FXUS61 KLWX 171931
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
331 PM EDT FRI MAY 17 2013

.SYNOPSIS...
A FRONTAL BOUNDARY OVER THE CENTRAL APPALACHIANS AND SOUTHERN 
MID-ATLANTIC WILL REMAIN STALLED THROUGH THE WEEKEND AS AN ONSHORE 
FLOW DEVELOPS WITH SURFACE HIGH PRESSURE BUILDING OFF THE NORTHERN 
MID-ATLANTIC COAST. HIGH PRESSURE WILL BUILD OVER THE EASTERN STATES 
THROUGH THE FIRST HALF OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
COLD FRONT HAS STALLED OVER THE WESTERN PORTION OF THE FORECAST 
AREA. NORTH OF THE FRONT THE AIRMASS WILL REMAIN STABLE WITH NOTHING 
MORE THAN SOME MID AND HIGH LEVEL CLOUDS EXPECTED FROM TIME TO TIME. 
THE AREA FROM WESTERN MARYLAND AND ESPECIALLY THE POTOMAC HIGHLANDS 
AND A PORTION OF THE SHENANDOAH VALLEY ARE MORE UNSTABLE. SCATTERED 
SHOWERS AND ISOLATED THUNDERSTORMS STILL EXPECTED LATER THIS 
AFTERNOON AND EVENING. EXPECTING PULSE TYPE STORMS...WEAK SHEAR AND 
STEERING FLOW. OVERNIGHT LOWS WILL FALL BACK INTO THE 50S TO LOWER 
60S.

MOISTURE WILL INCREASE OVERNIGHT AS EASTERLY FLOW TAKES SHAPE. LOW 
CLOUDS WITH INCREASING CHANCES FOR LIGHT RAIN/SHOWERS AND SOME FOG 
EXPECTED DURING THE DAY. ISOLATED THUNDER POSSIBLE FURTHER SOUTH BUT 
GENERALLY AN OVERCAST DAY WITH COOL TEMPERATURES AND PERIODS OF 
LIGHT RAIN. TEMPERATURES WILL STRUGGLE TO REACH 70 IN MANY 
LOCATIONS. 

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
AN UPR TROUGH EJECTING FROM THE NORTHERN INTERMOUNTAIN WEST TO THE 
GREAT PLAINS AND AN AMPLIFYING TROUGH OVER THE CANADIAN MARITIMES 
WILL AMPLIFY A LONG-WAVE RIDGE OVER THE MIDWEST THIS WEEKEND. AT THE 
SFC...HIGH PRESSURE WILL BUILD OFF THE NRN MID-ATLANTIC COAST WITH 
THE STALLED BOUNDARY PERSISTING OVER THE SRN MID-ATLANTIC. AS A 
RESULT...AN ONSHORE FLOW IS EXPECTED SATURDAY THROUGH SUNDAY NIGHT. 
EXPECT WIDESPREAD SHOWERS TO SPREAD NORTHEAST TO THE BALT-WASH METRO 
SATURDAY NIGHT AS MOIST SLY LLVL FLOW EXPANDS ACROSS THE CWA. CLOUDS 
AND ONSHORE FLOW MAKE FOR A MILD SATURDAY NIGHT WITH MIN TEMPS MID 
TO UPR 50S...LOW 60S URBAN/NEAR SHORE. WAA OVERRIDES THE CLOUDS 
MAKING FOR MAX TEMPS ONLY ABOUT 5 DEGREES BELOW NORMAL (LOW 70S). 

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
A LONG WAVE (WARM) RIDGE WILL PERSIST OVER THE ERN STATES MONDAY 
THROUGH MOST OF NEXT WEEK WITH A SLY FLOW AND ABOVE NORMAL 
TEMPERATURES. GENERALLY 80S MAX TEMPS THROUGH THE WEEK WITH MID TO 
UPR 60 FOR MINS IN THE HUMID AIR. AT LEAST DIURNALLY DRIVEN 
CONVECTION IS EXPECTED WITH ANY DISTURBANCE MAKING FOR ALL-DAY 
THUNDERSTORM POTENTIAL.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
VFR EXPECTED AT LEAST THROUGH MIDNIGHT. SCATTERED SHOWERS/ISOLATED 
STORMS FOCUSED OVER THE SOUTHWEST. MVFR CIGS/VSBYS EXPECTED AFTER 
09Z AS EASTERLY WIND TAKES SHAPE. EXPECT SUB VFR CIGS/VSBYS 
EVERYWHERE BY SATURDAY AFTERNOON/EVENING ALONG WITH RAIN/SHOWERS. 

MVFR/IFR CIGS SATURDAY NIGHT THROUGH SUNDAY NIGHT AS AN ONSHORE FLOW 
BRINGS AMPLE MOISTURE ACROSS THE REGION. PASSING SHOWERS THROUGH 
THIS TIME COULD CAUSE IFR VSBYS DURING THE HEAVIEST RAINFALL. 
UNSTABLE PATTERN CONTINUES THROUGH AT LEAST THE MIDDLE OF NEXT WEEK.

&&

.MARINE...
WINDS WILL REMAIN BELOW SCA TODAY BUT INCREASE OUT OF THE EAST 
OVERNIGHT. WINDS COULD APPROACH SCA LEVELS DURING SATURDAY BUT 
CONFIDENCE NOT HIGH ENOUGH TO ISSUE ATTM. VSBYS OVER THE WATERS WILL 
BE REDUCED AT TIMES IN RAIN/SHOWERS.

ONSHORE FLOW 10 TO 15 KT SATURDAY NIGHT THROUGH SUNDAY 
NIGHT...BECOMING SLY MONDAY MORNING. PERHAPS AN SCA FOR SLY 
CHANNELING MONDAY AFTERNOON/EVENING...OTHERWISE WINDS STAY BELOW 18 
KT. SWLY FLOW AROUND 10 KT THEN TUESDAY THROUGH WEDNESDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BAJ
NEAR TERM...KRW
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BAJ/KRW
MARINE...BAJ/KRW