Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 220119 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 919 PM EDT Mon Oct 21 2019 .SYNOPSIS... Mostly cloudy skies are expected Tuesday with temperatures near normal. A period of rainfall expected from the late afternoon into the overnight hours. Mainly dry and seasonable weather will return for Wednesday. It will become milder on Thursday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... As of 915 PM EDT, mainly clear skies and light to calm winds continue across the region. Some patchy fog has already formed per recent obs and also latest IR satellite imagery across the upper Hudson Valley in portions of southeast Saratoga/southern Washington Counties. Expect patchy fog to continue developing overnight, with potential for most dense and persistent fog across the upper Hudson River Valley. Temps have already dropped into the upper 30s to lower 40s across portions of the southern Adirondacks, Mohawk Valley and upper Hudson River Valley, and have therefore lowered forecast min temps in these areas. Low temps in many areas may tend to occur around or shortly after midnight, before possibly holding steady or even rising as clouds, patchy fog, and/or a light southeast wind develops depending on location. Otherwise, all else on track, and previous discussion follows... As of 350 pm, stratus has finally dissipated, with clear skies across the area. Tonight, the upper ridge axis and surface ridge will shift east of the forecast area with heights gradually lowering late. This is in response to a deep but vertically stacked upper low drifting across the Upper Midwest. Clouds will increase gradually ahead of this system, with easterly flow increasing as well especially for the Mohawk Valley and areas along and in the immediate lee of the Greens/Berkshires/Taconics. Before this happens, it appears there is a window for some fog development in the Hudson Valley, especially given the fact that the boundary layer moisture may not have mixed out due to today`s low clouds. Lows will likely be a bit milder than normal given the increasing clouds, with temps steadying and possibly rising late. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Vertically stacked cyclone will continue to drift northward Tuesday into Tuesday night. The low-level jet will increase in magnitude through the day, with H850 winds peaking at 35-45kt from the south from 00-06Z Wednesday. These winds will be almost due south, with the V-component +2 to +3 standard deviations. This will usher in an anomalously moist airmass with PWAT increasing to 1.25 to 1.50 inches, also +2 to +3 standard deviations. These winds will largely be parallel to the isentropes, and DCVA will not increase until after 00Z Wednesday when a shortwave trough will pivot through the area. The forecast area will also be on the equatorward exit region of the upper jet which is unfavorable for ascent. The upshot of all of this is that much if not all of the daylight hours will be dry Tuesday (except for possibly some light showers/drizzle over the eastern slopes of the higher elevations), and the rainfall will have to wait until the forcing associated with the shortwave trough and occluded front tracks through. It looks to be overcast for most if not all of the day, with high temperatures topping out near normal. The main bout of forcing for ascent tracks through 00-09Z Wednesday. A steady period of rainfall is expected given the above parameters, but as it will be a progressive system, hydro issues are not anticipated aside from some minor ponding where leaves clog drains. Easterly winds look to be gusty across the favored areas along and in the lee of the high terrain across western New England, with gusts of 25 to 40 kt possible from 15Z Tuesday through 06Z Wednesday. Wednesday, midlevel flow flattens out in the wake of the shortwave trough, allowing pressures to rise at the surface. Good mixing is forecast, which should allow clouds to scatter out during the morning. The exception will be to the lee of Lake Ontario over the western Adirondacks, where surface to 850 mb delta-Ts will near critical values, allowing for some lake effect clouds and perhaps a few rain showers. It will be a bit breezy, but with the mixing offsetting the cold advection, highs should reach near normal values. Wednesday night looks to be a tranquil period with low temps not far from normal.&& .LONG TERM /THURSDAY THROUGH MONDAY/... We begin this long term with the approach of short wave trough axis that, per this 12Z global model runs, takes most of the moisture and upper support to the north and west of Albany. Meanwhile, surface reflection frontal zone is forecast to slowly slide eastward later Thursday into Thursday night. So combination of clouds and low PoPs to the northwest of Albany will remain in the forecast grids. The GFS is the most aggressive with QPF overnight with the GGEM a little further behind and the ECMWF the most dry. As main upper support was departing, we will leave low PoPs/Wx until higher consensus can be achieved. Temperatures from the 50s and lower half of 60s for Thursday and overnight lows from the mid 30s to lower 40s. Friday, many signals in the guidance with a wave developing along an increasing baroclinic zone across the Ohio Valley and tracking northeastward. The GGEM is further suppressed southward which was not in alignment with the frontal placement and ensemble members of the GFS/ECMWF. So we will continue with the higher chance PoPs Friday into Friday evening. The other aspect is the low level colder air where some wet snow could mix in across the Dacks with no accumulation expected at this time. Highs Friday mainly into the 50s with Friday night lows into the lower 30s across the Dacks to lower 40s for the mid-Hudson Valley. Friday night and into the first half of the weekend, large consensus for a ridge of high pressure to build and crest across the region for seasonable weather for late October. Thereafter, large discrepancies in the guidance with the GFS leading with a drier Sunday as opposed to the ECMWF/GGEM with Texas upper low and surface reflection approaching with clouds and the threat of rainfall approaching later Sunday. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... Tonight, lingering low level moisture should allow fog to redevelop at all TAF sites. By 02z-05z, all sites should see IFR/LIFR fog return, as only thin high clouds will be moving in overnight and winds will remain very light. Towards sunrise, mid and high level clouds will increase and a southerly wind will pick up. This should allow fog to mix out, although it may lift into a stratus deck at KPSF/KPOU, resulting in MVFR conditions there for the day on Tuesday. Will allow KALB/KGFL to briefly return to VFR, but a return to MVFR looks to occur during the afternoon, as the southerly winds continue to bring more moisture into the area. Some spotty light rain or patchy drizzle will arrive later in the day as a frontal boundary approaches from the west, and low level moisture continues to increase from the south. Winds will become southeast to south and increase to 5-10 KT by late morning into the afternoon. There could be a few gusts up to 20-25 KT at KALB and KPSF in the afternoon. Outlook... Tuesday Night: High Operational Impact. Definite RA. Wednesday: Low Operational Impact. Breezy NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: Low Operational Impact. Slight Chance of SHRA. Friday: Moderate Operational Impact. Chance of RA. Friday Night: Moderate Operational Impact. Chance of RA. Saturday: Low Operational Impact. NO SIG WX. && .FIRE WEATHER... Southeasterly winds will increase Tuesday ahead of a frontal system. Though most of the rain will hold off until the late afternoon or evening, skies will be overcast much if not all of the day. Minimum RH values will remain elevated at 60 to 80 percent. A widespread soaking rainfall is likely Tuesday evening and Tuesday night. Breezy conditions and some sunshine will help conditions dry out Wednesday. Dry weather will continue Thursday with minimum RH values both days in the 45 to 60 percent range. && .HYDROLOGY... A period of steady rainfall is expected late Tuesday afternoon into Tuesday night. Although anomalously strong low-level winds will push precipitable water values to +2 to +3 standard deviations, the system is progressive and the moist axis quickly pushes east. Rivers will rise but are forecast to remain below flood stage. QPF is expected to range from 0.50 inches in parts of Litchfield County to 1.25 inches over the southern Adirondacks. Some nuisance ponding of water is possible, especially where leaves clog drains. At this time, no additional hydrologically significant precipitation is expected through the 7-day forecast period, which should allow river levels to subside. 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...Thompson NEAR TERM...KL/Thompson SHORT TERM...Thompson LONG TERM...BGM AVIATION...Frugis/KL FIRE WEATHER...Thompson HYDROLOGY...Thompson is the U.S. government's official web portal to all federal, state and local government web resources and services.