Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 011729
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
129 PM EDT SAT AUG 1 2015

.SYNOPSIS...
HIGH PRESSURE OVER THE OHIO VALLEY THIS MORNING WILL EXTEND NORTH
TO THE LOWER GREAT LAKES THIS AFTERNOON. WHILE THIS WILL PROVIDE
THE BULK OF OUR REGION WITH FAIR DRY WEATHER THROUGH THE
WEEKEND...A ROBUST MID LEVEL DISTURBANCE COULD TOUCH OFF A SHOWER
OR THUNDERSTORM THIS AFTERNOON OR EVENING. A COLD FRONT WILL THEN
BRING A HIGHER CHANCE FOR SHOWERS AND STORMS TO THE REGION SUNDAY
NIGHT AND MONDAY. THIS FRONT WILL USHER IN A MUCH COOLER AIRMASS
FOR MUCH OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY WILL NOSE NORTHWARDS TO
THE LOWER GREAT LAKES THIS AFTERNOON. THIS WILL PROVIDE THE BULK OF
OUR REGION WITH FAIR DRY WEATHER...ALTHOUGH ANOTHER IMPULSE OF
ENERGY IN THE MID LEVELS WILL HAVE TO BE WATCHED FOR LATER THIS
AFTERNOON AND EVENING. AS OF 17Z THIS CAN BE SEEN IN WATER VAPOR
IMAGERY MOVING EAST OF GEORGIAN BAY. THIS WEAK VORTICITY MAXIMA WILL
PROVIDE MODEST LARGE SCALE ASCENT DURING THE LATE AFTERNOON AND
EVENING AS IT CROSSES THE LOWER LAKES.

LATEST HIGH RESOLUTION MESOSCALE MODEL GUIDANCE SUCH AS THE HRRR...
OPERATIONAL NAM...AND EXPERIMENTAL 3KM NAMRR ARE NOT DEVELOPING MUCH
IN THE WAY OF CONVECTION THIS AFTERNOON WITH A FEW EXCEPTIONS.
SOMEWHAT DEEPER MOISTURE AND BETTER ASCENT THIS AFTERNOON ACROSS THE
SAINT LAWRENCE VALLEY SHOULD SUPPORT SCATTERED CONVECTION WITH
DAYTIME HEATING...MAINLY NORTH AND EAST OF THE WATERTOWN AREA. THE
HIGH RES GUIDANCE ALSO TARGETS THE NIAGARA FRONTIER CONVERGENCE ZONE
FOR LATE AFTERNOON AND EARLY EVENING CONVECTION. THE ENHANCED WSW
FLOW OFF LAKE ERIE AND GENERAL WNW FLOW OVER THE NIAGARA PENINSULA
WILL DEVELOP A NICE CONVERGENCE ZONE FROM NEAR GRAND ISLAND ACROSS
THE NORTHERN SUBURBS OF BUFFALO AND INTO GENESEE COUNTY LATER THIS
AFTERNOON...A LITTLE SOUTH OF ITS CLIMATOLOGICAL PLACEMENT GIVEN THE
WNW FLOW ALOFT. THIS BOUNDARY MAY BE THE FOCUS FOR A FEW HOURS OF
WIDELY SCATTERED CONVECTION FROM MID TO LATE AFTERNOON INTO THE
EVENING. OUTSIDE OF THE TWO AREAS MENTIONED ABOVE...EXPECT ANY
AFTERNOON CONVECTIVE COVERAGE TO REMAIN VERY SPARSE...IF ANYTHING
FORMS AT ALL. STABLE LAKE SHADOWS EAST OF LAKE ERIE AND ONTARIO WILL
KEEP AREAS EAST OF BOTH LAKES DRY.

TEMPERATURES TODAY WILL BE A FEW DEGREES LOWER THAN THOSE FROM
FRIDAY...AS H85 TEMPS AVERAGING 12C WILL ONLY ENCOURAGE THE
MERCURY TO CLIMB INTO THE UPPER 70S TO NEAR 80 IN MOST LOCATIONS.

