883 FXUS61 KALY 162336 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 736 PM EDT Sun Oct 16 2022 .SYNOPSIS... Mostly dry conditions are expected for much of tonight, then a frontal system will bring clouds and rounds of showers on Monday. Mainly dry but much cooler weather returns on Tuesday and Wednesday. && .NEAR TERM /THROUGH MONDAY/... A broad upper-level trough across the eastern CONUS will strengthen and and slowly drift eastward toward the area tonight through Monday. Surface low pressure will develop across the Great Lakes and send a warm front across the region Monday morning and a cold/occluded front Monday afternoon and evening. We will start out tonight partly to mostly clear and dry, though clouds will begin to increase as and warm front approaches from the south and west during the overnight. A few showers could break out around daybreak, primarily focused across the mid- Hudson Valley and the western Mohawk Valley/Adirondack region. Lows should dip into the mid-30s to mid-40s for most. Showers will then increase in coverage and lift northeastward along the warm front Monday morning. There could be a break in activity across many areas in the wake of the warm front during the midday hours. Scattered to numerous showers (in one or multiple bands) are then likely to develop ahead of the main cold/occluded front in the afternoon and track from west to east. Guidance suggests some shallow convective elements cannot be ruled out as weak instability develops (MUCAPE values in the 100-250 J/kg range). Coverage and timing of the afternoon showers will be dependent on the arrival of a mid-level dry slot, which looks to now hold off more toward Monday evening, though adjustments to timing may be needed in later updates. The combination of both the morning and afternoon shower activity was enough to include likely pops for all areas, though there will be periods of dry weather as well. With the clouds and occasional showers, high temperatures Monday will only reach the upper 40s to mid-50s across the higher elevations and the upper 50s to lower 60s in the valleys. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... A trend toward drier and cooler weather is expected as the main upper-level trough slowly pushes eastward. Any lingering showers along or ahead of the cold/occluded front Monday evening will push off to the east. There is uncertainty with where the front slows its eastward progression or stalls as an area of low pressure may develop along the front off the mid-Atlantic Coast and lift northward across New England. Due to this potential, slight to low chance pops were maintained mainly for areas east of the Hudson River Monday night into Tuesday morning. Otherwise, a mid-level dry slot will gradually push into the region ending shower chances. It will move into eastern New York during Monday night and spread eastward into western New England on Tuesday. This will also bring the return of some sunshine on Tuesday. Mainly dry weather should continue Tuesday night as the mid- level dry slot remains in control. Despite the upper-level low continuing to slowly progress eastward toward the lower Great Lakes, shower activity near the Great Lakes should remain to the west of the Adirondacks and Mohawk Valley as low and mid-level flow will be too south to southwesterly to advect any showers that far eastward. As mentioned earlier, cooler air will gradually filter into the region. 850 hPa temperatures will start out between +1 to +5C Monday evening falling to -1 to -4C by Tuesday night. Low temperatures Monday night will range from the lower to mid-30s across western areas to the upper 30s to lower 40s across western areas. Highs Tuesday will only reach the 40s across the higher terrain to the 50s in the valleys. Tuesday night is shaping up to be a cold night with frost/freeze potential across the remaining growing season areas (Hudson Valley and southern Litchfield County). Lows will dip into the mid to upper 20s across most higher terrain areas to the low to mid-30s in the valleys. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Large-scale pattern change possible in the medium range. Driven by modest -NAO/negative North Atlantic Oscillation and +PNA/Positive Pacific North American Oscillation anomalies, the extended starts off with an amplified large-scale pattern featuring anomalous ridging over the western CONUS and anomalous troughing over the eastern CONUS. This will feature a warm West U.S. vs. a cool East U.S. setup. However, global computer models and ensembles (GEFS/ECE/CMC) continue to signal the potential for a major, large- scale pattern flip that will feature troughing over the western CONUS and ridging over the eastern CONUS (cool West US vs. mild/warm East US). The large- scale pattern is expected to remain quite amplified during this time too. What this means for us locally is a cool start to the period with below normal temperatures moderating to warmer or above normal levels by the end of the period, potentially setting up for a mild/warm and very pleasant weekend. As far as precipitation, most of the forecast area will remain precipitation-free. The only real exception will be areas northwest of Albany, specifically Herkimer/Hamilton Counties that could be affected by lake effect rain/snow showers Wednesday into Thursday. We start off the period on Wednesday with the forecast area on the eastern flank of an anomalously strong mid to upper low axis centered over the eastern Ontario into the eastern Great Lakes Region. To put into perspective the strength of this strong mid- upper low/PV lobe, forecast models are indicating the low central pressure at H500 to range anywhere from 528-533 mb, some 1-3 STDEVs below normal for mid to late October standards, according to the NAEFS. In connection with this mid to upper low will be unseasonably cool temperatures. Deterministic forecast models continue to indicate H850 temps ranging between -2C to -5C, which is on the order of 1-2 STDEVs below normal. These cold temps aloft combined with a west- southwest fetch off the eastern Great Lakes (i.e. Erie and Ontario) will effectively result in a lake response in the form of lake effect rain/snow showers during the day on Wednesday. Given the synoptic and mesoscale setup, the focus for any lake effect rain/snow showers will be northwest of Albany, specifically Herkimer/Hamilton Counties. Outside of that, much of the area will remain precipitation-free. Clouds on Wednesday will range from mostly sunny southeast of Albany to mostly cloudy northwest of Albany. Wednesday night through the day on Thursday, lake effect rain/snow showers over our northwestern sections (Herkimer/Hamilton Counties) should wane as the aforementioned low weakens and retreats further north into Canada and high pressure begins building into the area from the south. Quiescent weather conditions will persist through the weekend or through the remainder of the period with high pressure in control over the region. Overall, temperature anomalies will be Autumn-like starting off below normal before trending to above normal levels by the end of the period in response to the large-scale pattern change highlighted above. Went along with guidance with temperatures through Friday and slightly above guidance for next weekend. High temperatures Wednesday and Thursday are progged to only reach the lower to mid 50s along the river valleys (40s higher elevations with pockets of 30s possible over the highest peaks of the Adirondacks). A bit warmer/milder and near normal levels on Friday with high temperatures expected to reach the upper 50s to lower 60s along the river valleys (upper 40s to mid 50s higher elevations). Unseasonably warm temperatures enter into the area over the weekend with high temperatures expected to be in the mid to upper 60s along the river valleys. A 70F degree or two is not out of question in some spots with the greatest confidence in that occurring over the mid-Hudson Valley. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... Through 00z Tuesday....Conditions are currently VFR at all of the terminals with unrestricted vsbys and just a few mid to high level clouds. Over the next 6-9 hours or tonight into the pre-dawn hours of Monday morning, clouds are expected to increase and lower in elevation from south to north ahead of an approaching warm front. This warm front could trigger some showers as it advances over the area from south to north during the morning hours. Have maintained Prob30 headlines with the most likely time window for the TAF sites to reflect this potential. Any showers that develop could lead to MVFR reductions. Once the first batch of showers move on, vsbys will return to VFR. Cigs, however, are expected to hover between low VFR and high MVFR, mid morning through the remainder of the TAF period. Confidence for MVFR cigs are greatest over KPOU and KPSF. After a brief reprieve from the morning showers, another (second) round of showers could develop during the afternoon/evening hours. Have included another set of Prob30s with the most likely time window to highlight this potential for all the TAF sites as well. Light and variable to calm winds this evening will persist through the rest of the night before picking up out of the south at 5-10 kts Monday morning. Outlook... Monday Night: Moderate Operational Impact. Likely SHRA. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Rathbun NEAR TERM...Rathbun SHORT TERM...Rathbun LONG TERM...Evbuoma AVIATION...Evbuoma