Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 070812
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
412 AM EDT TUE JUL 7 2015

.SYNOPSIS...
A VERY WARM AND MUGGY AIRMASS WILL REMAIN IN PLACE
TODAY...UNTIL A COLD FRONT WITH SHOWERS AND THUNDERSTORMS PASSES
ACROSS THE REGION LATE AFTERNOON AND EVENING. SOME OF THESE STORMS
COULD BECOME STRONG TO SEVERE WITH TORRENTIAL DOWNPOURS AND GUSTY
WINDS. BEHIND THE COLD FRONT...WEDNESDAY WILL DRY OUT WITH A RETURN
TO SUNSHINE THROUGH THE DAY AND NOTICEABLY COOLER DEWPOINTS.

&&

.NEAR TERM /THROUGH TONIGHT/...
ALOFT THIS MORNING A WEAK UPPER LEVEL
LOW IS FOUND OVER THE VICINITY OF THE WESTERN MID ATLANTIC
STATES...WITH A RIDGE OF HIGH PRESSURE OVER NEW ENGLAND AND THE
WESTERN ATLANTIC WATERS. TO OUR WEST OVER THE WESTERN GREAT LAKES A
SHORTWAVE TROUGH OF LOW PRESSURE IS FOUND. A COLD FRONT IS DRAPED
ACROSS THE CENTRAL GREAT LAKES REGION AND DOWN ACROSS THE CENTRAL
MISSISSIPPI VALLEY.

FOR THIS MORNING A FEW SHOWERS OVER CENTRAL PENNSYLVANIA WILL DRIFT
NORTHWARD ACROSS THE FINGER LAKES REGION AND EASTERN LAKE ONTARIO
REGION. THIS ACTIVITY FORMING AHEAD OF THE WEAK UPPER LEVEL
LOW...AND WEAK SURFACE CONVERGENCE WILL CONTINUE A LOW CHANCE
PROBABILITY FOR A SHOWER THROUGH THE MORNING HOURS TO OUR EAST.
ACROSS AREAS WEST OF THE GENESEE VALLEY THE MORNING HOURS SHOULD
LARGELY REMAIN DRY.

A SOUTHWEST WIND WILL DEVELOP TODAY AHEAD OF THE COLD FRONT TO OUR
WEST. WITH THE WIND DIRECTION TODAY OFF LAKE ERIE/ONTARIO...AREAS
ALONG THE SHORELINE AND METRO BUFFALO/WATERTOWN WILL BE SLIGHTLY
COOLER THAN YESTERDAY AS LAKE BREEZE CIRCULATIONS DEVELOP...WHILE
AREAS ACROSS THE GENESEE VALLEY AND FINGER LAKES REGION MAY BE A FEW
DEGREES WARMER WITH A DOWNSLOPE FLOW INTO THE VALLEYS. THIS
DOWNSLOPE FLOW MAY EVEN BRING A FEW LOWER 90S TO THE GENESEE VALLEY.
IN GENERAL HIGHS THIS AFTERNOON SHOULD REACH INTO THE 80S...COOLER
NEAR LAKE SHORELINES AND THE HILLS OF SW NYS.

THIS HEAT AHEAD OF THE COLD FRONT WILL RAPIDLY DESTABILIZE THE
ATMOSPHERE TODAY. SBCAPE VALUES WILL RISE TO 1000 TO 2000 J/KG WHICH
SHOULD BE ENOUGH TO OVERCOME THE WEAK LAPSE RATES ALOFT. THE LAPSE
RATES WILL BE POOR AS THE MID LEVEL SHORTWAVE OVER THE WESTERN GREAT
LAKES REGION WILL REMAIN WELL TO OUR NORTH THROUGH THE DAY AND
EVENING HOURS. THE GREATEST LAPSE RATES WILL ACTUALLY BE FOUND
ACROSS OUR EASTERN REGIONS...AND MORNING SHOWERS COULD QUICKLY TURN
TO THUNDERSTORMS BY LATE MORNING.

WIND FIELDS AHEAD OF THE COLD FRONT WILL REMAIN MODERATE...WITH A
LLJ CORE OF 35 TO 40 KNOTS AT 850 HPA OVER THE REGION. LIFT ALONG
THE COLD FRONT ALONG WITH DEEPER SYNOPTIC LIFT WITHIN THE RIGHT
ENTRANCE REGION TO A 110 KNOT 250 HPA JET OVER WESTERN QUEBEC
COUPLED WITH LARGE AFTERNOON SBCAPE VALUES SHOULD BE ENOUGH TO
GENERATE A LINE OF SHOWERS AND THUNDERSTORMS OVER OUR REGION. A FEW
PULSE STORMS INITIALLY ALONG LAKE BREEZE BOUNDARIES...AND BOWING LINE
SEGMENTS AHEAD OF THE COLD FRONT WILL REMAIN POSSIBLE THIS AFTERNOON
AND EVENING. IN ADDITION A SUFFICIENT LAYER OF DRY AIR NEAR 700 HPA
SHOULD ALLOW FOR EVAPORATIVE COOLING FUELING A DOWNBURST POTENTIAL
WITHIN PULSE STORMS. WET BULB ZERO HEIGHTS WILL AVERAGE AROUND 10K
FEET AND CAPE VALUES ALOFT MAY INCREASE ENOUGH SUCH THAT SOME SMALL
HAIL WILL FORM WITHIN THE PULSE STORMS.

