296
FXUS61 KPBZ 201725
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
125 PM EDT SAT APR 20 2019
SYNOPSIS
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE TODAY AS LOW
PRESSURE TRANSITIONS OVER THE AREA. COOLER AIR WILL FOLLOW ON SUNDAY
WITH DECREASING RAIN CHANCES. DRY CONDITIONS AND A WARMING TREND IS
EXPECTED MONDAY AND TUESDAY.
NEAR TERM /THROUGH TONIGHT/
WITH THE EARLY AFTERNOON UPDATE, PRIMARY UPDATE WAS TO RAISE
TEMPERATURES ACROSS EASTERN COUNTIES WHERE SKIES HAVE BEEN THE MOST
CLEAR. PROBABLY DID NOT GO HIGH ENOUGH IN INDIANA, ALTHOUGH THE
DEWPOINT READING IS A BIT SUSPECT. STILL THINK THAT THE COVERAGE OF
SLIGHT CHANCE POPS AT 2PM IS OVERDONE, BUT CAN'T RULE OUT THE CHANCE
OF SHOWERS OCCURRING AT THAT TIME EITHER. PREVIOUS DISCUSSION
FOLLOWS.
SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON WITH
INCREASING INSTABILITY AS THE COLD POOL FROM THE ASSOCIATED UPPER LOW
MOVES OVER THE AREA. COVERAGE WILL BE GREATEST EAST OF THE PA/OH
BORDER WHERE AMPLE AMOUNT OF SUNSHINE THIS MORNING WILL GIVE A BOOST
TO TEMPERATURES AND SFC BASED INSTABILITY.
THE SEVERE THREAT IS LOW AS CAPE SHOULD REMAIN UNDER 1000 J/KG BUT
THE CURRENT SYNOPTIC SITUATION IS FAVORABLE FOR SMALL HAIL WITH A LOW
WBZ HEIGHT AROUND 5KFT AND POTENTIAL FOR UPDRAFTS JUST STRONG ENOUGH
TO SUPPORT SMALL HAIL AND/OR GRAUPEL. WOULD NOT BE SURPRISED AT ALL
TO SEE MANY GRAUPEL/SMALL HAIL REPORTS LATER TODAY WITH
SHOWERS/STORMS...ALONG WITH STRONGER (SUB-SEVERE) WIND GUSTS WITH
STEEP LOW-LEVEL LAPSE RATES IN PLACE.
SHOWER/STORM ACTIVITY WILL TAPER OFF TOWARDS/AFTER SUNSET AS THE LOW
LEVELS STABILIZE AND THE LOW BECOMES CENTERED OVER THE PBZ CWA,
LEAVING LITTLE IN THE WAY OF DIFFERENTIAL POSITIVE VORTICITY
ADVECTION.
AS THE LOW BEGINS ITS DEPARTURE, THERE IS A SLIGHT CHANCE OF SOME
BRIEF WINTER WEATHER ACROSS THE HIGHEST ELEVATIONS IN THE
ALLEGHENIES. UPPER LIFT WILL DECREASE AS THE LOW GOES OVERHEAD, BUT
A COLD LOW INDUCED LOWERING OF THE DENDRITIC SNOW GROWTH ZONE AND
DECENT LAPSE RATES MAY BE FAVORABLE FOR SOME BRIEF SNOW PRODUCTION.
SHORT TERM /SUNDAY THROUGH MONDAY/
ONE LAST TROUGH AXIS ROTATING AROUND THE DEPARTING UPPER LOW WITH
SUBSEQUENT NORTHWEST FLOW WILL LEND ITS WAY TO A COOL DAY SUNDAY
UNDER A BROKEN STRATOCUMULUS DECK. A FEW BANDS IN THE MORNING MAY BE
DEEP ENOUGH TO PRODUCE VERY LIGHT RAIN, BUT OTHERWISE EXPECT A
RATHER PLEASANT DAY WITH INCREASING SUNSHINE AND HIGHS APPROACHING 60
BY LATE AFTERNOON.
MONDAY WILL START OFF IN THE LOW TO MID 40S FOR MOST OF THE REGION.
CLOUD COVER WILL GRADUALLY DECREASE AS RIDGING BUILDS IN. PLENTY OF
SUNSHINE AND WARMING MID-LEVEL TEMPS WILL GIVE WAY TO HIGHS IN THE
UPPER 60S TO MID 70S REGIONWIDE.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
UPPER LEVEL FLOW WILL BECOME QUASI-ZONAL MID-WEEK WITH A FEW PASSING
SHORTWAVES THAT WILL MAINTAIN SOME CHANCE (ALBEIT LOW) OF
PRECIPITATION FOR EACH DAY. GIVEN POOR LONG TERM MODEL PERFORMANCE AS
OF LATE, WILL ELECT TO AVOID ANY FORECAST DETAILS THIS FAR OUT.
THAT SAID, CONFIDENCE IS ON THE HIGH SIDE THAT TEMPERATURES WILL BE
NEAR OR ABOVE THE CLIMATOLOGICAL MEAN THROUGH LATE WEEK.
BOTH THE ECM AND GFS SUGGEST THE NEXT STRONG LONGWAVE TROUGH WILL
APPROACH THE REGION BY FRIDAY MORNING. HOWEVER, SOLUTIONS HAVE
DIFFERED WITH EACH MODEL RUN, SUGGESTING LOW CONFIDENCE IN THE UPPER
WAVE PROGRESSION.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
COVERAGE IN PRECIPITATION WILL INCREASE THIS AFTERNOON (ESPECIALLY
EAST OF THE PA/OH BORDER AS COLDER AIR MOVING IN ALOFT AND INSOLATION
INCREASE INSTABILITY.
THE CURRENT SYNOPTIC SETUP LOOKS FAVORABLE FOR GRAUPEL AND/OR SMALL
HAIL WITH ANY SHOWERS/STORMS THAT DEVELOP...AND GUSTY WINDS WILL BE
LIKELY IN THE VICINITY OF ANY STORMS. SUNSET WILL BRING A
DETERIORATION IN OVERALL FLIGHT CONDITIONS AS LOWER CEILINGS DEVELOP
ONCE AGAIN, WITH AT LEAST MVFR CONDITIONS AREAWIDE BY 06Z.
OUTLOOK
RESTRICTIONS AND SHOWERS ARE LIKELY INTO SUNDAY AS UPPER LEVEL LOW
PRESSURE TRAVERSES THE REGION.
PBZ WATCHES/WARNINGS/ADVISORIES
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
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