Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 250707
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
307 AM EDT MON MAY 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN THROUGH NEXT
WEEKEND. A SOUTHWEST FLOW WILL USHER IN WARMER AND MORE HUMID
CONDITIONS DURING THIS TIME. THE HEAT AND HUMIDITY WILL INCREASE
THE RISK OF THUNDERSTORMS STARTING TUESDAY AND CONTINUING THROUGH
THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN THROUGH TONIGHT
AND AN UPPER-LEVEL RIDGE CENTERED OFF THE SOUTHEAST COAST WILL
EXTEND NORTHWEST INTO THE MID-ATLANTIC DURING THIS TIME. THE
UPPER-LEVEL RIDGING ALONG WITH A SOUTHWEST FLOW WILL USHER IN
WARMER AND SLIGHTLY MORE HUMID CONDITIONS TODAY. LEANED TOWARD THE
WARMER SIDE OF GUIDANCE DUE TO THE SUBSIDENCE EXPECTED WITH THE
RIDGE AXIS OVERHEAD AND PLENTY OF SUNSHINE. MAX TEMPS ARE FORECAST
TO RANGE FROM THE 70S IN THE MOUNTAINS TO THE MID AND UPPER 80S
ACROSS MOST OTHER LOCATIONS.

A SOUTHERLY FLOW WILL CONTINUE TONIGHT AROUND THE HIGH CENTERED TO
OUR EAST. THEREFORE...WARMER CONDITIONS ARE EXPECTED. THE UPPER-
LEVEL RIDGE AXIS WILL START TO SHIFT OFF THE MID-ATLANTIC COAST
TONIGHT...ALLOWING FOR HIGH AND MID-LEVEL CLOUDS TO INCREASE
OVERNIGHT. MOST AREAS WILL REMAIN DRY...BUT A COUPLE SHOWERS
CANNOT BE RULED OUT ACROSS EXTREME WESTERN AREAS WELL AFTER
MIDNIGHT.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
THE UPPER-LEVEL RIDGE WILL REMAIN CENTERED TO OUR EAST WHILE
SURFACE HIGH PRESSURE REMAINS OVER THE ATLANTIC TUESDAY THROUGH
TUESDAY NIGHT. A SOUTHWEST FLOW FROM THE SURFACE THROUGH THE
UPPER-LEVELS OF THE ATMOSPHERE WILL USHER IN MORE MOISTURE DURING
THIS TIME. MAX TEMPS TUESDAY ARE FORECAST TO RANGE FROM THE 70S IN
THE MOUNTAINS TO THE MID AND UPPER 80S ACROSS MOST OTHER
LOCATIONS. DID TWEAK TEMPS A COUPLE DEGREES FROM CONTINUITY DUE TO
A BKN/OVC DECK OF HIGH AND MID-LEVEL CLOUDS EXPECTED.

THE INCREASED MOISTURE WILL LEAD TO THE CHANCE FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCE FOR CONVECTION WILL BE DURING THE
AFTERNOON AND EVENING HOURS DURING PEAK HEATING. ASIDE FROM WEAK
SHORTWAVE ENERGY...THERE WILL NOT BE A STRONG LIFTING MECHANISM TO
ENHANCE CONVECTION COVERAGE IS EXPECTED TO BE SCATTERED ACROSS
MOST AREAS. SHEAR PROFILES REMAIN RELATIVELY WEAK AND INSTABILITY
WILL BE MARGINAL DUE TO THE CLOUD COVER SO THE THREAT FOR SEVERE
THUNDERSTORMS WILL BE LOW. WILL CONTINUE WITH THE CHANCE FOR
SHOWERS/ISOLATED THUNDERSTORMS OVERNIGHT DUE TO SHORTWAVE ENERGY
SWINGING THROUGH AND DEEP MOISTURE. MIN TEMPS WILL RANGE FROM THE
LOWER 60S IN PORTIONS OF THE POTOMAC HIGHLANDS TO THE MID 70S IN
DOWNTOWN WASHINGTON AND BALTIMORE. IT WILL ALSO FEEL QUITE HUMID.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
MULTIPLE ROUNDS OF UNSETTLED WX EXPECTED IN THE EXTENDED WITH
MULTIPLE BOUNDARIES NEARING AND STALLING CLOSE TO THE REGION.
WHILE CONFIDENCE EXIST THAT EACH DAY WILL BRING A CHC FOR TSTM
ACTIVITY...THERE REMAINS SOME MODEL DISCREPANCIES ON THE PLACEMENT
OF THE BOUNDARIES AND AS SUCH TRYING TO FINE TUNE WHERE AND WHEN
THE PCPN OCCURS STILL HAS SOME UNCERTAINTY. AS SUCH...HAVE CAPPED
POPS THROUGH THE PERIOD AS HIGH END CHC. WELL ABOVE NORMAL TEMPS
WILL PERSIST THRU THE PERIOD...WITH HIGHS AND LOWS REACHING OVER
10 DEGREES ABV NORMAL EACH DAY. PLEASE REFER TO THE CLIMATE
SECTION FOR RECORD INFORMATION FOR THE COMING WEEK.