ALSO OF NOTE PWAT VALUES NEARING 2.00 INCHES AND A DEEP WARM CLOUD
LAYER MAY YIELD HEAVY RAINFALL FROM WITHIN THE STORMS. WILL CONTINUE
TO MENTION BOTH HEAVY RAIN AND GUSTY WINDS WITH THE THUNDERSTORMS
TODAY AND THIS EVENING.

SO IN SUMMARY...A FEW MORNING SHOWERS AND THUNDERSTORMS ACROSS OUR
EASTERN SECTIONS WILL LIFT NORTHEASTWARD THROUGH THE DAY...WITH A
FEW AFTERNOON PULSE SHOWERS AND THUNDERSTORMS FORMING ACROSS WESTERN
NEW YORK ON LAKE BREEZE BOUNDARIES. THEN LATE AFTERNOON AND EVENING
A COLD FRONT WILL PASS ACROSS THE REGION WITH WIDESPREAD SHOWERS AND
THUNDERSTORMS.

BEHIND THE COLD FRONT A FEW PATCHES OF FOG ARE POSSIBLE AS FALLING
TEMPERATURES WILL COOL TO NEAR THE DEWPOINTS. EXPECT CLOUDS TO
REMAIN ABUNDANT OVERNIGHT WITH LOWS DROPPING BACK TO THE LOW TO MID
60S.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
PROGRESSIVE POST-FRONTAL DRYING WILL OCCUR WEDNESDAY FROM NORTHWEST
TO SOUTHEAST. THIS WILL RESULT IN A PERIOD OF DRY AND STABLE
CONDITIONS WEDNESDAY AND WEDNESDAY EVENING AS HIGH PRESSURE BUILDS
ACROSS THE REGION. HIGHS WEDNESDAY OF LOWER TO MID 70S WITH
NOTICEABLY LOWER HUMIDITY COMPARED TO TODAY.

MID LEVEL FLOW TRANSITIONS TO LOWER AMPLITUDE SOUTHWESTERLIES
IMMEDIATELY UPSTREAM OF EXPANDING SUBTROPICAL RIDGING TAKING HOLD
OVER THE SOUTHEAST CONUS. THIS EVOLUTION WILL POTENTIALLY RESULT IN
A PERIODICALLY ACTIVE PERIOD THROUGH THE LATTER HALF OF THE SHORT
TERM PERIOD. THIS PROCESS WILL INITIATE LATE WEDNESDAY NIGHT AND
THURSDAY AS A LEAD WAVE EJECTS OUT OF THE GROWING UPPER HEIGHT FIELD
ACROSS THE SOUTHERN CONUS. RESPECTABLE SURFACE WAVE APPEARS TO
EMERGE WITH THIS FEATURE...RESULTING IN A COMPACT BUT STRONG
CORRIDOR OF FORCING AND ACCOMPANYING MOISTURE TRANSPORT THAT SHIFTS
INTO THE OHIO VALLEY/GREAT LAKES DURING THIS TIME. EXACT TIMING AND
POSITIONING REMAINS SOMEWHAT ILL-DEFINED YET...POTENTIAL EXISTS FOR
AT LEAST SOUTHERN PORTIONS OF WESTERN NEW YORK TO GET INTO THE
EVENTUAL PRECIPITATION SWATH. THIS CONTINUES TO WARRANT A BROADER
AND MORE CONSERVATIVE DISTRIBUTION OF PRECIPITATION CHANCES AT THIS
STAGE WITH STILL A GOOD DEAL OF MODEL SPREAD REMAINING. THE
EXTENSIVE HIGHER CLOUD COVER AND NORTHERLY LOW LEVEL GRADIENT WILL
CAP HIGHS IN THE 70S THURSDAY...REGARDLESS OF PRECIPITATION
TIMING/COVERAGE.

