Special Marine Warning 20, NWS Buffalo, NY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
325 PM EDT WED MAY 29 2002

AS WAS THE CASE YESTERDAY...CONVECTION IS THE MAIN FORECAST PROBLEM
FOR THE NEXT 48 HOURS OR SO.

CURRENTLY...THUNDERSTORMS ARE REALLY STARTING TO POP UP ACROSS OUR
AREA DUE TO DAYTIME HEATING AND THE PRESENCE OF A FEW WEAK TRIGGERS
(WEAK 500 MB SHORTWAVE/WEAK LAKE BREEZE BOUNDARIES). WE EXPECT THE
ACTIVITY TO INCREASE IN AREAL COVERAGE AS INSTABILITY CONTINUES TO
INCREASE AND EXISTING CONVECTION LAYS DOWN SOME OUTFLOW BOUNDARIES
THIS AFTERNOON. A GLANCE AT THE VAD WIND PROFILE SHOWS A STEERING
FLOW OF ONLY 20 KNOTS OR SO...SO EVEN THOUGH THE THUNDERSTORMS WILL
MOVE FASTER THAN YESTERDAY...THEY STILL WILL BE RELATIVELY SLOW
MOVING AND COULD PRODUCE LOCALLY HIGH RAINFALL AMOUNTS DUE TO THE
COPIOUS MOISTURE PRESENT IN THE ATMOSPHERIC COLUMN (PWATS AROUND
1.5 INCHES). WHILE THE SEVERE THREAT WILL BE MINIMAL DUE TO THE WEAK
FLOW...EVENTS AT KROC A FEW HOURS AGO INDICATE THAT WE WILL NEED TO
KEEP AN EYE OUT FOR ISOLATED SEVERE PULSE STORMS (1710Z OBSERVATION
SHOWED A THUNDERSTORM WIND GUST TO 53 KTS).

FOR TONIGHT...WE EXPECT THAT THE CONVECTION WILL WIND DOWN WITH THE
LOSS OF DAYTIME HEATING OVER MUCH OF THE AREA. THE EXCEPTION WILL BE
ACROSS THE NORTH COUNTRY. A WEAK AREA OF LOW PRESSURE WILL TRANSLATE
EAST ALONG A (WEAK) FRONTAL BOUNDARY SITUATED JUST NORTH OF THE
REGION TONIGHT...IN CONJUNCTION WITH A MODERATELY STRONG 500 MB
SHORT WAVE. IN ADDITION, A 30 KT LOW LEVEL (850 MB) JET WILL DEVELOP
TONIGHT OUT AHEAD OF THE LOW PRESSURE WAVE...WITH THE NOSE OF THE
JET IMPINGING RIGHT SMACK DAB ON JEFFERSON...LEWIS...AND OSWEGO
COUNTIES. THESE FACTORS WILL COMBINE WITH MODERATE LOW LEVEL
MOISTURE CONVERGENCE TO PRODUCE A FAIRLY DEEP LAYER OF MODERATE LIFT
ACROSS THE NORTH COUNTRY TONIGHT...AND IN A MOISTURE-LADEN AIRMASS
SUCH AS THIS...THAT WOULD IMPLY PRECIPITATION. WILL THEREFORE GO
WITH A LIKELIHOOD OF SHRA/TSRA IN THIS AREA FOR PRETTY MUCH THE
WHOLE NIGHT TONIGHT...AS THE AREA OF FORCING DOES NOT CLEAR THE
REGION UNTIL RIGHT AROUND 12Z THURSDAY.

ON THURSDAY...THE TROPICAL AIRMASS WILL CONTINUE TO RULE THE
ROOST...HOWEVER MOSTLY CLOUDY CONDITIONS WILL HELP TO KEEP
INSTABILITIES MUCH LOWER THAN TODAY (ONLY ABOUT 300 J/KG OF CAPE VIA
BUFKIT SOUNDINGS). IN ADDITION...A RELATIVE LACK OF TRIGGERS WILL
HELP TO KEEP CONVECTION MORE IN CHECK THAN TODAY. AT THIS POINT WE
FEEL LOW CHANCE POPS WILL PROBABLY COVER THE SITUATION. EVEN THOUGH
CAPES ARE MUCH LOWER TOMORROW...LIS ARE STILL AROUND 0...SO WE WILL
RETAIN THE MENTION OF THUNDER FOR NOW.

ANY CONVECTION WILL DIE OUT FOR AWHILE THURSDAY NIGHT WITH THE LOSS
OF DAYTIME HEATING...BEFORE A PREFRONTAL TROUGH/ASSOCIATED SHORTWAVE
AHEAD OF THE NEXT SYSTEM CROSSES THE AREA AFTER MIDNIGHT. DUE TO THE
TIME OF DAY/MODERATE STRENGTH OF THIS FEATURE...WILL AGAIN COVER
THIS WITH A CHANCE OF SHRA/TSRA. THE REAL ACTION WILL HOLD OFF UNTIL
FRIDAY WHEN A BAND OF SHOWERS AND STORMS AHEAD OF THE MAIN COLD
FRONT CROSSES THE REGION FROM WEST TO EAST DURING THE DAY. AT THIS
TIME THERE ARE SIGNIFICANT DIFFERENCES BETWEEN THE ETA AND
AVN...WITH THE ETA SOLUTION MUCH STRONGER IN TERMS OF LOWER (BETTER
LOW LEVEL MOISTURE CONVERGENCE) AND UPPER LEVEL SUPPORT (LFQ OF A
120+ KT 300 MB JET STREAK RIGHT OVERHEAD)...AND THEREFORE MUCH MORE
FAVORABLE FOR SEVERE WEATHER. DUE TO THE MODEL DIFFERENCES WE WILL
NOT REALLY TRY TO PICK ONE SOLUTION OVER THE OTHER AT THIS TIME...
HOWEVER REGARDLESS WHICH ONE VERIFIES...THERE WILL LIKELY BE AT
LEAST SOME POTENTIAL FOR SEVERE WEATHER ON FRIDAY GIVEN THE TROPICAL
AIRMASS THAT WILL BE IN PLACE AHEAD OF THE FRONT.

COOLER AND DRIER AIR WILL QUICKLY FOLLOW BEHIND THE FRONT FRIDAY
NIGHT...LEADING TO A PRETTY NICE WEEKEND BEFORE OUR NEXT WEATHER
MAKER ARRIVES SUNDAY NIGHT INTO MONDAY.

COMMENTS/QUESTIONS WELCOME.

.BUF...NONE.

JJR