920  
FXUS61 KBUF 201911  
AFDBUF  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BUFFALO NY  
311 PM EDT MON AUG 20 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE OVER NEW ENGLAND WILL SHIFT EAST TONIGHT. A DEEP  
LOW PRESSURE SYSTEM WILL SHIFT WEST THEN NORTH OF NEW YORK  
THROUGH TUESDAY. THIS STORM WILL BRING WIDESPREAD SHOWERS AND  
EMBEDDED THUNDERSTORMS WITH HEAVY RAINFALL POSSIBLE. A FEW  
SHOWERS MAY LINGER INTO WEDNESDAY BEFORE ANOTHER AREA OF HIGH  
PRESSURE BRINGS A RETURN OF FAIR WEATHER THURSDAY AND FRIDAY.  
 

 
   
NEAR TERM /THROUGH TUESDAY/
 
 
VISIBLE SATELLITE SHOWING RESIDUAL LOW LEVEL MOISTURE HAS  
DEVELOPED INTO A WIDESPREAD CUMULUS FIELD ACROSS WESTERN NEW  
YORK THIS AFTERNOON, WITH MAINLY SUNNY SKIES ACROSS CENTRAL NEW  
YORK. THE DIURNAL CLOUDS WILL ERODE THIS EVENING, WITH CIRRUS  
LEVEL CLOUDINESS OVERSPREADING THE AREA, WHICH WILL LIKELY LIMIT  
STRATUS AND FOG THREAT OVERNIGHT. OVERNIGHT LOWS WILL RANGE  
THROUGH THE 60S WITH THE WARMEST READINGS NEAR THE LAKE SHORES.  
 
WATER VAPOR IMAGERY THIS AFTERNOON SHOWING A WELL DEFINED CLOSED  
CIRCULATION OVER NORTHERN MISSOURI. THIS SYSTEM WILL DRIFT  
NORTHEAST REACHING THE SOUTHERN GREAT LAKES BY TUESDAY MORNING.  
STRONG NORTHWARD MOISTURE TRANSPORT WITHIN THE WARM CONVEYOR  
BELT WILL BRING INCREASING RAINFALL CHANCES INTO WESTERN NEW  
YORK WELL AFTER MIDNIGHT TONIGHT. EXPECT THE BULK OF  
PRECIPITATION TO BEGIN CLOSER TO DAYBREAK AND TUESDAY MORNING  
ACROSS WESTERN NEW YORK WITHIN THE GREATEST HEIGHT FALLS AND  
MOISTURE ARRIVAL IN CONJUNCTION WITH THE LOW LEVEL JET RAMPING  
UP. PRECIPITABLE WATER VALUES ASSOCIATED WITH THIS SYSTEM WILL  
BE QUITE HIGH PUSHING UP TO AROUND THE 2.00 INCH MARK.  
 
INITIALLY UNFAVORABLE DIURNAL TIMING WILL LIMIT GREATER CONVECTIVE  
POTENTIAL, BUT STILL ANTICIPATE A WEAKLY UNSTABLE PROFILE SO THERE  
COULD BE SOME EMBEDDED THUNDER THROUGH THE MORNING AND EARLY  
AFTERNOON HOURS. POTENTIAL FOR HEAVY RAINFALL MAY SUPPORT A  
LOCALIZED FLOODING THREAT.  
 
A STRONG TO SEVERE THREAT WILL START TO EVOLVE DURING THE MID TO  
LATE AFTERNOON HOURS AS AREAS OF HEATING/DESTABILIZATION DEVELOP.  
INCREASING SHEAR PROFILES AND ARRIVAL OF BETTER DYNAMICS MAY LEAD TO  
BETTER ORGANIZED THUNDERSTORMS WITH LOCALLY DAMAGING WINDS BEING THE  
PRIMARY THREAT.  
 

