441  
FXUS61 KPBZ 241048  
AFDPBZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PITTSBURGH PA  
548 AM EST SAT FEB 24 2018  
   
SYNOPSIS
 
 
PERIODIC RAIN CHANCES WILL CONTINUE THROUGH SUNDAY. CONDITIONS  
SHOULD BE DRY FOR THE BEGINNING OF THE WORK WEEK, WITH RAIN  
RETURNING TO THE FORECAST BY WEDNESDAY NIGHT.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
STEADY LIGHT TO MODERATE RAIN SHOWERS ARE BEGINNING TO MOVE INTO  
OUR SOUTHERN ZONES, AHEAD OF A SHORTWAVE TROUGH POISED TO MOVE  
THROUGH LATER TODAY. THIS WAVE WILL RIDE ALONG A SURFACE FRONTAL  
BOUNDARY THAT HAS TRIED TO CLEAR THE FORECAST AREA, BUT HAS  
THUSFAR BEEN DENIED. A SURGE OF WARM AND MOIST AIR THROUGH WEST  
VIRGINIA WILL STALL THE BOUNDARY NEAR THE MASON-DIXON LINE  
THROUGH MUCH OF THE DAY. AS THE WAVE MOVES WEST TO EAST OVER THE  
AREA, RAIN SHOWERS WILL SPREAD AREAWIDE, BUT THE PRIMARY FOCUS  
OF THE RAIN WILL BE SOUTH OF PITTSBURGH. HI-RES MODELS IN  
CONSIDERABLE AGREEMENT WITH THE EVOLUTION OF THIS WAVE THROUGH  
THE AFTERNOON, AND WERE RELIED ON HEAVILY.  
 
GIVEN THE SURGE OF PWATS ABOVE 1", A STRENGTHENING LOW-LEVEL  
JET, AND DEEP WARM CLOUD LAYER, RAIN PRODUCTION SHOULD BE  
EFFICIENT. THESE LOCATIONS WILL NEED TO BE MONITORED FOR ANY  
LOCALIZED FLOODING PROBLEMS. THE WAVE WILL PASS EAST THIS  
EVENING, AND A ANOTHER BRIEF LULL IN RAIN IS EXPECTED. POPS WERE  
CONSTRUCTED TO BE A BIT MORE DETERMINISTIC WITH THIS TREND IN  
MIND. SHOWERS AND THE COLD FRONT JUST SOUTH OF THE AREA WILL  
KEEP OUR HIGHS A LITTLE LOWER THAN THE LAST FEW DAYS, BUT STILL  
ABOVE-AVERAGES.  
 
THE AFOREMENTIONED FRONT WILL LIFT NORTH TONIGHT AS A WARM  
FRONT. STRONG MOIST AND WARM ADVECTION WILL FUEL MODERATE TO  
HEAVY SHOWERS LIFTING NORTH THROUGH OUR FORECAST AREA. THE AXIS  
OF THIS RAIN WILL SET UP NORTH OF THE AXIS OF TODAY'S RAIN,  
GIVING MORE SPATIAL DISPERSION OF QPF OVER THE ENTIRE AREA. THE  
RESULT IS A SLIGHTLY LOWER CONCERN OF AREAL FLOODING OVER  
ANY ONE SPECIFIC AREA. STILL, SOILS ARE PLENTY SATURATED AND AN  
ADDITIONAL 1-1.5" OF RAIN THROUGH TONIGHT MAY BE ENOUGH TO  
CAUSE SOME FLOODING PROBLEMS. THE AREAL FLOOD WATCH WILL  
CONTINUE.  
 

 
   
SHORT TERM /SUNDAY THROUGH TUESDAY/
 
 
THE PERIOD OF WET WEATHER COMES TO AN END SUNDAY AS THE COLD  
FRONT FINALLY SWEEPS THROUGH THE FORECAST AREA. THIS WILL USHER  
IN MUCH DRIER AIR THAT WILL LEAD TO CLEARING AND INCREASED  
SUNSHINE THROUGH SUNDAY. DRY WEATHER WILL CARRY INTO MONDAY AND  
TUESDAY AS HIGH PRESSURE BUILDS IN UNDER NEARLY ZONAL FLOW  
ALOFT. THE INCREASED SUN MONDAY AND TUESDAY WILL KEEP  
TEMPERATURES ABOVE-AVERAGE.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
 
 
DRY WEATHER ESTABLISHED EARLY NEXT WEEK WILL GIVE WAY TO ANOTHER  
DISTURBANCE NEAR THE END OF NEXT WEEK. MODELS CONTINUE TO SHOW  
GREAT DIFFICULTY IN HANDLING THE EVOLUTION OF THIS NEXT  
PRECIPITATION MAKER. WITH MUCH UNCERTAINTY, SUPERBLEND WAS  
UTILIZED HEAVILY IN THE CONSTRUCTION OF THE EXTENDED AND, IN  
GENERAL, POPS WERE KEPT IN THE HIGH CHANCE OR LOW LIKELY RANGE.  
THE TREND IN THE FORECAST THAT HAS BEEN A LITTLE MORE CONSISTENT  
IS A DOWNWARD MOVEMENT IN TEMPERATURES OVER NEXT WEEKEND.  
 

 
   
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
 
 
BAND OF MODERATE TO HEAVY RAIN WILL LIFT ACROSS THIS MORNING  
ACROSS MAINLY NORTHERN WV AND SOUTHWEST PA, WITH IFR CEILINGS  
AND VISIBILITIES IN THE HEAVIER RAIN. OTHERWISE, IFR/LOW MVFR  
CEILINGS WILL BE THE RULE IN MORE SCATTERED ACTIVITY. WAVES OF  
RAIN THROUGH TONIGHT WILL KEEP OCCASIONAL, HARD-TO-TIME IFR  
RESTRICTIONS IN THE FORECAST, WITH MVFR CEILINGS EXPECTED  
OUTSIDE THE HEAVIER RAIN. LOW LEVEL WIND SHEAR WILL BECOME A  
CONCERN OVERNIGHT AS A LOW LEVEL JET CONTINUES TO TRANSPORT  
MOISTURE INTO THE AREA, MAXIMIZING THE HEAVY RAIN THREAT.  
 
OUTLOOK...  
RESTRICTIONS ARE EXPECTED TO CONTINUE INTO SUNDAY AS A COLD  
FRONT PASSES.  
 

 
   
HYDROLOGY
 
 
NUMEROUS FORECAST POINTS ARE ALREADY AT ACTION STAGES ACROSS THE  
REGION.  
 
2 SUCCESSIVE DISTURBANCES OVER THE NEXT 36 HOURS WILL DROP  
RAINFALL AMOUNTS RANGING FROM 1.00 TO 2.00 INCHES ACROSS THE  
REGION.  
 
RIVER FLOOD WATCHES MAY NEED TO BE CONVERTED TO WARNINGS.  
 

 
   
PBZ WATCHES/WARNINGS/ADVISORIES
 
 
MD...FLOOD WATCH THROUGH SUNDAY EVENING FOR MDZ001.  
OH...FLOOD WATCH THROUGH SUNDAY EVENING FOR OHZ039>041-048>050-  
057>059-068-069.  
PA...FLOOD WATCH THROUGH SUNDAY EVENING FOR PAZ007>009-013>016-  
020>023-029-031-073>076.  
WV...FLOOD WATCH THROUGH SUNDAY EVENING FOR WVZ001>004-012-021-  
509>514.  
 

 
 

 
 
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