FXUS61 KPBZ 071349 RRA
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
847 AM EST MON DEC 7 2009
.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM MOVING EASTWARD THROUGH THE GREAT LAKES
TODAY MAY PROVIDE A FEW LIGHT SNOW SHOWERS. THEN A STRONG LOW
PRESSURE SYSTEM COMING FROM CALIFORNIA CAN BRING A WINTRY MIX
TUESDAY NIGHT FOLLOWED BY RAIN AND WIND WEDNESDAY AND COLDER
TEMPERATURES AND SNOW SHOWERS THURSDAY INTO FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
JUDGING FROM RECENT SREF MODEL OUTPUT CONTINUED TO FORECAST
ISOLATED LIGHT SNOW SHOWERS FOR THE UPPER OHIO VALLEY TODAY INTO
TONIGHT...AS A WEAK LOW PRESSURE SYSTEM MOVES EASTWARD THROUGH THE
GREAT LAKES.
FORECASTED TEMPERATURES USING CLOSELY CONCURRING GFS AND NAM MOS
VALUES.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
FORECASTED WEATHER EVOLUTION WITH STRONG LOW PRESSURE SYSTEM
COMING FROM CALIFORNIA BASED ON BLEND OF RECENT SREF AND GEFS
MODEL OUTPUT. THESE MODELS SHOWED THE FIRST PRECIPITATION FROM
THE SYSTEM SPREADING ACROSS THE UPPER OHIO VALLEY LATE TUESDAY
AFTERNOON AND EVENING.
DUE TO RECENT SURFACE LAYER COLDNESS...PRECIPITATION TYPE WILL BE
AN ISSUE TUESDAY NIGHT. EXPECT PRECEDING SOUTHWEST WINDS TO WARM
MOST LOCATIONS SOUTH AND WEST OF PITTSBURGH PA SUFFICIENTLY THAT
MOST OF THE PRECIPITATION TUESDAY NIGHT WILL BE RAIN. HOWEVER
CONCUR WITH HPC WWD GUIDANCE...THAT THERE CAN BE A PERIOD OF SNOW
OR SLEET NORTH OF PITTSBURGH...PARTICULARLY WITHIN THE I-80
CORRIDOR. THE PRECIPITATION TYPE FOR THE MOUNTAINS OF NORTHERN
WEST VIRGINIA AND WESTERN MARYLAND CAN VARY BETWEEN SNOW SLEET
FREEZING RAIN AND RAIN. AS SUGGESTED BY HPC WWD GUIDANCE...THERE
IS POTENTIAL FOR ICE AMOUNTS EXCEEDING A QUARTER INCH...SO THIS
SITUATION WILL HAVE TO BE MONITORED. ACROSS THE I-80
COUNTIES...SNOW AND SLEET AMOUNTS CAN REACH 2 INCHES.
RAIN AMOUNTS LATE TUESDAY NIGHT AND DAYTIME WEDNESDAY CAN BE OVER
0.50 INCHES.
WIND CAN BE ANOTHER HAZARD DAYTIME WEDNESDAY WITH GUSTS
POTENTIALLY REACHING 40 MPH IN THE WAKE OF THE COLD FRONTAL
PASSAGE.
POST SYSTEM COOL DOWN WILL RESULT IN A CHANGE BACK TO SNOW SHOWERS
WEDNESDAY NIGHT AND THURSDAY.
&&
.LONG TERM /FRIDAY THROUGH SUNDAY/...
BLEND OF RECENT GEFS AND ECMWF MODEL OUTPUT SHOW SNOW SHOWERS MAY
CONTINUE INTO FRIDAY FOLLOWED BY COLD DRY CONDITIONS FOR SATURDAY
AND SUNDAY.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
SNOW SHOWERS ARE MOVING ACROSS OHIO...BUT ARE RUNNING INTO DRIER
SURFACE AIR ACROSS EASTERN OHIO. THINK A FEW SHSN COULD REACH
ZZV IN THE NEXT 2-4 HOURS...WITH AREAS OF MVFR. OTHERWISE...VFR
WILL GENERALLY PREVAIL...WITH ISOLATED -SHSN AT FKL/DUJ THIS AFTN.
LIGHT SE WINDS THIS MORNING WILL BECOMING SW 5-8 KT THIS AFTN...AND
WEST AROUND 5 KT TNGT.
A STRONG LOW PRESSURE SYSTEM COMING FROM CALIFORNIA WILL PROVIDE
MULTIPLE AVIATION HAZARDS LATE TUESDAY INTO FRIDAY.
WIDESPREAD IFR CONDITIONS WILL SPREAD ACROSS THE UPPER OHIO VALLEY
TUESDAY NIGHT INTO WEDNESDAY DUE TO RAIN AT MOST LOCATIONS AND A
MIX OF SNOW SLEET AND FREEZING RAIN FOR TAF SITES NORTH OF KPIT
AND NEAR THE APPALACHIAN MOUNTAINS. THIS WINTRY MIX CAN PROVIDE
AN ICING HAZARD.
WIND GUSTS DAYTIME WEDNESDAY CAN POTENTIALLY GO OVER 35 KTS IN THE
WAKE OF THE COLD FRONTAL PASSAGE.
POST SYSTEM LAKE-ENHANCED SNOW SHOWERS WEDNESDAY NIGHT INTO
FRIDAY CAN PROVIDE PREVALENT MVFR CONDITIONS AND BRIEF EPISODES OF
IFR.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
