Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 221050 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 650 AM EDT Sun Sep 22 2019 .SYNOPSIS... Surface high pressure that brought a beautiful stretch of weather the past few days will settle southward towards the Carolinas today. A deep southwest flow around this surface high will make today mid summer-like with afternoon temperatures well into the 80s and a bit of humidity. It will remain very warm tonight before a cold front eases its way across our region tomorrow, bringing widespread rain showers along with a stiff southwest breeze. && .NEAR TERM /THROUGH MONDAY/... Surface high pressure this morning is now settling to the Carolinas, while a low pressure near Hudson Bay is swinging a cold front across the Northern Plains. Around this broad surface high a southwest flow has brought a mild start to Sunday...with the flow also advecting moisture northward. This deepening moisture will eventually send PWATS to 1.75" or greater later today and through early Monday. This flow will also bring a southwest breeze to the lake plain today...with gusts northeast of Lake Erie up to around 30 mph. Today will be the pinnacle of this warm spell, with 850 hPa temperatures of +15 to +17C that coupled with this southwest flow will bring afternoon temperatures well into the 80s. These temperatures will still be several degrees below daily records which are: 89F at Buffalo (1965)...93F at Rochester (1895)...and 91F at Watertown (1965). The increase in moisture and heat today will begin to develop instability. MUCAPE values potentially to around 500-700 J/KG may bring a few spot showers along a weak warm thermal boundary...with showers to the southeast of Lake Ontario and into Lewis County later this afternoon. Otherwise the region will remain mostly dry today. A warm southwest wind will flow across our region tonight, keeping overnight lows well above average. The last few hours of summer will remain in the 70s...with astronomical fall officially starting at 3:50 AM Monday morning. The upstream cold front will slowly edge eastward tonight, with the front remaining to our west through the night. This will leave our region mainly dry tonight, with perhaps a few showers entering far WNY late. The cold front will swing across our region finally during the day Monday. Widespread showers are expected...with precipitation amounts outside thunderstorms generally a tenth or two of an inch or less. Though high moisture content and deep warm cloud layer the strong flow aloft (40 knot jet at 925 and 50 knots at 700 hPa) should keep any storms moving. Instability is not overly impressive with this system...with modest instability over the Genesee River and Finger Lakes perhaps bringing a few rumbles of thunder. It will also be breezy to across the Lake Plain...windy tomorrow. Steepening lapse rates in the lower levels will bring daytime mixing layer heights to this LLJ at 925 that coupled with the tightening pressure gradient with the cold front passage will yield gusts 30 to 40 mph mixing down to the surface. Clusters of rain showers will shift across the CWA through the morning and early afternoon hours. Behind the cold front...and the approach of the base of the upper level trough should begin to end showers from west to east...though westerly breezy winds continue. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... A cold front will exit to the east of the area on Monday night with a cyclonic flow and much colder air off the deck replacing it. Temperatures at 850 hPa drop toward +4 to +6C, which should be cool enough to get some lake response. Lake effect rain showers will develop east and southeast of the lakes Monday night and last into Tuesday. Showers will be most numerous and last the longest east of Lake Ontario which will be closest to a closed 500 mb low which will track across southern Quebec. Lingering lake effect clouds will keep temperatures on the cool side Tuesday, with highs in the 60s. Surface high pressure centered near Tennessee will ridge northward into the region on Tuesday night. This high will drift off the eastern seaboard Wednesday, but will continue to provide dry weather across the eastern Great Lakes. Following a chilly start, temperatures will rise quickly on Wednesday with highs in the 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... A cold front will cross the eastern Great Lakes very late Wednesday night and early Thursday, supporting a chance of a few showers and increased cloud cover. The showers will end from west to east later Thursday following the cold frontal passage. High pressure will then build into the Ohio Valley and eastern Great Lakes Thursday night and Friday, bringing a dry end to the week. Temperatures will briefly cool off Thursday and Thursday night behind the cold front, but will then quickly warm to above normal Friday and Saturday as a strong ridge builds back into the eastern United States. High temperatures may approach 80 again on Saturday due to a warm southerly return flow when the high moves off the mid-Atlantic coast. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... For the 12Z TAFS VFR flight conditions are widespread, with some cirrus passing across WNY. Today will feature VFR flight conditions as surface high pressure settles towards the Carolinas. A deep southwest flow will bring a breeze to the airports this afternoon...especially KIAG/KBUF that could have occasional gusts 25 to 30 knots. Tonight a cold front will slowly ease its way eastward. Ahead of this cold front a LLJ of 40 to 50 knots will bring some minimal LLWS to WNY. As surface winds increase tonight this LLWS will become less of a factor. Precipitation may hold off at all TAF sites until after 12Z Monday. Outlook... Monday...Areas of MVFR with showers likely. Tuesday...MVFR/VFR with scattered showers. Wednesday...VFR. Wednesday night and Thursday...Mainly VFR with a chance of showers. && .MARINE... A deep southwest flow will begin today between a surface high pressure settling towards the Carolinas and an approaching front/mid level trough. Winds on Lake Erie and the western end of Lake Ontario will near small craft thresholds this afternoon...but it will not be until tonight with the pressure gradient tightening with the approaching cold front that winds will begin to increase into SCA criteria. We will issue SCA for the Lakes and Niagara River with this package...with southwest winds peaking during the day Monday as the cold front passes...and then veering to the west Monday evening. This will maintain waves above 4 feet on Lake`s Erie and Ontario through the night...with conditions not relaxing until during the day Tuesday as winds and waves diminish. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory from 6 AM to 8 PM EDT Monday for LEZ020. Small Craft Advisory from 11 PM this evening to 11 AM EDT Tuesday for LEZ040-041. Small Craft Advisory from 6 AM to 8 PM EDT Monday for LOZ030. Small Craft Advisory from 8 AM Monday to 5 PM EDT Tuesday for LOZ043-044. Small Craft Advisory from 2 AM Monday to 11 AM EDT Tuesday for LOZ042. Small Craft Advisory from 5 AM Monday to 2 PM EDT Tuesday for LOZ045. && $$ SYNOPSIS...Thomas NEAR TERM...Thomas SHORT TERM...Apffel LONG TERM...Apffel/Hitchcock AVIATION...Thomas MARINE...Thomas

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