TONIGHT...ANY LATE AFTERNOON CONVECTION WILL QUICKLY DIE OFF
EARLY IN THE EVENING...LEAVING SUBSIDENCE FROM THE AFOREMENTIONED
SFC HIGH AS THE DOMINATING WEATHER FEATURE. TEMPERATURES TONIGHT
WILL DROP INTO THE LOWER 60S ACROSS THE LAKE PLAINS WHILE MINS
WILL BE FOUND IN THE MID 50S IN THE COOLER SRN TIER VALLEYS AND
POSSIBLY THE FOOTHILLS OF THE ADIRONDACKS.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
ON SUNDAY SURFACE HIGH PRESSURE WILL REMAIN ANCHORED FROM THE
CENTRAL APPALACHIANS TO NEW ENGLAND...WHILE UPSTREAM THE NEXT
SIGNIFICANT SHORTWAVE TROUGH WILL DIG ACROSS THE UPPER GREAT
LAKES...ALONG WITH ITS ATTENDANT COLD FRONT. WITH THE 00Z GUIDANCE
SUITE HAVING UNIVERSALLY SLOWED THE TIMING OF THIS NEXT
SYSTEM...IT NOW APPEARS THAT SUNDAY SHOULD REMAIN MOSTLY IF NOT
ENTIRELY DRY...WITH JUST SOME LOW-END CHANCES OF A
SHOWER/THUNDERSTORM REACHING THE SAINT LAWRENCE VALLEY AND EXTREME
FAR WESTERN NEW YORK BY VERY LATE SUNDAY AFTERNOON/EARLY SUNDAY
EVENING. WITH THE WARM ADVECTION REGIME OUT AHEAD OF THE
APPROACHING SHORTWAVE HELPING TO PUSH 850 MB TEMPS INTO THE +13C
TO +16C RANGE AND A TIGHTENING PRESSURE GRADIENT PROMOTING AN
INCREASING SOUTHWESTERLY BREEZE/CONSEQUENT GOOD MIXING...AFTERNOON
HIGH TEMPERATURES SHOULD MOSTLY RANGE IN THE LOWER TO MID 80S.

DURING THE COURSE OF SUNDAY NIGHT AND MONDAY...THE AFOREMENTIONED
SHORTWAVE TROUGH WILL DIG FURTHER SOUTHEASTWARD INTO THE LOWER
GREAT LAKES...WHILE AT THE SURFACE A PRE-COLD FRONTAL TROUGH WILL
EASE INTO THE REGION SUNDAY NIGHT...FOLLOWED BY THE TRAILING COLD
FRONTAL BOUNDARY ON MONDAY. WHILE THE MAIN OPERATIONAL MODELS
CONTINUE TO EXHIBIT SOME MODEST TIMING DIFFERENCES...IN GENERAL
THE INCREASING MOISTURE AND LARGE-SCALE LIFT ATTENDANT TO THESE
FEATURES WILL BRING AN INCREASED RISK FOR SHOWERS AND
THUNDERSTORMS DURING THIS PERIOD. AT THIS JUNCTURE THE GREATEST
CONVECTIVE POTENTIAL/COVERAGE APPEARS AS IF IT WILL LIKELY FOCUS
ON THE OVERNIGHT SUNDAY NIGHT AND MONDAY TIME FRAME...DURING WHICH
THE LOW LIKELY POPS FROM OUR EXISTING CONTINUITY LOOKED VERY
REASONABLE AND HAVE THUS BEEN MAINTAINED.

WITH RESPECT TO SEVERE POTENTIAL...INSTABILITY LEVELS SHOULD
INITIALLY BE HELD IN CHECK BY THE UNFAVORABLE PORTION OF THE
DIURNAL CYCLE LATER SUNDAY NIGHT THROUGH THE FIRST PART OF MONDAY
MORNING...WHICH SHOULD HELP TO GREATLY LIMIT THE POTENTIAL FOR
STRONGER STORMS THROUGH THAT TIME. THIS COULD HOWEVER CHANGE BY
LATER MONDAY MORNING/AFTERNOON AS RENEWED DIURNAL HEATING MAY LEAD
TO INCREASING INSTABILITY OUT AHEAD OF THE APPROACHING COLD
FRONT...WITH THE EXACT AMOUNT OF DESTABILIZATION WE CAN EXPECT
REMAINING UNCERTAIN AT THIS POINT AND HIGHLY DEPENDENT ON BOTH THE
TIMING OF THE FRONT AND THE AMOUNT OF ANY CLOUD COVER/PRECIP
INITIALLY PRESENT MONDAY MORNING. SHOULD SUFFICIENT
DESTABILIZATION BE REALIZED...ENOUGH DEEP-LAYER SHEAR LOOKS TO BE
IN PLACE TO SUPPORT AT LEAST A LOW CHANCE FOR SOME STRONGER TO
MARGINALLY SEVERE STORMS. IN THEIR NEW DAY 3 CONVECTIVE
OUTLOOK...SPC HAS PLACED MUCH OF OUR REGION IN A MARGINAL RISK FOR
SEVERE STORMS ON MONDAY...AND THIS LOOKS QUITE REASONABLE GIVEN
THE ABOVE FACTORS.

