FXUS61 KPBZ 020002
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
702 PM EST TUE DEC 1 2009
.SYNOPSIS...
CLEAR AND COOL TONIGHT UNDER HIGH PRESSURE. LOW PRESSURE MOVING
NORTH FROM THE GULF OF MEXICO TO THE OHIO VALLEY WILL BRING RAIN
LATER WEDNESDAY INTO THURSDAY. IT WILL BE COLDER WITH SNOW SHOWERS
TO END THE WEEK.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
CLEARING LINE CONTINUES TO PROGRESS NORTHWARD THIS AFTERNOON AND
SKIES WILL BE CLEAR FOR MUCH OF THE NIGHT UNDER SURFACE HIGH
PRESSURE. CLOUDS WILL BEGIN OT MOVE INTO THE SOUTHERN CWA TOWARD
MORNING AS SURFACE LOW BEGINS TO PULL NORTH OUT OF THE GULF
STATES. CLOUDS AND RAIN WILL THEN QUICKLY SPREAD NORTH ACROSS THE
REGION DURING THE DAY AHEAD OF SURFACE LOW. SOUTHEAST WINDS WILL
BE ON THE INCREASE AHEAD OF SYSTEM AND ADDED HIGHER GUSTS TO THE
RIDGES IN DOWN SLOPE. TEMPERATURES CLOSER TO MAV MOS FOR MAX TEMPS
AS RAIN SHOULD HOLD TEMPERATURES DOWN.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
RAIN WEDNESDAY NIGHT AS SYSTEM TRACKS ACROSS OHIO VALLEY.
TEMPERATURES WILL HOLD STEADY OR RISE WEDNESDAY NIGHT THEN HOLD
STEADY DURING THE DAY THURSDAY IN COLD ADVECTION. RAIN SHOWERS IN
WRAP AROUND MOISTURE THURSDAY WILL TRANSITION TO SNOW SHOWERS
THURSDAY NIGHT AS COLDER AIR WORKS INTO REGION. COLD NORTHWEST
FLOW FRIDAY WITH SNOW SHOWERS.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
FOR THE WEEKEND...BROAD LOW PRESSURE IS PROGGED TO DEVELOP OVER
CENTRAL NORTH AMERICA, WITH TROUGH AXIS PROJECTED TO EXTEND FROM
OVER JAMES BAY TO TEXAS. ECMWF, OP. GFS, AND ENSEMBLE DEPICTIONS
ARE THAT THE CENTER OF THAT SYSTEM WILL DIG NORTHEASTWARD, LEAVING
THE UPPER OHIO VALLEY IN ZONAL FLOW THROUGH THE BASE OF THE TROUGH
FOR THE WEEKEND. THUS, FORECAST WILL FEATURE TEMPERATURES A FEW
DEGREES UNDER THE SEASONAL NORMALS WITH PRECIPITATION PROBABILITIES
AT, OR BELOW CLIMO-LEVEL. THESE WERE ADJUSTED FOR POTENTIAL LAKE
EFFECT, AND RIDGE ENHANCEMENT AS PER COLD ADVECTION PATTERN, BUT
EVENTUAL SCENARIO WILL DEPEND ON AMPLITUDE OF THE TROUGH AND FAST
MOVING SHORTWAVES IN THE FLOW.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
BASED ON RECENT SREF MODEL OUTPUT...NAM MODEL PROFILES...AND GFS
LAMP OUTPUT...EXPECT VFR WITH AT MOST SCATTERED CIRRUS OVERNIGHT
ACROSS THE UPPER OHIO VALLEY. THEN AS LOW PRESSURE SYSTEM FROM THE
GULF STATES MOVES NORTHEASTWARD THROUGH THE UPPER OHIO VALLEY
WEDNESDAY NIGHT...EXPECT IFR RAIN WITH THE SYSTEM TO LIKEWISE SPREAD
NORTHEASTWARD THROUGH THE UPPER OHIO VALLEY STARTING WEDNESDAY AFTERNOON.
SURFACE WINDS ACROSS THE UPPER OHIO VALLEY WILL BE SOUTHERLY NEAR
5 KTS OVERNIGHT AND THEN BECOME SOUTHEASTERLY TO EASTERLY DAYTIME
WEDNESDAY AT 10-15 KTS WITH GUSTS TO 20 KTS. DOWN SLOPE GUSTS NEAR
THE MOUNTAINS CAN REACH 25 KTS.
EXPECT IFR TO BE PREVALENT ACROSS THE UPPER OHIO VALLEY AS THE
SURFACE LAYER REMAINS SATURATED BY RAINFALL WEDNESDAY NIGHT INTO
THURSDAY MORNING. POST SYSTEM COLD ADVECTION WILL MAINTAIN MVFR
STRATOCUMULUS ACROSS THE UPPER OHIO VALLEY INTO SATURDAY.
INSTABILITY SNOW SHOWERS ASSOCIATED WITH AN UPPER TROUGH MOVING
THROUGH THE GREAT LAKES CAN INDUCE BRIEF IFR EPISODES THURSDAY
NIGHT INTO FRIDAY NIGHT.
GEFS MODEL OUTPUT AND GFS MODEL PROFILES SHOW ENSUING HIGH PRESSURE
FROM THE MIDWEST PROVIDING DRY CONDITIONS AND IMPROVEMENT TO VFR ACROSS
THE UPPER OHIO VALLEY SUNDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
