279  
FXUS61 KPBZ 171948  
AFDPBZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PITTSBURGH PA  
248 PM EST SUN FEB 17 2019  
   
SYNOPSIS
 
 
A WINTRY MIX OF PRECIPITATION CAN BE EXPECTED THROUGH TONIGHT  
WITH PASSING LOW PRESSURE. SNOW SHOWERS WILL LINGER ON MONDAY,  
AND THEN A DRY AND SEASONABLY COLD TUESDAY IS EXPECTED UNDER  
HIGH PRESSURE.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
A TYPICALLY CHALLENGING PRECIPITATION TYPE FORECAST DOMINATES  
FOR TONIGHT. PRECIPITATION ONSET WAS A BIT SLOWER THAN  
PREVIOUSLY THOUGHT, ALLOWING TEMPERATURES TO RISE ABOVE FREEZING  
IN MANY LOCATIONS BEFORE IT ARRIVED. HOWEVER, COVERAGE IS  
INCREASING RAPIDLY AHEAD OF THE ADVANCING SURFACE LOW, AIDED BY  
ISENTROPIC LIFT IN THE MID-LEVELS. DESPITE THE WARM START, T/TD  
SPREADS OF 10-15 DEGREES F POINT TO THE POSSIBILITY OF ENOUGH  
EVAPORATIONAL COOLING TO ALLOW FOR A PERIOD OF ICING AT ONSET.  
ALREADY SEE THIS OCCURRING IN THE LATEST PHD OBSERVATION. RECENT MPING  
REPORTS OF SLEET IN SOUTHEAST OHIO ALSO POINT TO THIS COOLING  
PROCESS.  
 
KEPT THE GOING HEADLINES UNCHANGED FOR NOW, RECOGNIZING THAT  
NEAR-TERM ADJUSTMENTS MAY NEED TO BE MADE THROUGH THE EVENING.  
GIVEN THE EVAPORATIVE COOLING POSSIBILITIES, DID EXPAND THE  
ADVISORY INTO LAWRENCE PA/BUTLER/ARMSTRONG FOR THE POSSIBILITY  
OF ICING, AND WOULD NOT BE SURPRISED TO SEE OTHERS ADDED AS  
WELL. WARM AIR WILL CONTINUE TO OOZE NORTHWARD WITH TIME,  
ESPECIALLY INTO SOUTHWEST PA, CHANGING PRECIPITATION TO RAIN.  
SNOW OR A MIX WILL LINGER TO THE NORTH OF PITTSBURGH THROUGH  
MUCH OF THE NIGHT, UNTIL THE WARM LAYER ALOFT IS ERODED BY COLD  
ADVECTION BEHIND THE DEPARTING LOW. A MODEST SNOW ACCUMULATION  
OF AN INCH OR TWO IS STILL PICTURED NORTH OF I-80. MID-LEVEL DRY  
AIR IS STILL SLATED TO ARRIVE TONIGHT, WHICH WILL REMOVE MUCH  
OF THE ICE NUCLEI AND RAISE THE POTENTIAL OF DRIZZLE/FREEZING  
DRIZZLE. HAVE KEPT THIS IN THE GRIDS AFTER MIDNIGHT. AN  
EXTENSION/EXPANSION OF THE ADVISORY FOR THIS THREAT IS ALSO A  
POSSIBILITY. COVERAGE OF MORE SUBSTANTIAL SHOWERS WILL SLOWLY  
DECREASE TOWARD MORNING.  
 

 
   
SHORT TERM /MONDAY THROUGH TUESDAY/
 
 
SCATTERED NORTHWEST FLOW SNOW SHOWERS WILL CONTINUE INTO MONDAY  
AFTERNOON FOR MUCH OF THE REGION, PERHAPS INTO THE EVENING  
HOURS ALONG THE SOUTHEAST RIDGES. MODEST SNOW TOTALS OF AN INCH  
OR LESS ARE FORESEEN FOR NOW GIVEN FAIRLY MEAGER MOISTURE IN THE  
DENDRITIC GROWTH LAYER AND LOW INVERSION HEIGHTS. HOWEVER, SOME  
DECENT LAPSE RATES ARE INDICATED BELOW THESE INVERSIONS, SO THE  
POSSIBILITY OF A FEW HEAVIER SNOW SHOWERS WILL NEED TO BE  
CONSIDERED.  
 
ADVANCING HIGH PRESSURE WILL CUT OFF THE SNOW SHOWERS, AND  
CLOUDS WILL DECREASE THROUGH MONDAY NIGHT. SOME SUNSHINE IS  
ANTICIPATED TUESDAY, BEFORE MID AND HIGH CLOUDS BEGIN TO  
INCREASE LATER IN THE DAY. TEMPERATURES THROUGH THIS PERIOD WILL  
RUN A BIT BELOW SEASONAL NORMS.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
 
 
ANOTHER MESSY SYSTEM WILL MOVE INTO THE REGION TUESDAY NIGHT  
INTO WEDNESDAY AND WEDNESDAY NIGHT. MANY PLACES WILL LIKELY SEE  
BOTH SOME MINOR SNOW AND FREEZING RAIN ACCUMULATION. THIS STORM  
IS ALREADY MENTIONED IN THE HWO. MODEL SOLUTIONS WAVER ON WHAT  
WILL HAPPEN WITH THE NEXT SYSTEM. RIGHT NOW THE ECMWF AND GFS  
BOTH SHOW A SYSTEM THAT SHOULD REMAIN TO THE SOUTH OF THE REGION  
THURSDAY AND FRIDAY, BUT THE GEFS KEEPS THIS STORM A BIT  
FARTHER TO THE NORTH. HAVE HEDGED WITH CHANCE POPS ACROSS THE  
SOUTHEAST AND SLIGHT CHANCE POPS FOR MOST OTHER LOCATIONS. THE  
NEXT STORM SYSTEM BEGINS TO WRAP ITSELF TOGETHER BY SUNDAY  
MORNING, MOVING ACROSS MICHIGAN AND CONTINUING ON TO THE  
NORTHEAST. CONSIDERING THE STORM TRACK, PRECIPITATION SHOULD  
GENERALLY BE RAIN BY DAY AND SNOW BY NIGHT. TEMPERATURES WILL BE  
SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD.  
 

 
   
AVIATION /20Z SUNDAY THROUGH FRIDAY/
 
 
ADVANCING LOW PRES WL BRING A WINTRY MIX OF PCPN TO THE AREA  
THIS AFTN AND TONIGHT. EXPECT REDETERIORATION OF CONDITIONS TO  
MVFR THROUGH THE DAY AT ALL TERMINALS, MOSTLY WITH LOWER  
CEILINGS, WITH EVENTUAL IFR TONIGHT.  
   
OUTLOOK
 
 
IMPROVEMENT WILL BE BRIEF AS LOW PRES IS EXPECTED TO REINTRODUCE  
PCPN AND WIDESPREAD RESTRICTIONS AGAIN ON WEDNESDAY.  
 

 
   
PBZ WATCHES/WARNINGS/ADVISORIES
 
 
MD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ001.  
OH...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR  
OHZ039>041-048-049-057-058.  
PA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR  
PAZ007>009-013>016-022-023-074-076.  
WV...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ514.  
 

 
 

 
 
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