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Area Forecast Discussion
Issued by NWS Albany, NY
Issued by NWS Albany, NY
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898 FXUS61 KALY 142345 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 745 PM EDT Wed Aug 14 2024 .SYNOPSIS... Scattered thunderstorms diminish after sunset tonight, with patchy fog developing as temperatures cool into the 50s and 60s. Tomorrow will be very similar to today with highs in the 70s to low 80s and scattered afternoon showers and thunderstorms. Friday will feature dry conditions, but humidity levels increase ahead of a frontal system that will bring unsettled conditions throughout the weekend and possibly into early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... .UPDATE...As of 0745 PM EDT, showers and thunderstorms beneath the cold pool aloft are diminishing following the loss of diurnal heating. A few pockets of CAPE around 500-1000 J/kg remain per SPC mesoanalysis, however a rapidly stabilizing boundary layer should prevent much more additional convection. Lingering orphaned anvils from earlier storms will continue to track southward within cyclonic flow about the upper low over Atlantic Canada, before skies clear overnight as high pressure builds from the west. The clearing trend in concert with decreasing winds will allow for efficient radiative cooling, dropping temperatures near to dewpoints in the 50s across much of the region. Radiation fog is expected to develop within sheltered valleys and where earlier rain showers have provided additional low-level moisture. Any fog will quickly dissipate after sunrise. Forecast therefore remains on track; see previous discussion below... .PREV DISCUSSION [0345 PM EDT]...Current GOES 16 WV imagery shows an upper disturbance located to the northeast of our region, while surface analysis shows a backdoor cold front approaching from the northeast. With north/northwest flow across our region, upslope flow and terrain-induced convergence boundaries have lead to the development of scattered thunderstorms beneath the cold pool aloft. Shear is relatively weak, but with mostly clear skies daytime heating has allowed MLCAPE values to increase to 1000 to 2000 J/kg with the highest values in the Mohawk Valley. This, combined with near dry adiabatic low-level lapse rates, may allow for some gusty winds or small hail, although the threat for more widespread severe weather remains on the low side. Temperatures are near the daytime highs with upper 70s to mid 80s for most places, although some areas that have received a shower or storm have seen temperatures drop into the 60s due to rain-cooled downdrafts. As we head through the evening into tonight, coverage of showers and storms should begin to diminish with the loss of daytime heating. High pressure will build in from the west, so skies are expected to become mostly clear and winds light to calm. This will set the stage for favorable radiational cooling conditions, and we therefore undercut NBM lows by a few to several degrees. Most places should see lows similar to last night, in the 50s to around 60. Patchy radiation fog, some locally dense, is expected especially in the typical sheltered river valleys and in areas that see rain this afternoon and evening. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... Thursday and Thursday night will be very similar to today and tonight. Thursday starts off seasonably cool with some patchy fog, but the fog should mix out shortly after daybreak. Temperatures rise through the 70s into the low 80s by early afternoon. However, the upper low and stalled cold frontal boundary will remain off to our east/northeast. With the cold pool aloft nearby and N/NW flow, we will once again see scattered afternoon showers and storms develop, especially over the high terrain due to upslope enhancement and along any terrain-induced low-level convergence boundaries. Instability looks slightly less impressive than what we are seeing today, although with around 1000 J/kg of MLCAPE and steep low-level lapse rates, we could see a few instances of small hail and/or gusty winds once again. Thursday night, showers and storms once again diminish with the loss of diurnal heating. High pressure remains overhead and ridging builds aloft over our region, so we will once again see favorable conditions for radiational cooling. Lows are expected to be just a degree or two warmer than the previous night, with low 60s for the valleys and 50s elsewhere. Patchy radiation fog, locally dense in river valleys and areas that see rain during the afternoon and evening, will once again be possible. Friday and Friday night...The surface high slides off to the east. The ridge aloft