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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 150031
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
831 PM EDT TUE MAY 14 2013

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE OFFSHORE TONIGHT AS A WARM FRONT
PASSES THROUGH THE MID-ATLANTIC REGION. A COLD FRONT WILL APPROACH
FROM PENNSYLVANIA LATE WEDNESDAY AND STALL OUT NEARBY THROUGH THE
END OF THE WEEK. ANOTHER UPPER LEVEL DISTURBANCE MAY BRING ANOTHER
ROUND OF INCLEMENT WEATHER OVER THE WEEKEND.

&&

.NEAR TERM /UNTIL 8 AM WEDNESDAY MORNING/...
-- Changed Discussion --
RADAR ECHOES ARE SHOWING UP ALL OVER THE PLACE THANKS TO
ISENTROPIC LIFT...BUT WITH AN EXTREMELY DRY AIRMASS IN PLACE
AHEAD OF THE PRECIP...A LARGE MAJORITY IS NOT REACHING THE
GROUND...AND WHAT DOES IS LARGELY ONLY IN THE FORM OF SPRINKLES.
SUSPECT THAT SOME OF THE ACTIVITY IN THE BALTIMORE METRO IS MORE
THAN SPRINKLES...AND POPS HAVE BEEN RAISED THERE TO REFLECT THIS.
SPRINKLES WERE ADDED ACROSS THE ENTIRE FORECAST AREA THIS
EVENING...AND SKY COVER UPDATED TO REFLECT MOSTLY CLOUDY TO CLOUDY
SKIES THROUGHOUT THE NIGHT.

WINDS OVER MOST OF THE AREA HAVE ACTUALLY TURNED BACK OUT OF THE
EAST...EVEN IN SPOTS THAT HAD TURNED SOUTHERLY EARLIER. THE GRIDS
REFLECT THIS...WITH A GRADUAL TURN OUT OF THE SOUTH OVERNIGHT.

LOW TEMPS SEEM ON TRACK AS THE CLOUD COVER WILL HOLD TEMPS UP
SIGNIFICANTLY COMPARED TO LAST NIGHT.
-- End Changed Discussion --
&&

.SHORT TERM /8 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
WARM FRONT LIFTS NEWD THRU NERN MD AND NJ ON WED...PLACING THE
MID-ATLANTIC REGION IN WARM SECTOR. WITH H8 TEMPS IN THE UPPER
TEENS...STRONG SFC HEATING ONCE MRNG CLOUDS ERODE AND DOWNSLOPING
FLOW WITH YIELD HIGHS IN THE MID TO UPPER 80S. SLIGHTLY COOLER TEMPS
EXPECTED NEAR THE CHSPK BAY AND IN NORTH-CENTRAL MD.

A COLD FRONT WILL DROP SWD FROM PA LATE IN THE DAY. HIRES WRF MODELS
DEVELOP CONVECTION ALONG THE FRONT DURING THE PEAK HEATING HRS.
THESE STORMS MAY MOVE SOUTH OF THE M-D LINE EITHER DURING THE LATE
AFTN OR EVE. THERE IS STILL UNCERTAINTY WITH THE STRENGTH/COVERAGE
OF THESE STORMS BY THE TIME THEY REACH US. PART OF THAT UNCERTAINTY
IS RELATED TO STRENGTH OF THE H8-H7 CAPPING INVERSION. WE ARE IN
AGREEMENT WITH SPC THAT MODEL FCST DEWPOINTS...ESPECIALLY THE 12Z
NAM /WITH SFC DEWPOINTS IN THE MU60S/...ARE WAY TOO HIGH FOR WED
AFTN. THIS YIELDED UNREALISTICALLY HIGH FCST CAPE. WILL KEEP WORDING
IN HWO THAT MENTIONS SVR THREAT ON WED...BUT FOCUS IT MORE FOR THE
NRN CWA.

CONVECTION ALONG THE FRONT SHOULD WEAKEN DURING THE MID TO LATE EVE.
WITH THE LOSS OF DAYTIME HEATING...HAVE LIMITED SWD EXTENT OF CHANCE
POPS WED EVE TO ABOUT AS FAR SOUTH AS THE I-66 CORRIDOR. WED NGT
WILL BE MILD WITH LOWS GENERALLY IN 60S.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
SLOW MOVING UPPER LEVEL DISTURBANCE COMBINED WITH A FRONTAL
BOUNDARY WILL HELP TRIGGER PERIODS OF SCATTERED SHOWERS AND
THUNDERSTORMS THURSDAY THROUGH THE WEEKEND. THE GFS IS MORE
BULLISH WITH PROBABILITIES VS THE ECMWF. STILL SOME UNCERTAINTY
AND WILL CONTINUE TO GO WITH CHANCE TO HIGH CHANCE POPS AND NOT
LIKELIES ATTM. THREAT FOR SEVERE STORMS LOOKS MINIMAL. TEMPERATURES
THROUGHOUT THE PERIOD WILL RANGE FROM THE 70S TO THE 80S FOR HIGHS
AND 50S TO 60S FOR LOWS.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
STILL EXPECTING VFR TONIGHT WITH A DECK OF MID CLOUDS. SCT
SPRINKLES POSSIBLE...PERHAPS A BRIEF -SHRA AT BWI OR MTN BUT
CHANCE TOO SMALL TO INCLUDE IN TAF.

