HAMweather.com Area Forecast Discussion for County Warning Area LWX

Thu, 16 Feb 2012 12:28:37 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
333 AM EST THU FEB 16 2012

.SYNOPSIS...
HIGH PRESSURE WILL SLIDE OFF THE MIDDLE ATLANTIC COAST AS AN 
AREA OF LOW PRESSURE AND COLD FRONT APPROACH FROM THE WEST TODAY.
RAIN WILL OVERSPREAD THE REGION DURING THE DAY WITH IMPROVING
CONDITIONS EXPECTED OVERNIGHT. HIGH PRESSURE WILL RETURN FOR
FRIDAY BEFORE ANOTHER STORM SYSTEM IMPACTS THE REGION OVER THE
WEEKEND. TRANQUIL WEATHER IS EXPECTED EARLY NEXT WEEK.

.NEAR TERM /THROUGH TONIGHT/...
INCLEMENT WEATHER IS EXPECTED TODAY AS A TROUGH OF LOW PRESSURE
AND COLD FRONT APPROACH FROM THE WEST. SOUTHERLY FLOW AND WARM AIR
ADVECTION WILL INCREASE AHEAD OF THE COLD FRONT WITH AMPLE LOW
LEVEL MOISTURE BEING DRAWN NORTHWARD ACROSS THE REGION TODAY. 

ABUNDANT CLOUD COVER HAS HELPED KEEP TEMPERATURES ON THE MILD SIDE
OVERNIGHT AND WE EXPECT ALL LIQUID FOR THIS EVENT. THE GREATEST
IMPACT WILL OCCUR BETWEEN 18-00Z AND HAVE INCREASED POPS TO 100
PERCENT TO SHOW HIGH LEVEL OF CONFIDENCE. HIGHEST POPS ALSO
ENCOMPASS THE WASHINGTON D.C/BALTIMORE METRO. SIDED VERY CLOSE TO
THE HPC QPF FOR THIS EVENT WITH A SOLID QUARTER TO THREE TENTHS OF
AN INCH EXPECTED DURING THE HIGH IMPACT 18-00Z TIMEFRAME OVER THE
METRO.

THE COLD FRONT WILL RACE EAST DURING THE DAY AND WE EXPECT A RAPID
PRECIPITATION CUTOFF AROUND 00Z AS DRIER AIR FILTERS IN BEHIND THE
SYSTEM. A FEW RAIN SHOWERS COULD CONTINUE A BIT LONGER OVER THE
COASTAL LOCALES. COLD AIR ADVECTION WILL TAKE OVER BEHIND THE
FRONT WITH WEST TO WEST-NORTHWEST FLOW EXPECTED OVER THE WESTERN
SLOPES OF THE ALLEGHENY FRONT TONIGHT. NOT THE IDEAL UPSLOPE
COMPONENT FOR THIS REGION BUT STILL ENOUGH TO GENERATE SNOW SHOWER
ACTIVITY. WILL FORECAST AN INCH OVER THE WESTERN 5 AND AM NOT
EXPECTING HIGHLIGHTS ATTM ALTHOUGH THE DAY SHIFT WILL NEED TO
MONITOR THE POTENTIAL.

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
HIPRES BUILDS IN FRI...PASSING OVHD FRI NGT AND OFFSHORE SAT. 
DESPITE CAA...DWNSLPG FLOW AND SUNNY SKIES WILL KEEP TEMPS ABV NRML 
THRU SAT. MAXIMA SHUD REACH U40S-M50S AND MINIMA FCST TO RNG FROM 
U20S-M30S.

