Area Forecast Discussion
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000
FXUS61 KPBZ 300437
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1237 AM EDT MON MAR 30 2015

.SYNOPSIS...
A WEAK COLD FRONT WILL CROSS THE REGION TONIGHT. LOW PRESSURE IS
EXPECTED TO TRACK ACROSS THE AREA TUESDAY.

&&

.NEAR TERM /THROUGH TODAY/...
WITH 1230AM UPDATE...TWEAKED HOURLY POPS/TEMPS/WEATHER. MANY
LOCATIONS HAD A BRIEF PERIOD OF 30-40 MPH GUSTS AS RAIN
BEGAN...BUT WITH NEARLY THE ENTIRE FORECAST AREA NOW EXPERIENCING
PRECIPITATION...ADDITIONAL WIND GUSTS SHOULD BE ON THE LIGHTER
SIDE. CONTINUE TO SPEED UP DEPARTURE OF OVERALL PRECIPITATION
BASED ON RADAR TRENDS. COULD STILL SEE A COUPLE TENTHS OF SNOW
ACCUMULATION ACROSS SOME ISOLATED LOCATIONS.

AFTER ANY REMAINING SHOWERS EXIT MONDAY MORNING...UPPER TROUGHING
ACROSS THE GREAT LAKES COULD ALLOW FOR A RAIN OR SNOW SHOWER NORTH
OF I 80...THOUGH LIMITED MOISTURE SHOULD CAP THESE CHANCES. CLOUD
COVER SHOULD BEGIN TO DECREASE BY AFTERNOON AS WELL. TEMPS SHOULD
BE NEAR SEASONAL LEVELS TONIGHT...AND SEVERAL DEGREES BELOW
AVERAGE ON MONDAY.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
UNSTABLE NORTHWESTERLY FLOW WILL BRIEFLY TURN WEST-SOUTHWESTERLY
BY LATE MONDAY EVENING TO ALLOW FOR THE CWA TO DRY OUT AND AT
LEAST PARTIALLY CLEAR OUT. HOWEVER...AN ACTIVE PATTERN LOOKS TO
CONTINUE THEREAFTER. RATHER DISTURBING MODEL TRENDS SEEM TO HAVE
TAKEN HOLD ON THE 06Z AND 12Z CYCLES TODAY...WITH THE MODELS
LARGELY FALLING INTO TWO CAMPS. THE NAM AND CANADIAN FAVOR A MORE
NORTHERN TRACK OF A SYSTEM THROUGH THE AREA ON TUESDAY...WHILE THE
GFS AND 00Z ECMWF FAVOR A MORE SOUTHERLY TRACK.
UNSURPRISINGLY...THE SREF BASICALLY SPLIT THE DIFFERENCE AND
ALLOWED FOR A MIDDLE GROUND FORECAST...WHICH WAS LARGELY IN LINE
WITH CONTINUITY...SO FORECAST CHANGES REALLY WERE NOT ALL THAT
LARGE AS A RESULT. IT DOES SEEM THAT THE GFS WAS SUFFERING FROM
SOME GRID SCALE ISSUES...WHILE THE NAM WAS LIKELY SUFFERING FROM
ITS HABITUAL OVER DEVELOPMENT ISSUES. THESE PROBLEMS FURTHER LEND
CREDENCE TO FAVORING AN ENSEMBLE MEAN APPROACH SUCH AS THE SREF
MEAN.

A COMPROMISE APPROACH STILL FAVORS RELATIVELY RAPID ENCROACHMENT
OF WARM ADVECTION ISENTROPIC ASCENT OVER THE FORECAST AREA LATE
MONDAY NIGHT INTO TUESDAY. THIS OCCURS AS A SURFACE LOW CROSSES
THE AREA WITH AT LEAST THE SOUTHERN HALF OF THE AREA LIKELY TO
ENTER THE WARM SECTOR FOR A PORTION OF THAT TIME AND PROBABLY HALT
RAINFALL THERE FOR A TIME. AT THE ONSET...SOME PRECIPITATION TYPE
ISSUES MAY BE PRESENT IF THE SOUTHERN SOLUTIONS VERIFY...HOWEVER
ANY FROZEN PRECIPITATION SHOULD QUICKLY CHANGE TO RAIN AS WARM
ADVECTION QUICKLY LOOKS TO ERODE ANY COLD AIR. THIS IS ESPECIALLY
TRUE GIVEN THE LACK OF ANTECEDENT DRY AIR AS THIS SYSTEM ROLLS
INTO THE AREA...MINIMIZING THE POTENTIAL FOR WET BULB COOLING AS
PRECIPITATION DEVELOPS.

A RELATIVELY QUICK DEPARTURE OF THE SYSTEM LOOKS TO OCCUR TUESDAY
NIGHT WITH MUCH DRIER AIR FLOODING INTO THE CWA ON WEDNESDAY. SOME
TEMPORARY COLD ADVECTION ON WEDNESDAY WILL LIKELY STILL HOLD
TEMPERATURES BACK. HOWEVER...DRASTIC PATTERN AMPLIFICATION OF THE
PATTERN TO OUR WEST LOOKS TO DEVELOP A STRONG THERMAL RIDGE THAT
WILL BE POISED TO PUSH INTO THE AREA LATER IN THE WEEK.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WHILE THE GFS HAS SLOWED THE ARRIVAL OF A FRONT ON THURSDAY FROM
PREVIOUS MODEL RUNS...00Z ECMWF IS EVEN SLOWER THAN THAT.
GIVEN THAT THE GFS IS THE MOST OPEN WAVE SOLUTION RELATIVE TO THE
CANADIAN...GEFS...AND ECMWF...TIMING SLOWER THAN THE GFS IS LIKELY
MORE OPTIMAL FOR THE ARRIVAL OF SHOWERS INTO THE CWA. AS A
RESULT...WARM ADVECTION WILL RULE THE ROOST ON THURSDAY...LIKELY
ALLOWING FOR THE WARMEST DAY OF THE SEASON TO THIS JUNCTURE.
HOWEVER ONCE PRECIPITATION ARRIVES...LOW PRESSURE FORMING ALONG
THE COLD FRONT WILL KEEP PRECIPITATION IN THE FORECAST FRIDAY
UNTIL IT MOVES INTO NEW ENGLAND SATURDAY. TEMPS WILL DROP AFTER
THURSDAY...LEADING BACK TO YET ANOTHER PERIOD OF BELOW NORMAL
VALUES.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
A WEAK UPPER LEVEL TROUGH WITH A SURFACE COLD FRONT WILL COMPLETE
PASSAGE ACROSS THE UPPER OHIO VALLEY THIS MORNING ACCOMPANIED BY
BRIEF WIND GUSTS OF 25 TO 30 KT AND SCATTERED LIGHT RAIN...AND SNOW
SHOWERS.  CONDITION DETERIORATION TO MVFR IS THUS ANTICIPATED AS THE
BOUNDARY LAYER MOISTENS IN THE PREDAWN HOURS WITH IMPROVEMENT AFTER
DAYBREAK AS SUBSIDENCE AND DRY ADVECTION INCREASE.

.OUTLOOK.../MONDAY NIGHT THROUGH FRIDAY/...
RESTRICTIONS ARE LIKELY WITH CROSSING LOW PRESSURE SYSTEMS ON
TUESDAY AND THURSDAY.

&&

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

&&

$$






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