Area Forecast Discussion
Issued by NWS Binghamton, NY

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000 FXUS61 KBGM 200841 AFDBGM AREA FORECAST DISCUSSION National Weather Service Binghamton NY 341 AM EST Wed Feb 20 2019 .SYNOPSIS... Another light wintry mix today and tonight will move across the region, along with gusty south winds. Mostly quiet conditions later in the day Thursday through Friday into early Saturday. The next low pressure system will impact the region later Saturday through Sunday into Monday with more wintry mix and strong winds. && .NEAR TERM /THROUGH THURSDAY/... 340 am update... Main concerns in the near term remain focused on the incoming wintery mix of snow, sleet and freezing rain later today and tonight...along with strong s/se winds across the Finger Lakes tonight and noticeably warmer temperatures on Thursday with lingering light rain/snow showers to the north. High pressure at the surface shifting off to the east this morning but still having enough influence on the area to keep weather conditions quiet. High clouds have moved in, and will continue to see clouds thicken through the morning before snow moves in from the s/sw around 9 to 10 am into ne PA. Atmosphere still expected to be cold enough for all snow through most of the afternoon with the snow shield spreading to the northeast, and dropping 1-2 inches across central NY and 2 to 3 inches into ne PA. This part of the forecast remains relatively unchanged. However, there have been slight adjustments made to the total snow and ice accumulations...especially during the evening and early overnight hours. Model guidance has come into slightly better agreement with respect to the the depth and amt of warm air aloft and cold air near the surface. At this time there appears to be a greater potential of sleet rather than freezing rain...although light ice amounts are still expected...so this result has caused total snow amounts to be slightly higher than the previous forecast, although not substantially higher. With the p-type leaning more toward sleet, this will cut back on the ice accretion...with most areas of central NY less than 0.05"...and areas of ne PA 0.10" or less. Still expecting a change over of snow to sleet from west to east during the late afternoon and early evening time frame...and then a couple hours later, mixing with freezing rain. The freezing precip may end up actually being fairly light...more likely freezing drizzle as the column loses ice crystals aloft and the dry wedge moves in from the west. The sfc pressure gradient tightens this evening as the surface low to the west deepens slightly and moves east...and the high off the coast takes its time moving out of the area. These two features will cause sustained south/se winds around 10 to 20 mph and gusts up to 30 mph into the Finger Lakes. Gusty winds are possible in the higher terrain of the Catskills and the Allegheny plateau, but the strongest winds will be from downsloping into the Finger Lakes. Wintry mix will taper off west to east after midnight and change to mostly liquid (drizzle or light rain) for most of the area by or just after sunrise Thursday morning. The air mass behind the departing system will be fairly cold once again...and allow for a weak lake reaction across the far nrn counties into Thursday afternoon. Surface temperatures will warm into the upper 30s north and into the lower 40s south. Even with temperatures above freezing, the air mass aloft will likely be supportive of light snow or drizzle off the lake into mainly Oneida county. Areas south of the Thruway will likely be dry most of the day Thursday as the dry punch and surface ridge axis pushes east. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... 310 AM Update... Fairly benign period expected in the short term with little if any precipitation behind the front Thursday night, then a gradual breakup of stratocumulus Friday into Friday night. Weak cold air advection will continue Thursday night along with west-northwest flow. The moisture that will exist will be quite shallow; confined to a sharp inversion around or below the 800mb level. While it appears that there will likely be stratocumulus for most of the area, the depth of the moisture will make precipitation hard to come by. The top of the layer reaches to about minus 10 Celsius Thursday evening, which should prevent drizzle/freezing drizzle by then. However, a few scant flurries cannot be ruled out in Central NY north of Cortland-Norwich and mostly east of Syracuse. With the clouds, temperatures will be prevented from dropping any lower than 20s for lows. Stratocumulus layer will thin with time of Friday, and as usual it will linger longest in North Central New York while others will start getting into more sunshine especially in afternoon. High pressure will pass across the region Friday afternoon- evening, then just east by dawn Saturday. Highs of mid 30s-lower 40s Friday, will be followed by lows of upper teens-mid 20s Friday night thanks to a mostly clear sky allowing for radiational cooling. && .LONG TERM /SATURDAY THROUGH TUESDAY/... 