Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 300813 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 413 AM EDT TUE SEP 30 2014 .SYNOPSIS...
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AN UPPER LEVEL DISTURBANCE WILL INTERRUPT THE FINE STRETCH OF AUTUMN WEATHER WE HAVE BEEN EXPERIENCING RECENTLY. THIS DISTURBANCE WILL BRING CLOUDS AND SCATTERED SHOWERS TO THE AREA TODAY AND TONIGHT. THERE WILL BE FAIR WEATHER AND AGAIN BECOMING MOSTLY SUNNY ON WEDNESDAY WITH THE SUNSHINE AND PLEASANT WARMTH LINGERING INTO THURSDAY. A STRONG COLD FRONT IS THEN EXPECTED TO CROSS THE REGION ON FRIDAY...BRINGING A LIKELIHOOD OF SHOWERS FOLLOWED BY MUCH COOLER TEMPERATURES FOR THE UPCOMING WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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WE WILL HAVE AN INTERRUPTION IN THE STREAK OF FINE AUTUMN WEATHER TODAY AS AN UPPER LEVEL DISTURBANCE BRINGS SCATTERED SHOWERS AND PERHAPS A THUNDERSTORM TO THE REGION TODAY. THIS MORNING AN UPPER LEVEL SHORTWAVE IS SEEN ON WATER VAPOR IMAGERY OVER CENTRAL MICHIGAN. AT THE SURFACE A WEAK AREA OF LOW PRESSURE IS NEAR LAKE HURON AND THE WESTERN END OF LAKE ERIE...WITH A FRONTAL BOUNDARY EXTENDING EASTWARD TO THE SOUTH OF LAKE ONTARIO. REGIONAL RADARS DISPLAY A SWATCH OF RAINFALL AHEAD OF THE UPPER LEVEL SHORTWAVE WITH THE RAIN SHOWERS OVER GEORGIAN BAY TO NEAR DETROIT AND THE WESTERN END OF LAKE ERIE. BEFORE THE CLOUDS ARRIVE FOG WILL FILL THE VALLEYS ACROSS THE SOUTHERN TIER THIS MORNING. RECENT SURFACE OBSERVATIONS DISPLAY SOME QUARTER MILE VISIBILITY WITHIN THIS FOG...WITH A HALF TO ONE MILE PREDOMINATE. WILL HOLD OFF ON A DENSE FOG ADVISORY AS FOG IS LIKELY RESTRICTED TO THE VALLEYS. SOME PATCHES OF FOG ARE POSSIBLE ACROSS THE NORTHERN NIAGARA FRONTIER WHERE TEMPERATURES ARE COOLING TO NEAR THE DEWPOINTS UNDER LIGHT WINDS. ALL FOG SHOULD DISSIPATE BY MID MORNING WITH THE DAYTIME MIXING AND INCREASED CIRRUS LIMITING RADIATIONAL COOLING. CLOUDS WILL THICKEN OVER OUR REGION THIS MORNING WITH RAIN SHOWERS ASSOCIATED WITH THE UPPER LEVEL DISTURBANCE AND AREA OF WEAK SURFACE LOW PRESSURE REACHING OUR FAR WESTERN AREAS LATE MORNING. THIS UPPER LEVEL FEATURE WILL DIVE SOUTHEASTWARD SUCH THAT THE CORE OF THE COLD AIR ALOFT WILL BRUSH BY THE SOUTHERN TIER. UNDER THIS COOL POOL ALOFT STEEPING LAPSE RATES AND SBCAPE UPWARDS TO 500 J/KG MAY ALLOW FOR SOME THUNDER THIS AFTERNOON NEAR THE STATE LINE. FARTHER NORTHWARD AND AWAY FROM THE INFLUENCES OF THE UPPER LEVEL LOW AND WEAK SURFACE LOW CHANCES FOR SHOWERS WILL DIMINISH...WITH JUST SLIGHT CHANCES FOR SHOWERS OVER THE NORTH COUNTRY TODAY. TONIGHT THE SURFACE LOW WILL OPEN UP TO A WEAK WAVE...WITH AN INVERTED SURFACE TROUGH EXTENDING NORTHWARD FROM NEAR WEST VIRGINIA NORTHWARD ACROSS WESTERN NEW YORK. A FEW SHOWERS MAY FORM ON CONVERGENT BOUNDARIES ASSOCIATED WITH THIS INVERTED TROUGH THROUGH THE NIGHT. A NORTHEAST WIND FLOW WILL ENSUE OVERNIGHT FROM A STRONG AREA OF HIGH PRESSURE OVER QUEBEC CANADA. THIS FLOW OVER THE WATERS OF