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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