FOLLOWING THE PASSAGE OF THE COLD FRONT...SUBSIDENCE IN ITS WAKE
ALONG WITH THE ARRIVAL OF A SWATH OF SOMEWHAT DRIER AIR SHOULD
LEAD TO PRECIP CHANCES DIMINISHING FROM WEST TO EAST LATER MONDAY
AFTERNOON AND EVENING... WITH MAINLY DRY WEATHER THEN FOLLOWING
FOR THE SECOND HALF OF MONDAY NIGHT.

WITH REGARD TO TEMPERATURES FROM SUNDAY NIGHT ONWARD...LOWS
SUNDAY NIGHT SHOULD RANGE SOLIDLY ABOVE NORMAL OUT AHEAD OF THE
APPROACHING COLD FRONT...WITH READINGS RANGING FROM THE LOWER 60S
ACROSS INTERIOR PORTIONS OF THE SOUTHERN TIER/NORTH COUNTRY TO
NEAR 70 ALONG THE LAKESHORES. AFTER THAT...EXPECT READINGS TO
RETURN TO NEAR NORMAL LEVELS FOR THE BALANCE OF THE PERIOD...WITH
DAYTIME HIGHS AVERAGING OUT NEAR 80 ON MONDAY...AND NIGHTTIME LOWS
THEN DROPPING BACK INTO THE UPPER 50S TO LOWER 60S MONDAY NIGHT.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
IN THE BIG PICTURE...THE EXTENDED PORTION OF THE FORECAST WILL
FEATURE UPPER LEVEL TROUGHING DIGGING ACROSS THE GREAT LAKES AND
NORTHEAST THROUGH MIDWEEK...BEFORE GRADUALLY LIFTING OUT INTO THE
CANADIAN MARITIMES THURSDAY AND FRIDAY AND ALLOWING THE LARGE-
SCALE FLOW ACROSS OUR REGION TO TREND MORE QUASI-ZONAL AGAIN BY
THE END OF THE PERIOD. FOR OUR REGION...THIS WILL RESULT IN
TEMPERATURES FALLING BACK TO BELOW NORMAL LEVELS FOR MOST IF NOT
ALL OF THIS PERIOD...WHEN DAILY HIGHS WILL MAINLY BE IN THE LOWER
TO MIDDLE 70S...AND NIGHTTIME LOWS WILL RANGE THROUGH THE 50S.