SFC LOW PUSHING NORTH THRU THE GREAT LAKES WED MORNING WILL DRAG ITS
ASSOCIATED COLD FRONT TO JUST WEST OF THE REGION. SFC HIGH PRESSURE
PERSISTING OFFSHORE WILL COUNTER THE PROGRESSION OF THE FRONT WHILE
RIDGING ALOFT NUDGES THE APPROACHING UPPER LVL TROUGH OFF WELL NORTH
OF THE REGION. GENERALLY EXPECTING WITH THIS SYNOPTIC SETUP FOR THE
FRONT TO PUSH INTO THE OHIO RIVER VALLEY...THEN STALLING/WEAKENING
WED INTO THURS. THIS STALLED BOUNDARY WILL BE THE TRIGGERING
MECHANISM FOR SCT-NUM TSTM ACTIVITY WED AFTN-FRI. GOOD MOISTURE
ADVECTION ON THE SWLY FLOW COMBINING WITH TEMPS IN THE 80S WILL
ENABLE DECENT INSTABILITY TO FORM BY WED AFTN. SOME QUESTION AS TO
HOW MUCH INSTABILITY WITH MORNING CLOUD COVER NEEDING TO SCATTER TO
ENABLE THE BEST DIURNAL HEATING. SHEAR IS MORE ON THE WEAKER SIDE
WITH MAINLY UNIDIRECTIONAL FLOW AROUND 20 KTS. THINKING MOST LIKELY
WILL END UP SEEING A STRONG SHEAR/WEAKER INSTABILITY WEST OF THE
BLUE RIDGE...AND STRONGER INSTABILITY/WEAKER SHEAR EAST OF THE BLUE
RIDGE WITH THE BETTER CHC OF HAVING BREAKS IN THE CLOUDS. MODELS ARE
ALREADY HINTING AT SOME SORT OF LINEAR FORMATION...PSBL OVER THE OH
RIVER VALLEY...CARRYING THEN SOUTH THRU CENTRAL MD AND INTO MD. MANY
SVR PARAMETERS ON THE WEAKER SIDE...BUT ITS DEFINITELY NOT OUT OF
THE QUESTION FOR GUSTY TO STRONGER WINDS TO FORM WITH SOME OF THE
STORMS LATE WED AFTN/DURING THE EVENING. WITH PWATS NEAR 1.8
INCHES...ANY STORM COULD ALSO RESULT IN BRIEF HEAVY RAINFALL...ESP
ALONG THE I-95 CORRIDOR. ISO-SCT SHOWERS WILL REMAIN PSBL WED NIGHT.

THE FRONTAL BOUNDARY SINKS FURTHER INTO THE MID ATLANTIC ON
THURS...RESULTING IN YET ANOTHER ROUND OF SHOWERS AND
TSTMS...ESPECIALLY OVER EASTERN AREAS WITH THE AXIS OF THE HIGHER
INSTABILITY ALIGNING FROM DC TO BALTIMORE. DESPITE THE HIGHER
INSTABILITY VALUES...SHEAR JUST CONTINUES TO LACK THOUGH THERE IS
MORE DIRECTIONAL SHEAR AS WINDS BACK TO THE SE. WOULD EXPECT TO SEE
TSTMS SCT IN NATURE THROUGHOUT THE DAY...THOUGH WITH MUCH LESS OF A
SVR POTENTIAL THAN THE PREVIOUS DAYS. MUCH OF THE SAME STORY FOR
FRIDAY.