S-SW WINDS INCREASE WED WITH GUSTS NEAR 20 KT EXPECTED DURING THE
AFTN. A COLD FRONT WILL APPROACH FROM THE NORTH WED EVE. SCT SHOWERS
AND STORMS POSSIBLE MAINLY ACROSS THE NRN TERMINALS.

MOSTLY VFR THROUGH THE REST OF THE WEEK AND INTO THE WEEKEND.
SCATTERED SHOWERS/STORMS COULD DEVELOP EACH DAY WITH BRIEF
RESTRICTIONS IN VSBY AND CIGS BELOW VFR AND POSSIBLE PATCHY
OVERNIGHT FOG.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
SOUTHERLY WINDS ALREADY HAVE BEGUN IN THE WATERS...ESPECIALLY
SOUTH OF THE BAY BRIDGE...BUT ARE NOT YET GUSTY. SCA REMAINS IN
EFFECT FOR THE MD BAY SOUTH OF POOLES ISLAND AND FOR THE MOUTH OF
THE TIDAL POTOMAC RIVER...AS SLY CHANNELING SHOULD ENHANCE WINDS
/AT LEAST IN GUSTS/ TO AROUND 20 KTS OVERNIGHT.

SLY WINDS INCREASE ON WED. SCA CONDITIONS EXPECTED ACROSS ALL OF THE
WATERS ONCE DAYTIME MIXING DEEPENS.

WILL NEED TO MONITOR ANY POTENTIAL STORMS DROPPING SOUTH OF PA WED
LATE AFTN AND EVE. STRONG WINDS WOULD BE POSSIBLE IF THESE STORMS
REMAIN ORGANIZED BY THE TIME IT REACHES THE NRN CHSPK BAY.

WINDS ARE EXPECTED TO REMAIN BELOW SCA LEVELS THROUGH THE REST OF
THE WEEK AND INTO NEXT WEEKEND.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
TIDAL ANOMALIES HAVE JUST TURNED POSITIVE ON THE WESTERN SHORE OF
THE BAY. WITH SOUTHERLY CHANNELING EXPECTED TONIGHT...THOSE
ANOMALIES SHOULD CONTINUE TO BUILD. THE WEDNESDAY MORNING HIGH
TIDE IS THE HIGHER OF THE TWO...BUT IT WOULD TAKE A ONE FOOT
ANOMALY TO REACH MINOR FLOOD THRESHOLD AT ANNAPOLIS...AND A FOOT
AND A HALF AT BALTIMORE. ALTHOUGH CBOFS MODEL OUTPUT SHOWS
MINOR FLOOD CRITERIA BEING REACHED...IT ALSO HAS BEEN RUNNING TOO
HIGH BY ABOUT A QUARTER FOOT ALL DAY...AND THUS MUST BE VIEWED
SKEPTICALLY. WILL BRIEF NEXT SHIFT TO MONITOR...BUT NO ADVISORY
WILL BE ISSUED AT THIS TIME. NO ISSUES ANTICIPATED ON THE TIDAL
POTOMAC AT THE MOMENT.
-- End Changed Discussion --

&&

.CLIMATE...
LOWS THIS MORNING AT THE CLIMATE SITES...
42F AT DCA...
34F AT BWI...
32F AT IAD...

BOTH BWI AND IAD TIED THEIR PREVIOUS RECORD MIN TEMP FOR MAY 14 THAT
WAS PREVIOUSLY SET IN 1996.

THIS MRNG WAS ONLY THE 4TH TIME SINCE 1962 THAT IAD HAS RECORDED
A FREEZING TEMP THIS LATE IN THE SPRING. THE OTHER TIMES WERE 17
MAY 1984 (30F)...22 MAY 2002 (31F)...AND 14 MAY 1996 (32F).

THIS MRNG WAS ONLY THE 4TH TIME SINCE 1873 THAT BALTIMORE RECORDED A
MIN TEMP OF 34F OR COLDER THIS LATE IN THE SPRING. THE OTHER TIMES
WERE 17 MAY 1956 (33F)...21 MAY 2002 (34F)...AND 14 MAY 1996
(34F).

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT EDT
     WEDNESDAY NIGHT FOR ANZ531>534-537-539>541-543.
     SMALL CRAFT ADVISORY FROM NOON TO 8 PM EDT WEDNESDAY FOR
     ANZ530-535-536-538-542.

&&

$$
SYNOPSIS...JRK
NEAR TERM...JE
SHORT TERM...JRK
LONG TERM...KRW
AVIATION...JE/JRK/KRW
MARINE...JE/JRK/KRW
TIDES/COASTAL FLOODING...JE
CLIMATE...JRK