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Area Forecast Discussion
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000
FXUS61 KBUF 192003
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
403 PM EDT TUE AUG 19 2014

.SYNOPSIS...
A SLOW MOVING AREA OF LOW PRESSURE WILL MOVE FROM THE CENTRAL GREAT 
LAKES ON WEDNESDAY TO WESTERN LAKE ONTARIO BY THURSDAY. THIS WILL 
PRODUCE AN UNSETTLED MIDWEEK PERIOD WITH OCCASIONAL SHOWERS AND 
SCATTERED THUNDERSTORMS LATE TONIGHT THROUGH THURSDAY BEFORE THE LOW 
WEAKENS BY FRIDAY. A FEW SHOWERS OR A THUNDERSTORM MAY BE LEFTOVER 
FRIDAY AND SATURDAY...BUT MUCH OF THE TIME WILL BE RAIN FREE.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
VISIBLE SATELLITE IMAGERY LATE THIS AFTERNOON SHOWING AN ENHANCED 
AREA OF CUMULUS FROM THE GENESEE VALLEY INTO THE FINGER LAKES WITHIN 
A PLUME OF DEEPER LOW LEVEL MOISTURE ADVECTING NORTH OUT OF 
PENNSYLVANIA. THIS AREA OF CLOUDS WILL CONTINUE TO DRIFT SLOWLY EAST 
THROUGH THIS EVENING AND SHOULD THEN TEND TO SLOWLY THIN OVERNIGHT 
AS SUBSIDENCE TAKES ITS TOLL ON THE LOW LEVEL MOISTURE FIELD. 
CUMULUS HAVE ALSO DEVELOPED OVER THE NIAGARA FRONTIER WITHIN A 
CONVERGENCE ZONE FROM NORTHEAST FLOW OFF LAKE ONTARIO AND SOUTHWEST 
FLOW OFF LAKE ERIE. THESE SHOULD QUICKLY DISSIPATE THIS EVENING WITH 
THE LOSS OF DAYTIME HEATING.

TONIGHT THE MID LEVEL CLOSED LOW OVER THE UPPER MIDWEST WILL MAKE 
EASTWARD PROGRESS INTO THE UPPER GREAT LAKES. A LEAD MID LEVEL 
VORTICITY MAX AHEAD OF THE MAIN TROUGH WILL REACH WESTERN NY LATE 
TONIGHT AND PROVIDE AN INCREASE IN LARGE SCALE ASCENT. AN 
ILL-DEFINED WARM FRONT WILL ALSO MOVE INTO WESTERN NY LATE TONIGHT 
WITH INCREASING WARM ADVECTION AND ISENTROPIC UPGLIDE IN THE 
900-700MB LAYER. THIS WILL BRING THICKENING AND LOWERING CLOUDS 
LATER TONIGHT WITH SHOWERS BECOMING LIKELY LATE ACROSS THE WESTERN 
END OF THE STATE. THE INCREASE IN CLOUD COVER...INCREASING SOUTHERLY 
FLOW AND INCREASING DEWPOINTS WILL KEEP LOWS MILDER THAN RECENT 
NIGHTS. EXPECT LOWS IN THE MID 60S ON THE LAKE PLAINS OF FAR WESTERN 
NY...WITH LOWER 60S ELSEWHERE AND MID TO UPPER 50S ACROSS THE NORTH 
COUNTRY.

ON WEDNESDAY THE MID LEVEL CLOSED LOW WILL PROGRESS TO LAKE HURON BY 
LATE AFTERNOON. SEVERAL CONVECTIVELY AUGMENTED VORTICITY MAXIMA WILL 
CROSS THE LOWER LAKES REGION DOWNSTREAM OF THE MAIN TROUGH DURING 
WEDNESDAY...WITH EACH ONE PROVIDING A PERIOD OF ENHANCED LARGE SCALE 
ASCENT. SUBTLE LOW LEVEL BOUNDARIES FROM OUTFLOW AND DIFFERENTIAL 
HEATING WILL PROVIDE THE NECESSARY LOW LEVEL CONVERGENCE TO FOCUS 
SHOWERS. THE TIMING AND PLACEMENT OF INDIVIDUAL BATCHES OF SHOWERS 
WILL BE VERY DIFFICULT GIVEN THE WEAK AND STOCHASTIC NATURE OF THE 
FINER SCALE FORCING MECHANISMS...BUT GIVEN THE PATTERN WILL CONTINUE 
WITH CATEGORICAL POPS FOR THE DAY. 

DESPITE CLOUD COVER...INCREASING BOUNDARY LAYER MOISTURE...MODEST 
SURFACE HEATING...AND COOLING MID LEVELS WILL ALLOW FOR SUFFICIENT 
INSTABILITY TO DEVELOP TO SUPPORT SCATTERED THUNDERSTORMS. PWAT 
RISES TO AROUND 1.8 INCHES...AND LOW/MID LEVEL FLOW IS WEAK SO A FEW 
STORMS MAY PRODUCE LOCALLY HEAVY RAINFALL. IF STORMS TRAIN LONG 
ENOUGH OVER THE SAME AREA THIS COULD PRODUCE LOCALIZED FLOODING 
ISSUES...BUT THE POTENTIAL APPEARS TOO LOW AND TOO ISOLATED TO 
CONSIDER ANY TYPE OF FLOOD WATCH.

