Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 201124
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
724 AM EDT MON APR 20 2015

.SYNOPSIS...
LOW PRESSURE OVER LOWER MICHIGAN WILL LIFT NORTHWARD INTO NORTHERN
ONTARIO PROVINCE TODAY AND TONIGHT. IN THE PROCESS...IT WILL FINISH
PUSHING ITS ASSOCIATED WARM FRONT ACROSS THE AREA THIS MORNING...
THEN WILL SWEEP ITS TRAILING COLD FRONT ACROSS THE REGION LATER THIS
AFTERNOON AND TONIGHT. PERIODS OF SHOWERS WILL ACCOMPANY THE PASSAGE
OF BOTH FRONTS...WITH THE COLD FRONT ALSO POTENTIALLY ACCOMPANIED BY
A FEW THUNDERSTORMS...SOME OF WHICH COULD PRODUCE GUSTY WINDS SOUTH
OF LAKE ONTARIO. IN THE WAKE OF THE COLD FRONT...MUCH COOLER AND
GENERALLY UNSETTLED WEATHER WILL THEN RETURN FOR THE REST OF THE
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
LOW PRESSURE OVER LOWER MICHIGAN WILL LIFT DUE NORTH INTO
NORTHERN ONTARIO PROVINCE TODAY AND TONIGHT. IN THE PROCESS...IT
WILL PUSH ITS ASSOCIATED WARM FRONT EASTWARD ACROSS THE AREA THIS
MORNING...BEFORE SWEEPING ITS TRAILING COLD FRONT ACROSS THE
REGION LATER THIS AFTERNOON AND TONIGHT.

EXPECT PERIODS OF SHOWERS TO PRECEDE AND ACCOMPANY THE PASSAGE OF
BOTH FRONTAL BOUNDARIES...WITH THE COLD FRONTAL PASSAGE ALSO
POTENTIALLY ACCOMPANIED BY A FEW THUNDERSTORMS GIVEN THE DEVELOPMENT
OF SOME WEAK TO MODEST DIURNAL INSTABILITY. IN BETWEEN THE TWO
FRONTS WILL BE A PERIOD OF MAINLY DRY WEATHER AND POSSIBLE PARTIAL
SUNSHINE TODAY...WITH ADDITIONAL MAINLY DRY WEATHER THEN EXPECTED TO
FOLLOW THE PASSAGE OF THE COLD FRONT TONIGHT.

LOOKING A LITTLE MORE CLOSELY AT THE FORECAST DETAILS...REGIONAL
RADARS STILL SHOW OCCASIONAL SHOWERS DRAPED ACROSS MUCH OF THE AREA
OUT AHEAD OF THE WARM FRONT...WITH THE BACK EDGE OF THESE WORKING
ACROSS FAR SOUTHWESTERN NEW YORK...WHERE THE DIMINISHING TREND IS
BEING AIDED BY A STRONG DRYING SOUTHEASTERLY DOWNSLOPE FLOW. THIS
DOWNSLOPE FLOW IS ALSO STILL PRODUCING SOME NEAR-ADVISORY TO
ADVISORY-LEVEL WIND GUSTS ALONG THE LAKE ERIE SHORELINE SOUTHWEST OF
BUFFALO...FOR WHICH A WIND ADVISORY REMAINS IN EFFECT UNTIL 11 AM
THIS MORNING.

THROUGH THE COURSE OF THE MORNING AND EARLY AFTERNOON HOURS...THE
FIRST ROUND OF SHOWERS WILL CONTINUE TO LIFT NORTHEASTWARD AND
DIMINISH AS THE WARM FRONT PASSES ACROSS OUR REGION FROM WEST TO
EAST...WITH STRONG DRYING ALOFT AND SUBSIDENCE IN ITS WAKE THEN
LEADING TO A SUBSEQUENT 6-HOUR LONG OR SO PERIOD OF MAINLY DRY
WEATHER AT ANY GIVEN LOCATION...ALONG WITH THE DEVELOPMENT OF SOME
PARTIAL SUNSHINE.

