Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 162006 AFDALY Area Forecast Discussion National Weather Service Albany NY 306 PM EST Thu Nov 16 2017 .SYNOPSIS... A cold front will move across the region today, while a coastal low pressure system develops south and east of Long Island and tracks into coastal New England. Rain showers will transition to snow showers tonight, with some accumulating snowfall over the higher terrain mainly north of the Capital District. Cold and brisk conditions in store for Friday, as high pressure builds eastward from the Great Lakes. A stronger storm system will approach on Saturday, bringing the next chance for widespread precipitation. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Quick update to add isolated thunder in eastern NY, the Berkshires and NW CT with some small hail possible as we have had some reports of a little small hail from some of the isolated thunderstorms. High temps will be in the lower to mid 40s in the higher terrain and around 50 to lower 50s in most larger valleys.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... Northwest winds will increase this evening, as the pressure gradient strengthens due to deepening low pressure over coastal Maine and high pressure building eastward from the upper Great Lakes. A relatively moist cyclonic flow will linger through much of the night across our area, with rain/snow showers changing to all snow showers. Fairly good signal for some upslope snows across parts of the far western Adirondacks and southern Green Mountain in VT. Forecast soundings indicate moisture up to at least 700 mb with steep lapse rates beneath, and embedded disturbances in the flow aloft. 00Z HREF indicating the potential for a few inches of snow in these areas. BTV Froude # calculations show values < 1, with some blocked flow expected. This will result in snow along and west of the spine of the southern Greens, and may back up as far west as the city of Bennington. However, thermal profiles indicate it will take until close to midnight for rain to change to snow, which will limit accumulation in valley locations. However, the mountains could receive 1-3 inches of fresh upslope flow. Outside of the snow showers it will be blustery and becoming colder. Northwest winds will gust to around 30 to 40 mph in favored spots mainly after midnight. Any lingering snow showers should quickly end by Friday morning, as high pressure builds east form the lower Great Lakes. It will be cold and brisk day though, with northwest winds persisting and gusting to around 25 to 40 mph at times, especially through the daylight hours. Temps will fall back to below normal levels, ranging from 30s in the higher terrain to lower/mid 40s in the valleys. Dry but cold conditions expected now through Friday night, as models trends continue to slow timing of the next system approaching from the Midwest. High pressure will be in control much of the night with temps dropping into the teens and lower 20s with cirrus clouds increasing. Saturday starts out cold, but warming will occur as S-SW low- level flow strengthens substantially. Precip will develop from west to east from the late morning through afternoon hours as isentropic lift increases. The parent cyclone is forecast to track northeastward across the lower Great Lakes and deepen considerably during the day. With cold air in place initially in the low-levels, precip may begin as a period of snow/rain mixed north of the Capital District, although with the later arrival of precip mostly rain is expected. Some minor accumulations will be possible in the higher terrain before the changeover to rain occurs. After a cold start, temps should warm into the 40s during the afternoon. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... The extended forecast begins with a deepening and intensifying low pressure system moving northeast from the central and eastern Great Lakes Region to southern Quebec Saturday night into Sunday morning. The cyclone track is in fairly good agreement with the latest 00Z GFS/ECMWF/CMC and the 00Z GEFS mean. The low does vary slightly in intensity based on the guidance ranging from 970-980 hPa. Nonetheless, this strong low pressure system appears it will move north of the St Lawrence River Valley with a cold front swinging through the region Saturday night with a period of moderate-heavy showers transitioning to snow showers/snow west of the Hudson River Valley initially, then also over the southern Greens Mtns based on the critical partial thicknesses, strong cold advection and lowering snow levels. Snow accums may range from 2 to 4 inches across portions of the southern Adirondacks, and southern Green Mtns with an inch or less in most other locations. Lows fall back into the upper 20s to mid 30s over the higher terrain mainly north and west of the Capital Region, and upper 30s to lower 40s south and east. Sunday will feature cold and blustery conditions with the deep cyclone lifting north and east across s-central Quebec towards the Canadian Maritimes. The GFS has the sfc rise-fall pressure couplet north of the forecast area over nrn NY and southeast Ontario/southern Quebec with 10-17 hpa/6 hr rises. The low level wind fields crank up with westerly winds of 35-45 kts at 925 hPa and 850 hPa winds of 45-55 kts. The latest 00Z GEFS indicates +u-component /westerlies/ wind anomalies of 1 to 3 STD DEVS above normal. Wind advisory gusts will be possible from the Capital Region/Mohawk Valley/Berkshires northward based on the track of the cyclone and if deeper mixing occurs. We currently have gusts of 30- 45 mph in the forecast grids, and some higher values in the 45-50 mph may be possible, and we will mention this in the HWO. Initially, some upper deformation zone and upslope snow showers will occur in the wake of the low, and then a transition to lake effect snow late Sunday. Impressive delta T`s between the warm lakes with temps in the 10-13C range coupled with H850 temps of -10C to -13C by late in day will promote conditional to moderate lake instability. The question will be where the bands set up, and if they will be more of a west to northwest low to mid level flow...westerly...or northwesterly. The