Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 221510 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1010 AM EST Mon Jan 22 2018 .SYNOPSIS...
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A warm front will lift across the region with some light rain and drizzle today. A large storm system tracks through the Great Lakes with another round of rain tonight. A cold front will then bring back more typical winter weather late Tuesday into Thursday. Another warm up is forecast Friday into next weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Dense Fog Advisory has been extend for southern Erie, Wyoming and the Southern Tier through 4 PM this afternoon. Regional observation and web cameras in these areas continue to show dense fog with visibilities dropping below a quarter of a mile especially across higher terrain. Elsewhere, visibilities have improve enough to discontinue the advisory. The leading edge of a warm front continues to slowly lifted into and across Western NY this morning with its eastern end yet to move across North Central New York. Radar returns show light rain showers moving across Lake Erie, Southern Tier, and across the Niagara Frontier late this morning. This is likely the leading edge of a low level jet which is forcing the rainfall. Ahead of this, mainly dry with some patchy foggy is found across Central NY ahead of the warm front. Temperatures across western and central NY remain mild with readings in the mid to upper 30s with only the immediate Saint Lawrence River Valley running near or below freezing. The low level jet will lift an area of light rain across western NY through late this morning and then shift into central NY this afternoon. Total QPF today is forecast to range from a few hundredths across the western Finger Lakes to near a quarter inch from the Niagara Frontier to the North County. The only exception to the plain rain will be across Northern Jefferson county where persistent northeasterly flow will likely keep sub-freezing air locked into tonight. This will result in precipitation falling as freezing rain this afternoon and evening before temperatures climb above freezing tonight. A winter weather advisory remains in place for Jefferson county to account for about two tenths of an inch ice accretion. The precipitation will wane across western NY this afternoon as the leading edge of the low level jet pushes north and east. Most areas south of Lake Ontario will lie within the warm sector with a short period of limited showers or dry but cloudy conditons. There could also be some redevelopment of fog. Temperatures will climb into the 40s south of Lake Ontario, possibly near 50 degrees closer to the Pennsylvania state line. Temps will linger near freezing along the Saint Lawrence River Valley but reach the low 40s south toward Fulton. Tonight, models continue to indicate a cold front will push across Lake Erie reaching western NY by daybreak Tuesday. This cold front will be associated with a storm system lifting from the Midwest States into the Central Great Lakes. Another several hour period of rain will bring an additional quarter to half inch of rain tonight. Some additional ice accumulations should be expected across the Saint Lawrence River Valley before temps rise above freezing. A steady southerly flow ahead of the cold front should prevent additional dense fog. Temps should linger in the low to mid 40s most of the night with upper 30s in the North Country late. The combination of snow melt and a half to three-quarters of an inch of rain fall may bring some ice jams. A flood watch remains in effect from this afternoon through Tuesday with additional details in the hydrology section below.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... A large and mature low pressure system centered near Georgian Bay Tuesday morning will continue to track northeast down the St. Lawrence valley Tuesday and Tuesday night before eventually turning north into Labrador on Wednesday. The cold front associated with this system will cross western/north-central New York during the day on Tuesday, and as this occurs we will likely see rain give way to a period of dry weather or a few scattered showers before wrap-around moisture/precipitation on the western side of the departing low works its way across the forecast area. The wrap-around precipitation will coincide with falling temperatures as cold air is advected into the region behind the low, and by the end of the day we should see rain showers changing over to snow showers, particularly across upslope areas east of the lakes. Temperatures will continue to fall Tuesday night, as sub-arctic air filters across the region in the wake of the departing low. Readings will fall into the low 20s by daybreak on Wednesday, ushering in a return to more winter-like conditions. As 850mb temps fall below -10C, we should see lake effect snows develop southeast of the lakes. Model QPF fields are having difficulty picking up on this feature, due likely to the very shallow moisture profiles, however BUFKIT profiles show instability and saturation within the dendritic growth zone, much as they did last week when we had light but persistent LES in spite of model QPF being negligible. With that in mind, have bumped up PoPs and snow amounts southeast of the lakes for Tuesday night into Wednesday with roughly 1-3 inches possible Tuesday night and 1-2 more inches possible Wednesday across the more lake-effect prone areas southeast of the lakes. Lake effect snows may linger into Wednesday night before winding down on Thursday, as surface ridging moves across the lower Great Lakes. This should lead to a return of sunshine on Thursday, though northwesterly