WITH RESPECT TO THE WINDS...THE STRONGEST WINDS ACROSS OUR REGION
WILL COME BETWEEN NOW AND MID TO LATE THIS MORNING AS THE CORE OF A
70-80 KT SOUTHEASTERLY LOW LEVEL JET PASSES THROUGH ALOFT...BEFORE
DIMINISHING SOME IN THE WAKE OF THIS FEATURE LATER THIS MORNING AND
THIS AFTERNOON. OUTSIDE OF THE WESTERN SOUTHERN TIER...THE WINDS
SHOULD END UP IN THE BREEZY TO WINDY RANGE BUT SHOULD GENERALLY
REMAIN BELOW ADVISORY LEVELS...WITH THE TYPICALLY FAVORED REGIONS OF
DOWNSLOPE FLOW OFF THE TUG HILL AND FUNNELING DOWN THE BLACK RIVER
VALLEY SEEING THE STRONGEST OVERALL /BUT LIKELY SUB-ADVISORY/ WIND
GUSTS.

COUPLED WITH 850 MB TEMPS REACHING TO AROUND +10C AND THE
AFOREMENTIONED DRYING TREND/BREAKS OF SUNSHINE...THE SOUTHEASTERLY
TO SOUTHERLY DOWNSLOPE FLOW SHOULD HELP BOOST HIGH TEMPS INTO THE
LOWER TO MID 70S ACROSS THE LAKE PLAINS AND MANY OF THE LOWER
ELEVATIONS FROM THE WESTERN FINGER LAKES WESTWARD TODAY...WITH
SLIGHTLY COOLER READINGS IN THE MID TO UPPER 60S FOUND ACROSS THE
SOUTHERN TIER. EAST OF THIS...HIGH TEMPERATURES SHOULD BE
PROGRESSIVELY LOWER THANKS TO THE LATER PASSAGE OF THE WARM FRONT
AND THE ENDING OF ITS ASSOCIATED SHOWERS...RANGING FROM THE MID AND
UPPER 60S ACROSS THE EASTERN FINGER LAKES TO THE MID AND UPPER 50S
ACROSS INTERIOR PORTIONS OF THE NORTH COUNTRY.

WHEN COUPLED WITH CONTINUED WARM ADVECTION ALOFT...THE DIURNAL
WARMING OF THE BOUNDARY LAYER SHOULD ALSO RESULT IN THE DEVELOPMENT
OF ENOUGH INSTABILITY THIS AFTERNOON AND EVENING TO WARRANT A CHANCE
OF THUNDERSTORMS AS THE COLD FRONT SWEEPS ACROSS THE REGION. WHILE
THUNDER WILL BE POSSIBLE PRETTY MUCH AREAWIDE...THE BEST CHANCES FOR
THIS WILL BE FOUND SOUTH OF LAKE ONTARIO WHERE SOME WEAK TO MODEST
SURFACE-BASED INSTABILITY WILL BE IN PLACE. COUPLED WITH SUFFICIENT
DEEP-LAYER SHEAR THAT SHOULD ALSO BE IN PLACE...THIS COULD ALLOW A
FEW STORMS IN THIS LATTER REGION TO GET A LITTLE BETTER ORGANIZED
AND ULTIMATELY PRODUCE SOME STRONGER WIND GUSTS LATER THIS AFTERNOON
AND THIS EVENING...THOUGH AT THIS POINT THE CURRENT LEVEL OF
PROJECTED INSTABILITY STILL APPEARS TO BE TOO LOW TO SUPPORT A
NOTEWORTHY SEVERE WEATHER THREAT.

