FXUS61 KPBZ 292053
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
353 PM EST SUN NOV 29 2009
.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT AND CROSS THE
AREA MONDAY MORNING. THE FRONT WILL BRING RAIN SHOWERS MONDAY
WITH A MIX OF RAIN AND SNOW SHOWERS POSSIBLE MONDAY NIGHT. HIGH
PRESSURE WILL BUILD IN BRIEFLY FOR THE MID-WEEK BEFORE A LOW
PRESSURE SYSTEM APPROACHES FROM THE SOUTHWEST WEDNESDAY NIGHT.
&&
.NEAR TERM /THROUGH MONDAY/...
THE LATEST SFC ANALYSIS INDICATES A 1004 MB LOW ACROSS MICHIGAN
WITH A COLD FRONT EXTENDING SWWD ACROSS ERN ILLINOIS. A WARM
FRONT EXTENDS EAST OF THE LOW INTO THE ERN GREAT LAKES.
LOCALLY...WITH THE WARM FRONT HAVING LIFTED NORTH OF THE
AREA...TEMPS ARE UNSEASONABLE WARM IN THE LOWER 60S ACROSS MUCH OF
THE AREA.
TONIGHT...CIRRUS WILL CONTINUE TO ADVECT INTO THE REGION...WITH
THE DEEPER MOISTURE AHEAD OF THE FRONT REACHING E-CNTRL OH BY 00Z.
SHOWERS WILL FIRST REACH E-CNTRL OH AHEAD OF THE FRONT AROUND
MIDNIGHT. FOR THE TIMING OF THE FRONTAL PASSAGE...FCST IS CLOSEST
TO THE GFS SOLN...AS THE NAM APPEARS TO BE AN OUTLIER ON THE SLOW
SLIDE WITH FROPA. THE COLD FRONT WILL REACH E-CNTRL OH AFTER
MIDNIGHT...AND EXTEND ACROSS THE CWA BY MONDAY MORNING.
CATEGORICAL POPS WITH A QUARTER OF AN INCH OF QPF ARE FCST ALONG
THE FRONT AS IT CROSSES THE AREA. AN UNSEASONABLY WARM NIGHT IS
EXPECTED BEFORE FROPA...WITH TEMPS DROPPING TO NEAR 40 BEHIND THE
FRONT AROUND DAYBREAK.
MONDAY...THE COLD FRONT WILL MOVE SOUTHEAST OF THE AREA...WITH RAIN
SHOWERS CONTINUING BEHIND THE FRONT MONDAY MORNING. 500MB TROF AXIS
WILL CROSS THE OHIO VALLEY WITH THE CWA AT THE BASE OF THE TROF BY
MONDAY EVENING. CAA WILL CONTINUE THROUGHOUT THE DAY...WITH TEMPS
STEADY AROUND 40 ACROSS THE AREA. CHC OF SHOWERS WILL DECREASE
BEHIND THE FRONT MONDAY EVENING BEFORE TRUE NWRLY FLOW AND LAKE
EFFECT KICKS IN.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
MONDAY NIGHT AND TUESDAY...THE MID-LEVEL TROF WILL ADVECT INTO THE
NORTHEAST...WITH A COLD NWRLY FLOW OFF OF LAKE ERIE IN ITS WAKE.
WITH CAA CONTINUING AND 850MB TEMPS COOLING TO AROUND -7C...RAIN
AND SNOW SHOWERS ACROSS WRN PA AND THE RIDGES WILL TURN OVER TO
SNOW SHOWERS ACROSS THE AREA MONDAY NIGHT. 850MB FLOW APPEARS TO
HAVE MORE OF WNW COMPONENT...IN COMPARISON TO THE FRIDAY UPSLOPING
EVENT WHICH HAD MORE OF A NW COMPONENT THAT FOCUSED ACCUMULATIONS
ACROSS THE RIDGES. WITH MORE OF A FETCH OFF OF LAKE ERIE...THE
LAKE EFFECT ZONES WILL HAVE A BETTER CHC OF SOME ACCUMULATING SNOW
WITH THIS EVENT. AT THE MOMENT...WITH LIGHT SNOW SHOWERS OR
FLURRIES FCST ACROSS WRN PA...LITTLE OR NO SNOW ACCUMULATION IS
EXPECTED. BETTER CHC FOR ANY ACCUMULATION WOULD BE ALONG AND
NORTH OF INTERSTATE 80 AND ACROSS THE RIDGES...WITH 1 TO 2 INCHES
NOT OUT OF THE QUESTION. TEMPS WILL RECOVER ONLY SLIGHTLY ON
TUESDAY WITH DENSE CLOUD COVERAGE...WITH FCST HIGHS NEAR MAV
GUIDANCE...STRUGGLING TO REACH 40.
