Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 242344
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
744 PM EDT MON AUG 24 2015

.SYNOPSIS...
COOLER AIR WILL BUILD INTO THE REGION BEHIND A COLD FRONT WHICH
WILL BRING A FALL-LIKE PATTERN WHICH WILL LAST THROUGH THE END OF
THE WEEK. THIS WILL RESULT IN BELOW NORMAL TEMPERATURES...WITH
QUITE A BIT OF CLOUD COVER AND PERIODIC RAIN SHOWERS.

&&

.NEAR TERM /THROUGH TUESDAY/...
A SURFACE COLD FRONT IS EXITING INTO WESTERN NEW ENGLAND THIS
EVENING. THE LAST FEW VISIBLE SATELLITE SHOTS OF THE EVENING SHOW
VARYING AMOUNTS OF CLOUD COVER ACROSS THE AREA...WITH EXTENSIVE
STRATOCU MOVING INTO MUCH OF WESTERN NY AND PORTIONS OF CENTRAL NY.
EXPECT THESE CLOUDS TO HANG ON THROUGH AT LEAST LATE EVENING BEFORE
MOST OF THE CLOUD COVER FOCUSES NORTHEAST OF LAKES ERIE AND ONTARIO
OVERNIGHT AS LAKE EFFECT PROCESSES BEGIN TO TAKE OVER.

TEMPERATURES BEHIND THE COLD FRONT ARE NOT THAT COLD YET...HOWEVER
850MB TEMPERATURES WILL DROP DOWN TO AROUND +7C BY DAYBREAK TUESDAY
MORNING. THE CAUSE WILL BE THE GRADUAL APPROACH OF AN UPPER LEVEL
TROUGH WHICH WILL RESULT IN INCREASING LAKE INDUCED INSTABILITY ON
LAKE ERIE AND EVENTUALLY LAKE ONTARIO. IN ADDITION...A CONSENSUS OF
HIGH RESOLUTION GUIDANCE FORECASTS A WELL DEFINED SOUTHWESTERLY
CONVERGENCE BOUNDARY DEVELOPING ON LAKE ERIE. THIS SHOULD INITIALLY
FOCUS SOME RAIN SHOWERS ON BUFFALO AROUND OR SHORTLY AFTER
MIDNIGHT...WITH THESE THEN EXPECTED TO DROP SOUTHWARD AS THE
APPROACHING UPPER LEVEL SYSTEM PROMPTS A MORE WSW FLOW. FORECAST
WILL CARRY A NARROW BAND OF LIKELY POPS WHICH WILL BE ALONG THIS
CONVERGENCE BOUNDARY. THE SHOWERS ARE LIKELY TO REMAIN DISORGANIZED
AND CELLULAR GIVEN THE TIME OF YEAR AND BACKGROUND BOUNDARY LAYER
MIXING WITH THE APPROACH OF THE MID LEVEL TROUGH.

THE LAKE EFFECT RAIN SHOWERS OFF LAKE ONTARIO SHOULD REMAIN MORE
DISORGANIZED GIVEN THE WEAKER INSTABILITY AND LESS SYNOPTIC SCALE
MOISTURE. EXPECT JUST A FEW SCATTERED SHOWERS LATE TONIGHT AND EARLY
TUESDAY NORTHEAST OF THE LAKE NEAR THE THOUSAND ISLANDS REGION.

LOWS SHOULD MAINLY BE IN THE 50S...WITH SOME UPPER 40S POSSIBLE
ACROSS THE INTERIOR VALLEYS ACROSS THE SOUTHERN TIER WHERE THERE
SHOULD BE AT LEAST A PARTIAL CLEARING TONIGHT.