THE COLD FRONT ITSELF SHOULD PUSH ACROSS THE REGION BETWEEN LATE
THIS AFTERNOON AND THE EARLY OVERNIGHT HOURS OF TONIGHT...WITH THE
BULK OF ANY OF ITS ATTENDANT SHOWER AND THUNDERSTORM ACTIVITY COMING
DURING THIS TIME FRAME. FOLLOWING THE FROPA...GENERALLY DRY WEATHER
SHOULD RETURN FROM WEST TO EAST... WHILE DEVELOPING COLD AIR
ADVECTION SENDS TEMPERATURES MOSTLY BACK DOWN INTO THE 40S BY
SUNRISE ON TUESDAY MORNING.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
A HIGH AMPLITUDE BLOCKING PATTERN WILL BE IN PLACE ACROSS NORTH
AMERICA DURING THE BULK OF THIS PERIOD. THIS REGIME WILL BE ANCHORED
BY A PATTERN INDUCING OMEGA BLOCK OVER THE CANADIAN ROCKIES WHILE AN
ANOMALOUSLY DEEP CLOSED LOW WILL BE FOUND OVER THE GREAT LAKES. THIS
WILL SET THE STAGE FOR INCREASINGLY CHILLY AND UNSETTLED WEATHER
OVER OUR REGION...BUT WHILE THERE WILL BE DAILY SHOWERS TO CONTEND
WITH...THE MAJORITY OF THE TIME WILL ACTUALLY BE PCPN FREE. NOTE
THAT THE TERM `PCPN` IS USED RATHER THAN RAIN. MORE ON THIS IN A
MOMENT. IN ANY CASE...THE SHOWERS THAT WE DO RECEIVE WILL LARGELY BE
GENERATED BY SUBTLE SHORTWAVES ROTATING AROUND THE BASE OF THE
NEARLY STATIONARY GREAT LAKES UPPER LOW...WITH A LITTLE ASSISTANCE
GIVEN BY DIURNAL HEATING/INSTABILITY. AS FOR THE DETAILS...

THE LARGE UPPER LOW WILL BE CENTERED OVER LAKE SUPERIOR AS WE OPEN
THIS PERIOD ON TUESDAY...WHILE A DEEP CYCLONIC FLOW WILL BE FOUND
DOWNSTREAM OVER OUR REGION. AT THE SFC...WEAK RIDGING OVER OUR
FORECAST AREA IN THE MORNING WILL FLATTEN OUT AND PUSH EAST DURING
THE COURSE OF THE DAY. AS WE LOSE THE SFC BASED RIDGING...A 100KT H3
JET WILL RACE ACROSS THE UPPER OHIO VALLEY DURING THE AFTERNOON AND
EVENING. THIS WILL PLACE WESTERN NEW YORK UNDER THE INFLUENCE OF THE
JET ENTRANCE REGION...WHICH WHEN COMBINED WITH A LITTLE DIURNAL
INSTABILITY...SHOULD GENERATE A PERIOD OF SHOWERS OVER OUR REGION.
AGAIN...THIS SHOULD COME AFTER GENERALLY RAIN FREE CONDITIONS FOR
MUCH OF THE DAY. ITS ALSO WORTH NOTING THAT A CHILLY SOUTHWEST FLOW
OFF LAKE ERIE WILL NEGATE ANY DIURNAL INSTABILITY OVER THE IAG
FRONTIER AND THUS GREATLY LESSEN THE POTENTIAL FOR SHOWERS.
OTHERWISE...IT WILL BE NOTABLY COOLER ON TUESDAY AS TEMPERATURES
OVER THE WESTERN COUNTIES WILL BE AS MUCH AS DEGREES LOWER THAN
THOSE FROM MONDAY.

AN ILL DEFINED SHORTWAVE ROTATING THROUGH THE MEAN UPPER LEVEL
TROUGH COULD TOUCH OFF A FEW NUISANCE SHOWERS TUESDAY NIGHT...BUT
AGAIN THE BULK OF THE TIME SHOULD BE RAIN FREE. IT WILL BE QUITE
COOL WITH TEMPERATURES TUESDAY NIGHT FALLING OFF INTO THE 30S.

