUD COVER 
ON FRIDAY COMPARED TO TODAY...BUT FORECAST WILL BE DRY. MAXIMA 
SIMILAR OR SLIGHTLY ABOVE TODAY.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
NORTHERN AND SOUTHERN STREAM LOWS WILL SPLIT THE AREA OVER THE 
WEEKEND. IN THE NORTHERN STREAM...LOW PRESSURE NORTH OF THE GREAT 
LAKES WILL PRODUCE A WEAK COLD FRONT THAT WILL DETERIORATE AS IT 
MOVES OVER THE APPALACHIAN MOUNTAINS. THIS FRONT WILL BE DRY BY THE 
TIME IT REACHES OUR AREA SATURDAY MORNING...THOUGH IT COULD PROVIDE 
A BIT OF A REINFORCEMENT OF COOL AIR FOR THE DAY ON SATURDAY. 

THE FEATURE THAT WILL HAVE A STRONGER INFLUENCE ON THE MID ATLANTIC 
WEATHER WILL BE A SOUTHERN STREAM LOW THAT WILL CUT OFF FROM THE 
UPPER LEVEL FLOW OVER THE GULF STATES FRIDAY NIGHT AND MOVE INTO THE 
ATLANTIC OCEAN NEAR THE GA/FL BORDER EARLY SATURDAY MORNING. THE 
PRIMARY MODEL DIVERGENCE AT THIS TIME IS WITH THE TRACK OF THIS LOW 
AND THE SIZE OF THE PRECIPITATION SHIELD ASSOCIATED WITH IT. ECMWF 
AND NAM KEEP US DRY THROUGH THE WEEKEND WHILE THE GFS IS WETTER 
OVERALL...WITH PRECIPITATION COVERING THE SOUTHERN PORTIONS OF THE 
CWA THROUGH THE DAY ON SATURDAY. HAVE LEFT ANY CHANCE OF POPS OUT OF 
THE FORECAST GIVEN THAT THE GFS IS CLEARLY THE OUTLIER. 

EXPECT PLEANTY OF SUNSHINE TO REACH THE GROUND BETWEEN SOME DAYTIME 
CUMULUS CLOUDS THIS WEEKEND EVERYWHERE EXCEPT FOR THE MOST SOUTHERLY 
TIER OF COUNTIES IN THE CWA AS STRATUS CLOUDS ASSOCIATED WITH THE 
LOW STAY MOSTLY TO OUR SOUTH AND EAST. WITH THE LOW TO OUR SOUTH AND 
HIGH PRESSURE TO THE NORTH SOME COLD AIR WEDGING IS POSSIBLE OVER 
THE WEEKEND...BUT WITH NORTH TO NERLY 850 MB FLOW A STRONG CAD EVENT 
IS NOT EXPECTED...MOSTLY JUST A WEAK INFLUX OF COOL AIR AT THE 
SURFACE WHICH SHOULD BE EASILY OVERCOME BY DAYTIME HEATING. HIGHS 
WILL BE IN THE MID TO UPPER 60S SAT AND SUN AND WEAK NWRLY FLOW WILL 
KEEP NIGHTS COLD...WITH SAT AND SUN LOWS NEAR 40 EVERYWHERE EXCEPT 
THE CITIES...WHERE MID TO UPPER 40S ARE EXPECTED. 

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AN AXIS OF HIGH PRESSURE WILL REMAIN ANCHORED ALONG THE EASTERN 
SEABOARD INTO EARLY NEXT WEEK AS AN AREA OF LOW PRESSURE DRIFTS OFF 
THE GA/FL COAST AND EAST TOWARDS BERMUDA...WELL SOUTH OF THE AREA. A 
GENERALLY LIGHT EASTERLY FLOW WILL PERSIST ACROSS THE AREA BETWEEN 
THESE TWO FEATURES. TEMPERATURES WILL BE NEAR NORMAL SUNDAY NIGHT 
INTO MONDAY NIGHT...WITH DAYTIME HIGHS AT OR ABOVE 70 FOR MOST OF 
THE AREA /WARMEST WEST AWAY FROM THE COOLER WATER/ AND OVERNIGHT 
LOWS IN THE 40S TO AROUND 50.

