FXUS61 KLWX 040739
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
339 AM EDT SAT JUL 4 2009

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL PASS JUST SOUTH OF THE AREA SATURDAY 
NIGHT THROUGH SUNDAY BRINGING GOOD CHANCES FOR SHOWERS. THE COLD 
FRONT ASSOCIATED WITH THIS LOW WILL STALL OUT TO OUR SOUTH EARLY 
NEXT WEEK WITH A WEAK COLD FRONT CROSSING THE AREA LATE TUESDAY. 
HIGH PRESSURE WILL BUILD IN TOWARDS THE MIDDLE OF THE WEEK.
&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE IS CENTERED ACROSS THE TENNESSEE VALLEY AND STRETCHES 
INTO THE WESTERN HALF OF THE CWFA. LATEST SURFACE ANALYSIS SHOWS A 
WEAK TROUGH ACROSS THE CHESAPEAKE BAY/DELMARVA. ISOLATED SHOWERS 
POPPED UP EARLIER THIS EVENING ACROSS WESTERN MARYLAND...BUT THE 
REGIONAL RADAR IS CURRENTLY DRY. THE NEAREST PRECIPITATION IS ACROSS 
THE MID MISSISSIPPI VALLEY AND ASSOCIATED WITH A LOW PRESSURE SYSTEM.

WEAK SURFACE TROUGH WILL REMAIN ACROSS THE EASTERN CWFA TODAY. IN 
ADDITION...SOME WEAK SHORTWAVE ENERGY IS PROGGED TO MOVE EAST WITHIN 
THE FAST FLOW ALOFT. SURFACE INSTABILITY WILL BE MARGINAL...BUT 
ENOUGH TO MAINTAIN ISOLATED POPS THIS AFTERNOON. 

MAX TEMPS ARE EXPECTED TO RIGHT AROUND CLIMO. 
&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
PRECIPITATION CHANCES WILL INCREASE OVERNIGHT AS THE LOW PRESSURE 
SYSTEM TO THE WEST APPROACHES THE MID ATLANTIC REGION. THE HIGHEST 
CHANCES OF POPS SHOULD BE ACROSS THE SOUTHERN CWFA THROUGH THE 
OVERNIGHT HOURS. MARGINAL INSTABILITY DOES LINGER INTO THE 
OVERNIGHT...SO KEPT ISOLATED THUNDER. 
&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
A DEVELOPING S/W LOW OVER KS/NEB WILL TREK ESE ACROSS THE REST OF 
THE CONUS...WITH THE CENTER OF CIRCULATION REACHING THE MID ATLANTIC 
/WITH GOOD NAM/GFS PROG AGREEMENT WITH SRN WV CROSSING/ SUNDAY 
AFTERNOON. AFTER SOME ONGOING SCT PRECIP WELL AHEAD OF THIS SYSTEM 
TONIGHT...EXPECT CORE OF SOLID SHIELD OF PRECIP TO CROSS THE SRN 
HALF OF THE CWA WITH PRECIP REACHING TO/IF NOT NEAR THE MASON/DIXON 
LINE. RAISED POPS TO LIKELY FOR AREAS DIRECTLY AHEAD OF THE H9 
CENTER OF CIRCULATION...ESSENTIALLY FROM KOKV TO KBWI AND SOUTH. WX 
TYPE IS SHOWERS WITH STABLE 1 KM MIXED LAYER... HALF TO ONE INCH QPF 
FOR AREAS WITH LIKELY POPS...MARKED DROP NORTH TO THE MASON/DIXON 
LINE. WITH SOLID CLOUD COVER AND LONGER FUSED PRECIP EVENT 
TEMPERATURES WILL BE HELD TO QUITE LOW VALUES FOR JULY 5 /10 TO 15 
DEG BELOW NORM/. UNLESS SUNLIGHT IS ABLE TO BREAKOUT FOR A 
SIGNIFICANT LENGTH OF TIME...MAX-T LIKELY BELOW 75...A FEAT ONLY 
SEEN 30 TIMES IN THE FIRST SEVEN DAYS OF JULY WASH DC RECORD DATING 
BACK TO 1872. THE LOW MAX TEMP FOR DCA ON JULY 5 IS 71F.