ON WEDNESDAY...THE UPPER LOW WILL SLOWLY SPIN EAST AND BECOME
CENTERED IN THE VCNTY OF THE SOO...WHILE THE VARIOUS GUIDANCE
PACKAGES ARE IN ROUGH AGREEMENT THAT A PRONOUNCED SFC TROUGH WILL
PASS OVER OUR REGION. THE ADDITION OF THE LOW LEVEL FORCING WILL
COME AT A TIME WHEN DEEPENING CHILLY AIR OVER THE LOWER GREAT LAKES
WILL LEAD TO INCREASINGLY UNSTABLE CONDITIONS. LAPSE RATES OF 7 TO 9
DEG/C KM UP THROUGH H7 ARE EXPECTED OVER OUR FORECAST AREA...SO
WEDNESDAY SHOULD BE MORE UNSETTLED WITH MORE FREQUENT/WIDESPREAD
SHOWER ACTIVITY. WILL CARRY HIGH CHC TO LIKELY POPS. GIVEN H85 TEMPS
OF -2 TO -4C...IT WILL BE RATHER RAW ON WEDNESDAY WITH MAX TEMPS
RANGING FROM THE MID AND UPPER 40S IN THE WEST TO THE LOWER 50 EAST
OF THE GENESEE VALLEY. IN FACT...THERE WILL PROBABLY BE SOME WET
SNOW MIXING AT TIMES WITH THE SHOWERS OVER THE HIGHER TERRAIN OF THE
SRN TIER. THIS WILL ADDED TO THE GRIDS FOR ELEVATIONS OVER 1500 FEET.

AS THE CORE OF THE CLOSED LOW SETTLES SOUTH OVER EXTREME SOUTHERN
ONTARIO WEDNESDAY NIGHT...H85 TEMPS ARE EXPECTED TO DROP ARND -8C.
THIS SHOULD ALLOW ANY RAIN SHOWERS TO MIX AND EVENTUALLY CHANGE OVER
TO SOME WET SNOW SHOWERS. SINCE THE QPF WILL BE UNDER A TENTH OF AN
INCH...ACCUMULATIONS (OTHER THAN ON CARS, ETC) ARE NOT EXPECTED.
OVERNIGHT LOWS SHOULD BE WITHIN A FEW DEGREES OF FREEZING.

THE DEEP CLOSED LOW WILL FINALLY START TO FILL ON THURSDAY AS THE
CENTER OF THIS ANOMALOUS FEATURE IS FORECAST TO PASS BY JUST TO THE
NORTH OF LAKE ONTARIO. THIS MAY MAKE THIS THE CHILLIEST DAY OF THE
FORECAST PACKAGE AS H85 TEMPS WILL BE IN THE VCNTY OF -6 TO -8C.
AGAIN...WHILE THERE WILL NOT BE MUCH PCPN TO DEAL WITH...WHAT WE DO
RECEIVE WILL BE A MIX OF RAIN AND WET SNOW SHOWERS. MAX TEMPS ON
THURSDAY WILL BE MORE THAN 10 DEG F BELOW NORMAL VALUES AS THEY WILL
RANGE FROM THE LOW TO MID 40S.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
WHILE THE UPPER LEVEL FLOW WILL NOT BE AS AMPLIFIED AS DURING THE
DAYS LEADING INTO THIS PERIOD...A CLOSED LOW SPIRALING TO THE EAST
ACROSS NEW ENGLAND AND THE CANADIAN MARITIMES WILL KEEP TEMPERATURES
BELOW NORMAL ACROSS OUR FORECAST AREA. THERE WILL ALSO BE A
CONTINUED LOW CHANCE FOR SOME MIXED RAIN OR WET SNOW SHOWERS...
MAINLY OVER THE EASTERN LAKE ONTARIO REGION IN THE PROXIMITY OF
SUBTLE SHORTWAVES ROTATING AROUND THE CLOSED MID LEVEL CIRCULATION.
THE VAST MAJORITY OF THIS TIME PERIOD THOUGH WILL BE PCPN FREE.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
LOW PRESSURE OVER LOWER MICHIGAN WILL LIFT DUE NORTH INTO NORTHERN
ONTARIO PROVINCE THROUGH TONIGHT. IN THE PROCESS...IT WILL PUSH
ITS ASSOCIATED WARM FRONT EASTWARD ACROSS THE AREA THIS
MORNING...BEFORE SWEEPING ITS TRAILING COLD FRONT ACROSS THE
REGION LATER THIS AFTERNOON AND TONIGHT.

