FXUS61 KPBZ 300210
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
910 PM EST SUN NOV 29 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM MOVING THROUGH THE UPPER OHIO VALLEY
OVERNIGHT WILL BRING RAIN SHOWERS INTO MONDAY...AND SCATTERED SNOW
SHOWERS MONDAY NIGHT. HIGH PRESSURE FROM KANSAS WILL BRING DRY
CONDITIONS TUESDAY AND EARLY WEDNESDAY. THEN A LOW PRESSURE SYSTEM
FROM TEXAS WILL MOVE NORTHEAST ALONG THE EAST COAST AND SPREAD
RAIN AND POSSIBLY SNOW ACROSS THE UPPER OHIO VALLEY THURSDAY AND
FRIDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
HAVE ADJUSTED FORECAST OF EASTWARD MOVEMENT OF COLD FRONTAL BAND
OF SHOWERS OVERNIGHT ACROSS THE UPPER OHIO VALLEY BASED ON RECENT
SURFACE AND RADAR DATA. THEN USED BLEND OF SREF MODEL OUTPUT AND
NAM MODEL PROFILES TO FORECAST TRANSITION OF EXITING COLD FRONTAL
SHOWERS DAYTIME MONDAY AND DEVELOPMENT OF LAKE ENHANCED AND
OROGRAPHICALLY INDUCED SNOW SHOWERS MONDAY NIGHT. RAIN AMOUNTS
THROUGH MIDDAY MONDAY SHOULD BE LESS THAN 0.25 INCHES. MOST SNOW
AMOUNTS MONDAY NIGHT SHOULD BE LESS THAN AN INCH.
MADE MINOR ADJUSTMENTS TO TEMPERATURE FORECAST USING BLEND OF GFS
MOS AND NAM AND SREF MODEL OUTPUT.
WINDS SPEEDS SHOULD BE LESS THAN 25 MPH EVEN IN GUSTS.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
RECENT SREF MODEL OUTPUT CONTINUES TO SHOW HIGH PRESSURE COMING
FROM KANSAS TO PROVIDE DRY CONDITIONS ACROSS THE UPPER OHIO VALLEY
TUESDAY INTO EARLY WEDNESDAY.
REGARDING LOW PRESSURE SYSTEM COMING NORTHEAST FROM TEXAS...GEFS
MODEL OUTPUT IS FASTER THAN ECMWF MODEL OUTPUT IN SPREADING RAIN
ACROSS THE UPPER OHIO WEDNESDAY AFTERNOON. APPEARS
TEMPERATURES WILL BE NEAR NORMAL VALUES FOR THIS PERIOD BASED ON
RECENT GFS MOS.
&&
.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 /02Z MONDAY THROUGH FRIDAY/...
WITH RAIN SHOWERS AND A COLD FRONT MOVING INTO THE AREA...CONDITIONS
WILL QUICKLY DROP TO MVFR ACROSS THE UPPER OHIO VALLEY BY
MIDNIGHT. A LOW LEVEL JET IS EXPECTED TO SUBSIDE BY MIDNIGHT...SO
LLWS SHOULD COME TO AN END BY THEN. AS ADDITIONAL LOW LEVEL
MOISTURE MOVES IN WITH THE FRONT...EXPECT MOST SITES TO DROP TO
IFR VIS/MVFR CIGS BRIEFLY BY DAYBREAK MONDAY. CONDITIONS SHOULD
SLOWLY IMPROVE BY EARLY 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.
&&
$$