NNW FLOW AFTER THE LOW PUSHES OFF THE MID ATLANTIC COAST LATE SUNDAY 
NIGHT CLEARS THE SKIES EXCEPT FOR FAR SE ZONES WHERE WRAP AROUND 
CLOUDS/MAYBE SPRINKLES PERSISTS INTO MONDAY.

NEAR NORMAL TEMPERATURES THEN RETURN FOR MONDAY THROUGH THE LATER 
PART OF THE WEEK WITH WLY/NWLY FLOW. A WEAK COLD FRONTAL PASSAGE TUE 
NIGHT /00Z EURO KEEPS ZONE N OF MASON/DIXON...UNLIKE 00Z GFS/ COULD 
BRING SOME PRECIP...PARTICULARLY NORTH. 

WARMING TREND AS RIDGE OVER CNTRL CONUS BEGINS TO SHIFT EWD...MORE 
SUMMERLIKE TEMPS FOR FRI/NEXT WEEKEND.
&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDTIONS ACROSS THE CWFA FOR MOST OF THE TODAY PERIOD. FORECAST 
CIGS SHOULD BE AROUND 6KFT WITH ANOTHER DECK AROUND 10 KFT DURING 
THE AFTERNOON. ISOLD CONVECTION EXPECTED ACROSS THE AREA THIS 
AFTERNOON...BUT TOO ISOLATED TO INCLUDE IN THE TERMINALS CURRENTLY. 
LOW PRESSURE WILL APPROACH FROM THE WEST OVERNIGHT...WITH INCREASING 
CHANCES OF PRECIP. CIGS SHOULD BEGIN TO DECREASE TO AROUND 4 KFT 
AFTER 8PM TONIGHT...ESPECIALLY AT KCHO.

SUBVFR CIGS/VSBYS ALL DAY SUNDAY INTO SUNDAY NIGHT WITH SHIELD OF 
SHOWERS /NO THUNDER EXPECTED ATTM/ AHEAD OF A LOW...MVFR PREVAILS 
ACROSS METRO AREAS WITH IFR POSSIBLE AT CHO. VFR RETURNS SUNDAY 
NIGHT AND CONTINUES THROUGH NEXT WEEK WITH WELCOME QUIET PERIOD 
/SOME TSTMS POSSIBLE...ESP NORTH LATE TUESDAY WITH WEAK CD FROPA/.
&&

.MARINE...
FORECAST SOUNDINGS DO INDICATE SOME POTENTIAL FOR SCA CONDITIONS ON 
THE WATERS TODAY. THE MIDDLE BAY HAS BEEN FLIRTING WITH 20KT GUSTS 
FOR THE PAST SEVERAL HOURS...WILL GO AHEAD AND ISSUE THE HEADLINE. 
THE TIDAL POTOMAC AND THE REMAINDER OF THE CHESAPEAKE BAY ARE MORE 
MARGINAL...BUT WILL INCLUDE GUSTS TO 15 KT FOR THE DAY. REALIZE 
THERE WILL LIKELY BE SOME BREAKS IN THE GUSTS EARLY THIS 
MORNING...BUT DO EXPECT THEM TO PICK UP AGAIN DURING MAX MIXING THIS 
AFTERNOON. 

LOW PASSES JUST SOUTH OF THE WATERS LATE SUNDAY WITH RAIN/SHOWERS 
SUN MRNG THRU SUN NIGHT. NNW WINDS BUILD IN BEHIND THE 
SYSTEM...COULD EASILY BRING SCA CRIT WINDS LATE SUN NIGHT INTO 
MONDAY DEPENDING ON HOW STRONG THE SYSTEM BECOMES...WENT WITH 15 KT 
ATTM...WILL HAVE TO CLOSELY MONITOR SCA POTENTIAL FOR MONDAY MORNING 
IN PARTICULAR. WLY/NWLY FLOW MONDAY NIGHT THROUGH LATE NEXT WEEK 
WITH NO HEADLINES ANTICIPATED AFTER MONDAY ATTM.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ533-
     534.

&&

$$
LISTEMAA/BAJ