Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 210503 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 103 AM EDT Wed Aug 21 2019 .SYNOPSIS... Clouds, scattered showers and thunderstorms will approach our area from the southwest later tonight. Warm muggy conditions, along with showers and thunderstorms are forecast for Wednesday, with some storms possibly becoming severe. Some additional rain showers are possible on Thursday as a cold front slowly crosses the area. Fair and cool weather is forecast for Friday into the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 105 AM EDT, skies are still mainly clear across central and northern areas, which has allowed temps to drop off into the lower/mid 50s across portions of the southern Adirondacks, and upper 50s to mid 60s elsewhere. Mid level clouds were increasing across southern areas, especially across the Catskills in response to increasing mid level warm advection ahead of approaching warm front. Isolated showers were developing across south central NYS and the western Catskills as well. Temps were slightly warmer for the I-90 corridor and points south, generally in the 60s, although some lower 70s persisted in some valley locales. The isolated showers across south central NYS and the Catskills are expected to continue drifting northeast through sunrise, and as a low level jet segment strengthens across the northern mid Atlantic states, coverage of showers should increase by daybreak, especially across the Mohawk Valley, Capital Region and eastern Catskills. Elevated instability should also promote some embedded thunderstorms as well. Some locally heavy rain, and frequent lightning will be possible with any stronger convective elements around sunrise. Elsewhere, temps will likely reach mins over the next 1-2 hours, with slowly rising temps expected thereafter as clouds and moisture increase. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... The weather will become active Wednesday into Wednesday night as a cold front and associated mid-to-upper level short wave approaches our area from the west. Wednesday morning will start with scattered showers and maybe a few thunderstorms in association with a warm front lifting north across the area. Dew points will rise substantially with the passage of this front, returning to the mid 60s to near 70 by midday Wednesday. A pre- frontal surface trough will likely develop over central NY during the day Wednesday ahead of a cold front moving east from the Great Lakes. The trough will become the focus for thunderstorm development by early afternoon. Increasing low- level moisture will allow for MLCAPE to rise through the morning. The amount of MLCAPE available to fuel the convection on Wednesday afternoon will depend partially on how much cloudiness in association with scattered early morning showers manages to linger across the area. SREF plumes indicate most likely MLCAPE values of 1000 to 2000 J/kg during the afternoon Wednesday and this would certainly be sufficient for a round of strong to severe storms given increasing mid-level flow and shear associated with the approaching mid-level trough with deep layer shear increasing to 30 to 35 kts during the afternoon. The CAMS are strongly suggesting organized convection in the form of short lines of storms Wednesday afternoon. Some discrete storms are also likely and they will be rotating given the moderately strong deep-layer shear and confirmed by CAM forecasts of enhanced updraft helicity. Strong winds will likely be the primary threat with storms Wednesday afternoon, but large hail associated with discrete supercells is also possible. Model soundings are also showing 0-1 km shear values to 30 kts with 0-1 km helicity well over 100 s-1. Based on this, it would seem possible that a few tornadoes could also occur over the northeast CONUS where storms can interact with enhanced low- level shear associated with boundaries left over from previous or ongoing convection. Based on all of the above the SPC has put our entire area in a slight risk for severe storms Wednesday. Storms will be moving east of the area Wednesday night, followed by a more quiet pattern for the rest of the week with much lower humidity. A few isolated showers may occur Thursday with the passage of a mid-level cold pool, but low-levels will be drying out which should keep shower activity to a minimum. High temperatures Thursday will range from the 70s over higher terrain to near 80 in the Hudson Valley. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A mainly dry and seasonable weekend is anticipated as a positively tilted upper level trough moves through the area and Canadian high pressure takes control through early next weekend. Northerly flow should keep temperatures a few degrees below normal and keep humidity levels low through the weekend. High temperatures generally should be pleasant in the 70s with overnight lows in the 50s before temperatures gradually warm heading into early next week, rising back towards normal around 80. The potential for rain increases towards the middle of next week as the next system approaches from the Midwest. Read on for details. Our cold front from Thursday should be just south of forecast area on Friday, around NYC/southern New England but the guidance still shows potential for a shortwave to ride along the boundary Friday morning. Should this happen, the southern areas of the mid-Hudson Valley and NW CT could see some showers, mainly Friday morning. For now kept a dry forecast to be in line with the neighboring WFOs but we will monitor trends and adjusts POPs upwards, if necessary. Otherwise, our positively tilted trough will progress southward from Canada into the Northeast Friday into Saturday. The base of the trough looks to feature a 500mb shortwave with an associated cold pool which guidance suggests moves right over through eastern NY and western New England during the day on Saturday. Since 700mb moisture on most members of the latest guidance is very dry, the models are not producing QPF. However, we will monitor trends as the cold pool aloft could generate a few scattered diurnally driven showers. For now we maintained a dry forecast which is in line with the neighbors. Temperatures under the northerly flow should fall a degrees shy of normal for late August and stay in the low to mid 70s with low humidity. The higher terrain in the Adirondacks, Catskills and Greens could even stay in the upper 60s. Overnight lows should turn chilly in the 50s (40s higher terrain) as clear skies and calm winds lead to good radiational cooling. The GFS and CMC-NH show heights rising on Sunday as strong upper level ridging and an expansive/rather strong ~1025hPA surface high from southern Canada kicks our shortwave out to sea. The ECMWF continues to linger the shortwave over New England but this seems to be the outlier. Expecting mainly sunny skies on Sunday under the strong surface high pressure with temperatures slightly warmer than Saturday in the mid - upper 70s. Again, cool temperatures overnight in the 50s expected once again Sunday night. High pressure stays in control Monday with similar temperatures anticipated. The next chance for precipitation along with an increase in temperatures and humidity looks to arrive in the middle of the week. The latest 12z guidance still shows discrepancies in timing and intensity of precipitation so continued to only show slight chance POPS for the Monday night and Tuesday period. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... VFR conditions will prevail across all TAF sites through midnight tonight (21/04Z) as high pressure slides off the New England coast. As a warm front slowly progresses northward tonight, clouds increase from south to north after 04z/21. There is potential for showers and storms at all TAf sites towards morning which is covered with a PROB30 group from 09z/21 to 12z/21. In addition, any TAF site that experiences precipitation could easily see MVFR or even a period of IFR conditions due to low clouds and/or fog. For now, we allowed the reduced ceilings and visibility in the PROB30 group to illustrate this potential. MVFR ceilings may linger into the morning hours, especially at sites that experiences rain overnight. Ceilings may improve/break towards 17z/18z which is why However, additional showers and an increased threat for thunderstorms, some severe with potential for damaging winds, are expected during the afternoon. Winds should stay southerly and under 5kt overnight before becoming south-southwesterly after sunrise and increasing to 5-15 kt. Strong gusty winds are possible in and around thunderstorms. Outlook... Wednesday: High Operational Impact. Likely SHRA...TSRA. Wednesday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Thursday: Low Operational Impact. Slight Chance of SHRA. Thursday Night: Low Operational Impact. Slight Chance of SHRA. Friday: Low Operational Impact. Breezy NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Dry, warm weather will continue this evening, then clouds and scattered showers and thunderstorms will develop late tonight as a warm front approaches the area. Showers and thunderstorms will become more likely during the day Wednesday and especially Wednesday afternoon as a cold front approaches from the west. RH values Wednesday afternoon will fall to 55 to 65 percent. A drier and milder airmass returns Thursday into the weekend, allowing for good drying conditions. RH values Thursday will fall to 45 to 55 percent. Winds will be generally 10 kts or less, except briefly higher near thunderstorms Wednesday. && .HYDROLOGY... An anomalously moist airmass will spread back into the region tonight into Wednesday with PWAT values increasing to 1.50-2.00 inches. Numerous showers and thunderstorms are expected to develop in the moist airmass Wednesday as moderate instability develops, and any storm will be capable of heavy rainfall. Though a strong wind field will result in fast moving storms, there is potential for repeated rounds of storms which will lead to the threat of urban/poor drainage flooding and possible isolated flash flooding. Mainly dry weather is expected Thursday into the weekend. 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...SND NEAR TERM...SND/MSE/KL SHORT TERM...MSE LONG TERM...CS AVIATION...SND/Thompson FIRE WEATHER...MSE/Thompson HYDROLOGY...MSE/Thompson

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