TUESDAY NIGHT AND WEDNESDAY...HIGH PRESSURE WILL BUILD IN FROM THE
SOUTHWEST...WITH THE AREA DRYING OUT TEMPORARILY BEFORE A LOW
APPROACHES FROM THE SOUTHWEST. THE GFS IS MORE PROGRESSIVE WITH
THE LOW CENTERED WRN OVER NC WITH RAIN SPREADING NWD INTO N-CNTRL
WV BY WEDNESDAY EVENING. NAM/ECMWF ARE TRENDING SLOWER...SO FCST
ONLY CONSISTS OF CHC POPS WEDNESDAY EVENING ACROSS THE SOUTH.
TEMPERATURES WILL BE NEAR NORMAL VALUES FOR THIS PERIOD.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
PRECIP SHIELD IN ADVANCE OF DEEPENING SURFACE LOW PROGGED TO BE
AROUND TN BY WEDNESDAY EVENING WILL OVERSPREAD THE AREA WEDNESDAY
NIGHT THEN SURFACE LOW MOVES THROUGH OHIO VALLEY THURSDAY. EXACT
TIMING AND PATH OF SURFACE LOW WILL HAVE A BIG IMPACT ON
PRECIPITATION TYPE THURSDAY WITH GFS FASTER TO MOVE SYSTEM NORTH AND
WRAP IN COLD AIR ACROSS REGION. ECMWF IS SLOWER WITH SYSTEM AND COLD
AIR BUT TOOK A MIDDLE OF THE ROAD APPROACH AS WITH EITHER SOLUTION
PRECIP WILL BE ALL SNOW BY LATER THURSDAY. MUCH UNCERTAINTY WILL
REMAIN WITH THIS STORM AND FUTURE FORECASTS WILL LIKELY CHANGE QUITE
A BIT. STRONG COLD ADVECTION BEHIND THIS SYSTEM INTO WEEKEND AND
STAYED CLOSE TO HPC SOLUTION WHICH IS NEARER THE 12Z ECMWF. SNOW
SHOWERS WILL REMAIN INTO THE WEEKEND AS QUITE COLD UPPER TROF OR
CLOSED LOW MOVES ACROSS THE OHIO VALLEY. KEPT TEMPERATURES WELL
BELOW NEW MEX MOS WHICH HAS FLIP FLOPPED FROM PAST COUPLE RUNS.
&&
.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
VFR CONDITIONS FIRST HALF OF TONIGHT WILL DETERIORATE AS THE NIGHT
PROGRESSES AS A COLD FRONT MOVES EAST ACROSS REGION. MID CLOUDS WILL
OVERSPREAD THIS EVENING THEN A QUICK LOWERING TO MVFR CONDITIONS
FROM MIDNIGHT AND BEYOND AS LOW LEVEL MOISTURE ALONG AND BEHIND THE
FRONT LOWERS CIGS AND VSBY IN LIGHT RAIN. EXPECT A PERIOD OF IFR
TOWARD DAYBREAK INTO EARLY MONDAY IN COLD ADVECTION BEHIND FRONT
THEN SLOW IMPROVEMENT WEST TO EAST IN THE AFTERNOON. COLD ADVECTION
WILL KEEP SCATTERED MVFR IN SNOW SHOWERS MONDAY NIGHT THEN
DIMINISHING TUESDAY AS SURFACE HIGH PRESSURE TAKES CONTROL.
VFR IN BETWEEN SYSTEMS WEDNESDAY THEN A STRONG STORM SYSTEM MOVING
NORTHEAST FROM THE DEEP SOUTH WILL BRING RESTRICTIONS IN MIXED
PRECIPITATION LATER WEDNESDAY NIGHT AND THURSDAY WITH SNOW SHOWERS
FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