THERE SHOULD BE ENOUGH BREAKS IN THE RAIN ESPECIALLY ACROSS THE 
EASTERN HALF OF THE AREA TO ALLOW THE LOWER ELEVATIONS TO REACH THE 
LOWER 80S...WITH MID TO UPPER 70S ACROSS WESTERN NY AND THE HIGHER 
TERRAIN WHERE CLOUD COVER WILL BE THICKER THROUGH THE ENTIRE DAY.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
WEDNESDAY'S RAINS WILL CONTINUE INTO THE OVERNIGHT HOURS AS THE 
LOWER GREAT LAKES WILL REMAIN ENVELOPED IN A WARM AND MOIST AIRMASS 
JUST AHEAD OF A BROAD VERTICALLY STACKED LOW CENTERED JUST TO OUR 
NORTHWEST. SYNOPTIC-SCALE LIFT ASSOCIATED WITH THIS FEATURE SHOULD 
BE ENOUGH TO SUSTAIN SHOWERS...AND POSSIBLY A FEW EMBEDDED 
THUNDERSTORMS...FOR MUCH OF THE NIGHT EVEN WITH THE LOSS OF DIURNAL 
INSTABILITY. AN AVERAGE OF ONE-QUARTER TO ONE-HALF INCH IS EXPECTED 
ACROSS THE FORECAST AREA. HOWEVER GIVEN THAT PWATS WILL CONTINUE TO 
RUN IN THE 1.6-2.0 INCH RANGE...LOCALLY HIGHER AMOUNTS IN EXCESS OF 
AN INCH ARE LIKELY...PARTICULARLY FROM THE GENESEE VALLEY EAST WHERE 
THE HIGHER PWATS WILL BE FOUND. THE WARM AND MOIST AIRMASS OVER THE 
REGION WILL MAKE FOR A MUGGY NIGHT WITH LOWS RANGING FROM THE LOWER 
60S ACROSS HIGHER TERRAIN TO THE UPPER 60S NEAR THE LAKES. 

THE CENTER OF THE WEAKENING UPPER LOW WILL MOVE ACROSS THE FORECAST 
AREA ON THURSDAY. THIS SHOULD RESULT IN ANOTHER ROUND OF SHOWERS AND 
SCATTERED THUNDERSTORMS. WHILE THE DEEPEST MOISTURE WILL BE SHIFTING 
TO THE HUDSON VALLEY BY THIS TIME...PWATS WILL STILL BE IN THE 
NEIGHBORHOOD OF 1.5 INCHES AND THE VERY WEAK FLOW ALOFT COULD RESULT 
IN LOCALLY HEAVY RAINS ONCE AGAIN...PARTICULARLY ACROSS EASTERN 
PORTIONS OF THE FORECAST AREA. THE ABUNDANT CLOUD COVER SHOULD AID 
IN KEEPING HIGHS IN THE MID 70S IN SPITE OF THE RELATIVELY WARM 
AIRMASS OVERHEAD.

THE TROUGH WILL FINALLY MOVE AWAY TO THE EAST THURSDAY NIGHT...AND 
SHOWERS SHOULD TAPER OFF FROM WEST TO EAST DURING THE EVENING HOURS 
THOUGH GIVEN HOW SLOW THIS SYSTEM IS MOVING...CANNOT RULE OUT A FEW 
SHOWERS HANGING AROUND THE EASTERN HALF OF THE AREA OVERNIGHT. IN 
FACT THE CHANCE FOR SHOWERS WILL LINGER INTO FRIDAY NIGHT AS THE 
REGION WILL REMAIN CAUGHT IN MOIST SOUTHEASTERLY LOW LEVEL FLOW 
BETWEEN HIGH PRESSURE OVER ATLANTIC CANADA AND WEAK LOW PRESSURE 
OVER THE WESTERN GREAT LAKES WHILE A STATIONARY FRONT WILL BE DRAPED 
ACROSS THE GREAT LAKES...JUST TO OUR WEST. SHOULD THIS STATIONARY 
FRONT END UP SLIGHTLY FARTHER WEST THAN CURRENTLY PROGGED...WESTERN 
NEW YORK COULD END UP BEING MUCH WETTER THAN CURRENTLY 
FORECAST...HOWEVER WILL STICK WITH LOWER CHANCE POPS FOR NOW PENDING 
FURTHER GUIDANCE. TEMPERATURES WILL REMAIN SEASONABLE WITH HIGHS IN 
THE MID TO UPPER 70S ON FRIDAY...THANKS MAINLY TO THE ADVECTION OF 
SLIGHTLY COOLER AIR ALOFT IN THE WAKE OF THE UPPER LEVEL LOW. 
NONETHELESS IT WILL CONTINUE TO FEEL QUITE STICKY WITH LOWS IN THE 
LOW TO MID 60S FRIDAY NIGHT...THOUGH HIGHER ELEVATIONS MAY DIP INTO 
THE UPPER 50S.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
THE POSITION OF THE AFOREMENTIONED STATIONARY FRONT WILL CONTINUE TO 
BE THE BIG QUESTION MARK FOR THE COMING WEEKEND. THIS 
FRONT...MARKING THE BOUNDARY BETWEEN A HOT CONTINENTAL AIRMASS OVER 
THE CENTRAL U.S. AND RELATIVELY COOLER AND MOIST MARITIME AIR TO THE 
EAST AND NORTH...WILL SERVE AS THE FOCAL POINT FOR SHOWERS AND 
THUNDERSTORMS THROUGH MUCH OF THE WEEKEND. AT THIS POINT IT APPEARS 
THAT THIS FRONT SHOULD LARGELY REMAIN JUST WEST OF OUR FORECAST 
AREA...ACROSS OHIO AND THE CENTRAL GREAT LAKES...BUT WILL CARRY LOW 
CHANCE POPS ACROSS WESTERN NEW YORK FOR THE TIME BEING GIVEN ITS 
PROXIMITY TO OUR AREA. 