ANOTHER LOW TRACKING THROUGH SOUTHERN CANADA WILL DRAG ITS
ASSOCIATED COLD FRONT INTO THE MID ATLANTIC SAT...WITH SOME QUESTION
THEN HOW LONG THIS BOUNDARY REMAINS STALLED IN THE VICINITY. THE GFS
AND ECMWF HAVE TWO VERY DIFFERENT SLNS IN THE HANDLING OF THE RIDGE
ALOFT AND THUS THE MOVEMENT OF THE FRONT. WITH THE AREA STILL ON THE
WESTERN PERIPHERY OF THE OFFSHORE HIGH HOWEVER...EXPECT PLENTY OF
WARM AIR AND MOISTURE ADVECTION ON THE SWLY FLOW OVER THE WEEKEND TO
KEEP THE POTENTIAL FOR SCT SHOWERS AND TSTMS...ESP EACH AFTN.


&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT. SOUTH TO SOUTHWEST
WINDS WILL GUST AROUND 20 TO 25 KNOTS LATE THIS MORNING AND
AFTERNOON. WINDS SHOULD DIMINISH AFTER SUNSET THIS EVENING. A FEW
THUNDERSTORMS ARE POSSIBLE TUESDAY AFTERNOON INTO TUESDAY NIGHT.
HOWEVER...COVERAGE WILL REMAIN SCATTERED DUE TO A LACK OF A STRONG
LIFTING MECHANISM. THEREFORE...MUCH OF THE TIME MAY END UP
PRECIPITATION FREE. THE THREAT FOR SEVERE THUNDERSTORMS IS
LOW...BUT BRIEF GUSTY WINDS AND SUBVFR CONDITIONS ARE POSSIBLE.

VARYING CONDITIONS THROUGH THIS WEEKEND...WITH PERIODS
OF MVFR OR LOWER PSBL WITH ANY SHOWER/TSTM. STRONGER TSTMS PSBL WED
AFTN...WITH GUSTY WINDS AND HEAVY RAINFALL. WED COULD ALSO SEE OCNL
GUSTS UP TO 20 KTS OUTSIDE OF ANY PCPN...WITH WINDS GENERALLY 10 KTS
OR LESS OUTSIDE OF PCPN THE REMAINDER OF THE EXTENDED.

&&

.MARINE...
HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN THROUGH TUESDAY
NIGHT. SOUTH TO SOUTHWEST WINDS ARE EXPECTED DURING THIS TIME. THE
GRADIENT WILL BE STRONGEST TODAY SO A SMALL CRAFT ADVISORY IS IN
EFFECT FOR ALL OF THE WATERS INTO THIS EVENING. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR MIDDLE PORTIONS OF THE MARYLAND
CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER LATE TONIGHT THROUGH
TUESDAY. THE SMALL CRAFT ADVISORY MAY HAVE TO BE EXTENDED FARTHER
NORTH TUESDAY...BUT CONFIDENCE IS LOW AT THIS TIME DUE TO A
SLIGHTLY WEAKER GRADIENT AND RELATIVELY COOLER WATERS. SOUTHERLY
WINDS ARE EXPECTED TO CHANNEL UP THE BAY AND LOWER TIDAL POTOMAC
RIVER TUESDAY NIGHT. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR
THESE AREAS.

INCREASED MOISTURE WILL LEAD TO A CHANCE FOR
THUNDERSTORMS...MAINLY TUESDAY AFTERNOON AND EVENING. COVERAGE
SHOULD REMAIN SCATTERED AT BEST SINCE THERE WILL NOT BE A STRONG
LIFTING MECHANISM. THE THREAT FOR SEVERE THUNDERSTORMS IS
LOW...BUT BRIEF GUSTY WINDS AND REDUCED VISIBILITIES FROM RAIN ARE
POSSIBLE IN ANY THUNDERSTORMS THAT DO DEVELOP.