LAKE ONTARIO WILL ADD LOW LEVEL MOISTURE SUCH THAT LOW CLOUDS...PERHAPS A SPRINKLE AND PATCHES OF FOG ARE POSSIBLE SOUTH OF LAKE ONTARIO. LIKELIEST AREAS FOR THIS FOG FORMATION WOULD BE AROUND ROCHESTER WESTWARD ACROSS THE NIAGARA FRONTIER AND THEN DOWN INTO THE SOUTHERN TIER. TEMPERATURES TODAY WILL NOT BE AS WARM AS RECENT DAYS DUE TO THE THICKER CLOUD COVER. HIGHS WILL RANGE ACROSS THE LOWER TO MID 70S TODAY. TONIGHT TEMPERATURES WILL FALL BACK INTO THE LOW TO MID 50S. COOLEST SPOTS WILL BE ACROSS THE NORTH COUNTRY WHERE SOME BRIEF CLEARING MAY DEVELOP.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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AN UPPER LEVEL LOW WILL MOVE EASTWARD ACROSS SOUTHERN NEW ENGLAND ON WEDNESDAY WHILE A 500 MB RIDGE AXIS BUILDS ACROSS THE LOWER LAKES. THIS RIDGE AXIS WILL REMAIN ACROSS OUR REGION INTO THURSDAY NIGHT WITH DRY CONDITIONS. NAM/SREF GUIDANCE CONTINUE TO SHOW LOW LEVEL MOISTURE TRAPPED BENEATH AN INVERSION IN A NORTHEAST FLOW SOUTH OF LAKE ONTARIO. THIS WILL RESULT IN LINGERING CLOUD COVER WEDNESDAY MORNING WHICH SHOULD GRADUALLY DISSIPATE DURING THE AFTERNOON HOURS. OTHERWISE...THE CLOSE PROXIMITY OF THE DEPARTING UPPER TROUGH MAY SPARK A STRAY SHOWER ON WEDNESDAY...BUT THE VAST MAJORITY OF THE REGION WILL STAY DRY. TEMPERATURES WILL CLIMB INTO THE UPPER 60S TO LOWER 70S...WHICH IS STILL ABOVE NORMAL FOR THE DATE. SURFACE HIGH PRESSURE CENTERED IN THE CANADIAN MARITIMES WILL RIDGE ACROSS OUR REGION WEDNESDAY NIGHT...WITH THIS RIDGE AXIS EVENTUALLY MOVING EAST THURSDAY AND THURSDAY NIGHT. THIS WILL SET UP A SOUTHERLY FLOW WHICH WILL LIMIT LAKE BREEZE DEVELOPMENT THURSDAY AFTERNOON. THIS WILL RESULT IN A SUNNY AND WARM EARLY FALL DAY ON THURSDAY. THE COMBINATION OF WARM 850MB (AROUND +11C) AND DOWNSLOPE FLOW SHOULD ALLOW BUF-ROC AND MUCH OF THE GENESEE VALLEY TO WARM INTO THE MID TO UPPER 70S...WITH ELSEWHERE TOPPING OUT IN THE LOWER TO MID 70S. THE SOUTHERLY FLOW WILL INCREASE THURSDAY NIGHT...WITH 925MB WINDS INCREASING TO 30 TO 35 KTS BY 12Z FRIDAY. THIS WILL KEEP THE ATMOSPHERE WELL MIXED AND CONTINUED DOWNSLOPING WILL RESULT IN UNSEASONABLY WARM OVERNIGHT TEMPERATURES IN THE 60S NORTH OF I-90. 00Z GUIDANCE (NAM/GFS/GGEM) IS SLIGHTLY SLOWER WITH THE NEXT SYSTEM WITH THIS PRETTY MUCH KEEPING OUR REGION DRY THROUGH EARLY FRIDAY MORNING.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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OUR STRETCH OF INDIAN SUMMER WILL COME TO A CLOSE DURING THIS PERIOD AS MUCH COOLER AIR WILL INVADE THE GREAT LAKES REGION. DAYTIME HIGHS WILL BE SOME 20 DEG F LOWER DURING THE WEEKEND THAN FROM READINGS DURING THE PREVIOUS WEEK. SYNOPTICALLY...THIS PERIOD WILL BE HIGHLIGHTED BY A DEEPENING CUTTER STORM THAT WILL LIFT ALMOST DUE NORTH FROM CHICAGO FRIDAY...WHILE SWEEPING A PATTERN CHANGING COLD FRONT ACROSS THE LOWER GREAT LAKES LATE FRIDAY AND FRIDAY NIGHT. A CONSENSUS OF 00Z GUIDANCE (GFS/ECMWF/GGEM) IS SLIGHTLY SLOWER WITH THIS SYSTEM. OUR REGION IS LIKELY TO STAY DRY