will be overhead to start the day, but also slides east of the region overnight as upper troughing digs into the Great Lakes region. The ridge overhead and subsidence should keep us dry through the day Friday, although mid and high clouds begin to increase through the afternoon. Flow turns more southerly around the periphery of the high, and the airmass aloft will be warmer, so high temperatures are expected to also be a few degrees warmer than previous days with mid to even upper 80s in the valleys with upper 70s to around 80 for the higher elevations. It will also turn more humid with dew points in the mid to upper 60s. Friday night, clouds continue to increase with increasing chances for showers as the upper trough and an associated occluded front slowly track towards our region from the west. It will be warmer than previous nights with lows mainly in the 60s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Long term period begins at 12z Saturday the upper trough over the Great Lakes shifting eastwards through the weekend. At the surface an occluded front will slowly track through the region Saturday into Sunday. PWATs climb to 1.6-1.8", which is 1-2 sigma above normal for mid August. The overlap of forcing and moisture will lead to scattered to numerous showers and a few thunderstorms Saturday and especially Sunday. The best instability remains west of our region Saturday, and shear does not look overly impressive Saturday and Sunday. However, with the moist airmass in place, locally heavy rainfall will be possible with any thunderstorms. Due to mostly cloudy skies it won`t be overly warm with highs in the 70s to around 80 both days, although it will be humid with dew points in the upper 60s to around 70. Overnight lows will be mainly in the 60s, and shower chances will continue each night with the upper trough and surface front nearby. Will also mention that what is currently Hurricane Ernesto is expected to track well to our east over the Atlantic and is currently not expected to result in any impacts to our area. Monday through Wednesday...Monday, chances for showers and thunderstorms look to continue as the upper trough and associated upper deformation axis will be tracking over our region. Highs should be similar to the previous couple days and it will remain humid. Then, a stronger cold front is expected to track through the region Monday night into Tuesday. While the exact timing is uncertain, we should see a drying and cooling trend behind the cold front as high pressure builds into the region from the west. For days 8-14, the CPC is leaning towards slightly above normal temperatures and precipitation. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Through 00Z Friday...VFR conditions across the region will continue this evening. A few showers and very isolated thunderstorms are tracking southward across portions of the region, but will end in the coming hours following the loss of daytime heating. No further impacts from showers and storms are expected at area terminals. Sct- bkn coverage of orphaned anvils from earlier thunderstorms will persist for a few hours, before skies trend clearer after 03-06Z Thu. Areas of dense fog are expected to develop overnight, particularly within sheltered valleys and where rain fell in earlier showers. GFL/PSF remain the most likely sites to see IFR/LIFR fog, with conditions rapidly deteriorating after 03-04Z Thu. POU may also see IFR/LIFR conditions within fog, though confidence is lower in onset timing, more likely after 06-09Z Thu. ALB may only see VCFG, but restricted vsbys cannot be ruled out nearer to sunrise. Any fog will quickly dissipate after sunrise, with VFR conditions returning to all terminals after 12-13Z Thu. Diurnal rain showers will again develop, particularly over areas of terrain, after 16-18Z Thu. Winds will rapidly diminish this evening to calm or light and variable at all terminals by 03-04Z Thu, and continuing through the remainder of the overnight period. Winds increase to 4-8 kt out of the west to northwest at ALB/POU/PSF after 12Z Thu, while south to southwest winds at 3-6 kt are expected at GFL. Outlook... Thursday Night: No Operational Impact. Patchy FG. Friday: No Operational Impact. NO SIG WX. Friday Night: Moderate Operational Impact. Slight Chance of SHRA. Saturday: Moderate Operational Impact. Breezy. Chance of SHRA...TSRA. Saturday Night: High Operational Impact. Likely SHRA...TSRA. Sunday: High Operational Impact. Likely SHRA...TSRA. Sunday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Monday: High Operational Impact. Likely SHRA...TSRA. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Gant/Main NEAR TERM...Main/Picard SHORT TERM...Main LONG TERM...Main AVIATION...Picard