SCA CONDITIONS PSBL ON WED...ESP ON THE CHESAPEAKE BAY...WITH A
TIGHTENING PRESSURE GRADIENT AND SLY CHANNELING. AS THE PRESSURE
GRADIENT SLACKENS BY WED NIGHT...EXPECTING SUB-SCA CONDITIONS THEN
THURS AND FRI FOR MOST OF THE ZONES. MID CHESAPEAKE BAY COULD SEE
GUSTS TO 20 KTS EACH AFTN THRU FRI.

A TIGHTENING PRESSURE GRADIENT YET AGAIN WITH THE NEXT COLD FRONT ON
SAT WILL INCREASE WINDS...WITH PSBL SCA CONDITIONS ON ALL WATERS SAT-
SAT NIGHT.

OUTSIDE OF THE SYNOPTIC FLOW...EACH DAY WILL BRING A CHC FOR SHOWERS
AND TSTMS...WHICH COULD ALSO RESULT IN GUSTY WINDS.

&&

.CLIMATE...
UNUSUALLY WARM TEMPERATURES FOR THIS EARLY IN THE YEAR ARE
FORECAST DURING MUCH OF THE UPCOMING WEEK. BELOW IS A LIST OF
RECORD DAILY WARM TEMPERATURES FOR THE UPCOMING WEEK. CURRENT
FEELING IS THAT HIGH AND MID-LEVEL CLOUDS WILL PREVENT RECORD-
BREAKING HIGH TEMPERATURES THIS WEEK...BUT SHOULD WE GET MORE
SUNSHINE THEN EXPECTED SOME OF THESE RECORDS COULD BE CHALLENGED.
SOME OF THE RECORD HIGH MIN TEMPS COULD BE CHALLENGED.

.......RECORD WARM TEMPERATURES FOR DCA........
DATE...RECORD HIGH...........RECORD HIGH MIN...
5/25...94 (1880).............71 (2012).........
5/26...96 (1880).............74 (1991).........
5/27...95 (1965/1914/1880)...75 (1991).........
5/28...97 (1941).............75 (1991).........
5/29...97 (1991/1969)........74 (1991).........
5/30...98 (1991).............74 (1991).........

.......RECORD WARM TEMPERATURES FOR BWI........
DATE...RECORD HIGH...........RECORD HIGH MIN...
5/25...94 (1991).............70 (1936).........
5/26...94 (1914).............74 (1880).........
5/27...95 (1965/1941)........75 (1880).........
5/28...97 (1941).............78 (1941).........
5/29...97 (1969).............71 (1908).........
5/30...98* (2011/1991).......72 (1895).........
*ALSO HIGHEST OBSERVED MAY MONTHLY TEMPERATURE

.......RECORD WARM TEMPERATURES FOR IAD........
DATE...RECORD HIGH...........RECORD HIGH MIN...
5/25...92 (1991).............67 (2004).........
5/26...92 (2007).............70 (1991).........
5/27...92 (2010/1965)........69 (2008/1991)....
5/28...90 (2012/1991)........70 (1991).........
5/29...97* (1969)............69 (2012).........
5/30...95 (2006/1991/1987)...70 (2011).........
*ALSO HIGHEST OBSERVED MAY MONTHLY TEMPERATURE

BELOW IS THE LONGEST STRETCH OF CONSECUTIVE DAYS AT OR ABOVE 90 F
DURING THE MONTH OF MAY.

DCA...7 DAYS (05/25-05/31/1991)
BWI...7 DAYS (05/25-05/31/1991)
IAD...7 DAYS (05/25-05/31/1991)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 AM EDT
     TUESDAY FOR ANZ531-538-539.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM EDT
     TUESDAY FOR ANZ540-542.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ532>534-537-
     541-543.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 2 AM EDT
     TUESDAY FOR ANZ530-535-536.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...SEARS
AVIATION...BJL/SEARS
MARINE...BJL/SEARS
CLIMATE...DFH/BJL



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