THE UPPER LEVEL RIDGE WILL GRADUALLY SHIFT EAST THROUGH THE WEEKEND 
AND INTO MONDAY...BRINGING WITH IT A WARMING AND DRYING TREND. 
HOWEVER...IT CURRENTLY APPEARS THAT MORE UNSETTLED WEATHER WILL BE 
ON THE WAY NEXT WEEK AS ANOTHER TRAIN OF SHORTWAVES MOVING ACROSS 
THE NATION'S NORTHERN TIER WILL FLATTEN OUT THE RIDGE.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
A PLUME OF DEEPER LOW LEVEL MOISTURE ADVECTING NORTH OUT OF 
PENNSYLVANIA WILL CONTINUE TO PRODUCE ENHANCED CUMULUS FIELDS 
THROUGH LATE AFTERNOON FROM THE GENESEE VALLEY INTO THE FINGER 
LAKES. MVFR CIGS ACROSS HIGHER TERRAIN SHOULD IMPROVE TO THE LOWER 
END OF THE VFR CATEGORY BY LATE AFTERNOON AS DAYTIME MIXING REACHES 
ITS MAX. THIS PLUME OF MOISTURE WILL GRADUALLY DIMINISH AS IT DRIFTS 
INTO CENTRAL NY TONIGHT.

OTHERWISE MID LEVEL CLOUDS WILL THICKEN AND LOWER FROM WEST TO EAST 
TONIGHT IN ADVANCE OF A WARM FRONT AND UPPER LEVEL DISTURBANCE. A 
FEW SHOWERS WILL DEVELOP ACROSS WESTERN NY BY LATE TONIGHT AND 
BECOME MORE WIDESPREAD THROUGHOUT THE REGION ON WEDNESDAY. EXPECT 
CIGS/VSBY TO INITIALLY BE VFR...BUT MVFR WILL BECOME MORE LIKELY IN 
THE HEAVIER SHOWERS ON WEDNESDAY AS THE LOW LEVELS SATURATE AND 
SHOWER INTENSITY INCREASES. A FEW OF THE HEAVIEST SHOWERS MAY 
PRODUCE BRIEF/LOCAL IFR CONDITIONS...BUT TIMING AND PLACEMENT OF 
THESE LOWER CONDITIONS IS VERY UNCERTAIN AT THIS TIME RANGE. 

OUTLOOK... 
WEDNESDAY NIGHT AND THURSDAY...OCCASIONAL SHOWERS AND THUNDERSTORMS 
WITH ATTENDANT LOCALIZED REDUCTIONS TO IFR/MVFR.
FRIDAY AND SATURDAY...MAINLY VFR WITH A CHANCE OF SHOWERS AND 
THUNDERSTORMS.
SUNDAY...MAINLY VFR.

&&

.MARINE...
WEAK LOW PRESSURE WILL MOVE FROM THE CENTRAL LAKES WEDNESDAY MORNING 
TO NEAR THE WEST END OF LAKE ONTARIO BY THURSDAY MORNING WHERE IT 
WILL DISSIPATE IN PLACE. THE PRESSURE GRADIENT WILL REMAIN WEAK 
THROUGH THE END OF THE WEEK WITH RELATIVELY LIGHT WINDS AND FLAT 
WAVE ACTION. A FEW THUNDERSTORMS ARE POSSIBLE WEDNESDAY AND THURSDAY 
WHICH MAY PRODUCE LOCALLY HIGHER WINDS AND WAVES.

&&

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

&&

$$

SYNOPSIS...HITCHCOCK
NEAR TERM...HITCHCOCK
SHORT TERM...WOOD
LONG TERM...WOOD
AVIATION...HITCHCOCK
MARINE...HITCHCOCK





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