Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 041140
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
740 AM EDT TUE AUG 4 2015

.SYNOPSIS...
SOMEWHAT UNSETTLED WEATHER WILL BE FOUND ACROSS THE REGION
THROUGH THIS EVENING...IN ADVANCE OF A SECONDARY COLD FRONT THAT
WILL CROSS THE REGION TONIGHT. FOLLOWING THE PASSAGE OF THIS
SECOND COLD FRONT... SOME SCATTERED SHOWERS WILL LINGER ACROSS THE
NORTH COUNTRY THROUGH WEDNESDAY...OTHERWISE IT WILL TURN DRIER AND
COOLER FOR THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
DURING THE COURSE OF TODAY...THE AXIS OF THE MAIN UPPER LEVEL
TROUGH WILL SETTLE FROM THE WESTERN GREAT LAKES INTO SOUTHERN
ONTARIO...ALONG WITH A CORRESPONDING SECONDARY COLD FRONT.

EXPECT THIS MORNING TO BE MAINLY DRY...SAVE FOR SOME SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS FOUND IN THE VICINITY OF A
WEAK DIABATICALLY-INDUCED TROUGH DRAPED ACROSS LAKES ERIE AND
ONTARIO. AFTER THAT...DIURNAL HEATING OF OUR COOLER AIRMASS ALOFT
IN CONJUNCTION WITH THE APPROACHING SECONDARY FRONT/ATTENDANT
SHORTWAVE WILL LEAD TO THE DEVELOPMENT OF A ROUND OF SCATTERED TO
NUMEROUS SHOWERS AND POSSIBLE THUNDERSTORMS THIS AFTERNOON AND
EVENING. INITIALLY...THIS ACTIVITY SHOULD FIRST FIRE AWAY FROM
THE STABILIZING INFLUENCES OF THE LAKES AND ALONG A LAKE BREEZE
CONVERGENCE ZONE NORTH OF BUFFALO...BEFORE TURNING A BIT MORE
WIDESPREAD LATER ON THIS AFTERNOON AND THIS EVENING AS THE FRONT/
SHORTWAVE EASES INTO OUR REGION... AND AS THE STABILIZING EFFECTS
OF THE LAKES WANE WITH DIMINISHING HEATING. WHILE A SHOWER OR STORM
WILL BE POSSIBLE JUST ABOUT ANYWHERE THIS AFTERNOON AND EVENING...
THE GREATEST POTENTIAL FOR THESE WILL BE LOCATED FROM THE NIAGARA
FRONTIER EASTWARD ACROSS THE NORTHERN FINGER LAKES TO THE NORTH
COUNTRY...AS THESE AREAS WILL MORE DIRECTLY IMPACTED BY THE
AFOREMENTIONED SHORTWAVE. SOUTH OF THIS...PRECIP CHANCES WILL
GENERALLY EXHIBIT A GRADUAL DECREASE WITH INCREASING SOUTHWARD EXTENT.

WITH RESPECT TO TEMPERATURES...850 MB TEMPS WILL GENERALLY RANGE
FROM +9C NEAR THE SAINT LAWRENCE VALLEY TO +12/+13C NEAR THE
PENNSYLVANIA BORDER THIS AFTERNOON. IN CONJUNCTION WITH GOOD
DIURNAL HEATING/MIXING... THIS SHOULD TRANSLATE INTO DAYTIME HIGHS
REACHING THE MID TO UPPER 70S IN MOST LOCATIONS TODAY...THOUGH IT
WILL BE A LITTLE COOLER ACROSS THE HIGHER TERRAIN AND IMMEDIATELY
DOWNWIND OF THE LAKES.

