Area Forecast Discussion
Issued by NWS Binghamton, NY

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680 FXUS61 KBGM 171736 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 1236 PM EST Fri Nov 17 2017 .SYNOPSIS... High pressure builds in for Friday bringing an end to any lake effect flurries. This will be quickly followed by a strong low pressure system that will track north and west of the region bringing rain for Saturday followed by gusty and colder conditions with lake effect snow by late Sunday. && .NEAR TERM /THROUGH TONIGHT/... 1030 AM update...Clouds continue to hold tuff mainly east of I81 where shallow layer of moisture remains under a subsidence inversion. This cloud deck will mix out later this morning through early afternoon as temperatures at 850mb continue to warm therefore decreasing lake moisture. Just increased cloud cover in the above mentioned area through early afternoon otherwise no changes. 625 AM update...No major changes to forecast. Only real change was to increase cloud cover / delay clearing by a couple hours this morning but still expect strato Cu deck to break up by this afternoon. For further details, please see discussion below. 2 AM...Some weak lake effect snow showers and flurries continue at this hour over central NY on a cold NW flow near 300/310 degrees. Radar indicates relatively weak multi-bands. Heading through the late overnight hours into Friday morning, the upper trough will continue moving off to the east resulting in subsidence and falling inversion heights which will further weaken lake effect. Thus, only expecting at most an inch or two in the higher terrain south and SW of Syracuse. Otherwise, a half inch or less across central NY and nothing in NE PA. Heading into the day Friday, conditions will still be breezy with a chilly NW wind due to the gradient between the strengthening low over the Canadian Maritimes and high pressure moving in from the west. This cold flow may continue to bring a few light, inconsequential lake effect flurries into the morning across portions of central NY before the high moving in results in clearing skies by midday. Temps will be chilly with highs ranging from the mid 30s to low 40s. Friday night, the high crests over the area in the early evening before moving off to the south and east as the next system approaches with increasing clouds and a milder SW flow. This will result in temps quickly dropping off in the evening before holding steady or rising overnight. Evening lows will range from the mid 20s to low 30s. The forecast models continue to indicate a slower arrival of this next system so we only begin introducing low chances for precip overnight after 6z. The later arrival time should mean that by the time precip moves in it will fall mainly in the form of rain. && .SHORT TERM /SATURDAY THROUGH MONDAY/... 430 AM Update... Main concerns during this active period, are prospects for gusty winds along and behind strong cold front that passes through early Sunday, followed by potential for accumulating lake effect snow in parts of Central NY late Sunday into Monday. Before all of that happens, Saturday itself looks rather wet. Warm front will be lifting through the region Saturday, well ahead of deepening surface low that will be ejecting out of the Midwest en route to the Central Great Lakes. A well-marked negatively-tilted shortwave will run along the front Saturday morning, which will also introduce deeper moisture to the area. This along with isentropic lift and upper level divergence aloft, will cause rain to break out across the region Saturday. Temperatures will already be rising prior to dawn, and will surge well above freezing as the rain develops. It is not totally impossible that mixed rain/snow could occur in some spots on the leading edge of the rain shield, as wet bulbing occurs in the initially drier air of the lower levels, but this will be exception not the rule. Regardless, temperatures will be well into 40s areawide by afternoon. After that lead shortwave, multiple ripples will continue to traverse through the area along with good moisture transport, so waves of rain will occur most of the day through evening. We are figuring on roughly half to three quarters of an inch for most of the area Saturday through Saturday night, though a few spots could approach an inch. Cold front is set to blast through during the predawn hours Sunday. This occurs as the low tracks down the Saint Lawrence Seaway, and very sharp negatively tilted wave punches through aloft. When comparing parameters of this set up with past wind events, thresholds of local studies are generally met for the 925mb winds, 850mb winds, 3 hour pressure rise/fall couplets, and 1000/850mb lapse rates. Along the front and for a time afterwards, we are thus figuring on 35 to 45 mph gusts to be common with some areas perhaps 50 mph - especially higher terrain portions of Central New York. This would probably lead to scattered power outages on Sunday. This potential is now being highlighted in our local Hazardous Weather Outlook, and if confidence increases, a Wind Advisory may end up being issued. Cold air advection will cause temperatures to hold steady and then fall Sunday, changing post-frontal rain showers to snow showers with lake-enhancement. Accumulations at first will be fairly nominal, however, secondary arctic front still appears likely late Sunday afternoon. This will send 850mb temps to minus 10-12 deg C Sunday night, initiating a period of accumulating lake effect snow east-southeast of Lake Ontario which will persist into Monday. Generally speaking a mean 290-300 degree flow will favor Onondaga-Madison-Oneida counties for accumulation, but additional shortwave passages and occasional lake-to-lake connections will cause wavering of lake effect bands. Thus, Northern Seneca-Central Cayuga-Northern Cortland- Northern Chenango-Otsego counties could also be involved at times, especially Sunday night. By Monday, flow will become more westerly which will gradually shift area of main concern to along and north of the NY Thruway. While too early to get into specifics for accumulations, a few to several inches appears quite likely along with blowing-drifting snow since gusts will often be in the 15-30 mph range. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... 315 pm update... The trough is expected to lift to the ne later in the day Monday and Monday night, which will shift any lake bands to the north. As the air mass warms slowly in a broad upper ridge building in the snow will end and leave most of the area under quiet weather conditions Tuesday with noticeably warmer temperatures too. Highs will top out in the mid to upper 40s. The next clipper system will swing through Tuesday night and Wednesday with a quick round of rain and/or snow showers possible and slightly cooler temperatures. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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High pressure over the region will keep VFR conditions over the terminals through tonight. This afternoon through early evening just high clouds are expected with increasing mid level clouds primarily after 06Z. On Saturday, low pressure in the eastern Great Lakes will bring light rain to the terminals beginning mid to late morning. Conditions through 18Z will remain primarily VFR with unrestricted light rain and ceiling around 4K feet. After 18Z conditions will lower into the MVFR/Alternate Required category in rain. West/northwest winds around 10 knots with gusts still continuing until late afternoon at KAVP. Winds becoming light and variable this evening then becoming southeast late tonight at 5-8 knots. Southerly winds on Saturday at 10-15 knots. Outlook... Saturday night...Widespread restrictions in rain showers mixing with snow showers. Sunday / Monday...Variable ceiling restrictions with scattered lake effect snow showers north, generally VFR south half. Winds will also be quite strong and gusty Sunday. Tuesday...Generally VFR. Tuesday night/Wednesday...Restrictions possible in scattered rain/snow showers.
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&& .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...PCF NEAR TERM...PCF/RRM SHORT TERM...MDP LONG TERM...BJT AVIATION...RRM

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