Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 311731 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 131 PM EDT FRI JUL 31 2015 .SYNOPSIS... HIGH PRESSURE RIDGED FROM THE OHIO VALLEY INTO NEW YORK STATE WILL KEEP DRY AND QUIET WEATHER ACROSS OUR REGION THROUGH MOST OF TODAY. A NUMBER OF DISTURBANCES PASSING THROUGH A BROAD UPPER LEVEL TROUGH WILL THEN BRING PERIODIC OPPORTUNITIES FOR SCATTERED SHOWERS AND THUNDERSTORMS FROM LATE THIS AFTERNOON AND EVENING ONWARD INTO EARLY NEXT WEEK...THOUGH MUCH OF THE TIME WILL STILL BE RAIN FREE. && .NEAR TERM /THROUGH TONIGHT/... VISIBLE SATELLITE IMAGERY SHOWING PLENTY OF DIURNAL CUMULUS DEVELOPING EARLY THIS AFTERNOON ALONG AND INLAND FROM THE LAKE BREEZE BOUNDARIES. SKIES MAY BRIEFLY GO MOSTLY CLOUDY ACROSS THE HIGHER TERRAIN OF THE WESTERN SOUTHERN TIER...BUT THESE CONGESTED CUMULUS SHOULD SCATTER OUT AGAIN AS THE MEAGER LOW LEVEL MOISTURE BECOMES DILUTED THROUGH THE MIXED COLUMN. STABLE LAKE SHADOWS WILL KEEP AREAS ENE OF LAKES ERIE AND ONTARIO INCLUDING BUFFALO AND WATERTOWN WITH FULL SUNSHINE THROUGH THE AFTERNOON. FOR MUCH OF TODAY...OUR REGION WILL REMAIN UNDER THE INFLUENCE OF HIGH PRESSURE AND DRY AIR RIDGED FROM THE OHIO VALLEY INTO NEW YORK STATE. THIS WILL RESULT IN FAIR/DRY WEATHER AND MOSTLY SUNNY SKIES PERSISTING THROUGH THE BULK OF THE DAY...WITH 850 MB TEMPS OF +14C TO +16C SUPPORTING WIDESPREAD HIGHS IN THE LOWER TO MID 80S. COUPLED WITH DEWPOINTS RANGING FROM THE MID 50S TO AROUND 60 AND A DECENT BREEZE...THIS WILL RESULT IN A PLEASANTLY WARM LAST DAY OF JULY. LATE THIS AFTERNOON AND TONIGHT...THE NEXT IN A SERIES OF SHORTWAVE IMPULSES WILL ROUND THE BASE OF THE DEEPENING LARGE- SCALE UPPER TROUGH ACROSS THE GREAT LAKES AND NORTHEAST...AND IN THE PROCESS WILL PUSH INTO OUR REGION IN CONCERT WITH ITS ATTENDANT WEAK SURFACE REFLECTION. AS THESE FEATURES BEGIN TO IMPINGE UPON OUR AREA LATE THIS AFTERNOON...INCREASING LIFT/MOISTURE ASSOCIATED WITH BOTH THESE AND A LAKE BREEZE CONVERGENCE ZONE COULD TOUCH OFF A SHOWER/THUNDERSTORM OR TWO ACROSS NIAGARA AND ORLEANS COUNTIES...FOR WHICH SOME LOW CHANCE POPS REMAIN IN PLAY. BETTER AND MORE GENERAL OPPORTUNITIES FOR SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL THEN FOLLOW FOR TONIGHT AS THE SHORTWAVE DIGS FURTHER INTO OUR REGION...WITH CONVECTIVE COVERAGE MOST LIKELY TO PEAK DURING THE LATE EVENING AND EARLY OVERNIGHT HOURS...THEN DIMINISH OVERNIGHT. AS FOR TEMPS...OVERNIGHT LOWS ARE AGAIN EXPECTED TO RANGE FROM THE UPPER 50S ACROSS INTERIOR PORTIONS OF THE SOUTHERN TIER AND NORTH COUNTRY TO THE LOWER AND MID 60S ELSEWHERE...WITH THE WARMEST OVERALL TEMPS FOUND ALONG THE IMMEDIATE LAKESHORES. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... A SOMEWHAT AMPLIFIED UPPER LEVEL PATTERN WILL BE IN PLACE OVER NORTH AMERICA DURING THIS PERIOD. BROAD TROUGHINESS OVER THE GREAT LAKES WILL BE ANCHORED BY AN ANOMALOUSLY DEEP CLOSED LOW OVER JAMES BAY... WHILE A STRONG SUB-TROPICAL RIDGE WILL BE CENTERED OVER NEW MEXICO. THIS WILL KEEP OPPRESSIVE SUMMER HEAT OUT WEST WHILE OUR REGION WILL EXPERIENCE TEMPERATURES THAT WILL AVERAGE WITHIN A COUPLE DEGREES OF NORMAL. IN TERMS OF RAINFALL...IMPULSES TRACKING SOUTHEAST FROM THE CANADIAN PRAIRIES AND UPPER GREAT LAKES WILL BE CONDUCIVE FOR PERIODIC SHOWER AND THUNDERSTORM ACTIVITY...BUT THE BULK OF THE PERIOD WILL BE PCPN FREE. THE DEEP CYCLONIC FLOW WILL ESSENTIALLY CUT OFF ANY GULF MOISTURE...AND WITHOUT ANY ORGANIZED SFC FEATURES...PCPN WILL BE SCATTERED IN NATURE WITH GENERAL INSIGNIFICANT QPF. THIS IS IMPORTANT TO NOTE AS PARTS OF WRN NEW YORK HAVE RECEIVED LITTLE RAINFALL OVER THE PAST TWO WEEKS. GETTING TO THE DETAILS... WHILE SATURDAY WILL BE LARGELY DRY ACROSS THE REGION...A SHORTWAVE WILL TRACK SOUTHEAST FROM LAKE HURON DURING THE MORNING HOURS AND CROSS TO OUR NORTH DURING THE MIDDAY AND AFTERNOON. GIVEN THE DISCREPANCIES BETWEEN THE GUIDANCE PACKAGES...THERE IS RELATIVELY LOW CONFIDENCE WITH THE TIMING OF THIS FEATURE. THIS IS IMPORTANT IN THAT A SLOWER PASSAGE WOULD ALLOW FOR INCREASED DIURNAL INSTABILITY AND THEREBY A GREATER COVERAGE OF MIDDAY AND AFTERNOON CONVECTION. WILL FOLLOW CONTINUITY...WHICH FAVORS CHC POPS FOR THE SECOND HALF OF THE DAY. A SLOWER PASSAGE OF THE MID LEVEL FEATURE WOULD ALSO INCREASE THE RISK FOR STRONG TO SEVERE CONVECTION. WHILE SBCAPES OF 1000-1500 J/KG STILL APPEAR POSSIBLE...AM LESS IMPRESSED WITH THE AMOUNT OF SHEAR (BULK <30KTS) BEING EXPRESSED BY THE NEW GUIDANCE PACKAGE. SPC ALSO LOOKS TO BE UNIMPRESSED AS THE AREA IS ONLY IN A GENERAL RISK FOR THUNDERSTORMS. OTHERWISE THE VAST MAJORITY OF THE DAY THOUGH WILL BE RAIN FREE. MAX TEMPS WILL GENERALLY RANGE FROM 75 TO 80...WITH THE HIGHER END OF THE RANGE BEING FOUND IN THE GENESEE VALLEY AND ON THE LAKE PLAINS SOUTH OF LK ONTARIO. IN THE WAKE OF THE DEPARTING MID LEVEL SHORTWAVE SATURDAY EVENING... ANY RESIDUAL AFTERNOON CONVECTION WILL DIE OFF FAIRLY QUICKLY WITH THE LOSS OF DAYTIME HEATING. THIS SHOULD LEAVE A MAINLY DRY NIGHT ACROSS OUR REGION WITH TEMPERATURES SETTLING TO NEAR 60 ACROSS THE LAKE PLAINS AND THE MID TO UPPER 50S EAST OF LK ONTARIO AND ACROSS THE BULK OF THE SRN TIER. SUNDAY SHOULD FEATURE GENERALLY FAIR WEATHER AND SLIGHTLY HIGHER TEMPERATURES AS LOW LEVEL RIDGING WILL EXTEND ACROSS OUR REGION FROM THE UPPER OHIO VALLEY. IT IS WORTH NOTING THOUGH THAT THE GFS IS PAINTING A MUCH MORE UNSETTLED DAY. THE PROBLEM WITH THIS SOLUTION THOUGH IS THAT IT STEMS FROM A SPURIOUS LOOKING AREA OF CONVECTION THAT THE 00Z GFS GENERATES OVER THE CENTRAL PLAINS SATURDAY EVENING...THEN TRACKS THE REMNANTS EAST ACROSS OUR REGION FOR SUNDAY. WILL CONTINUE WITH OUR LOW CHC AFTERNOON POPS FROM CONTINUITY...WHICH IS SUPPORTED BY THE ECMWF. WHILE THERE WILL BE SEVERAL SHORTWAVES PASSING ACROSS OR JUST NORTH OF OUR REGION DURING THIS PARTICULAR PERIOD...THE STRONGEST IMPULSE IS FORECAST TO MOVE THROUGH OUR REGION MONDAY AFTERNOON OR EVENING. THIS FEATURE WILL PUSH A FAIRLY STRONG COLD FRONT ACROSS OUR REGION...BUT AS HIGHLIGHTED IN PREVIOUS DISCUSSIONS...THE MAIN FORCING FOR CONVECTION MAY COME FROM A PRE-FRONTAL TROUGH. IN EITHER CASE...HAVE BUMPED POPS TO HIGH CHC FOR THE SECOND HALF OF MONDAY WHEN THE DEEPEST MOISTURE FIELD...JET INDUCED LIFT AND DIURNAL INSTABILITY IS EXPECTED TO BE