flow aloft will keep it cold across the region, with highs ranging from the low teens in the North Country to the low to mid 20s in western New York. Wednesday night will likely be the coldest night of the week, with lows in the lower teens across most areas, except for the North Country, which will be flirting with sub- zero temperatures. Thursday night will be slightly less cold, as upper level troughing will be in the process of departing the region. && .LONG TERM /FRIDAY THROUGH SUNDAY/... High pressure, fair weather, and milder temperatures will be the name of the game on Friday, as an amplifying upper level ridge moves overhead the region. The respite will be short-lived however, as the next storm system in what continues to be a very progressive upper level pattern approaches the region. While the main surface low associated with this system will pass well to our north across James Bay and into Quebec, a deep plume of GOMEX moisture will be drawn towards this low around the western periphery of the Bermuda high and across our region, where it will interact with a sharp upper level trough over the Midwest and a favorably positioned upper level jet-streak to produce widespread rainfall from the Mississippi valley to the lower Great Lakes Saturday into Saturday night. The system should be fast-moving enough to keep rainfall amounts from raising flooding concerns at this point. Warm temperatures will accompany the moisture plume, with highs easily climbing back into the 40s for much of the weekend. Rainfall should wind down from west to east Sunday, as the progressive system presses on to the east and a cold front crosses the region Sunday, with temperatures falling back below freezing Sunday night. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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A warm front is lifting across WNY bringing a mixture of IFR/LIFR CIGS/VSBYS to almost all terminals across the forecast area this morning. The lone exception is KART which is currently VFR as of 15Z. IFR/LIFR CIGS and VSBYS will continue for most terminal locations through the rest of the morning hours. Conditions will slowly improve early this afternoon behind the warm front as it slowly moves north of Western and Central NY. Tonight, a cold front will push across Lake Erie and approach WNY with another area of widespread rain shifting across the terminals. This should bring a return of MVFR/IFR cigs. There could be potentially some additional fog as well but a steadier southerly flow should keep it more limited. Additionally, Low Level Wind Shear looks likely as a strong low level jet shifts over our region just ahead of the front which will be near western NY around 12z Tuesday. Outlook... Tuesday...MVFR/IFR with rain showers changing to snow showers before ending...then areas of lake effect snow also developing east of the lakes Tuesday night. Wednesday...VFR/MVFR with a chance of snow showers. Thursday and Friday...Mainly VFR.
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&& .MARINE... East winds will freshen on today on Lake Ontario with a warm front slowly lifting across the south shore of the lake. This front will be associated with an area of low pressure tracking into the mid- Mississippi Valley then towards the Great Lakes tonight. Winds and waves will reach small craft advisory on the western half of Lake Ontario this afternoon into this evening. The low will sweep a cold front across the lower Great Lakes Tuesday with winds becoming westerly by Tuesday night. This will likely bring another round of solid small craft advisory conditions and near Gale Force winds to Lake Ontario behind the front Tuesday night into Wednesday morning. && .HYDROLOGY... A flood watch for ice jam flooding is in effect for all of western New York from this afternoon into Tuesday evening. Temperatures continue to hover in the low to mid 40s across much of western New York allowing a continuation of the snowpack across the region to melt. Temperatures will remain above freezing into Tuesday evening...with daytime readings peaking between 45 and 50 and widespread rain coming tonight. This will allow a true melt down of the snowpack over the western counties with the runoff flowing into creeks...many of which are ice covered/clogged. Using research proven over several decades...the melting degrees experienced from the above described temperature forecast suggests that ice jam flooding could prove to be a problem as early as this afternoon. This potential problem will be exacerbated by a general quarter to as much as three quarters inch of rain later today through tonight. While there will be a risk for ice jam flooding...a less impressive snowpack...lower temperatures and less rainfall compared to last weeks flooding should translate into more localized flooding. In other words...flooding should not be as widespread as the last event. In any case...those living in areas prone to ice jam flooding should pay attention to water levels and subsequent statements and warnings issued by the Buffalo National Weather Service office. && .BUF WATCHES/WARNINGS/ADVISORIES...
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NY...Winter Weather Advisory until 1 AM EST Tuesday for NYZ007. Flood Watch through Tuesday evening for NYZ001>005-010>014- 019>021-085. Dense Fog Advisory until 4 PM EST this afternoon for NYZ012- 019>021-085. MARINE...Small Craft Advisory until 1 AM EST Tuesday for LOZ042-043.
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&& $$ SYNOPSIS...AR/SMITH NEAR TERM...AR/SMITH SHORT TERM...WOOD LONG TERM...WOOD AVIATION...AR/SMITH MARINE...AR/SMITH HYDROLOGY...RSH/SMITH

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