 
   
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/
 
 
LOW PRESSURE WILL CONTINUE TO DEEPEN AS IT TRACKS ACROSS EASTERN  
ONTARIO PROVINCE TUESDAY EVENING. A WARM FRONT WILL BE LOCATED  
ACROSS THE NORTH COUNTRY WHILE STRONG MOISTURE ADVECTION CONTINUES  
ACROSS WESTERN AND NORTH CENTRAL NY. SHOWERS AND THUNDERSTORMS WILL  
BE IN VICINITY OF THE WARM FRONT AS 40-50KT FLOW AT 850MB WILL  
PRODUCE ENHANCED LIFT NEAR THE BOUNDARY. FURTHER WEST,  
DESTABILIZATION WILL HAVE OCCURRED ACROSS WESTERN NY TUESDAY  
AFTERNOON AND 500-1000 J/KG INSTABILITY IS EXPECTED INTO EARLY  
TUESDAY EVENING. THIS SKINNY CAPE AND A 30-40KTS OF 0-6KM SHEAR WILL  
PRODUCE SOME THUNDERSTORMS AHEAD OF AN APPROACHING COLD FRONT AS IT  
TRACKS ACROSS THE FORECAST AREA TUESDAY NIGHT. ANOTHER LINE OF  
SHOWERS AND THUNDERSTORMS MAY ALSO FORM RIGHT ALONG THE FRONT BEHIND  
THE MAIN AREA OF SHOWERS AND THUNDERSTORMS. THIS ACTIVITY WILL  
LIKELY BE SHORT LIVED. THE INTENSITY OF THUNDERSTORMS WILL DIMINISH  
AS THEY TRACK INTO THE NORTH COUNTRY. TEMPERATURES WILL STAY ON  
THE WARM SIDE TUESDAY NIGHT, WITH LOWS IN THE MID 60S.  
 
HEAVY RAIN IS THE BIGGEST CONCERN FROM THUNDERSTORMS TUESDAY EVENING  
AS PWATS OF 2-3 SD ABOVE NORMAL TRACK ACROSS THE FORECAST AREA.  
TRAINING AND BACKBUILDING STORMS ARE A CONCERN AS THE LLJ AND CLOUD  
LAYER ARE ALMOST PARALLEL MAKING THE CORFIDI VECTORS VERY SMALL.  
HEAVY RAIN MAY LEAD TO HYDROLOGIC ISSUES CAUSING PONDING AND RISES  
ON CREEKS AND STREAMS.  
 
THE COLD FRONT WILL EXIT EAST OF THE NORTH COUNTRY BY WEDNESDAY  
MORNING AND COOLER AIR WILL MOVE INTO THE FORECAST AREA.  
LOW LEVEL LAPSE RATES WILL STREGTHEN WEDNESDAY AS AN UPPER  
LEVEL TROUGH PERSISTS ACROSS THE LOWER GREAT LAKES. LOW LEVEL  
MOISTURE AND COOL AIR MOVING ACROSS THE WARM (75 DEG) LAKES WILL  
RESULT IN A DENSE CUMULUS FIELD AND LAKE EFFECT RAIN SHOWERS  
DOWNWIND OF THE LAKES BY WEDNESDAY AFTERNOON. AIR TEMPERATURES  
WILL STRUGGLE TO REACH 70 DEG WEDNESDAY.  
 
A SHARP MID-LEVEL TROUGH AXIS WILL CROSS THE FORECAST AREA WEDNESDAY  
NIGHT AND ALTHOUGH COOL AIR ALOFT WILL STILL BE PRESENT, MOISTURE  
WILL DIMINISH QUICKLY OVERNIGHT AND LAKE EFFECT SHOWERS WILL  
DIMINISH. HIGH PRESSURE WILL MOVE ACROSS THE OHIO VALLEY  
THURSDAY AND INTO WESTERN NY THURSDAY NIGHT. DRY WEATHER IS  
EXPECTED DURING THIS TIME.  
 