TONIGHT...THE SECONDARY COLD FRONT WILL TRAVERSE OUR REGION IN
CONJUNCTION WITH THE MAIN UPPER LEVEL TROUGH AXIS. IN GENERAL...
ONGOING SCATTERED TO NUMEROUS SHOWERS AND STORMS OUT IN ADVANCE
OF THE FRONT AT THE START OF THE EVENING WILL TEND TO DIMINISH
OVER TIME WITH BOTH THE LOSS OF DAYTIME HEATING AND THE
INTRODUCTION OF DRIER AIR/SUBSIDENCE BEHIND THE BOUNDARY. THE ONE
EXCEPTION TO THIS WILL BE EAST OF LAKE ONTARIO... WHERE A WESTERLY
FLOW OF PROGRESSIVELY COOLER AIR CROSSING THE WARMER LAKE WATERS
WILL CONTINUE TO GENERATE SCATTERED TO NUMEROUS SHOWERS RIGHT
THROUGH THE NIGHT VIA A COMBINATION OF OROGRAPHIC AND LAKE EFFECT
PROCESSES...AS 850 MB TEMPS ACROSS THE LAKE WILL FALL TO BETWEEN
+7C AND +8C. AS FOR TEMPERATURES...EXPECT COMFORTABLE CONDITIONS
FOR SLEEPING WITH OVERNIGHT LOWS RANGING FROM THE LOWER TO MID 50S
ACROSS INTERIOR PORTIONS OF THE SOUTHERN TIER/NORTH COUNTRY TO
RIGHT AROUND 60 ALONG THE IMMEDIATE LAKESHORES. ACROSS THE
SOUTHERN TIER... THE NOCTURNAL COOLING MAY ALSO BE ENOUGH TO ALLOW
SOME PATCHY VALLEY FOG TO REDEVELOP LATER ON TONIGHT.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
A DEEP CYCLONIC FLOW OVER THE GREAT LAKES AT THE START OF THIS
PERIOD WILL SET THE STAGE FOR BELOW NORMAL TEMPERATURES INTO THE
UPCOMING WEEKEND...BUT WITH UPSTREAM H85 TEMPS GENERALLY ABV +5C
AND STRONG AUGUST INSOLATION TO MODIFY THE AIRMASS...THE STRETCH
OF COOL WEATHER WILL NOT BE ANYTHING TO GET EXCITED ABOUT. IN
FACT...OUR MERCURY WILL START TO CLIMB BACK TOWARDS NORMAL THIS
COMING WEEKEND. MORE ON THAT IN THE LONG TERM SECTION.

THE COMFORTABLY COOL AIR WILL BE ACCOMPANIED BY MAINLY RAIN FREE
CONDITIONS...WHICH IS NOT PARTICULARLY GOOD NEWS FOR REGIONAL
AGRICULTURALISTS THAT HAVE BEEN WITNESSING SIGNIFICANT DRYING
SINCE THE FOURTH OF JULY. THE ONLY AREA THAT IS EXPECTING RAINFALL
DURING THIS PERIOD WILL BE EAST OF LAKE ONTARIO...WHERE A
COMBINATION OF A LITTLE EARLY SEASON LAKE EFFECT AND A STRONG
SHORTWAVE COULD PRODUCE SOME WELCOMED SHOWERS. THIS IS WHERE WE
WILL START WITH THE DETAILS.

A PLETHORA OF SHORTWAVES CAN BE SEEN IN THIS MORNINGS WV IMAGERY
SPINNING AROUND THE AXIS OF AN ANOMALOUSLY DEEP CLOSED LOW OVER
EASTERN CANADA. ONE OF THESE BUNDLES OF ENERGY...CURRENTLY OVER
THE WESTERN SHORES OF JAMES BAY...WILL MAKE ITS WAY SOUTHWARDS TO
THE UPPER GREAT LAKES TONIGHT BEFORE CROSSING OUR FORECAST AREA ON
WEDNESDAY. A SOMEWHAT MOISTURE STARVED AIRMASS OVER THE LOWER
GREAT LAKES SHOULD KEEP THIS FEATURE FROM GENERATING ANY PCPN OVER
THE WRN COUNTIES...BUT IT SHOULD ENHANCE A BLOSSOMING CU FIELD
(`SELF DESTRUCT SUN`) THAT WILL TAKE ADVANTAGE OF 10 DEG C/KM LOW
LEVEL LAPSE RATES. THE SAME WILL NOT BE TRUE EAST OF LAKE ONTARIO
THOUGH WHERE A DEEP CYCLONIC FLOW OF 8C H85 AIR SHOULD BE ABLE TO
ESTABLISH SOME LAKE EFFECT RAIN SHOWERS. DIURNAL MIXING WOULD
NORMALLY BREAK UP THE LAKE EFFECT DURING THE COURSE OF THE
DAY...BUT THE PASSAGE OF THE SHORTWAVE SHOULD ENCOURAGE THE SHOWER
ACTIVITY TO PERSIST WELL INTO THE AFTERNOON. AN UNSTABLE UPSLOPE
FLOW WILL HELP AS WELL. TEMPERATURES ON WEDNESDAY WILL BE SOME 5
TO 10 DEG F BELOW NORMAL VALUES...WITH MAX TEMPS GENERALLY
EXPECTED TO BE WITHIN A FEW DEGREES OF 70.