medium range guidance still varies with the GFS leaning more with a multi-lake connection with a single band in W/NW flow lifting northward as a single band late Sunday night into Monday...whereas the 00Z ECMWF shows more persistent multi-bands in northwest flow before lifting northward and weakening Monday afternoon with ridging building in from the TN Valley and Mid Atlantic Region. Overall, late Sunday afternoon through Monday features lake effect snow for the western Adirondacks, w-central Mohawk Valley, and northern and eastern Catskills, and westerly upslope snow showers for the Taconics, southern VT and the Berkshires. Light to moderate snow accums are possible from the Lake Effect snow and upslope snowfall. Some snow showers may also impact the Capital Region with light accums. Highs Sunday will be in the mid 30s to lower 40s west of the Hudson River Valley, and lower to upper 40s to the east with a few colder readings in the southern Greens. Lows Sunday night will be in the 20s, except for some teens over the southern Adirondacks, and southern Greens. Brisk and cold conditions continue on Monday with highs only in the the mid 20s to lower 30s over the higher terrain, and mid and upper 30s predominately in the valleys. Monday night, the lake effect snows end with just a slight to low chance of snow showers early on over the western Adirondacks, and western Mohawk Valley with little additional accumulation with the ridge building in from the south. Lows will be in the 20s. Tuesday...The sfc ridge slides off the mid Atlantic Region Coast with southwest flow aloft over the region. A warm advection pattern set up with a warm front moving through, and temps rebound back above normal with mid 40s to around 50F in some of the valley areas, and upper 30s to lower 40s over the mountains. Tuesday night into Wednesday...A cyclone passes well north and east of the region with a cold front and a short-wave impacting the forecast area with a slight to low chance of rain and snow showers Tuesday night into Wednesday. After lows in the mid 20s to lower 30s. High temps will only be in the 30s to lower 40s for the mid week, as another surge of cold advection occurs in the wake of the front. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... A low pressure system will track across southern Quebec this afternoon as a secondary low forms southeast of Long Island. The occluded front between the lows will move across the region this afternoon. Brisk winds will occur in the wake of the system tonight into Friday morning. Scattered rain showers will continue to track across the TAF sites this afternoon with and ahead of the front. Some gusty winds could accompany some of these showers, esp at KPOU. After the front passes, some additional isolated/scattered rain showers will develop this evening and persist into tonight, but should be mainly confined to higher elevations east and west of the TAF sites. This may impact KPSF at times tonight, and as colder air builds back into the region, some snow showers could occur at KPSF. As for overall flight categories, conditions should become mainly VFR at KALB/KPOU through this afternoon, while remaining MVFR, mainly for Cigs, at KGFL and especially KPSF. Some occasional IFR conditions could occur at KPSF this afternoon as showers pass through. Elsewhere, brief reductions to MVFR Vsbys will be possible this afternoon as showers occur. For tonight, mainly VFR conditions are expected with the exception of KPSF, where MVFR Cigs are expected. Conditions are expected to be mainly VFR at the TAF sites after 12Z/Fri. South to southwest winds at 5-10 KT will shift into the west this afternoon at similar speeds, although may gust up to 20-25 KT or stronger as the front moves through, esp at KPOU. For tonight, west to northwest winds will increase to 10-15 KT with gusts of 25-30 KT possible, strongest at KALB and KPSF. These winds should continue through midday Friday. Outlook... Friday: Low Operational Impact. Breezy NO SIG WX. Friday Night:No Operational Impact. NO SIG WX. Saturday: High Operational Impact. Breezy Likely RA. Saturday Night: High Operational Impact. Windy Definite SHRA. Sunday: Moderate Operational Impact. Windy Chance of SHRA. Sunday Night:Low Operational Impact. Breezy Slight Chance of SHSN. Monday: Low Operational Impact. Breezy Slight Chance of SHRA...SHSN. && .FIRE WEATHER... A cold front will move across the region today, while a coastal low pressure system develops south and east of Long Island and tracks into coastal New England. Rain showers will transition to snow showers tonight, with some accumulating snowfall over the higher terrain mainly north of the Capital District. Cold and brisk conditions in store for Friday, as high pressure builds eastward from the Great Lakes. A stronger storm system will approach on Saturday, bringing the next chance for widespread precipitation. && .HYDROLOGY... No hydrologic problems are expected on the main stem rivers through the next week. A frontal system passing through today will continue to bring precipitation to the Hydro Service Area into this morning. A coastal low and an upper level low will keep the precipitation going into tonight, especially across the higher terrain north of the Capital District, where a changeover to snow showers will occur. Total liquid equivalents will range from about two tenths to a half of an inch over the area. The higher totals will likely be across the southern Adirondacks and the southern Green Mountains. Snow amounts may range form 1 to 3 inches or so over the southern Adirondacks and southern Greens through tonight. High pressure will then briefly build in on Friday before a strong low pressure system approaches from the Great Lakes Region on Saturday. A bout of rain/snow will change to to all rain ahead initially. A cold front will sweep through Saturday night into Sunday with additional precipitation. At this time, total QPF from this system looks to range from a half inch to near an inch. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...JPV NEAR TERM...NAS SHORT TERM...JPV LONG TERM...Wasula AVIATION...KL FIRE WEATHER...JPV HYDROLOGY...JPV

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