EXPECT PERIODS OF SHOWERS TO PRECEDE AND ACCOMPANY THE PASSAGE OF
BOTH FRONTAL BOUNDARIES...WITH THE COLD FRONTAL PASSAGE ALSO
POTENTIALLY ACCOMPANIED BY A FEW THUNDERSTORMS...SOME OF WHICH COULD
PRODUCE SOME LOCALLY GUSTY WINDS SOUTH OF LAKE ONTARIO. IN BETWEEN
THE TWO FRONTS WILL BE A PERIOD OF MAINLY DRY WEATHER TODAY...WITH
ADDITIONAL MAINLY DRY WEATHER THEN FOLLOWING THE PASSAGE OF THE COLD
FRONT TONIGHT.

IN TERMS OF FLIGHT CONDITIONS...EXPECT THESE TO REMAIN PREDOMINANTLY
VFR THROUGH MUCH OF TODAY...SAVE FOR SOME AREAS OF MVFR ACROSS THE
SOUTHERN TIER THROUGH EARLY TO MID THIS MORNING. THE COLD FRONT WILL
THEN BRING A PERIOD OF POSSIBLE MVFR AS IT PASSES THROUGH THE REGION
LATER THIS AFTERNOON AND TONIGHT...FOLLOWED BY A RETURN TO MORE
GENERAL VFR CONDITIONS IN ITS WAKE.

A STRONG LOW LEVEL JET PASSING OVERHEAD THROUGH THIS MORNING WILL
ALSO PRODUCE GUSTY WINDS ACROSS THE HIGHER TERRAIN OF THE SOUTHERN
TIER AND ALSO ALONG THE LAKESHORE REGION OF CHAUTAUQUA AND SOUTHERN
ERIE COUNTIES...WHERE SURFACE WINDS COULD GUST TO AS HIGH AS 40-45
KNOTS AT TIMES.

OUTLOOK...
TUESDAY THROUGH FRIDAY...VFR/MVFR WITH SCATTERED RAIN SHOWERS...
WHICH MAY BE MIXED WITH SNOW SHOWERS AT NIGHT.

&&

.MARINE...
LOW PRESSURE OVER LOWER MICHIGAN WILL LIFT NORTHWARD INTO NORTHERN
ONTARIO PROVINCE TODAY AND TONIGHT. IN THE PROCESS...IT WILL FINISH
PUSHING ITS ASSOCIATED WARM FRONT ACROSS THE AREA THIS MORNING...
THEN WILL SWEEP ITS TRAILING COLD FRONT ACROSS THE REGION LATER THIS
AFTERNOON AND TONIGHT. BRISK SOUTHEASTERLIES/SOUTHERLIES TO AS HIGH
AS 30 KNOTS OUT AHEAD OF THE WARM FRONT WILL GRADUALLY DIMINISH FROM
WEST TO EAST TODAY...BEFORE VEERING TO SOUTHWESTERLY FOLLOWING THE
PASSAGE OF THE COLD FRONT TONIGHT.

AT PRESENT...SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR MOST OF OUR
NEARSHORE ZONES TO COVER THE INITIAL ROUND OF BRISK SOUTHERLIES/
SOUTHEASTERLIES TODAY. WHILE IT IS ALSO POSSIBLE THAT THE
SOUTHWESTERLY WINDS BEHIND THE COLD FRONT MAY EVENTUALLY NECESSITATE
AN ADDITIONAL ROUND OF SMALL CRAFT ADVISORIES FOR PORTIONS OF
TONIGHT AND TUESDAY...AT THIS TIME THESE APPEAR TO BE TOO MARGINAL
FOR THE ISSUANCE OF ANY SUCH ADDITIONAL FLAGS.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...WIND ADVISORY UNTIL 11 AM EDT THIS MORNING FOR NYZ012-019>021-
     085.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR LEZ020-
         040-041.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
         LOZ042-043.
         SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
         LOZ044-045.

&&

$$

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







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