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Area Forecast Discussion
Issued by NWS Albany, NY
Issued by NWS Albany, NY
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512 FXUS61 KALY 132037 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 437 PM EDT Tue Aug 13 2024 .SYNOPSIS... Beautiful weather today with seasonable temperatures before chances for isolated to scattered showers and thunderstorms increase tomorrow and Thursday, especially in the higher terrain, thanks to a disturbance in the Canadian Maritimes. Humidity levels turn more uncomfortable Friday into the weekend as a disturbance from the Great Lakes slowly pushes eastward. Chances for showers and thunderstorms increase Saturday and Sunday as the occluded boundary approaches. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Beautiful August day continues across the Northeast as a 1020hPa anticyclone centered over the Great Lakes builds eastward. Morning sun will continue to mix with some fair weather cumulus clouds as areas reach their respective convective temperature. 12 UTC ALY sounding shows low PWATs under 1 inch once again thanks to northerly flow through the column as we remain on the east side of the incoming high. Thus, humidity levels will once again be low/comfortable today. Forecast soundings support deep boundary layer mixing extending up to and even above 5kft this afternoon and with 850hPa isotherms ranging from +11C to +13C, high temperatures this afternoon should easily reach the mid to upper 70s with even around 80 in the valley. Cumulus clouds dissipate late this afternoon once we cool below the convective temperature. Sfc high pressure building eastward will support ideal radiational cooling tonight thanks to clear skies, light winds, and low humidity. Another great night to open up the windows as temperatures cool into the mid to upper 50s across eastern NY and western New England with even mid to upper 40s in the southern Adirondacks, southern Greens, and higher peaks of the eastern Catskills. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... An upper level disturbance from the Canadian Maritimes will shift into the Gulf of Maine Wednesday into Thursday as a subtle backdoor front gradually progresses south and westward through northern New England. Meanwhile, upper level ridging from the Great Lakes and sfc high pressure will be slowly building into the Northeast. Such a synoptic set-up will maintain northwest flow over the region and keep dew points comfortable in the upper 50s to around 60 with temperatures trending a bit warmer rising into upper 70s to low 80s but remaining seasonable. As the cold pool from the disturbance in the Canadian Maritimes shifts south and westward, lapse rates will steepen over much of eastern NY and western New England both days ranging 5.5C/km to 6C/km. After morning fog burns off, morning insolation will contribute to increased surface based instability but marginal dew points will keep CAPE values in check only rising to 500 - 1000J/kg. Deep layer shear values will also be minimal both days only reaching 15 - 25kts. Thus, expecting cumulus clouds to develop once we reach the convective temperature mid to late morning with isolated to scattered showers and thunderstorms developing early to mid afternoon, initially in the southern Adirondacks and southern Greens before northerly flow directs showers/storms southward. Any shower/storm should be short-lived but some areas could see more than one brief shower/storm, especially in the Mohawk Valley and Upper Hudson Valley as shower/storms track southward out of the Adirondacks. While storms will likely not turn severe given weak shear/instability, the cold pool aloft (500hPa isotherms cooling to -13C to -14C) will keep wet- bulb zero heights near or slightly below 10kft so any updrafts that can grow tall enough may be able to support small hail. Isolated to scattered showers/storms diminish once we loss peak heating late afternoon into the evening with clouds clearing and wind becoming light/variable. With dew points remaining near 60 and radiational cooling setting in, fog looks to develop both nights, especially in valley areas and where rain falls during the day. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The upper level low from the Canadian Maritimes finally exits by Friday as the upper level shortwave ridge finally tracks overhead with our weakening 1020 hPa high building at the sfc. This will support a dry and very pleasant end to the work week with mostly sunny skies and temperatures warming into the low to mid 80s across the region. Dew points will be on the rise as southerly flow ensues making it feel more humid. Clouds increase overnight as a closed/mature upper level disturbance from the Great Lakes slowly tracks eastward. Shortwave ridging remains in place most of Friday night keeping conditions dry but will gradually exit into New England by Saturday. Heights slowly fall through the day Saturday with southerly flow ahead of the incoming warm front keeping humidity levels high/uncomfortable. Continued warm air and moisture advection will keep skies partly to mostly cloudy which will keep temperatures lower compared to Friday in the mid to upper 70s. Guidance has slowed down the eastward progression of the upper level low which has thus slowed down the onset of the best forcing for ascent. We thus delayed the west to east onset of likely POPs for showers and thunderstorms until Saturday afternoon, especially for areas west of the Hudson River. Areas in western New England should have a better chance of staying dry longer into the day as the upper level ridge looks to maintain control into the first half of Saturday so we capped POPs at chance. Given cloud coverage, instability may be limited as well despite the high humidity so there is low confidence in storms becoming severe. High humidity and PWATs rising above 1.50" means heavy downpours are possible from any storm. The occluded boundary/triple boundary look to track into the region on Sunday with the parent closed low remaining upstream in southern Ontario or western NY. Continued height falls and increased sfc convergence along the incoming boundary keeps POPs in play for Sunday and we show widespread chance POPs Sunday morning trending to likely during the afternoon diurnal peak heating times. High humidity levels and PWATs >1.50" means heavy downpours will once again be possible. Again, cloud coverage will temper temperatures albeit very uncomfortable humidity levels so highs only expected to rise into the mid to upper 70s to perhaps around 80 in the valley. Guidance suggests our upper level low opens up by Monday but remains nearby as trough axis tracks into the Northeast so we continue to show chance POPS trending to likely by the afternoon throughout the area. Temperatures again remain seasonable in the upper 70s to around 80 with high humidity continuing. We should finally trend drier by Tuesday as our upper level lows should exit but there remains some differences among the guidance on when drier conditions ensue. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... Flying conditions are currently VFR across the region with just some diurnal cumulus and some passing thin high cirrus clouds. Through the rest of the day, flying conditions will be VFR with light north to northwest winds. Skies will clear out for tonight with very light or calm winds. This could allow for some radiational fog to develop for the late night hours at KGFL and KPSF, but the other sites should have a large enough T/TD spread to prevent any fog from developing. On Wednesday, any early morning fog or mist will dissipate shortly after daybreak. This will allow for another day of VFR conditions with just few-sct clouds for the morning and early afternoon hours around 4-6 kft. North to northwest winds on Wednesday will be around 5 kts for all sites. A stray shower or t-storm cannot be ruled out for the mid afternoon into early evening hours, mainly for the northern sites. Outlook... Wednesday Night: No Operational Impact. NO SIG WX. Thursday: Moderate Operational Impact. Scattered SHRA...TSRA. Thursday Night: No Operational Impact. Patchy FG. Friday: No Operational Impact. NO SIG WX. Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Saturday: Moderate Operational Impact. Likely SHRA...TSRA. Saturday Night: Moderate Operational Impact. Likely SHRA...TSRA. Sunday: High Operational Impact. Likely SHRA...TSRA. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Speciale NEAR TERM...Speciale SHORT TERM...Speciale LONG TERM...Speciale AVIATION...Frugis