468 FXUS61 KALY 061953 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 353 PM EDT Mon Sep 6 2021 .SYNOPSIS... High pressure will bring generally fair weather, and near seasonable temperatures tonight through Tuesday night. A strong frontal system will approach from the west later Wednesday, bringing showers and thunderstorms Wednesday afternoon and night, with some locally heavy downpours possible. && .NEAR TERM /THROUGH TUESDAY NIGHT/... As of 345 PM EDT, cold front was located from southern Berkshire County into the southern Taconics/northeast Catskills, and tracking southeast. Isolated showers/sprinkles remain with the front, with mainly some clouds and a wind shift otherwise denoting the boundary. As the front continues tracking south and east, slightly warmer temps aloft and decreased mid/upper level forcing should limit any additional impacts with front other than isolated showers, and some gusty winds. In the wake of the front, subsidence has allowed for skies to become mostly sunny across the I-90 corridor, with more clouds and a few passing showers across the southern Adirondacks, closer to the mid/upper level cold pool aloft and some lake enhancement. Expect breezy conditions to persist through sunset, with some gusts of 25 to 35 mph possible within the Mohawk Valley, Capital Region and Berkshires. Tonight...In the wake of the cold frontal passage, mostly clear skies and dry weather are expected as we should be in a regime favoring large-scale subsidence thanks to height rises and anticyclonic vorticity advection aloft. At the lower levels, a 1018 mb surface high will build into the region from the southwest. As the high builds in, the pressure gradient is expected to weaken, which will allow winds to become light to (in sheltered valleys) calm by morning. While dew point depressions will be larger than the previous few nights with the drier airmass overhead soils moisture is anomalously high due to recent wet weather. Therefore, some radiational fog may still develop in sheltered and/or valley locations towards sunrise due to favorable radiational cooling conditions. With cold air advection for the first half of the night and more radiative cooling towards morning, overnight lows will drop into the mid-upper 40s in the high terrain and low-mid 50s in the valley locations. Tuesday...Heights continue to rise aloft, and we will end up under the axis of an amplifying upper-level ridge tomorrow afternoon. This will help keep tranquil weather for our region during the day tomorrow. Meanwhile, the surface high will slide to our southeast during the day, which will result in northwesterly winds and cold air advection early in the day switching to southwesterly winds and warm air advection tomorrow afternoon. After a cool start to the day, high temperatures will recover to the mid and upper 70s for valley locations, although higher elevations will only have highs in the 60s. Tuesday Night...Looking aloft, the upper-level ridge axis will depart to our east as an impressive closed upper low digs south from Ontario towards the Great Lakes Tuesday night. A surface low is expected to develop in response to the upper low and track north of the Great Lakes. As this low deepens to 992 mb by Wednesday morning, it will drag a strong cold front towards our region. Therefore, even though the best upper forcing (cyclonic vorticity advection, height falls) will remain to our west through much of the nigh, a few showers will be possible towards daybreak for our far northwestern areas ahead of the approaching front. In the lower levels...as the surface high slides further to the east, warm air advection into the region continues, with a warm front expected to lift through the region overnight. Behind this warm front, advection of higher theta e air into the region will continue, with PWAT values rising to around 1.2-1.3" by Wednesday morning. The combination of warm air advection, higher dewpoints, and more cloud cover than the previous night will result in warmer overnight lows, with mid 50s expected in the high terrain and upper 50s to around 60 for valley locations. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... A cold front will slowly approach from the west later Wednesday into Wednesday night. Strong south/southwest flow will develop, especially within the mid and upper levels of the atmosphere. As the front tracks east, it should tend to slow down a bit, especially as ridging off the New England coast potentially builds a bit stronger, while Hurricane Larry tracks into the northwest Atlantic Ocean. PWAT's are forecast to increase to 1.5-1.75 inches across eastern New York/western New England, and with winds becoming nearly parallel through a deep portion of the troposphere, the potential for training showers/thunderstorms with locally heavy rainfall exists for late Wednesday afternoon into at least the first half of Wednesday night. The best chance for heavier downpours currently appears to be the region from the northeast Catskills, Capital Region into southern VT, however this could change. There could be some embedded thunderstorms as well, although the coverage of stronger thunderstorms will be modulated by timing of frontal passage, which may not occur until after sunset in some areas. However, mid level wind fields will be strong, with H500 winds of 40-50 KT, so strong wind gusts could occur within any bowing line segments. Even outside convection, some strong south winds may occur ahead of the front, perhaps gusting 25-35 mph within some north/south oriented valleys, including portions of the Hudson River Valley close to the Capital Region. As for temperatures, some morning breaks of sun and warm temps aloft should allow max temps to reach 75-80 in most valley areas, with upper 60s to lower 70s across higher elevations. Lows Wednesday night mainly in the mid 50s to lower 60s. && .LONG TERM /THURSDAY THROUGH MONDAY/... A mostly quiescent weather pattern can be anticipated during the long-term forecast period. The large-scale upper level pattern during this period will still undergo a transition from a more amplified (warm West U.S. vs. a cooler East U.S.) configuration to start the period to a more zonal/semi-zonal setup later on in the extended. This transition will contribute to some of the uncertainty in the weather pattern later in the extended. The weather pattern will