WHILE THERE MAY BE A COUPLE LEFTOVER LIGHT SHOWERS OVER THE
EASTERN LAKE ONTARIO WEDNESDAY EVENING...THE NIGHT SHOULD FEATURE
VERY COOL UNEVENTFUL WEATHER. COLLAPSING CU WITH THE LOSS OF
DIURNAL HEATING WILL LEAD TO MAINLY CLEAR STARLIT SKIES OVER THE
WESTERN COUNTIES AS RIDING AT ALL LEVELS WILL GRADUALLY BUILD TO
THE EAST ACROSS THE LOWER GREAT LAKES. TEMPERATURES WILL SETTLE
INTO THE LOW TO MID 50S FOR ALL BUT THE IMMEDIATE LAKE
SHORES....WITH FAIRLY WIDESPREAD 40S EXPECTED ACROSS THE SOUTHERN
TIER AND POSSIBLY IN THE FOOTHILLS OF THE ADIRONDACKS.

ON THURSDAY...AS DEAMPLIFICATION TAKES PLACE IN THE CHILLY MID
LEVEL FLOW...AN AXIS OF HIGH PRESSURE STRETCHING FROM HUDSON BAY
TO THE MID ATLANTIC STATES WILL CROSS OUR REGION. THIS WILL
SUPPORT A DRY PLEASANT DAY ACROSS OUR FORECAST AREA WITH H85 TEMPS
IN THE VCNTY OF 10C ALLOWING MAX TEMPS TO RECOVER SOMEWHAT INTO
THE MID 70S FOR MOST AREAS. FAIR WEATHER WILL PERSIST THROUGH
THURSDAY NIGHT AS THE SFC BASED RIDGING PUSHES TO OUR EAST...BUT
IT SHOULD NOT BE AS COOL AS SUBTLE WARM ADVECTION AHEAD OF AN
APPROACHING SHORTWAVE SHOULD KEEPS THE MERCURY A FEW DEGREES
HIGHER THAN THE PREVIOUS NIGHT.

A PAIR OF SHORTWAVES WITHIN A SOMEWHAT COMPLEX SPLIT UPPER LEVEL
FLOW WILL HAVE TO BE WATCHED ON FRIDAY. ONE SHORTWAVE IS FORECAST
TO CROSS THE MID ATLANTIC REGION AND JUST GRAZE OUR SOUTHERN TIER
IN THE PROCESS...WHILE A SECOND MID LEVEL DISTURBANCE IS EXPECTED
TO WEAKEN OVER THE UPPER GREAT LAKES. THIS SCENARIO WOULD PROBABLY
LEAD TO A FAIR AMOUNT OF CLOUDS OVER OUR SOUTHERN COUNTIES...BUT
DRY WEATHER WOULD STILL PREVAIL.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
A LOW AMPLITUDE FLOW WILL BE IN PLACE ALONG THE CANADIAN BORDER
DURING THIS PERIOD...WITH THE PREDOMINANT FEATURES BEING A STRONG
SUB-TROPICAL RIDGE CENTERED OVER TEXAS AND A BROAD TROUGH OVER
EASTERN CANADA. THIS PATTERN WILL RESULT IN NEAR NORMAL
TEMPERATURES OVER OUR FORECAST AREA...WHILE LITTLE IN THE WAY OF
RAINFALL IS EXPECTED.

ON SATURDAY...OUR REGION WILL BE SANDWICHED BETWEEN A STACKED...
ANOMALOUSLY DEEP STORM SYSTEM ALONG THE NEW JERSEY COAST AND A
FRESH SHORTWAVE OVER THE CANADIAN PRAIRIES. BETWEEN THE TWO WILL
BE A WEDGE OF HIGH PRESSURE THAT SHOULD KEEP OUR REGION
RAINFREE...WHILE TEMPERATURES WILL ONCE AGAIN CLIMB INTO THE LOW
TO MID 70S.

THE CANADIAN SHORTWAVE WILL TRACK EAST ACROSS THE UPPER GREAT
LAKES SATURDAY NIGHT WHILE THE MATURE COASTAL STORM WILL MAKE ITS
WAY NORTH ACROSS NEW ENGLAND. THE TWO SYSTEMS WILL PHASE OVER
QUEBEC SUNDAY AND SUNDAY NIGHT. THIS WILL ALLOW TROUGHINESS TO
DEVELOP OVER THE LOWER GREAT LAKES WITH OUR WEATHER BECOMING
SOMEWHAT UNSETTLED. WHILE SIGNIFICANT RAIN IS NOT EXPECTED AT THIS
POINT...HAVE REINTRODUCED SOME SHOWERS INTO THE PACKAGE.