SFC LOPRES ASSOCIATED WITH UPR TROF IN SUBTROPICAL JET WILL MOVE 
FROM DEEP SOUTH SAT INTO SRN PORTIONS OF MID-ATLC SAT NGT. THIS 
SYSTEM IS THEN FCST TO MOVE N/E OFF MID-ATLC COAST ON SUN. 0Z 
GUIDANCE HAS COME INTO BETTER AGREEMENT IN FCSTG CYCLONE TO INTERACT 
WITH NRN STREAM SHRTWV TROF...CREATING A STRONGER LOPRES WITH A 
TRACK FARTHER N...CLOSER TO CWA. THIS WARRANTS INCRG POPS TO HIGH 
CHC/LOW LIKELY ACRS RGN SAT NGT/SUN...WITH GREATEST POPS ACRS SRN 
ZONES. VERTICAL THICKNESSES/H8 TEMPS LOOK COLD ENUF TO SUPPORT SNOW
...BUT SFC/LLVL TEMPS APPEAR RELATIVELY WARM UNLESS SIGNIFICANT
DYNAMICAL COOLG OCCURS. KEPT PTYPE RN/SN MIX FOR MOST OF
CWA...WITH MOSTLY SNOW AT HIGHER ELEVATIONS...AND MAINLY RAIN E OF
I-95. UNCERTAINTY IS STILL HIGH IN WKEND FCST...BUT ACCUMULATING
SNOW DOES APPEAR PSBL.

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
LOPRES EXITS BY SUN NGT...WITH STRONG NW FLOW AND COOLER...YET 
SEASONABLE...TEMPS INTO MON...AS HIPRES BUILDS IN. SW FLOW SHUD AIDE 
IN WARMER CONDS BY TUE. CDFNT/LOPRES MAY APPROACH RGN BY TUE NGT/WED.

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS TO START THE DAY BUT DETERIORATING RAPIDLY WITH THE
APPROACH OF THE UPPER TROUGH AND ASSOCIATED COLD FRONT. CIGS AND
VSBYS WILL LOWER TO IFR IN RAIN OVER THE HIGHER TERRAIN BY LATE
MORNING. SOLID IFR CIGS AND VSBYS EXPECTED AT ALL TERMINALS
INCLUDING KIAD/KDCA/KBWI WITH THE HIGHEST IMPACT BETWEEN 18-00Z. 

CONDITIONS WILL IMPROVE AFTER 00Z AS DRIER AIR WORKS IN FROM THE
WEST. PATCHY FOG/LOW CLOUDS COULD DEVELOP OVERNIGHT INTO EARLY
FRIDAY. 

HIGH PRESSURE WILL BUILD OVER THE TERMINALS FRIDAY THROUGH FRIDAY 
NIGHT. LOW PRESSURE MAY IMPACT THE TERMINALS SATURDAY NIGHT INTO 
SUNDAY WITH RAIN/SNOW AND SUBVFR CIGS/VSBYS. UNCERTAINTY WITH THIS 
SYSTEM REMAINS HIGH. HIGH PRESSURE WILL RETURN EARLY NEXT WEEK. 

.MARINE...
INCREASING SOUTHERLY FLOW WILL LEAD TO SMALL CRAFT CONDITIONS FROM
MID MORNING THROUGH LATE AFTERNOON OVER THE WATERS. WIDESPREAD
RAIN WILL LIMIT VISIBILITIES TO 5SM OR LESS PREDOMINANTLY BETWEEN
18-00Z. WIND SHIFT TO THE NORTHWEST IS EXPECTED LATE TONIGHT WITH
INCREASING SPEEDS ON FRIDAY.

NW FLOW FRI SHUD SUPPORT SMALL CRAFT ADVISORY THRESHOLD WIND GUSTS 
AS MIXING INCREASES DIURNALLY. ADZY HOISTED FROM 12-0Z.

HIGH PRESSURE WILL BUILD OVER THE WATERS FRIDAY NIGHT BEFORE MOVING 
OFF THE COAST SATURDAY. LOW PRESSURE MAY IMPACT THE WATERS SATURDAY 
NIGHT INTO SUNDAY. UNCERTAINTY REMAINS HIGH WITH THIS SYSTEM. HIGH 
PRESSURE WILL BUILD TOWARD THE WATERS EARLY NEXT WEEK. NORTHWEST 
WINDS MAY APPROACH SCA CRITERIA DURING THIS TIME. 

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM EST THIS 
     EVENING FOR ANZ530>543.