310 AM Update... Main concern in the long term period, is the increasing signal for a possible wind event as a deepening low pressure system passes through the region Sunday into Monday. Also, the same system will bring varying types of precipitation ahead of, during, and behind the system. A low pressure center is projected to exit the Central Plains Saturday, which then rapidly deepens Saturday night into Sunday while moving through the western Great Lakes into Ontario- Quebec. To differing degrees, yet with the same general idea, the ECMWF Canadian and especially GFS models have this occur as southern stream and northern stream upper waves phase with each other while lifting northeastward. Based on local studies there are several parameters meeting thresholds of past stronger wind events including 925-850mb winds exceeding 50 knots, low level lapse rates in excess of 8 deg C/km, as well as a strong pressure rise-fall couplet in terms of 6 hour pressure change. While zone of strongest winds and pressure rises appears to translate from western to northern NY and especially into Canada, areawide it appears that it will get quite gusty Sunday through Sunday night and perhaps into Monday as well. If a verbatim GFS solution were to pan out, damaging gusts are not out the question especially from the Finger Lakes to Mohawk Valley areas but perhaps further south too. Sometimes the magnitude of a potential wind event looks high several days out, only to diminish as it gets closer. For now though, we will be adding mention of this potential to our local Hazardous Weather Outlook for northern parts of our area to raise awareness, where potential is higher, and we will otherwise continue to monitor trends in coming days. Besides wind, the other impacts of this system of course will involve precipitation. Strong warm air advection will occur especially later Saturday into Sunday. As increasing moisture and lift occur on the front side of the system, a shield of precipitation will lift south to north across the area later Saturday through especially Saturday night. It is not totally impossible that a brief wintry mix could occur, especially higher terrain east of I-81, but overall it appears strength of warm air advection as well as relatively limited cold air damming in the low levels will make rain the predominant precipitation type. Temperatures will surge into Sunday with highs of at least upper 40s-lower 50s expected. Blast of cold air advection and gusty winds will then occur later Sunday through Monday. What is left of rain showers will change back to snow showers Sunday night. Some accumulating lake snows could occur into Monday in parts of Central New York with gusty cyclonic flow on the back side of the system with potential to pick up Great Lakes moisture from well upstream. Then, brief ridging by Monday night into Tuesday appears to yield a temporary respite of quiet weather. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... An area of snow will move in after 15Z from southwest to northeast and eventually change to a snow/sleet mix for period after 21Z, and then mix in some freezing rain after 02Z Thursday. Expect IFR visibilities between 3/4SM and 2SM in moderate snow with ceilings between 1000 and 2000 feet. Vsbys will improve with the transition to a wintry mix...with cigs remaining in the fuel alternate required to low-end MVFR range. A strong s/sw low level jet around 40-50 kt will induce some LLWS across the area after 00Z Thursday. Outlook... Wednesday night through Thursday...MVFR/IFR restrictions likely as the snow and sleet transition to rain around sunrise Thursday morning. Rain showers continue Thursday with brief isolated restrictions possible. Light lake effect rain and eventually snow showers at KRME may reduce vsbys and cigs as well Thursday night. Friday and Saturday...VFR under high pressure. Saturday night through Sunday...Restrictions likely in mixed precipitation. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory from 10 AM this morning to 7 AM EST Thursday for PAZ038>040-043-044-047-048-072. NY...Winter Weather Advisory from 10 AM this morning to 7 AM EST Thursday for NYZ009-015>018-022>025-036-037-044>046- 055>057-062. && $$ SYNOPSIS...BJT NEAR TERM...BJT SHORT TERM...MDP LONG TERM...MDP AVIATION...BJT/DJP

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