A BROAD CYCLONIC FLOW OVER THE LOWER GREAT LAKES WILL THEN BE
CONDUCIVE FOR MORE SHOWERS ON MONDAY...WITH COVERAGE AND INTENSITY
REMAINING LESS THAN SIGNIFICANT.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
PATCHY IFR/MVFR FOG/LOW STRATUS ACROSS THE SOUTHERN TIER SHOULD
MIX OUT FAIRLY QUICKLY THROUGH MID MORNING WITH INCREASING DAYTIME
HEATING...LEAVING BEHIND GENERAL VFR CONDITIONS THROUGH LATE MORNING/
MIDDAY. AFTER THAT TIME...THE COMBINATION OF AN APPROACHING
SECONDARY COLD FRONT AND DIURNAL HEATING WILL LEAD TO INCREASING
CLOUD COVER AND THE DEVELOPMENT OF SCATTERED TO NUMEROUS SHOWERS
AND POSSIBLE THUNDERSTORMS THIS AFTERNOON AND EVENING...ANY OF
WHICH COULD PRODUCE RESTRICTIONS TO IFR/MVFR.

THE FRONT ITSELF WILL CROSS THE REGION TONIGHT...WITH DRYING AND
SUBSIDENCE IN ITS WAKE GENERALLY LEADING TO A RETURN TO DRIER
WEATHER/VFR CONDITIONS IN MOST LOCATIONS OVERNIGHT...THOUGH THE
SHOWERS/POSSIBLE ATTENDANT RESTRICTIONS WILL LIKELY LINGER THROUGH
THE NIGHT EAST OF LAKE ONTARIO OWING TO A COMBINATION OF UPSLOPE
FLOW AND INCREASING LAKE INFLUENCES. ADDITIONALLY...SOME PATCHY
VALLEY FOG MAY REDEVELOP WITHIN THE SOUTHERN TIER VALLEYS LATE...
AND COULD LEAD TO LOCALIZED REDUCTIONS TO IFR/MVFR.

OUTLOOK...
WEDNESDAY...SCATTERED SHOWERS/POSSIBLE MVFR ACROSS THE NORTH COUNTRY
AND SAINT LAWRENCE VALLEY...OTHERWISE VFR.
THURSDAY THROUGH MONDAY...VFR.

&&

.MARINE...
IN ADVANCE OF AN APPROACHING SECONDARY COLD FRONT...AN INCREASING
WEST-SOUTHWESTERLY FLOW ACROSS LAKE ERIE SHOULD ALLOW WINDS AND
WAVES TO REACH LOW-END ADVISORY CRITERIA FROM THIS AFTERNOON INTO
THIS EVENING...BEFORE IMPROVING CONDITIONS FOLLOW FOR THE BALANCE
OF THE NIGHT. FOR THIS REASON...A SMALL CRAFT ADVISORY HAS BEEN
ISSUED AS OUTLINED BELOW.

OTHERWISE...CONDITIONS ARE GENERALLY EXPECTED TO REMAIN BELOW
ADVISORY LEVELS THROUGH TONIGHT...THOUGH LOCALLY HIGHER WINDS AND
WAVES WILL BE POSSIBLE IN AND NEAR ANY THUNDERSTORMS THAT DEVELOP
IN ADVANCE OF/ALONG THE COLD FRONT THIS AFTERNOON AND EVENING.

IN THE WAKE OF THE SECONDARY COLD FRONT...AN INCOMING COOLER
AIRMASS WILL SET THE STAGE FOR POSSIBLE WATERSPOUTS ACROSS THE
LOWER LAKES FROM LATER TONIGHT INTO WEDNESDAY MORNING. THE BEST
POTENTIAL FOR THESE WILL BE FOUND ACROSS LAKE ONTARIO...WHERE THE
COMBINATION OF LAKE-850 MB DELTA-T VALUES OF 14C TO 15C AND AN
EXPECTED BAND OF LAKE-ENHANCED SHOWERS/LOW LEVEL CONVERGENCE
APPEARS ENOUGH TO JUSTIFY A CHANCE OF WATERSPOUTS IN THE FORECAST
FOR LATER TONIGHT AND WEDNESDAY MORNING.

MEANWHILE ACROSS LAKE ERIE...SOMEWHAT LOWER LAKE-850 MB DELTA-T
VALUES AND MORE LIMITED/SHORTER-DURATION SHOWER COVERAGE SHOULD
KEEP ANY WATERSPOUT POTENTIAL CONFINED TO THE SLIGHT CHANCE
RANGE...AND MAINLY LATER ON TONIGHT.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 11 PM EDT
         THIS EVENING FOR LEZ040-041.

&&

$$

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



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