ON TUESDAY THE UPPER LEVEL TROUGH AXIS WILL GRADUALLY PUSH TOWARD
THE REGION WHICH WILL SHIFT 850MB WINDS TO THE WEST AND DISRUPT THE
CONVERGENT FLOW ON LAKE ERIE. AS A RESULT...SHOWERS WILL BREAK UP
AND SPREAD INLAND WITH HIT OR MISS SHOWERS DURING THE DAY TUESDAY
BOTH FROM LAKE EFFECT AND FROM DIURNAL INSTABILITY ENHANCED BY THE
CYCLONIC FLOW ALOFT. THERE WILL ALSO BE MOSTLY CLOUDY SKIES WITH
HIGHS IN THE UPPER 60S TO LOWER 70S...COOLEST ACROSS THE HIGHER
TERRAIN EAST OF LAKE ERIE.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY NIGHT/...
A DEEP CLOSED UPPER LOW WILL SLOWLY MEANDER ITS WAY EAST ACROSS
NORTHERN ONTARIO AND NORTHERN QUEBEC WHICH WILL RESULT IN AN AUTUMN-
LIKE AIRMASS ACROSS THE FORECAST AREA THROUGH THE MID WEEK PERIOD.
ASSOCIATED COLD POOL ALOFT SHOULD ALLOW FOR AT LEAST SCATTERED
COVERAGE OF INSTABILITY SHOWERS ACROSS THE AREA DURING THE PEAK
HEATING CYCLE BOTH TUESDAY AND WEDNESDAY. THE COLDER AIR FILTERING
IN WILL DROP 850 MB TEMPERATURES DOWN TO AROUND +6C...YIELDING LAKE
DELTA-T VALUES AROUND 15C...MORE THAN SUFFICIENT FOR LAKE EFFECT
SHOWERS DOWNWIND OF THE LAKES. ALONG WITH THE LAKE EFFECT RAIN
SHOWERS... THE COOL TEMPS ALOFT AND THE LAKE INDUCED INSTABILITY
WILL BE CAPABLE OF PRODUCING WATERSPOUTS WITH THE STRONGER
CONVECTIVE CLOUDS WITH THE 15C SFC-850MB DELTA-T AND APPROX 20KFT
CONVECTIVE CLOUD DEPTH.

BY THURSDAY... THE UPPER LOW STARTS TO SHEAR OUT AND TAKE OFF TO THE
EAST AS AN OPEN TROUGH. THE FLOW ACROSS THE FORECAST AREA TURNS MORE
NORTHWESTERLY AS THE TROUGH EXITS TO OUR EAST.  WITH THE COOLER AIR
STICKING AROUND THROUGH THE DAY... LOCATIONS SOUTHEAST OF LAKE
ONTARIO FROM ROCHESTER ACROSS TO SOUTHERN OSWEGO COUNTY COULD PICK
UP SOME LAKE EFFECT SHOWERS THROUGH THE DAY THURSDAY.

HIGH PRESSURE WILL NOSE INTO THE REGION THURSDAY NIGHT THROUGH THE
END OF THE WEEK WITH A SHIFT IN THE PLACEMENT AND WEAKENING OF ANY
REMAINING LAKE EFFECT SHOWERS.

