National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 130121
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
921 PM EDT SUN MAY 12 2013

.SYNOPSIS...
SURFACE HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH
TUESDAY...WITH AN UPPER LEVEL TROUGH CROSSING THE MID-ATLANTIC ON
MONDAY. SURFACE HIGH PRESSURE WILL MOVE OFF THE COAST TUESDAY
NIGHT AND PERSIST OFF THE SOUTHEASTERN COAST INTO FRIDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
SKIES WILL CONTINUE TO DECREASE IN COVERAGE EAST OF THE ALLEGHENY
FRONT THROUGH THE EARLY MORNING. WINDS WILL CONTINUE TO SLOWLY
DECREASE THROUGH MIDNIGHT. STILL ONLY EXPECT PATCHY FROST FOR THE
VA/MD PIEDMONT (MIN TEMPS GENERALLY UPR 30S). FROST ADVISORY LATE
TONIGHT WEST OF THE BLUE RIDGE (MIN TEMPS IN THE MID 30S) WITH A
FREEZE WARNING FOR THE HIGHLANDS (UPR 20S TO LOW 30S) ABOVE ABOUT
2000 FT.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
-- Changed Discussion --
UPR TROUGH AXIS SWINGING THROUGH MONDAY WILL PRODUCE STRATOCU
CLOUDS SIMILAR TO WHAT WAS OVER THE OHIO VALLEY THIS AFTERNOON.
THEREFORE MOSTLY CLOUDY CONDITIONS EXPECTED TO DEVELOP THROUGH THE
MIDDAY. MAX TEMPERATURES LIMITED TO UPR 50S TO LOW 60S AND WINDS
TEMPERED A BIT WITH LESS INSOLATION. ISOL SHRA FOR SRN HALF OF
THE CWA WHERE THE VORT MAX IS PROGGED TO GO THROUGH IN THE LATE
AFTERNOON. ADDED SPRINKLES FOR NRN MD WHERE LESS DOWNSLOPING
OCCURS IN NWLY FLOW.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
UPPER TROUGH AXIS WILL PASS THRU MON EVE BEFORE THE TROUGH MOVES OFF
THE ERN SEABOARD LATE MON NGT AND TUE. GOOD RADIATIONAL COOLING
SETUP FOR MON NGT WITH THE SFC HIGH BUILDING OVERHEAD. AN UPPER JET
STREAK APPROACHING FROM THE NW MAY BE ACCOMPANIED BY CI OVNGT...BUT
IMPACTS ON TEMPS SHOULD BE MINIMAL. MIN TEMP FCST BASED OFF A BLEND
OF BIAS-CORRECTED MOS-MAV GUIDANCE...WHICH HAVE THE HIGHEST
VERIFICATION SCORES FOR MIN TEMPS IN RECENT. ISSUED A FREEZE WATCH
FOR ALL COUNTIES WEST OF THE BLUE RIDGE. BASED ON CURRENT FCST...
FROST ADVISORIES MAY BE NEEDED FARTHER EAST TO ABOUT I-95.

UPPER RIDGE AND SFC HIPRES OVERHEAD TUE EVENTUALLY MOVES OFF THE
SOUTHEAST COAST TUE NGT AND WED. A WARM FRONT WILL MOVE THRU DURING
THIS TIME. WINDS BACKING TO SLY NEAR THE SFC AND TO WLY ALOFT WILL
YIELD STRONG WAA /12Z GFS SHOWS H8 TEMPS AT IAD INCREASING FROM -2C
TUE MRNG TO 17C BY WED EVE/. DUE TO ISENTROPIC LIFT FOLLOWED BY A
RETURN OF MOISTURE...CLOUDS AND POSSIBLY LIGHT SHOWERS OR SPRINKLES
MAY ACCOMPANY THE WARM FRONTAL PASSAGE ON WED.

A WEAK SHORTWAVE TROUGH THAT IS FCST TO TRACK EWD INTO THE SRN
PLAINS ON WED MAY BREAK DOWN THE ERN CONUS RIDGE THU AND FRI AS IT
MOVES OVER THE MID-ATLANTIC REGION. CHANCES FOR SHOWERS AND TSTMS
INCREASE LATE IN THE WEEK WITH THE APPROACH OF THE TROUGH. ABOVE
NORMAL TEMPS WILL PERSIST THRU THE WEEKEND.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
VFR CONDS TNGT AND MON. NW FLOW DECREASES THROUGH THE EARLY
MORNING. W-NW FLOW WITH GUSTS TO 20 KT LATE MONDAY AFTERNOON UNDER
AN UPR TROUGH.

HIPRES IN CONTROL THRU MIDWEEK RESULTING IN VFR CONDITIONS. A WEAK
DISTURBANCE APPROACHES THU/FRI. GENERALLY VFR DURING THIS TIME
ALTHOUGH SHOWERS/STORMS MAY TEMPORARILY/LOCALLY RESTRICT CIGS/VSBYS.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
NWLY GUSTS CONTINUE TO DECREASE BEFORE DROPPING BELOW SCA CRIT BY
4 AM. SCA FOR MONDAY FOR NRN WATERS /NORTH OF NORTH BEACH AFTER
3PM...THEN EXPAND TO MAIN STEM...ERN TRIBS...LOWER TIDAL POTOMAC
FOR THE OVERNIGHT AS WIND VEERS NLY WITH CHANNELING EFFECTS.

WINDS DIMINISH MON NGT AS HIPRES BUILDS IN. WARM FRONT MOVES THRU
WED...WHICH MARKS THE ONSET OF SLY FLOW. GIVEN DEEP MIXING...GUSTS
TO 20 KT POSSIBLE DURING THE DAY WED.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...NONE.
MD...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
     FOR MDZ003-501-502.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT MONDAY FOR MDZ501.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR MDZ003-502.
VA...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
     FOR VAZ025>031-503-504.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT MONDAY FOR VAZ503-504.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR VAZ025>031.
WV...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
     FOR WVZ050>053-055-501>506.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT MONDAY FOR WVZ501-503-505-
     506.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR WVZ050>053-055-
     502-504.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR ANZ530>534-537-
     539>541-543.
     SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO 6 AM EDT TUESDAY FOR
     ANZ532-540.
     SMALL CRAFT ADVISORY FROM 6 PM MONDAY TO 6 AM EDT TUESDAY FOR
     ANZ533-534-537-541-543.
     SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO 2 AM EDT TUESDAY FOR
     ANZ530-531-539.
     SMALL CRAFT ADVISORY FROM 3 PM TO 6 PM EDT MONDAY FOR ANZ538.
-- End Changed Discussion --

&&

$$
UPDATE...JACKSON