THE LATEST GFS/ECMWF AND THEIR RESPECTIVE ENSEMBLE MEMBERS HAVE A 
COLD FRONT CROSSING THE AREA FROM WEST TO EAST ON TUESDAY WITH 
VARYING INTENSITY. THIS FRONT WILL BRING A CHANCE OF RAIN SHOWERS TO 
THE AREA...AND COULD BE ACCOMPANIED BY A FEW THUNDERSTORMS DEPENDING 
ON THE EXACT TIMING OF THE FRONTAL PASSAGE AND THE AMOUNT OF 
MOISTURE/INSTABILITY RETURN AHEAD OF THE FRONT.

HIGH PRESSURE WILL BUILD TOWARDS THE AREA FROM THE NORTHERN PLAINS 
AND GREAT LAKES WITH BRIEFLY COOLER TEMPERATURES EXPECTED WEDNESDAY. 
TEMPERATURES LOOK TO START WARMING AGAIN BY NEXT THURSDAY AS THE 
HIGH PUSHES TO THE EAST.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
PREVAILING VFR CONDITIONS THROUGH FRIDAY UNDER LIGHT EAST FLOW. 
SREFS SUGGESTS THE POSSIBILITY OF LOWER CIGS DEVELOPING LATE 
TONIGHT/EARLY FRIDAY. CONFIDENCE IS ON THE LOW SIDE...BUT GIVEN 
EASTERLY FLOW OFF THE OCEAN THIS CAN/T BE RULED OUT.

OUTLOOK...VFR CONDITIONS IN EASTERLY FLOW OF 5 TO 10 KNOTS IS
FORECAST THROUGH EARLY NEXT WEEK.

&&

.MARINE...
WINDS HAVE ABATED A LITTLE THIS AFTERNOON BUT ARE FORECAST TO 
INCREASE AGAIN THIS EVENING IN E/SE FLOW. SCA IS IN EFFECT FOR PARTS 
OF THE BAY INTO THE LOWER TIDAL POTOMAC INTO TONIGHT. CURRENT 
FORECASTS ARE FOR WINDS UNDER SCA CRITERIA FRIDAY. 

A SMALL CRAFT ADVISORY MAY BE NECESSARY FOR THE LOWER MARYLAND 
CHESAPEAKE BAY SUNDAY NIGHT AS LOW PRESSURE MOVES AWAY FROM THE MID 
ATLANTIC SEABOARD. SUB-SMALL CRAFT ADVISORY CONDITIONS ARE
EXPECTED IN GENERALLY LIGHT EASTERLY FLOW AROUND HIGH PRESSURE
SUNDAY NIGHT THROUGH MONDAY NIGHT...THEN MODEST SOUTHERLY AHEAD OF
A COLD FRONT BY TUESDAY. SMALL CRAFT ADVISORY LEVEL WINDS ARE
POSSIBLE WEDNESDAY IN GUSTY NORTHWEST FLOW BEHIND DEPARTING COLD
FRONT AND AHEAD OF APPROACHING HIGH PRESSURE.

&&

.CLIMATE...
THIS MORNING WAS ANOTHER ABNORMALLY COLD MORNING FOR THIS TIME OF 
YEAR...WITH MUCH OF THE AREA EXPERIENCING LOW TEMPERATURES AT OR 
BELOW FREEZING /AROUND 10 DEGREES BELOW NORMAL/. DESPITE THE 
COLD...NO RECORD MINIMUM TEMPERATURES WERE OBSERVED. BELOW IS A LIST 
OF WHAT THE RECORD LOWS ARE FOR TODAY COMPARED TO THE PRELIMINARY 
LOW TEMPERATURES THAT WERE OBSERVED THIS MORNING.

SITE...RECORD........LOW TEMP...
DCA....26 F (1875)...39 F.......
BWI....26 F (1962)...30 F.......
IAD....27 F (1983)...28 F.......

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FROST ADVISORY FROM 2 AM TO 8 AM EDT FRIDAY FOR MDZ004>007-
     009>011.
VA...FROST ADVISORY FROM 2 AM TO 8 AM EDT FRIDAY FOR VAZ036>040-042-
     050-051-501-502.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 3 AM EDT FRIDAY FOR 
ANZ532>534-537-     540-541-543.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 3 AM EDT FRIDAY 
     FOR ANZ531-536-538-539-542.

&&

$$
SYNOPSIS...BPP
NEAR TERM...BPP
SHORT TERM...CEB
LONG TERM...DFH
AVIATION...BPP/CEB/DFH
MARINE...BPP/CEB/DFH









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