Area Forecast Discussion
Issued by NWS Albany, NY

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734 FXUS61 KALY 222011 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 411 PM EDT Wed May 22 2019 .SYNOPSIS... Clouds will increase tonight with some showers possible late as a low pressure system approaches from the Great Lakes region. A frontal system associated with this low will bring humid conditions for Thursday along with some showers and scattered thunderstorms, mainly during the afternoon and evening. Seasonable temperatures and breezy conditions will return for Thursday night into Friday. Another frontal system approaching from the west could bring some showers by late Saturday afternoon. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... As of 4 PM EDT, a mix of sun and patchy high clouds continue across the region, with thicker high/mid level clouds lurking upstream across western NY and southern Ontario. Temps have warmed to 65-70 within most valley areas, and 60-65 across higher elevations. There were some sprinkles falling from the mid level clouds across portions of extreme western NYS. As these clouds track east and south, the leading edge may initially erode upon reaching our region at times early this evening. However, as mid level isentropic lift increases, the clouds should thicken from NW to SE later this evening, with some light showers/sprinkles possible reaching the SW Adirondacks and western Mohawk Valley toward midnight. The best isentropic lift appears to be across the SW Adirondacks/Mohawk Valley region overnight, and even stronger across central and western NYS. Areas and/or bands of showers should develop and track across these regions after midnight, before settling south and east into the eastern Catskills. Capital Region and mid Hudson Valley closer to daybreak. Portions of southern VT and NW MA may tend to remain dry much of the night as the bulk of moisture and forcing may be held to the south and west. A few rumbles of thunder can not be ruled out closer to daybreak across the SE Catskills and mid Hudson Valley, where some weak elevated instability and steeper mid level lapse rates will graze. Temps may initially drop into the 40s to lower 50s across portions of the southern Adirondacks and southern VT before midnight, before rising slightly after midnight. Elsewhere, lows should be mainly in the lower/mid 50s. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Morning showers across southern areas should depart by mid morning, with a relative lull in precipitation until early afternoon. However, models suggest quite a bit of mid level clouds persisting in most areas during this time, limiting heating, and also dewpoints are forecast to only slowly rise into/through the 50s. By afternoon, showers and thunderstorms are expected to develop across western/central NYS, closer to greater mid level height falls and low level forcing ahead of an approaching cold/occluded front. Mid level wind fields are expected to increase dramatically Thursday afternoon, with H700-H500 winds reaching 50-60 KT or slightly higher by late afternoon. So, kinematics will be very strong, but it remains questionable whether enough thermodynamics will be present to create sufficient updrafts to work in tandem with the strong deep layered shear and allow for any discrete storms to become supercellular. It appears that instability will remain weak, with MU CAPES likely only reaching several hundred J/kg across the western Mohawk Valley/SW Adirondacks, and less farther south and east. The weaker instability may not be enough to overcome the strong mid level wind fields, and could result in highly tilted updrafts with any discrete cells that can form. Showers and some thunderstorms will likely move into the region from the west during the mid to late afternoon, some of which could contain strong wind gusts if they become tall enough and/or organize into a line. The best chances for this may be if discrete cells upstream of our region form into a QLCS, which could then propagate into the Mohawk Valley/SW Adirondack region and possibly points immediately south and east, potentially mixing down strong winds from aloft due to momentum transfer. Again, this is a possibility, but not certain, but should this mode develop, then a better chance for damaging wind gusts would occur across the Mohawk Valley/SW Adirondack region and perhaps as far S/E as the greater Capital Region of NY and into southern VT. As for any discrete cells, this potential, albeit small, would mainly be areas west of the Hudson River across the SE Catskills and perhaps western mid Hudson Valley region. SPC has trimmed the Slight Risk area westward from earlier issuances (now only covering extreme western Mohawk Valley and SW Adirondacks) with Marginal Risk also trimmed back farther west, extending to just east of the Hudson River. High temperatures Thursday may reach the lower/mid 70s in some valley areas, especially across the Mohawk Valley, Schoharie Valley and Capital Region, with mainly 60s to around 70 elsewhere. Gusty south winds will also develop later in the day, with some gusts possibly reaching 25-35 mph in some north/south valleys including portions of the Capital Region. For Thursday night, showers and scattered thunderstorms may linger into the evening hours, before ending from west to east before midnight. Breezy and cooler conditions will then filter into the region behind an occluded front, with some spotty showers/sprinkles possible across the southern Adirondacks and southern VT. Lows mainly in the 50s, with some 40s possible across higher terrain of the southern Adirondacks. Strong west/northwest winds may reach 25-35 mph later at night behind the front, especially within the Mohawk Valley/Capital Region and Berkshires. Friday-Friday night, breezy and cool for Friday, with clouds and some showers/sprinkles possible across northern areas due to the passage of main upper level trough/cold pool. Better chances for clearing will be across southern areas. Highs mainly in the 60s, although some lower 70s could occur late in the day in some valley areas, while some higher elevations across the Adirondacks and southern VT remain in the 50s. Gusty west/northwest winds may reach 25-35 mph. Clearing for Friday night, and cool with lows mainly in the 40s to lower 50s. Some 30s could occur across the SW Adirondacks and eastern Catskills if skies remain clear long enough. Saturday, the next fast moving frontal system will approach from the Great Lakes region later in the day or at night. Expect increasing clouds during Saturday, with chances for showers increasing in the afternoon. Some thunder could also occur, although initial instability parameters look fairly limited through sunset. Highs mainly in the mid 60s to lower 70s, although could be warmer if more sunshine occurs through the morning hours. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... The extended forecast period begins unsettled for the middle portion of the Memorial Day holiday weekend, but high pressure looks to build in late Sunday pm into Monday. If the ridge holds on, then fair weather may continue into early Tuesday before unsettled weather returns for the mid-week. Saturday Night into Sunday...A prefrontal sfc trough and a cold front will bring an increase of showers and thunderstorms across the forecast area Saturday night. The better instability looks to be from the Capital Region north and west early in the evening. A slight to low chance of thunderstorms was kept in until midnight. The higher PoPS were maintained from roughly the Capital Region north and west. Lows Sat night will be on the mild side with 50s to around 60F. The latest medium range guidance has the cold front moving through the forecast area in the late morning into the early pm. We kept a slight chance of showers with perhaps a thunderstorm over the higher terrain in the pm especially over the southern Greens and southern Adirondacks. Overall, we will favor a clearing trend for the afternoon and lean towards the latest 12Z ECMWF and WPC guidance. Highs will be close to normal with mid 70s to around 80F in the lower elevations, and mid 60s to mid 70s over the hills and mtns. Sunday night into Monday...High pressure builds in from the southeast Ontario and the central and eastern Great Lakes Region with west to northwest flow aloft. A cool and pleasant night is expected with lows in the upper 40 to upper 50s. The weak sfc high settles over NY and New England by Memorial Day. H850 temps will be near normal based on the latest GEFS guidance, and will be in the +13C to +15C range with highs in the mid and upper 70s over the valley locations, and mid 60s to lower 70s over the higher terrain. A weak warm front starts to move towards the region late in the day ahead of a quick moving short-wave trough. The latest 12Z EC keeps the sfc ridge in control, while the latest GFS has a few showers over the southern Adirondacks. We placed a slight chance of showers from the Hudson River Valley eastward for the afternoon, and a very low chance to west. This short-wave does not have a lot of low- level moisture to work with, so an increase of clouds may be all that occurs during the day. Monday night into Tuesday...A weak sfc anticyclone may settles back in across the region in the wake of the short-wave trough and weak cold front late Mon night. A low chance of showers was