THURSDAY NIGHT THIS SURFACE WAVE WILL EXIT INTO NEW ENGLAND WITH
RAIN CHANCES DIMINISHING FROM WEST TO EAST.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
FRIDAY AND SATURDAY A BUBBLE OF HIGH PRESSURE WILL STALL IN PLACE
OVER THE LOWER LAKES AND NEW ENGLAND WHILE A STALLED FRONTAL ZONE
REMAINS TO THE WEST ACROSS THE LOWER OHIO VALLEY AND WESTERN LAKES.
THIS SHOULD BRING DRY WEATHER BOTH DAYS WITH TEMPERATURES SLOWLY
WARMING BACK TO JUST ABOUT AVERAGE AFTER A FEW COOLER DAYS MIDWEEK.
THIS WILL TRANSLATE INTO HIGHS IN THE LOWER 80S ACROSS LOWER
ELEVATIONS.

SUNDAY INTO EARLY NEXT WEEK A MID LEVEL TROUGH WILL MOVE FROM THE
UPPER MIDWEST INTO THE WESTERN LAKES. THIS WILL FORCE INCREASING
MOISTURE AND INSTABILITY BACK INTO OUR REGION...WITH LARGE SCALE
FORCING INCREASING BY MONDAY AS THE MID LEVEL WAVE AND WEAK SURFACE
REFLECTION MOVE TOWARDS THE LOWER LAKES. THIS WILL BRING A CHANCE OF
SHOWERS AND STORMS AGAIN FROM LATER SUNDAY THROUGH MONDAY.
TEMPERATURES WILL REMAIN WARM SUNDAY AND MONDAY AS LONG AS SHOWERS
DONT BECOME TOO WIDESPREAD...WITH HIGHS IN THE LOWER 80S BOTH DAYS.
HUMIDITY WILL BE ON THE INCREASE AS WELL.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
AT 06Z VFR/MVFR FLIGHT
CONDITIONS WERE FOUND ACROSS THE REGION. THROUGH 12-14Z THE BIG
CONCERN WILL BE FOG AND LOWER VSBYS. EXPECT SOME PATCHES OF IFR
FLIGHT CONDITIONS TO DEVELOP ACROSS THE SOUTHERN TIER...WHILE MVFR
CONDITIONS WILL BE POSSIBLE EAST OF LAKE ONTARIO...AND ACROSS KBUF
AIRFIELD WHERE THE GROUND IN MOIST FROM RECENT RAINFALL.

THROUGH THE MID MORNING TO MID AFTERNOON HOURS EXPECT VFR FLIGHT
CONDITIONS TO BE PREDOMINATE. A FEW DIURNALLY DRIVEN SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE ACROSS THE GENESEE VALLEY/FINGER
LAKES REGION WITH ACTIVITY DRIFTING NORTHEASTWARD.

THE SECOND CONCERN THIS TAF PERIOD WILL BE A CONVECTIVE LINE OF
SHOWERS AND GUSTY THUNDERSTORMS PASSING ACROSS THE TAF SITES. A COLD
FRONT WILL DEVELOP A LINE OF STORMS...WITH ACTIVITY NEARING FAR WNY
AROUND 00Z...AND THEN PUSHING EASTWARD ACROSS THE TAF SITES BETWEEN
00Z AND 06Z. EXPECT A THUNDERSTORM THIS EVENING WITH PERHAPS A
STRONG GUST OF WIND...TO BE FOLLOWED BY TRAILING SHOWERS AND AREAS
OF LOW FOG DEVELOPING WHERE RAIN HAS FALLEN. SOME MVFR/IFR VSBYS
WILL BE LIKELY FOR A FEW HOURS BEHIND THE COLD FRONT BEFORE DRIER
AIR ARRIVES TOWARDS DAYBREAK...ALLOWING FOR IMPROVING FLIGHT
CONDITIONS.

OUTLOOK...
WEDNESDAY...VFR. THURSDAY...MAINLY VFR WITH A CHANCE
OF SHOWERS AND THUNDERSTORMS. FRIDAY AND SATURDAY...VFR.

&&

.MARINE...
ON THE LAKE WATERS SOUTHWESTERLY WINDS WILL FRESHEN TO
AROUND 15KTS TODAY AHEAD OF THE COLD FRONT...HOWEVER CONDITIONS
SHOULD REMAIN BELOW SMALL CRAFT LEVELS ON TUESDAY.

THE COLD FRONT WILL CROSS THE LAKES TUESDAY EVENING...POTENTIALLY
GENERATING A SQUALL LINE WITH A SHORT PERIOD OF STRONGER WINDS AS IT
CROSSES THE LAKES. WINDS WILL QUICKLY SLACKEN BEHIND THE FRONT AS
WEAK HIGH PRESSURE MOVES ACROSS THE REGION AND LINGERS THROUGH THE
REST OF THE WEEK.

&&

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

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...THOMAS
SHORT TERM...TMA
LONG TERM...HITCHCOCK
AVIATION...THOMAS
MARINE...THOMAS



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