


Area Forecast Discussion
Issued by NWS Albany, NY
Issued by NWS Albany, NY
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903 FXUS61 KALY 220841 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 441 AM EDT Thu May 22 2025 .SYNOPSIS... Unseasonably cool today with light showers in eastern NY but steadier rain in western New England as a coastal low tracks off shore. Light wet snow accumulations expected late this afternoon into tonight mainly for elevations 1500 feet and higher in southern VT. Cool and cloudy with additional scattered light showers on Friday and Saturday before temperatures finally trend warmer Sunday into Monday albeit a few light showers still not ruled out. && .NEAR TERM /THROUGH TONIGHT/... Key Message: - Rainfall amounts have trended lower mainly in eastern NY for today as morning showers turn quite light and more intermittent for the afternoon. Steadier rain still expected in western New England where total rainfall amounts of 1 to 1.50 inches still expected. - Light wet snow accumulations likely in southern Vermont for elevations 1500 feet and higher late this afternoon into tonight with snow accumulation ranging from coatings up to 1 inch. There is even a 20 to 40% chance for snow amounts to exceed 2 inches above 2000 feet. Discussion: Latest water vapor imagery shows our coastal low beginning to develop off the coast of New Jersey in response to a compact shortwave rotating around the main parent trough resulting in increased CVA and forcing for ascent. Further north over eastern NY and western New England, a band of more organized showers tracks northward early this morning given enhanced warm air advection in the low and mid-levels ahead of the coastal low. After this band of steadier rain exits by mid- morning, showers will turn lighter and more intermittent as we remain north and west of the developing coastal low and well east of the parent trough over the Great Lakes. While weak warm air advection and plenty of moisture in the low levels will maintain overcast skies and drizzle/patchy light showers, organized steady rain should remain generally to our south/east for much of the day. Easterly flow upsloping the terrain will support steadier light showers along the east slopes of the southern Green, Berkshires, and the northern/eastern Catskills. Otherwise, we remain in the cool conveyor belt ahead of the coastal low and daytime temperatures will struggle to rise out of the 40s to only around 50 in valley areas. Needless to say, this is unseasonably cool for late May and we likely will challenge record low maximum temperatures for May 22. See our climate section for details. Given the expectation for rather light showers/patchy drizzle for most of the area, we trended QPF amounts downwards except in western New England were more of the effect of the coastal low will be felt. By late this afternoon into this evening, our developing coastal low undergoes cyclogenesis as the aforementioned compact shortwave aloft takes on negative tilt resulting in strong CVA while the low`s positioning in the equatorward exit region of a 110-1220kt cyclonic curved jet streak provides notable upper level divergence. The coastal low therefore deepens to ~995hPa as it tracks northward towards Cape Cod and the 40W/70N benchmark. While the coastal low will be quite compact with much of its precipitation shield focused in New England, bands of steadier rain look to extend into our western New England zones. In fact, strong deformation within its NW quadrant likely results in a pivoting band (as discussed in our previous forecast discussion) with CAMs and sources of higher resolution guidance pointing to this band pivoting across parts of southern VT. With such a cool air mass in place and low dew points around freezing within the southern Greens, as precipitation turns moderate in intensity late this P.M (21 - 00 UTC), forecast soundings show wet-bulb cooling processes resulting in a deep isothermal layer in the low to mid-30s which should support a changeover to wet snow. Wet-bulb zero heights drop to around 1500ft by around 00 UTC with moderate precipitation continuing through 03 - 06 UTC before the low lifts north/eastward into the Gulf of Maine. During this window, steady enough snow looks to fall in the southern Greens to result in snow accumulations from coating to 1 inch with probabilistic guidance showing 20-40% for up to 2 inches in elevations above to 2000ft. While generally low snow amounts are expected, this is rather unusual for late May and anyone planning to be on the road this evening in the southern Green should allow extra travel time and be prepared for a period of moderate wet snow. After 06 UTC, the steady precipitation turns into scattered light rain showers. Widespread clouds and lingering light spotty showers will limit the diurnal temperature change overnight with many remaining in the 40s. Total rainfall amounts expected to range from the 0.25 to 0.75" with up to 1 - 1.50" in the mid-Hudson Valley, eastern Catskills, and western New England. Still not expected any flooding impacts. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Cool, cloudy, and unseasonably cool conditions continue into Friday and Saturday and the start of the Memorial Day Holiday weekend. The parent trough over the Great Lakes gradually shifts eastward and absorbs the secondary low, maintaining moist cyclonic flow overhead. With the cool pool aloft and daytime heating in play, scattered areas of showers will be around most Friday. As an inverted trough develops on the back side of the weakening parent low and swings through the region late Friday P.M into Friday night, a more organized area of showers look to develop. We therefore trended POPs upwards to 50-70% chance range by 00 - 06 UTC Friday for much of the area. Only slight improvements expected for Saturday as the parent flow slowly exits into northern New England. While the core of its cool pool shifts to our north/east, enough of it remains nearby and with the upper deformation zone of the low overhead, additional diurnally driven showers are expected. Northwest cool air advection around the low will maintain a fetch of moisture off Lake Ontario so the highest POPs were placed in the western Adirondacks, northern/eastern Catskills and southern Greens where upslope flow could enhance shower activity. Elsewhere, shower coverage should be less numerous compared to Friday and there should be periods of dry time. Otherwise, it will be the third day in a row with unseasonably cool temperatures struggling to rise out of the 50s (low 60s mid- Hudson Valley) under mainly cloudy skies once again. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... The unsettled pattern of late remains in place through much of the extended forecast period. With the aforementioned closed, upper low remaining within reach through at least Monday evening, eastern New York and western New England will remain locked into cyclonic flow about its southwestern periphery. Numerous shortwave perturbations will rotate through the region about the slow, eastward-tracking low through Monday evening, generating sufficient ascent to support several rounds of scattered showers. Coverage remains a bit uncertain at this time courtesy of discontinuities within the medium to long-range guidance. However, with the cold pool aloft beginning to weaken and much weaker forcing with the gradual departure of the primary low, showers will be fairly light and contribute little in the way of additional precipitation to what will have preceded in the previous week. The scattered nature of showers also means that the end of the Memorial Day weekend will not be complete wash outs, so expect opportunities for outdoor activities. Surface high pressure and shortwave ridging aloft build in Monday night, reinforcing regionwide dry conditions into Tuesday. Most of the region should remain dry through Tuesday afternoon before rain chances increase once again Tuesday evening into Wednesday. However, at this point, there is still quite a bit of uncertainty in the conditions expected Tuesday night into Wednesday. General consensus indicates a Southern Stream surface low developing in and around the Southern Plains/Deep South, tracking eastward and off the coast of the Carolinas/Mid-Atlantic Tuesday night/Wednesday morning whilst another upper-level, closed low develops over the Great Lakes. A secondary surface low also looks to develop along the Appalachians, which, along with the upper closed low, looks at this time to be our primary rain producer. However, the significant differences in the depiction of the track and timing of the coastal low are what impact this forecast the most at this point. Should this disturbance hug the Atlantic Coast, rainfall could be enhanced especially south and east of Albany. If it`s track is more easterly, our main precipitation source will be the secondary surface and upper-level closed low which would likely mean lower QPF. Temperatures finally begin to moderate through Wednesday with Sunday`s mid/upper 50s to mid 60s likely being the coolest highs of the period. Values rise to the 60s and low 70s Monday with widespread 60s expected Tuesday and Wednesday. Lows will primarily be in the 40s and 50s. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Through 06z Friday...MVFR to VFR conditions currently prevail across all terminals with light rain showers scattered throughout eastern New York and western New England. Throughout the 06z cycle, rounds of rain will force mainly MVFR conditions through lowered ceiling heights, though some improvements to VFR heights are anticipated in between batches. As rain is anticipated to be relatively light in terms of rates per hour, visibility will generally remain within the VFR category, though some MVFR visibility could occur at KPSF where some upslope enhancement could strengthen rainfall rates. There is some uncertainty in timing and evolution of the rain bands that will cause the less than ideal flying conditions, but included TEMPOs and PROB30s where confidence is greatest in rain, and subsequent category change, occurrence. Winds throughout the period will generally prevail out of the northeast at speeds under 10 kt. However, KPSF could see some sustained speeds at or just above 10 kt with gusts up to around 20 kt due to the terminal`s proximity to the coastal low that will be responsible for some of the rain incoming this afternoon and tonight. Outlook... Friday Night: High Operational Impact. Numerous SHRA. Saturday: Moderate Operational Impact. Scattered SHRA. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Low Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Memorial Day: Low Operational Impact. Slight Chance of SHRA. Monday Night: Low Operational Impact. NO SIG WX. Tuesday: Moderate Operational Impact. Chance of SHRA. && .CLIMATE... Record low maximum temperatures for May 22: Albany: 52F (2005) Glens Falls: 52F (2005) Poughkeepsie: 56F (2005, 2003) && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Speciale NEAR TERM...Speciale SHORT TERM...Speciale LONG TERM...Gant AVIATION...Gant CLIMATE...Rathbun