kept in the forecast early in the evening. The question will be how quickly a warm front and strong low pressure system approaches from the Upper Midwest and Great Lakes Region. The 12Z GFS is more aggressive than the latest 12Z ECMWF, with some spread in the Ensemble guidance brining showers back into the region by Tue pm. Low confidence forecast here with the better chance of showers from the Capital Region north and east. Lows Monday night will be in the 40s north and west of Albany, and upper 40s to lower 50s south and east. Highs Tuesday will depend on the amount of sunshine and placement of the warm front. We did not stray too far from the superblend with 60s to lower 70s over most the region. Tuesday night into Wednesday...A strong subtropical ridge attempts to build in centered over the Gulf of Mexico and Florida. Mid and upper level heights try to increase over NY and New England. If the warm front lifts through the entire area quickly, then we could be in a warm and more humid air mass that the latest 12Z ECMWF MOS/MEXMOS, as well as the 12Z GEFS /850 hPa temps +1 to +2 STD DEVs above normal/ are indicating. We kept a slight or low chance of showers in across the region with the highest PoPs over the northern most zones. We went a little higher than the Superblend with upper 70s to around 80F in many of the valley areas, and mid/upper 60s to lower/mid 70s over the higher terrain. Sfc dewpts increase into the mid 50s to lower 60s. && .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... VFR conditions for the balance of the afternoon into the evening hours as high and mid level clouds increase and thicken. Eventually, these clouds will lower further to MVFR thresholds tonight with the threat of showers. At this time, seems the best potential for showers will be south of KGFL-KALB where we will place VCSH. PROB30 for KPOU-KPSF where showers might be a bit more concentrated. Winds will generally be northerly around 10kts or less. Winds subside to light and variable this evening. Then overnight and toward sunrise, southerly winds with an increase of 10-18 kts expected. Outlook... Thursday Night: High Operational Impact. Breezy Likely SHRA...TSRA. Friday: Low Operational Impact. Breezy NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: Moderate Operational Impact. Breezy Likely SHRA...TSRA. Saturday Night: Moderate Operational Impact. Breezy Chance of SHRA...TSRA. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Memorial Day: Low Operational Impact. Slight Chance of SHRA. && .FIRE WEATHER... ...Wind gusts of 25-35 mph possible Thursday... Clouds will increase tonight with some showers possible late as a low pressure system approaches from the Great Lakes region. A frontal system associated with this low will bring humid conditions for Thursday along with some showers and scattered thunderstorms, mainly during the afternoon and evening. Seasonable temperatures and breezy conditions will return for Thursday night into Friday. Another frontal system approaching from the west could bring some showers by late Saturday afternoon. RH values will climb to 70-90 percent tonight, then fall to 55-65 percent Thursday afternoon. Winds will become light/variable after sunset, then become south to southwest and increase to 10-20 mph by Thursday afternoon, with some gusts of 25-35 mph possible. Spotty showers will develop after midnight, with a better chance for showers and scattered thunderstorms Thursday afternoon and evening as a frontal system moves across. && .HYDROLOGY... Some showers will develop late tonight, with showers and scattered thunderstorms expected Thursday afternoon and evening as a frontal system moves across. Total rainfall amounts for late tonight through Thursday night are expected to range from one quarter to one half inch for most areas, except up to three quarters of an inch across portions of the Mohawk Valley and southwest Adirondacks. Rainfall amounts may remain under one quarter of an inch across portions of the mid Hudson Valley and NW CT. This rainfall should not have significant impacts on rivers/streams. However, brief heavy downpours could lead to temporary ponding of water in poor drainage/urban and low lying areas. Additional showers and embedded thunderstorms are possible late Saturday into Saturday night with another fast moving frontal system passing through. Please visit our Advanced Hydrologic Prediction Service /AHPS/ web page for specific area rivers and lakes observations and forecasts. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...IAA/KL NEAR TERM...KL SHORT TERM...KL LONG TERM...Wasula AVIATION...BGM FIRE WEATHER...IAA/KL HYDROLOGY...IAA/KL

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