Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 270243 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1043 PM EDT Mon Jun 26 2017 .SYNOPSIS... Unseasonably cool temperatures with showers and thunderstorms will continue through Tuesday. The upper level disturbances responsible for the cool and unsettled weather will move east Wednesday with a return to warmer temperatures by mid-week. && .NEAR TERM /THROUGH TUESDAY/... While much of the convection from earlier this evening has weakened or dissipated...the environment is still very unstable. The 00z KBUF sounding depicted over 1400 j/kg of CAPE...and amounts will be in excess of 2000 j/kg over Lake Erie where the water temp is >70 deg. That being said...storms are trying to re fire on an outflow boundary that pushed through the BUF metro around 8 PM. This boundary extends southwest to Lake Erie and could serve to spark the lake induced convection that has been advertised for several days. This convection could become rather strong with areas of heavy rain likely. Fortunately...the expected band of lake effect rain should move from south to north during the overnight so that one area should not pick up excessive rainfall amounts. Lapse rates to cloud base will exceed 10 deg c/km and with no cap...we can expect plenty of thunder and lightning as convective cloud depths will be greater than 20k ft. Initially...a 240-250 flow will be in place. This will direct lake effect rain showers parts of Chautauqua COunty and especially the southern half of Erie county. During the course of the night...the lake effect activity should consolidate into a more organized plume that will push north across the northern half of Erie County...including the BUF Metro area. The rain will likely be heavy at times and should be accompanied by some thunder and lightning. Given the very efficient nature of lake induced pcpn (esp rain)...rainfall rates in excess of an inch an hour will be possible. Localized flooding will not be out of the question. Off Lake Ontario...the airmass will not be quite as unstable and will have less fetch to work with...so the lake effect rain showers are not expected to be as organized nor as heavy. Will keep chc pops in place for much of the Eastern Lake Ontario region...especially north of the Tug Hill. Outside of these lake effect areas...it will be partly to mostly cloudy and generally rainfree after 9 PM. Temperatures tonight will bottom out between the low-mid 50s on the lake plains to the mid and upper 40s across the Southern Tier and for sites est of the Tug Hill. On Tuesday...the lake effect rain will weaken and dissipate as the strong late June heating will break apart the lake driven convection. Nevertheless...scattered showers and thunderstorms can be expected as the core of the Lake Huron shortwave will pass directly across our region. H85 temps in the vcnty of 4c will once again establish very steep low level lapse rates...so any subtle boundaries will be able to focus convection that could support torrential downpours and small hail. Temperatures Tuesday afternoon will only make it into the 60s. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... Following the upper shortwave, lingering showers will dissipate off Lake Erie Tuesday Night while those off Lake Ontario will persist through the night, albeit weakening towards daybreak. It will be another cool night with lows generally dropping into the low 50s and interior valleys down into the upper 40s. Wednesday will begin to transition to a bit of a warmer pattern as high pressure moves across the Ohio Valley and a west to southwest flow develops across the region. Expect fair weather across much of the region with the exception of the north country where the lingering cyclonic flow aloft will keep more clouds and the risk of showers through midday. Temperatures, while somewhat milder reaching into the low 70s will still be below normal. On Thursday the first in a series of surface waves will bring the likelihood of showers and thunderstorms and the threat of locally heavy rain. Temperatures continue their slow upward trend with highs Thursday in the mid to upper 70s. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... A series of systems will affect the region from Thursday night through at least Saturday and possibly Sunday. As is often the case during the summer, rainy periods are not expected to last too long and there will be several-hour periods of dry weather, but not long enough to keep any particular day complete dry any part of WNY. Thus expect at least a chance of showers for each 12 hour period through Sunday. Thursday night...The first of a series of systems should move through on Thursday and drop a frontal system across the region during or by Thursday night. Thus have a likely chance of showers and possible thunderstorms in the forecast. Friday...The frontal system should continue into PA with weak ridging aloft. This should mean a lower threat for showers overall, but still non-zero. The lowest threat should near/N of Lake Ontario while areas toward the PA border will have a higher threat for measurable rain. Friday night and Saturday...The next system will move into the Great Lakes region and will drag the frontal band back north (warm front) across the region. This will be followed by another frontal system later on Saturday (cold front). Saturday night and Sunday...Finally the last shortwave associated with the long wave trough over the east will bottom out over the Great Lakes region. Expect a continued threat for showers, with some lake shadows east of the lakes for Sunday. Sunday night and Monday...this period should be dry with weak high pressure moving overhead. This isn`t a guarantee this far out, but if the timing of the current pattern holds, the natural progression should be subsidence behind the Sunday system, with the exception of isolated summer convection on lake breeze convergent regions by Monday afternoon. Daily temperatures won`t stray too far off normals for this time of year, with highs in the mid 70s to near 80 and lows mostly in the 60s. Humidity levels will vary, with some nights possibly warranting A/C while in the warm sector, but at this time don`t see any extreme sultry days or nights for late into the week/weekend. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/...
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While VFR conditions are anticipated across western and north central New York tonight...there will be some issues to contend with. Fairly significant lake effect rain will develop east of Lake Erie after 05z. It is likely that moderate to heavy rain within the increasingly well structured band could produce MVFR conditions at KBUF between 09z and 12z. On Tuesday...the lake driven convection will fall apart during the initial daylight hours. The attention will then turn to more scattered showers and thunderstorms as the core of a mid level disturbance will pass over the region. Again...while short lived MVFR conditons will be possible with any of the storms...VFR conditons will prevail. Outlook... Wednesday...Mainly VFR. Thursday through Saturday...VFR/MVFR with a chance of showers and thunderstorms.
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&& .MARINE... Small craft advisories have been dropped for the BUF Harbor/Upper Niagara River and for the western portion of Lake Ontario from the mouth of the IAG River to Hamlin Beach as winds and waves have dropped below small craft advisory criteria. The only other change to the marine package has been to add the potential for waterspouts with any showers on Lake erie tonight and Tuesday morning. A convective cloud depth in excess of 20k ft with a lake delta t of 18c will be quite conducive for waterspout development. In fact...when examining the Szilagyi waterspout nomogram...it places this event square in the center of the most favorable parameters. The main concern for tonight will be the residual convection over Lake Ontario to the east of Irondequoit Bay...and particularly the convection will undoubtably fire up on Lake Erie as a result of lake effect processes. On going convection at 01z over the Ohio nearshore waters of Lake erie should track up the lake and may be the match stick to `light` the convection on this end of the lake. The 00z KBUF sounding already depicted 1400 j/kg of CAPE...so when you add +70 deg f lake water to that environment...you will easily generate +2000 j/kg of CAPE with lapse rates exceeding 10 deg c/km in the lowest 5 k ft. On Tuesday...a persistent southwest graident will once again support gusty winds as high as 30 knots on Lake Erie. A long lived small craft advisory will still be in place for this body of water...and it is possible that the BUF Harbor and Upper IAG River will once again have to be added. Lighter winds will promote sub-advisory wave action on the lakes from Tuesday night and Wednesday. Winds and waves will again increase Thursday ahead of the next frontal system pushing toward the eastern Great Lakes. && .BUF WATCHES/WARNINGS/ADVISORIES...
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NY...None. MARINE...Small Craft Advisory until midnight EDT Tuesday night for LEZ040-041.
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&& $$ SYNOPSIS...AR NEAR TERM...RSH SHORT TERM...LEVAN LONG TERM...ZAFF AVIATION...RSH MARINE...RSH

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