IN TERMS OF PRECIPITATION CHANCES...THE TREND TOWARD COOLER
WEATHER WILL BE USHERED IN BY THE PASSAGE OF A SECONDARY COLD
FRONT LATER TUESDAY AND TUESDAY NIGHT...WHICH WILL PROBABLY BE
ACCOMPANIED BY ANOTHER ROUND OF SCATTERED SHOWERS AND
THUNDERSTORMS AS IT CROSSES OUR REGION. ADDITIONAL SCATTERED
SHOWERS MAY THEN LINGER INTO WEDNESDAY ACROSS THE EASTERN HALF OF
THE AREA IN CONJUNCTION WITH THE PASSAGE OF THE MAIN UPPER LEVEL
TROUGH AXIS AND POSSIBLE LAKE ENHANCEMENT DOWNWIND OF LAKE
ONTARIO...BEFORE INCREASING SURFACE- BASED RIDGING AND DRIER AIR
THEN BRINGS A RETURN TO MAINLY DRY WEATHER FOR BOTH THURSDAY AND
FRIDAY.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VISIBLE SATELLITE IMAGERY SHOWING EXTENSIVE CUMULUS FIELDS THIS
AFTERNOON INLAND FROM THE STABILIZING INFLUENCE OF THE COOLER LAKES.
MOST OF THE AREA WILL STAY DRY THROUGH THIS EVENING...BUT WIDELY
SCATTERED STORMS WILL DEVELOP IN A FEW AREAS. EXPECT THE BEST
COVERAGE TO BE ACROSS THE SAINT LAWRENCE VALLEY MAINLY NORTH AND EAST
OF KART FROM MID AFTERNOON THROUGH MID EVENING WHERE DEEPER MOISTURE
AND INSTABILITY IS FOUND. A CONVERGENCE ZONE WILL ALSO SET UP VERY
CLOSE TO KIAG AND KBUF MARKING THE BOUNDARY BETWEEN THE STRONGER WSW
FLOW OFF LAKE ERIE AND THE WNW FLOW OFF THE NIAGARA PENINSULA. THIS
MAY ALLOW A FEW WIDELY SCATTERED THUNDERSTORMS TO DEVELOP FROM ABOUT
20Z-00Z NEAR KBUF AND KIAG. VFR WILL PREVAIL...BUT ANY OF THESE
STORMS MAY PRODUCE VERY BRIEF MVFR/IFR CONDITIONS.

ANY ISOLATED CONVECTION WILL END BY MID EVENING WITH THE LOSS OF
DAYTIME HEATING. THIS WILL LEAVE VFR TO PREVAIL OVERNIGHT WITH JUST
A FEW PATCHES OF VFR LEVEL STRATUS. THERE SHOULD BE ENOUGH WIND
TO PREVENT ANY RIVER VALLEY FOG LATE TONIGHT.

ON SUNDAY HIGH PRESSURE WILL REMAIN IN CONTROL FROM THE OHIO VALLEY
TO THE MID ATLANTIC. THIS SHOULD PROVIDE ENOUGH SUBSIDENCE TO
PREVENT ANY CONVECTION UNTIL A SYSTEM BEGINS TO APPROACH FROM THE
WEST SUNDAY EVENING. VFR WILL PREVAIL THROUGH THE DAY WITH JUST SCT
DIURNAL CUMULUS AND SOME MODEST INCREASE IN CIRRUS LEVEL CLOUDINESS.

OUTLOOK...
SUNDAY NIGHT...MAINLY VFR WITH SCATTERED SHOWERS AND THUNDERSTORMS
AND ASSOCIATED BRIEF/LOCAL MVFR/IFR CONDITIONS.
MONDAY...VFR TO OCCASIONALLY MVFR WITH SHOWERS AND STORMS LIKELY.
TUESDAY...MAINLY VFR WITH A CHANCE OF A FEW LIGHT SHOWERS.
WEDNESDAY AND THURSDAY...MAINLY VFR.

&&

.MARINE...
ANOTHER WEAK TROUGH AND RELATIVELY TIGHT SFC PRESSURE GRADIENT
WILL PRODUCE ANOTHER ROUND OF SMALL CRAFT ADVISORY CONDITIONS
TODAY ACROSS THE EASTERN ENDS OF BOTH LAKES ERIE AND ONTARIO.

THIS SAME BASIC PATTERN WILL CONTINUE THROUGH THE WEEKEND WITH
WINDS DROPPING OFF SOME TONIGHT AND EARLY SUNDAY BEFORE INCREASING
TO NEAR SMALL CRAFT ADVISORY CONDITIONS AGAIN ON BOTH LAKES LATER
SUNDAY. THE SMALL CRAFT ADVISORY CONDITIONS MAY LAST SUNDAY NIGHT
INTO MONDAY AS A STRONGER COLD FRONT CROSSES THE REGION.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LEZ040-
         041.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
         LEZ020.
         SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
         LOZ043>045.

&&

$$

SYNOPSIS...RSH
NEAR TERM...HITCHCOCK/RSH
SHORT TERM...JJR
LONG TERM...JJR
AVIATION...HITCHCOCK
MARINE...RSH


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