Area Forecast Discussion
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000
FXUS61 KPBZ 300118
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
918 PM EDT FRI APR 29 2016

.SYNOPSIS...
DRY AND COOL OVERNIGHT INTO SATURDAY MORNING. LOW PRESSURE WILL
BRING RAIN SATURDAY AFTERNOON INTO SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
SHOWERS HAVE EXITED THE REGION AND HAVE REMOVED POPS. ONLY SLIGHT
ADJUSTMENTS TO SKY COVER OVERNIGHT. PREVIOUS DISCUSSION FOLLOWS.

SHORTWAVE TROUGH MOVING ACROSS NEW YORK STATE IS TAKING BULK OF
THE SHOWERS NORTH OF I-80 WITH IT. HAVE TRIMMED BACK POPS MORE
QUICKLY THIS EVENING. ADJUSTED HOURLY TEMPERATURES AND DEW POINTS TO
REFLECT CURRENT OBSERVATIONS. COOL ADVECTION BEHIND SYSTEM WILL
DROP TEMPERATURES TO NEAR THE SEASONAL AVERAGES BY DAYBREAK.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
SOME CLEARING WILL BE LIKELY EARLY SATURDAY AS LOW LEVEL MOISTURE
FINALLY MIXES OUT BEHIND THE SYSTEM FROM FRIDAY AND IN ADVANCE OF
ANOTHER SYSTEM FOR THE LATTER HALF OF SATURDAY. IN THE
INTERIM...DIURNAL MIXING COMBINED WITH A DECREASE IN LAYER
MOISTURE SHOULD ALLOW FOR A PERIOD OF CLEARING IN THE
INTERCESSION. HOWEVER...THIS DECREASE WILL BE FLEETING AS
ISENTROPIC ASCENT AHEAD OF A NORTHEASTWARD TRANSLATING WARM FRONT
WILL MEAN CLOUDS WILL AGAIN OVERSPREAD THE AREA BY LATER IN THE
AFTERNOON.

AFOREMENTIONED ISENTROPIC ASCENT WILL SPREAD DEEP MOISTURE AND
LIFT OVER THE AREA BY SATURDAY EVENING WITH A COUPLED JET
STRUCTURE LIKELY TO TRANSLATE DOWN I-70. THE COMBINATION OF THESE
TWO ASSURES RAIN WILL OVERSPREAD THE AREA...AND POPS WERE THUS
RAISED TO 100 PERCENT. THE WARM FRONT IS SET TO MOVE NORTHWARD AND
THROUGH THE AREA BY SUNDAY MORNING...PLACING THE MAJORITY OF THE
CWA INTO THE WARM SECTOR BY THAT JUNCTURE. POPS WERE WOUND DOWN A
BIT IN THE WARM SECTOR...HOWEVER KEPT AT LEAST CHANCE AS THE MODE
WILL EVOLVE FROM STRATIFORM TO CONVECTIVE.

IN THE WARM SECTOR...THE 12Z GUIDANCE HAS TRENDED DECIDEDLY TOWARD
SOME AMOUNT OF CLEARING BY THE LATE MORNING ON SUNDAY. THIS WOULD
WORK TO STRONGLY DESTABILIZE THE COLUMN...AND MEAN A SECONDARY
INCREASE IN SHOWER AND THUNDERSTORM ACTIVITY ON SUNDAY
AFTERNOON...PARTICULARLY SOUTH OF I-80. NAM PROFILES SUGGEST UP TO
2000 J/KG OF CAPE WITH THE VAST MAJORITY OF IT ABOVE A FAIRLY LOW
FREEZING LEVEL. EVEN IN THE ABSENCE OF STRONG VERTICAL
SHEAR...THIS CLOUD LEAD TO SOME HAILERS. THIS WILL NEED TO BE
MONITORED GOING FORWARD TO SEE HOW THE MODELS HANDLE THE WARM
SECTOR IN SUBSEQUENT RUNS.

EVEN AFTER A WEAK WAVE ON SUNDAY MOVES DOWN THE FRONT AND FORCES
THE SHOWERS AND THUNDERSTORMS...THE UPPER JET AXIS LOOKS TO REMAIN
RELATIVELY PARKED OVER THE OHIO VALLEY. THIS MEANS MOISTURE WILL
BE SLOW TO DECREASE INTO EARLY NEXT WEEK WITH SHOWER CHANCES
CURTAILING PAINFULLY SLOWLY. HOWEVER...AS A DEEPER UPPER LOW DIVES
TOWARD THE TENNESSEE VALLEY BY TUESDAY...THE UPPER JET AXIS SHOULD
FINALLY EVOLVE SOUTHWARD ENOUGH TO DRY OUT OUR AREA. FRIES

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
THE EXTENDED PERIOD LOOKS TO FEATURE A VERY STRONGLY ANCHORED
PATTERN OVER THE WESTERN CONUS AS A RIDGE LOOKS TO EVOLVE OVER THE
INTERMOUNTAIN WEST. DOWNSTREAM TROUGHING WILL THUS EVENTUALLY
BECOME ESTABLISHED OVER THE GREAT LAKES AND NORTHEAST BY THE END
OF THE WEEK AFTER A DRY MID-WEEK. THIS WILL MEAN SHOWER CHANCES
WILL RETURN AND TEMPERATURES WILL GENERALLY TREND NEAR OR BELOW
NORMAL. FRIES

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
MVFR/PATCHY IFR CIGS SHOULD CONTINUE THRU MUCH OF TNGT WITH LOW
LVL MOISTURE IN PLACE. BUILDING SFC RIDGING SHOULD RESULT IN SOME
DECREASE IN LOW LVL CLOUDS...WHICH HAS ALREADY RESULTED IN VFR AT
ZZV. THIS SHOULD CONTIUE ELSEWHERE OVRNGT/ERLY SAT. SOME MVFR BR
IS PSBL LATE WITH THE CLRG...THOUGH INCRG CI SHOULD PRECLUDE A
SIGNIFICANT VSBY DCRS.

VFR IS EXPD TO RETURN SAT MRNG AS MID LVL CLOUDS INCREASE AHD OF
APPROACHING LOW PRESSURE. THE LOW IS EXPECTED TO RESULT IN
MVFR...AND EVENTUAL IFR...RESTRICTIONS AND RAIN LATE SAT FOR
PORTS S OF I 80.

.OUTLOOK /SATURDAY NIGHT THROUGH WEDNESDAY/...
RESTRICTIONS ARE EXPECTED THRU MON AS LOW PRESSURE SLOWLY CROSSES
THE REGION.

&&

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

&&

$$


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