Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 230939 AFDALY Area Forecast Discussion National Weather Service Albany NY 439 AM EST Thu Feb 23 2017 .SYNOPSIS... Mild conditions with well above normal temperatures are expected to persist into Saturday. A weak cold front will cross the region this evening bringing some showers. The front will stall just south of the region tonight, before lifting back northward as a warm front on Friday. There will be increasing chances for heavy rainfall associated with a strong cold front passage late Saturday into Saturday night. Gusty winds are possible along the cold front and into Sunday as much colder air rushes in. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM EST...widely varying temps across the region tonight, with areas with clearing skies having fallen into the low and mid-30s, while areas with a little wind and more cloud cover are still up in the mid-40s. An area of clearing is working into the region from the southeast, so the areas still in the 40s do have the potential to cool yet before sunrise. Fog has yet to develop, but is still possible for some areas as the clearing works in. Today, surface low ahead of a quick-moving upper impulse will track across southern Quebec, putting the local area into the warm sector. Another unseasonably warm day is on tap, with H925 temps averaging around +10C, which is around +2 sigma. Thus far during the warm stretch, guidance has been on the low side, possibly underestimating the degree of mixing. Think that trend will continue today, so have forecasted high temps a few degrees above MET/MAV guidance and closer to the HRRR 2-m temps. Southwest winds above the surface at low levels from the southwest should allow for some downsloping from the Catskills/Helderbergs as well. There is a good chance that we break the high temp of 62 at Albany set in 1984. Only fly in the ointment is if the area of low/mid level clouds over OH/PA work into the region. NAM RH progs suggest that they may not arrive until later in the afternoon. Have also increase winds a bit expecting to mix into stronger winds than forecast soundings indicate. Chance for showers late afternoon into the overnight hours as the system`s cold front passes through and washes out over the center of our CWA. Best chances across the Adirondacks. Otherwise, another mild night in store with lows in the mid-30s to mid-40s. The front will lift back north as a warm front late, possibly focusing more showers across the northern portions of the region. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Deep upper disturbance will go negatively tilted across the Upper Midwest, resulting in a strong surface low tracking roughly from northern Missouri to western Quebec from 12Z Friday to 00Z Sunday. The aforementioned warm front connected to this system will continue to lift northward through our region Friday, possibly resulting in a few showers and perhaps even a thunderstorm, especially in the morning and from the Capital District northward. More clouds/low-level moisture will likely be around so forecast highs are not quite as warm as Thursday, but if any breaks in the cloud cover can develop, highs could be higher than what we have forecast. Friday afternoon into Saturday morning, we look to be firmly in the warm sector under strong upper ridging, so expect mainly dry conditions aside from possible pockets of drizzle or a light shower or two. Models are in pretty good agreement that a very strong cold front will track through the local area Saturday afternoon into Saturday evening. Forecast temp contrasts across this front are impressive - for instance, NAM shows 2-m temp difference across the front of around 20F, and 850 mb temp difference near 10C, as it tracks through the local area. Though forecast instability is expected to be very little, there is some concern for a strongly forced, narrow frontal rain band that could mix some of the strong wind field down to the surface. Also have to worry about the downward momentum transport immediately behind the front. NAM cross section shows the front-normal component of the winds of 35-40 kt just off the surface, along with a midlevel dry intrusion, which CSTAR research has shown to be associated with high wind events. NAM also shows 3-h pressure rise center of 7-8 mb tracking through the area. Will continue to mention this potential in the HWO. A period of moderate to heavy rainfall is likely along and behind the front (see Hydrology discussion below for more details), tapering to showers several hours after frontal passage. Lake effect snow showers will commence downstream of Lake Ontario late in the night with 850 mb temps falling toward -15C. Windy conditions will continue overnight. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... A return to more seasonable weather is in store during the long term period along with several chances for at least some snow. For Sunday...In the wake of the cold front it will be a blustery day with strong gusty winds and much more seasonable temperatures. There will also be some lake effect snow showers downwind of Lake Ontario mainly across the western Adirondacks and Mohawk Valley with some minor accumulations possible. Highs on Sunday will be in the upper 20s to mid 40s with west to northwest winds gusting over 40 mph at times. For Sunday night...Some lake effect will continue but be primarily confined to the northwest Adirondacks with the remainder of the area dry. It will be much cooler than recent nights with lows ion the upper teens to upper 20s. Monday and Monday night...A clipper type system will be moving from the upper Great Lakes Monday morning quickly into the Canadian Maritimes by late Monday night. This clipper type system will leave a cold front draped across northern New York late Monday night. As a result there will be a chance of precipitation mainly across the northern half of the forecast area. Highs on Monday will be in the mid 30s to mid 40s with lows Monday night in the upper teens to lower 30s. Tuesday through Wednesday...Another system approaches from the Great Lakes region bringing increasing chances of precipitation. At this point it appears it will be cold enough for some snow at least across the northern half of the forecast area, but the precipitation will likely change to rain by Wednesday. Highs on Tuesday are expected to be in the upper 30s to upper 40s with lows Tuesday night in the upper 20s to mid 30s and highs on Wednesday in the mid 40s to mid 50s. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... VFR conditions will prevail until late tonight as a warm front lifts through our region. This will allow for good low level moisture advection late this evening/overnight and increased fog potential after 08Z. Combined with calm winds and snowpack on the ground, MVFR fog is possible. Since this is more of an advective fog event, cloud cover shouldn`t impact the potential for fog development overnight. Have placed a TEMPO group in the TAFs between 08Z and 12Z for MVFR conditions in fog. Conditions should gradually improve after daybreak Thursday although ceilings will be borderline MVFR/VFR for much of the day. Winds will be mainly light at less than 10 kts from the south for much of the TAF period. Outlook... Thursday Night: Moderate Operational Impact. Chance of SHRA. Friday: Moderate Operational Impact. Chance of SHRA. Friday Night: Moderate Operational Impact. Chance of SHRA. Saturday: High Operational Impact. Breezy Likely SHRA...RA...TSRA. Saturday Night: Moderate Operational Impact. Chance of SHRA. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX. && .HYDROLOGY... A mild and increasingly moist airmass will be in place through Saturday. Light showers are possible later today into Friday. This will cause gradual snow melt and subsequent runoff. Also, a quick-moving, strong storm system may bring a period of moderate to heavy rainfall Saturday afternoon and evening. The Meteorological Model Ensemble River Forecasts /MMEFS/ continue to suggest significant river rises will occur, with flooding possible Saturday into Sunday due to the combination of snow melt and moderate to heavy rain. Total QPF forecast of 0.50 to 1.50 inches is forecast through Saturday night, with the lowest amounts in the Mid- Hudson Valley and Northwest Connecticut, and the highest amounts over the Western Adirondacks. The majority of the rainfall is expected to occur with the frontal passage Saturday afternoon/evening. At this time, at least minor flooding appears possible for at least a few points along main stem rivers, especially over the Adirondacks and Green Mountains where the snowpack is greatest. We will have more specific information as the weekend draws nearer. A flood watch may be necessary if confidence in flooding increases. 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...11/Thompson/JPV NEAR TERM...Thompson SHORT TERM...Thompson LONG TERM...11 AVIATION...BGM/11 HYDROLOGY...Thompson/JPV

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