TEMPERATURES OVERALL THROUGH THIS PERIOD WILL RUN ABOUT 10 DEGREES
BELOW NORMAL...WITH DAYTIME HIGHS IN THE 60S TO AROUND 70 AND
NIGHTTIME LOWS MAINLY IN THE UPPER 40S TO LOWER 50S. THERE WILL BE A
RETURN TO NEAR NORMAL TEMPS ON FRIDAY WITH HIGHS IN THE MID 70S AND
LOWS IN THE LOWER TO MIDDLE 50S.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
SURFACE HIGH PRESSURE FROM THE LOWER GREAT LAKES TO THE MID ATLANTIC
STATES WILL BLOCK THE EASTWARD PROGRESSION OF A PACIFIC WAVE
CROSSING THE MIDWESTERN STATES. THIS SHOULD BRING MOSTLY DRY AND
WARMER WEATHER TO THE REGION FOR THE WEEKEND AND EARLY NEXT WEEK.
THERE WILL BE A LOW CHANCE OF AFTERNOON SHOWERS ACROSS THE SOUTHERN
TIER AND TUG HILL PLATEAU SUNDAY AND MONDAY BUT OTHERWISE DRY AND
BACK TO SLIGHTLY ABOVE SEASONAL AVERAGE TEMPS.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
LOW PRESSURE WILL REMAIN IN PLACE JUST NORTH OF THE GREAT LAKES
THROUGH TUESDAY WITH DEEPER MOISTURE SLOWLY CIRCULATING BACK INTO
THE AREA. THIS WILL SET THE STAGE FOR LAKE EFFECT RAIN SHOWERS EAST
AND NORTHEAST OF LAKE ERIE LATER TONIGHT THROUGH TUESDAY MORNING.
THESE SHOWERS WILL INITIALLY DEVELOP NEAR KBUF BY AROUND 06Z TUE...
THEN DRIFT SLOWLY SOUTH AND EAST THROUGH TUESDAY MORNING. LAKE
EFFECT SHOWERS WILL BE LESS ORGANIZED NORTHEAST OF LAKE
ONTARIO...WITH JUST A FEW SCATTERED SHOWERS ACROSS THE THOUSAND
ISLANDS REGION MAINLY NORTH OF KART LATE TONIGHT AND TUESDAY
MORNING. CONDITIONS WILL REMAIN MAINLY VFR OVERNIGHT INTO TUESDAY
MORNING...WITH AREAS OF MVFR AND BRIEF IFR DEVELOPING IN THE LAKE
ERIE LAKE EFFECT RAIN SHOWERS INITIALLY NEAR KBUF...THEN MOVING SOUTH
AND EAST INTO THE SOUTHERN TIER BY TUESDAY MORNING.

BY TUESDAY AFTERNOON THE LAKE EFFECT RAIN SHOWERS WILL PUSH INLAND
AND TRANSITION INTO DIURNAL CONVECTION...ESPECIALLY ACROSS THE
HIGHER TERRAIN OF THE SOUTHERN TIER AND FINGER LAKES. VFR CONDITIONS
WILL PREVAIL...ALTHOUGH ANY HEAVIER SHOWERS MAY PRODUCE BRIEF MVFR
CONDITIONS.

OUTLOOK...

WEDNESDAY THROUGH THURSDAY...MAINLY VFR WITH SOME LAKE EFFECT
SHOWERS EAST OF LAKES ERIE AND ONTARIO PRODUCING LOCAL MVFR. FRIDAY
AND SATURDAY...VFR.

&&

.MARINE...
SOUTHWESTERLY WINDS HAVE INCREASED TO 15 TO 20 KTS BEHIND THE COLD
FRONT. THIS WILL CAUSE WAVES TO BUILD TO 3 TO 5 FEET ON EASTERN
PORTIONS OF LAKE ERIE AND LAKE ONTARIO WITH SLIGHTLY LESSER WAVES
ELSEWHERE. WINDS WILL MAINTAIN THE LONGEST ON LAKE ERIE WITH A
CONVERGENCE BOUNDARY LIKELY TO ENHANCE THE SW FLOW SOUTH OF DUNKIRK
TONIGHT. FOLLOWING A BRIEF DROP OFF ON TUESDAY MORNING WINDS WILL
PICK UP AGAIN LATE TUESDAY SO BASED ON THIS...HAVE EXTENDED THE
SMALL CRAFT ADVISORIES AS OUTLINED BELOW.

COOLER CONDITIONS REMAIN IN PLACE THROUGH MID-WEEK...WITH A
CHANCE FOR SOME LAKE EFFECT SHOWERS AND CONDITIONS MORE FAVORABLE
FOR WATERSPOUT DEVELOPMENT. A CONVERGENCE BOUNDARY FORECAST TO
DEVELOP TONIGHT ON LAKE ERIE WILL POTENTIAL PROVIDE A FOCUS FOR
WATERSPOUTS TO FORM...BUT IN THIS ENVIRONMENT ANY SHOWER COULD
POTENTIALLY PRODUCE A WATERSPOUT ON THE OPEN WATERS.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR LEZ040-041.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR
         LOZ045.
         SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR LOZ044.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL/HITCHCOCK
SHORT TERM...WCH
LONG TERM...WCH
AVIATION...HITCHCOCK
MARINE...APFFEL



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