remain progressive too through the extended. As far as temperatures, we're expecting to see a cooler than normal bias in anomalies with things feeling more Autumn-like over the region during this period. We start off the long-term period Thursday with eastern New York and western New England on the backside (cold-side) of a pretty potent storm system that will be centered well off to our north near the Hudson Bay and it's associated cold front to our east just off the coast of New England. Cooler and drier conditions will be in place as cold air advection (CAA) ensues. Thermodynamics between Lake Ontario and the air just above it plus several mid-upper level impulses overhead associated with an upper level trough/broad- cyclonic flow aloft will be supportive of some lake-enhanced rain showers over parts of the area as backing winds out of the west flows downwind of Lake Ontario. Additionally, there could also be areas of orographic enhancement during the diurnal peak hours on Thursday. Lake-enhanced and any diurnal-orographically driven rain showers should wane during the evening/nighttime hours due to the loss of energy from the sunlight and westerly winds subsiding. On Friday, a broad 1016 hpa surface high pressure system is progged to build into the region from the west-southwest. This will effectively result in dry and tranquil conditions returning to the ALY forecast area. Expect a mostly sunny to partly cloudy day with areas south of Albany seeing the clearer conditions due to its proximity to the aforementioned high pressure system building in. On Saturday, expect a sunny to mostly sunny day as the high pressure system gets a firmer grip over the region with the center of the 1020 hpa high over the Mid-Atlantic states into the Carolinas. For Sunday, forecast models are advertising a powerhouse storm system that's currently forecast to track from the Northern Plains/Upper Midwest Region northeastward into Ontario and eventually Quebec. It's uncertain this far out as to how much influence weatherwise this storm system will have over our area. Current thinking is that clouds will increase during the day on Sunday especially over our northwestern zones (Herkimer and Hamilton Counties). Most areas at this point will remain dry with the exception of Herkimer and Hamilton Counties. Will have to continue to monitor trends on how much extent and thus influence this storm system will have on the area. For now, have just low-grade PoPs for areas northwest of Albany with the 30% PoPs over Herkimer and Hamilton Counties. Dry and tranquil conditions return to the area to start the new workweek, should we have any precipitation over the area on Sunday. The passage of a cold front associated with the aforementioned storm system will result in cooler, more Fall-like temperatures on Monday. With the exception of Sunday, high temperatures will hover in the lower 70s along the river valleys (60s and even some upper 50s in the higher elevations). On Sunday, high temperatures will top out in the mid 70s along the river valleys (60s higher elevations). Overnight low temperatures during this period will be mostly in the 50s (40s higher elevations) with the exception of Sunday night where lows are progged to be in the upper 50s to lower 60s along the river valleys (mid 50s higher elevations). && .AVIATION /20Z MONDAY THROUGH SATURDAY/... Through 18z Tuesday...Fog and low stratus were slow to erode this morning, but ceilings and visibilities are now VFR at all TAF sites. Main concern through the next few hours is a broken line of showers moving through the region. This line of showers has already passed GFL, and will pass ALB by 19z, PSF by 20z, and POU by 21z. Due to broken nature of this line of showers, have included VCSH at all sites except for GFL early this afternoon. At this time, lightning activity has diminished with this line of showers, but an isolated thunderstorm will be possible during the next couple of hours. However, given sparse coverage of thunder, will not mention in the TAFs at this time. This line of showers is associated with a cold front currently moving through the region. Behind this cold front, skies will become partly to mostly sunny, with just FEW to SCT clouds above 6000 ft. VFR conditions will persist through at least the end of the TAF period at ALB and POU, but some patchy fog is possible at GFL and PSF tonight with clear skies and high pressure building into the region. Fog should not be as widespread or as dense as it was this morning. Any early fog should lift by 13z Tuesday with VFR conditions at GFL and PSF as well through the end of the TAF period. Winds will switch to northwesterly behind the cold frontal passage within the next few hours, and will be sustained at around 10-15 kts with gusts of 20-25 kt possible. Winds gradually decrease this evening and tonight, becoming light to calm after midnight. Tuesday morning, winds will gradually increase to 5-10 kt again and will be mainly from the west/northwest. Outlook... Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: High Operational Impact. Breezy. Definite SHRA...TSRA. Wednesday Night: High Operational Impact. Definite SHRA...TSRA. Thursday: Moderate Operational Impact. Chance of SHRA. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... High pressure will bring generally fair weather, and near seasonable temperatures tonight through Tuesday night. A strong frontal system will approach from the west later Wednesday, bringing showers and thunderstorms Wednesday afternoon and night, with some locally heavy downpours possible. RH values will increase to 90-100 percent tonight with areas of dew formation likely. RH should drop to 45-55 percent Tuesday afternoon. Gusty west to northwest winds of 15-25 mph should diminish to less than 5 mph after midnight, then become west to southwest at 5-15 mph on Tuesday. && .HYDROLOGY... Mainly dry conditions are expected tonight through Tuesday night. More showers and thunderstorms are possible for Wednesday afternoon and night. Thunderstorms could produce locally heavy rain, resulting in ponding of water on roadways and standing water in low lying areas. However, river flooding is not expected at this time. 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...KL NEAR TERM...Main SHORT TERM...KL LONG TERM...Evbuoma AVIATION...Main FIRE WEATHER...KL/NAS HYDROLOGY...KL/NAS