THE GREATEST. THE CONVECTION WILL THEN WEAKEN AND DISSIPATE DURING THE COURSE OF MONDAY NIGHT WHEN THE FRONT WILL PUSH TO OUR EAST. && .LONG TERM /TUESDAY THROUGH THURSDAY/... A GENERAL DEAMPLIFICATION OF THE LONGWAVE PATTERN IS EXPECTED OVER NORTH AMERICA DURING THIS PERIOD...AS THE GFS AND ECMWF BASED ENSEMBLES ARE SUGGESTING THAT THE ANOMALOUSLY DEEP CLOSED LOW CENTERED NEAR JAMES BAY WILL OPEN UP AND PUSH OUT ACROSS FAR EASTERN QUEBEC. MEANWHILE...EXPANSIVE SFC HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL NOSE SOUTHEAST ACROSS THE UPPER GREAT LAKES TO THE OHIO VALLEY. THIS SHOULD PROVIDE MAINLY FAIR DRY WEATHER ACROSS OUR REGION...WITH THE CANADIAN BASED AIRMASS SUPPORTING BELOW NORMAL TEMPERATURES. MAX TEMPS WILL BE IN THE 70S WHILE OVERNIGHT LOWS WILL BE IN THE 50S. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... SCT-BKN DIURNAL CUMULUS WILL CONTINUE THROUGH THE AFTERNOON HOURS ACROSS MUCH OF WESTERN NY ALONG AND INLAND FROM THE LAKE BREEZE BOUNDARIES WITH BASES IN THE 4-6K FOOT RANGE. STABLE LAKE SHADOWS ENE OF LAKES ERIE AND ONTARIO WILL KEEP THE KBUF AND KART AREAS MAINLY CLEAR. BY LATE AFTERNOON WIDELY SCATTERED CONVECTION MAY BEGIN TO FORM ALONG THE CONVERGENCE ZONE OVER THE NIAGARA PENINSULA NEAR KIAG. TONIGHT A WEAK TROUGH WILL CROSS THE AREA WITH WIDELY SCATTERED SHOWERS AND STORMS MOVING IN A BROKEN LINE FROM NORTHWEST TO SOUTHEAST ACROSS THE AREA. THE COVERAGE OF THIS ACTIVITY LOOKS TO REMAIN ON THE SPARSE SIDE...SO FOR NOW HAVE JUST GONE WITH VCSH QUALIFIERS AT THE TAF SITES. ANY HEAVIER SHOWERS THAT DEVELOP MAY CONTAIN BRIEF/LOCAL MVFR OR IFR CONDITIONS...BUT VFR WILL PREVAIL THE MAJORITY OF THE TIME. ANY SCATTERED CONVECTION WILL END LATE TONIGHT WITH AT LEAST PARTIAL CLEARING FOR SATURDAY MORNING. EXTENSIVE DIURNAL CUMULUS ARE THEN EXPECTED TO DEVELOP FROM LATE MORNING THROUGH THE AFTERNOON ON SATURDAY WITH MOST AREAS GOING BKN BY MIDDAY. STABLE LAKE SHADOWS WILL KEEP SKIES MORE CLEAR EAST OF BOTH LAKES. WIDELY SCATTERED SHOWERS AND ISOLATED STORMS WILL DEVELOP DURING THE AFTERNOON MAINLY ALONG AND INLAND FROM THE LAKE BREEZES...BUT AGAIN COVERAGE SHOULD REMAIN SPARSE. OUTLOOK... SUNDAY AND MONDAY...MAINLY VFR WITH WIDELY SCATTERED SHOWERS AND THUNDERSTORMS. TUESDAY...MAINLY VFR WITH A CHANCE OF A FEW LIGHT SHOWERS. WEDNESDAY...MAINLY VFR WITH A SLIGHT CHANCE OF A LIGHT SHOWER. && .MARINE... IN ADVANCE OF AN APPROACHING SURFACE TROUGH...A BRISK WEST- SOUTHWESTERLY FLOW WILL INCREASE THIS AFTERNOON...THEN WILL LINGER INTO THE EARLY EVENING HOURS. FOR THIS REASON SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR LAKE ERIE AND THE BUFFALO HARBOR/NIAGARA RIVER. WINDS WILL INCREASE AGAIN ON SATURDAY ON BOTH LAKES ERIE AND THE EAST HALF OF LAKE ONTARIO. ADDITIONAL SMALL CRAFT ADVISORIES MAY BE NEEDED FOR THIS TIME FRAME. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT SATURDAY FOR LEZ040-041. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LEZ020. && $$ SYNOPSIS...JJR NEAR TERM...HITCHCOCK/JJR SHORT TERM...RSH LONG TERM...RSH AVIATION...HITCHCOCK MARINE...HITCHCOCK/JJR

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