000
FXUS61 KPBZ 231908
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
208 PM EST MON NOV 23 2009

.SYNOPSIS...

AREAS OF LIGHT RAIN WILL END LATER THIS EVENING AS AN UPPER
DISTURBANCE COMPLETES A CROSSING OF THE UPPER OHIO VALLEY.
HOWEVER...CLOUDS AND AREAS OF DRIZZLE WILL PERSIST INTO TUESDAY AS
MOISTURE CONTINUES TO BE FUNNELED OVER THE REGION WITH LOW
PRESSURE MOVING UP THE EAST COAST. A STRONGER LOW IS FORECAST TO
CROSS THE GREAT LAKES AND BRING SHOWERS FOR MID WEEK AND COLDER
TEMPERATURES FOR THE HOLIDAY WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AREA OF LIGHT RAIN WILL CROSS THE REGION THIS EVENING AS SHORTWAVE
IN SOUTHWEST FLOW CROSSES THE UPPER OHIO VALLEY. GIVEN ADVANCE OF
DRY SLOT WITH THIS DISTURBANCE, THINK THAT MEASURABLE PRECIP WILL
END BY MIDNIGHT, BUT AREAS OF DRIZZLE SHOULD CONTINUE THROUGH THE
NIGHT, ESPECIALLY FOR COUNTIES EAST OF I 79, AS LOW MOVING UP THE
COAST CONTINUES TO THROW LOW LEVEL MOISURE AROUND ITS WESTERN
FLANK.

BY TUESDAY, RISING HEIGHTS/WARM ADVECTION MAY BE EXPECTED WITH
DEVELOPMENT OF SHORTWAVE RIDGE IN ADVANCE OF MISSISSIPP VALLEY
LOW. THUS, DRY WEATHER IS PROGGED WITH HIGHS 5 TO 10 DEGREES ABOVE
NORMAL.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...

FOR MID WEEK AND THANKSGIVING...AFORE-MENTIONED MISSISSIPPI VALLEY
LOW IS PROGGED TO DIG TOWARD THE GREAT LAKES AND PHASE WITH
EASTWARD MOVING TROUGH. SCENARIO WILL SEND A COLD FRONT ACROSS
THE UPPER OHIO REGION ON WEDNESDAY EVENING WITH SCATTERED SHOWERS
EXPECTED WITH THE ADVANCE...COVERAGE IS ANTICIPATED TO BE LIMITED
BY MOISTURE SUPPLY. DEEPENING MID/UPPER LEVEL LOW-TROUGH
AXIS/COLD AIR IS CURRENTLY TIMED TO SWEEP OVER THE UPPER OHIO ON
THANKSGIVING EVENING, WITH CHANGEOVER TO SNOW SHOWER POTENTIAL
DURING THE NIGHT.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...

STRONG UPPER LEVEL LOW OVER THE EASTERN UNITED STATES WILL AID IN 
THE DEVELOPMENT OF A SURFACE LOW ALONG THE EAST COAST. WRAPAROUND 
PRECIPITATION SHOULD ARRIVE THURSDAY NIGHT...AND HAVE INCREASED POPS 
TO LIKELY DURING THIS TIME PERIOD. AS WRAPAROUND MOISTURE BEGINS TO 
DECREASE ON FRIDAY...COLD 850MB TEMPERATURES AND FLOW OFF LAKE ERIE 
SHOULD AT THE VERY LEAST ALLOW FOR HIGH CHANCE POPS TO EXTEND FROM 
FRIDAY INTO SATURDAY MORNING. WITH WARM GROUND TEMPERATURES AND LOWS 
ONLY DROPPING A COUPLE OF DEGREES BELOW FREEZING THURSDAY AND FRIDAY 
NIGHTS...STILL FEEL THAT NO SNOW ACCUMULATION WOULD OCCUR THURSDAY 
NIGHT...AND ONLY SMALL ACCUMULATIONS TO THE NORTH FRIDAY NIGHT. AS 
THE LOW DEVELOPS FRIDAY AND THEN MOVES TO THE NORTHEAST...A STRONGER 
PRESSURE GRADIENT SHOULD ALSO BRING AN INCREASE IN WINDS...UP TO 30 
MPH. PRECIPITATION SHOULD COME TO AN END ON SATURDAY AS FLOW TURNS 
OUT OF THE SOUTHWEST WITH HIGH PRESSURE MOVING IN. NEXT SYSTEM IS 
EXPECTED TO ARRIVE BY MONDAY...WITH CHANCE POPS ADDED TO THE 
FORECAST FOR THAT TIME PERIOD.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...

REMAINING LOW VFR CEILINGS ARE EXPECTED TO LOWER TO HIGH MVFR
THIS EVENING...AS SCATTERED AREAS OF RAIN MOVING ACROSS AREA
PORTS. CONDITIONS ARE EXPECTED TO DROP TO LOW MVFR/IFR AFTER
MIDNIGHT AS ADDITIONAL MOISTURE MOVES INTO THE AREA. MEASURABLE
RAIN IS NOT EXPECTED OVERNIGHT...BUT DRIZZLE IS POSSIBLE MAINLY TO
THE NORTH AND EAST OF PITTSBURGH. EXPECT IMPROVEMENTS BY TUESDAY
AFTERNOON.

CONDITIONS COULD RETURN TO VFR TUESDAY NIGHT BEFORE LOW PRESSURE 
MOVES INTO THE GREAT LAKES AND BRINGS A COLD FRONT THROUGH ON 
WEDNESDAY...YIELDING ADDITIONAL RESTRICTIONS. ANOTHER LIFTING OF 
CONDITIONS COULD OCCUR WEDNESDAY NIGHT BEFORE YET ANOTHER ROUND OF 
PRECIPITATION AND RESTRICTIONS OCCURS FOR THE HOLIDAY WEEKEND.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$

15/33