931 FXUS61 KALY 070531 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 131 AM EDT Sat Oct 7 2023 .SYNOPSIS... Tonight into Saturday, a slow moving cold front will bring widespread rain, heavy at times, and breezy conditions to the region. Behind the cold front, much cooler weather is expected for the second half of the weekend into next week with chances for lake effect showers each day, mainly across lake effect favored areas. && .NEAR TERM /THROUGH TODAY/... Scattered showers in eastern NY should slowly increase in coverage through the morning. An organized line of showers and isolated thunderstorms with locally heavy rain is just beginning to enter the western Mohawk Valley and is inching very slowly east. By daybreak it will be into the southern Adirondacks and in the western Mohawk Valley, where again, there could be locally heavy rain and a rumble of thunder. Temperatures will approach dew points by daybreak and lows will be in the upper 50s to lower 60s. PREVIOUS DISCUSSION: Most of the more widespread rain will hold off until better forcing arrives later tonight into early Saturday morning. Large scale ascent will increase as a deepening upper level trough approaches from the Great Lakes, with a short wave/trough axis rounding the base of the trough becomes negatively tilted as it tracks into our region on Saturday. Southerly low level flow will strengthen starting tonight (850 mb v-component wind anomalies of +1 to +2 STDEV) resulting in deep layer moisture increasing across our area (PWAT anomalies of +1 to +2 STDEV). At the surface, a cold front approaching from the west will move east across the area on Saturday. Convergence along the front, combined with anomalous moisture and some instability (MUCAPE ~100- 300 J/Kg), will focus an area of rain with embedded downpours and isolated thunder. This area of rain will be the main concern for possible localized flooding of urban, poor drainage and low lying areas, and even isolated flash flooding depending on how quickly the line moves through. Rainfall rates should be efficient in this environment. Guidance still showing potential for a fairly wide swath of 2 to 3+ inches of rain late tonight through Sat, but still differ on where the max amounts will occur. In general, ensembles and CAMs have trended slightly east compared to yesterday, with the main focus on most of eastern NY into western New England. This is also where there is a Slight Risk of excessive rainfall from WPC. See hydro section for additional details. High temperatures will be cooler on Sat (ranging from upper 50s to mid 60s) due to widespread clouds and rain with the cold front pushing through. The widespread rain should end Sat evening although some guidance is indicating a slower movement of the cold front, but generally the rain should taper off to mainly scattered showers by mid to late Sat evening. Winds will shift to the west and increase overnight as post-TC Philippe tracks inland into northeast Maine as a strong mid 980s mb cyclone. Colder air aloft will filter in, with 850 mb temperatures dropping to around 0 deg C. Lake effect rain showers will start to develop late across the western Adirondacks. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... Sunday looks to be much cooler with a large upper level trough in place across the Great Lakes and Northeast. The core of the upper low is forecast to track northwest into southern Quebec through the day, becoming vertically stacked as the circulation merges with post TC Philippe. Lake affect rain showers will be prevalent in favored areas due to a well-aligned westerly flow and cold temperatures aloft moving over the much warmer Lake Ontario water surface (+20C). The lake effect showers will be most likely across the western/southwest Adirondacks and northern portions of the Mohawk Valley. Some instability showers under the upper low will be possible outside any lake effect mainly north of Albany. Highs will only range from the mid/upper 40s in the mountains to upper 50s in the Hudson Valley. With good mixing conditions developing, westerly winds are expected to gust between 20-30 mph. The core of the upper low will track farther north/west to near the Quebec/Ontario border Sunday night, which will allow mixed- layer winds to back to a more W-SW direction. So lake effect will be more focused farther north across the western Adirondacks. Some snow showers may mix in at times over the higher peaks, especially overnight with a dusting possible in some spots. Precip will mainly be rain below 3000 ft. It will be continued cool and breezy with lows in the mid 30s to lower 40s. && .LONG TERM /MONDAY THROUGH FRIDAY/... Large upper level low is forecast to retrograde west into Ontario, with the system becoming vertically stacked and nearly stationary through the middle of next week. Overall cyclonic west-southwest flow will persist across our region, with a few disturbances rotating around the periphery of the upper low. This will result in periodic chances for isolated to scattered showers, mainly on Tuesday. Generally more clouds than sunshine expected especially for areas north/west of the Capital District. Temperatures will continue to be below normal Monday through Wednesday, then warming back to normal levels later in the week. A large storm system approaching from the southeast CONUS may bring some some rain starting Thursday into Friday, although the bulk of precip from this storm looks to hold off until next weekend. There is a large amount of spread in the guidance with regards to the track and timing of this system though. Stay tuned for updates as the event draws closer. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... Through 06z Sunday...Conditions as of 1:25 AM EDT range from VFR at PSF and GFL to IFR at POU. Cigs should trend down to MVFR at ALB/GFL/PSF and MVFR to IFR at POU through 10-12z this morning. There are also some isolated to scattered showers around, which could lead to brief MVFR vsby reductions, so have handled all of this with tempo groups through the next several hours. This morning, mainly low-end MVFR cigs prevail and showers increase in coverage and intensity through mid morning. Then, a sharp cold front will bring a period of moderate to potentially heavy rain to all of the terminals from mid-late morning through mid afternoon with MVFR to IFR cigs and vsbys. There is still some uncertainty in the exact timing of this band of heavy rain and how quickly it moves through the region, but have moved up the end time and the associated wind shift with the front an hour or two from the previous TAF issuance. Periods of rain/widespread showers will continue into the evening behind the cold front with MVFR vsbys and cigs continuing into tonight. Showers finally come to and end from southwest to northeast between 2-6z with improvement back to VFR conditions once the showers end. Winds will be from the southeast at around 5 kt through the remainder of the overnight period, then increase to 5-10 kt from the southeast this morning after sunrise. Winds abruptly shift to the west/northwest at 10-15 kt with gusts to around 20-25 kt behind a strong cold front this afternoon. The exact timing of the wind shift is still somewhat uncertain, but the best estimate for timing looks to be between 17-19z at ALB/GFL/POU and 19-21z at PSF. Winds remain gusty from the west at ALB and PSF through the end of the TAF period, but gusts may subside to around 15 kt from the west at GFL and POU for the last few hours of the TAF period. Outlook... Saturday Night: High Operational Impact. Definite SHRA...TSRA. Sunday: Moderate Operational Impact. Breezy. Chance of SHRA. Sunday Night: Low Operational Impact. Slight Chance of SHRA. Columbus Day: Low Operational Impact. Slight Chance of SHRA. Monday Night: Moderate Operational Impact. Chance of SHRA. Tuesday: Moderate Operational Impact. Chance of SHRA. Tuesday Night: Low Operational Impact. Slight Chance of SHRA. Wednesday: Low Operational Impact. Slight Chance of SHRA. && .HYDROLOGY... Widespread rain, heavy at times, is expected late tonight through Saturday as a slow moving cold front pushes east across the region. While exact location of the heaviest rainfall amounts is still not certain, there is potential for 2 to 3+ inches of rain across much of our hydro service area. River rises will occur, with a few points forecast to reach action stage, however no river flooding is anticipated at this time. Localized flooding of urban, poor drainage, and low lying areas may occur where the heaviest rain falls. Isolated flash flood is possible. Widespread rain will taper off Saturday night as the front moves through. Any additional rain will be lighter and come from lake effect showers Saturday night through the rest of the weekend mainly over the western Adirondacks. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Main/JPV NEAR TERM...JPV SHORT TERM...JPV LONG TERM...JPV AVIATION...Main HYDROLOGY...