FOR A GOOD PART OF FRIDAY WHICH WILL ALLOW TEMPERATURES TO WARM WELL INTO THE 70S WITH BREEZY CONDITIONS. A SWATH OF MODERATELY HEAVY SHOWERS WILL SWEEP ACROSS THE REGION...ENTERING FRIDAY AFTERNOON...THEN MOVING ACROSS THE REGION FRIDAY EVENING AND NIGHT. MUCH COOLER AIR WILL THEN CHARGE ACROSS OUR REGION AS THE AXIS OF THE NEGATIVELY TILTED H5 TROUGH WILL BECOME ALIGNED OVER THE LOWER GREAT LAKES FROM SATURDAY THROUGH MONDAY. SHOWERS WITH THIS TROUGH WILL LINGER INTO SATURDAY...ESPECIALLY ACROSS EASTERN PORTIONS OF THE CWA. H85 TEMPS WILL AVERAGE WITHIN A DEGREE OR SO OF ZERO C...WHICH WILL NOT ONLY RESULT IN BELOW NORMAL TEMPERATURES...BUT WILL ALSO SUPPORT SOME NUISANCE LAKE INDUCED RAIN SHOWERS FOR SITES EAST OF BOTH LAKES.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/... AT 06Z SOUTHERN TIER VALLEY FOG HAS BROUGHT LIFR VSBYS ACROSS THE VALLEYS...INCLUDING THE KJHW TERMINAL. ELSEWHERE MAINLY VFR WITH SOME PATCHES OF MVFR VSBYS IN FOG. CLOUDS WILL THICKEN THROUGH THE LATE OVERNIGHT WITH SCATTERED SHOWERS REACHING FAR WESTERN NEW YORK AROUND NOONTIME. GREATEST CHANCES FOR SHOWERS WILL BE ACROSS THE SOUTHERN TIER. OTHERWISE MAINLY VFR CIGS WILL BE THE RULE THROUGH THE DAYLIGHT HOURS. TONIGHT CLOUDS WILL LOWER SOUTH OF LAKE ONTARIO AS WINDS VEER AROUND TO NORTHEASTERLY. A STILL CONVERGENCE BOUNDARY IN THE LOW LEVELS MAY SERVE AS A FOCUS FOR SPRINKLES AND LOW MVFR OR IFR CLOUDS SOUTH OF LAKE ONTARIO AS THE NORTHEAST WINDS MAINTAIN AMPLE LOW LEVEL MOISTURE. ACROSS THE NORTH COUNTRY VFR FLIGHT CONDITIONS SHOULD PREVAIL THROUGH THE TAF CYCLE. OUTLOOK... WEDNESDAY THROUGH THURSDAY...VFR...EXCEPT FOR LOCALIZED IFR IN SOUTHERN TIER VALLEY FOG BETWEEN 06Z-15Z EACH DAY. FRIDAY...VFR LOWERING TO MVFR WITH SHOWERS BECOMING LIKELY. SATURDAY...MVFR WITH A CHANCE OF SHOWERS. && .MARINE...
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AN UPPER LEVEL LOW...AND WEAK SURFACE LOW WILL DIVE SOUTHEASTWARD ACROSS LAKE ERIE AND TOWARDS PENNSYLVANIA TODAY AND TONIGHT. A LIGHT WIND TODAY WILL BECOME NORTHEASTERLY TONIGHT AND INCREASE TO AROUND 15 KNOTS ON LAKE ONTARIO...AND 10 KNOTS ON LAKE ERIE. THESE STRONGER WINDS ON LAKE ONTARIO WILL BRING WAVES 2 TO 4 FEET TONIGHT. WEAKER WINDS WILL ALLOW FOR 1 TO PERHAPS 2 FOOT WAVES ON THE EASTERN END OF LAKE ERIE TONIGHT. WAVES AND WINDS WILL DIMINISH THROUGH THE DAY WEDNESDAY AS HIGH PRESSURE AGAIN BUILDS ACROSS THE LOWER LAKES REGION. LATE IN THE WEEK...A STRONG AREA OF LOW PRESSURE IS EXPECTED TO LIFT ACROSS THE GREAT LAKES REGION ON FRIDAY...WHILE SWINGING A STRONG TRAILING COLD FRONT ACROSS THE LOWER LAKES. THE TIGHTENING PRESSURE GRADIENT ASSOCIATED WITH THE LOW WILL LEAD TO A PERIOD OF STRONGER WINDS...WITH ADVISORY-LEVEL WINDS AND WAVES BECOMING POSSIBLE.
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&& .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...THOMAS NEAR TERM...THOMAS SHORT TERM...APFFEL LONG TERM...APFFEL/RSH AVIATION...THOMAS MARINE...THOMAS

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