 
   
LONG TERM /THURSDAY THROUGH MONDAY/
 
 
THIS PERIOD WILL BECOME QUIETER AS SURFACE HIGH PRESSURE OVER THE  
MID MISSISSIPPI VALLEY THURSDAY ADVANCES TO OUR REGION FRIDAY, AND  
THEN DRIFTS EAST OF THE EASTERN GREAT LAKES FRIDAY. THIS FEATURE  
WILL PRESENT FAIR WEATHER AND LOWER HUMIDITY, WITH DAY TO DAY  
WARMING...WITH HIGHS THURSDAY IN THE MID 70S RISING TO THE LOW TO  
MID 80S BY SATURDAY. THIS PERIOD WILL BE MAINLY DRY, WITH MORNING  
FOG FORMING IN THE RIVER VALLEYS OF THE SO. TIER.  
 
LATER SATURDAY AND INTO SUNDAY A TROUGH OF LOW PRESSURE ALOFT WILL  
CUT NORTHEASTWARD THROUGH THE GREAT LAKES. WHILE THE MAIN IMPACTS  
WITH THIS WAVE WILL REMAIN TO OUR WEST THERE WILL BE LOW CHANCES FOR  
A FEW SHOWERS OR THUNDERSTORMS ACROSS OUR REGION LATER SATURDAY AND  
INTO SUNDAY. AS TEMPERATURES WARM ALOFT AT 850 HPA SUNDAY, TO +16 TO  
+18C, OUR SURFACE TEMPERATURES WILL ALSO WARM WITH MID 80S  
FORECASTED ACROSS THE LAKE PLAINS.  
 

 
   
AVIATION /19Z MONDAY THROUGH SATURDAY/
 
 
EXPECT AN AREA OF MVFR CIGS FROM KBFD-KELZ-KJHW TO LIFT TO IMPROVE  
TO VFR BY 21Z. OTHERWISE VFR CONDITIONS WILL PREVAIL THROUGH THE  
FIRST HALF OF TONIGHT. LATER TONIGHT, CHANCES FOR SHOWERS AND  
THUNDERSTORMS WILL BEGIN TO MOVE OVER FAR WNY CLOSER TO 09-12Z  
TUESDAY. THIS WEATHER IS ASSOCIATED WITH LOW PRESSURE TRACKING TO  
OUR WEST. IFR/MVFR CIGS WILL DEVELOP IN THE WESTERN SOUTHERN TIER  
DURING THIS TIME AS WELL.  
 
OUTLOOK...  
 
TUESDAY...MVFR/IFR. SHOWERS AND THUNDERSTORMS.  
WEDNESDAY...MAINLY VFR. A CHANCE OF SHOWERS.  
THURSDAY AND FRIDAY...VFR.  
SATURDAY...MAINLY VFR.  
 

 
   
MARINE
 
 
HIGH PRESSURE OVER THE NEW ENGLAND STATES WILL MOVE EAST  
TONIGHT. ON TUESDAY, AN UNSEASONABLY DEEP SURFACE LOW WILL  
TRACK NORTH ACROSS THE CENTRAL GREAT LAKES WITH SOUTHERLY WINDS  
PICKING UP ON THE EASTERN GREAT LAKES. WIDESPREAD SHOWERS AND  
EMBEDDED THUNDERSTORMS WILL BE ACCOMPANIED BY A CHANCE OF  
ADVISORY LEVEL WINDS AND WAVES BUT THE SOUTHERLY DIRECTION  
SHOULD DIRECT THE HIGHEST WAVES INTO CANADIAN WATERS.  
 
A SHARP COLD FRONT WILL CROSS THE LOWER GREAT LAKES TUESDAY NIGHT  
WHICH WILL BRING WESTERLY WINDS AND HIGHER WAVES. SMALL CRAFT  
ADVISORIES ARE LIKELY LATE TUESDAY NIGHT THOUGH WEDNESDAY FOR LAKE  
ONTARIO.  
 
HIGH PRESSURE WILL RETURN FOR THE END OF THE WEEK WITH A RETURN OF  
FAIR CONDITONS.  
 

 
   
BUF WATCHES/WARNINGS/ADVISORIES
 
 
NY...NONE.  
MARINE...NONE.  
 

 
 

 
 
SYNOPSIS...TMA  
NEAR TERM...TMA  
SHORT TERM...HSK  
LONG TERM...THOMAS  
AVIATION...TMA  
MARINE...AR/SMITH/TMA  
 
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