Area Forecast Discussion
Issued by NWS Albany, NY
Issued by NWS Albany, NY
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944 FXUS61 KALY 281058 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 658 AM EDT Fri Jun 28 2024 .SYNOPSIS... After a chilly start to our Friday, high pressure will give us a sunny and comfortable end to the work week. Winds turn gusty for Saturday with areas of rain tracking slowly from northwest to southeast through the day. Rain turns moderate to potentially heavy at times Saturday night with additional rain and thunderstorms for Sunday as a cold front pushes through the region. && .NEAR TERM /THROUGH TONIGHT/... As of 640 AM EDT, we start our Friday clear and quite cool by late June standards with much of eastern NY and western New England in the 40s to low 50s thanks to ideal radiational cooling conditions overnight. We even have pockets of upper 30s in the southern Adirondacks. Previous discussion...Large scale subsidence and sfc high pressure strengthening to ~1020hPa will build over the Northeast today giving us sunny skies. The very dry air mass (PWATs around 0.50") will also maintain low dew points in the 40s and thus very low humidity once again. While winds today will be much lighter than yesterday, northwest flow aloft will keep temperatures seasonably cool with high temperatures only rising into the mid to upper 70s (upper 60s in the southern Greens and southern Adirondacks). This is about 5 degrees below normal as late June high temperatures typically reach into the low 80s. Cirrus clouds spill overtop the ridge late this afternoon into this evening with skies becoming cloudy overnight as the upper level ridge axis shifts to our east, allowing warm air and moisture advection to increases. The increasing sky coverage will keep temperatures milder than Thurs night with overnight lows only dropping into the mid to upper 50s with low 60s in the valley. Coolest temperatures likely in western New England where the thicker clouds will be delayed. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... Broad troughing develops over the Great Lakes on Saturday with an amplifying shortwave tracking across the Upper Great Plains while a 595dm Bermuda high sits just off the East Coast. This set-up will result in a conveyor belt of strong southwest winds directed into the Northeast with a sfc warm front tracking northward through the mid-Atlantic. Guidance is in good agreement keeping this boundary mainly to our south through most of Saturday with gusty south to southeast sfc winds ahead of the front reaching up to 25kts (strongest in the Hudson Valley). Otherwise, mainly cloudy skies keep temperatures in the mid to upper 70s with around 80 in valley. The conveyor belt of strong southwesterly winds (including a corridor of 45-50kts in the 850 - 700hPa layer) will advect a moisture rich air mass from the Gulf of Mexico into the Northeast with dew points soaring into the mid to upper 60s and PWATs 2 - 2.25". Per the NAEFS, such high PWATs rank 2.5 standard deviations above normal and even reaches the 99th percentile of the model`s PWAT forecast. The combination of high moisture content and strong kinematics also supports impressive moisture transport ahead of the broad upstream trough with a rather large breath of integrated water vapor transport approaching 2 - 3 standard deviation above normal. The broad positively tilted upstream troughing will support areas of showers advancing into our southern Adirondacks/Mohawk Valley Saturday morning. Enough subsidence looks to remain for areas along and east of the Hudson River that Saturday morning remains mainly dry outside of some isolated showers. Southwesterly flow deep through the column will slow the eastward progression of rain showers until Saturday afternoon for areas east of the Hudson. Western New England will remain drier for much of Saturday with showers reaching this area late P.M or early evening. Overall instability Saturday based on forecast soundings is quite limited thanks to cloud coverage and warm temperatures aloft impeding steep lapse rates. Despite this, the high moisture content and strong deep layer shear (0-6km shear values 40 - 45kts) means we cannot discount some strong to possible severe thunderstorms developing, especially along the leading edge of the incoming rain. SPC maintains its marginal risk for severe weather on Saturday through much of eastern NY but leaves out western New England given even less of a chance for sufficient instability further east. Showers become more organized and expand in coverage Saturday evening with areas of moderate to heavy rain developing as the aforementioned amplified shortwave trough progresses into southern Ontario, resulting in stronger height falls over the Northeast. The increased forcing for ascent including a broad anti-cyclonically curved jet aloft within such a moisture laden environment (freezing heights nearing 15kft) will easily support efficient warm rainfall processes. In addition, elevated instability advances eastward Saturday night into our area which will support embedded thunderstorm activity and potential for higher rainfall rates. With an impressive belt of 40-45kt southwest flow both at 850hPa and within the 850-300hPa layer, there are increasing signs that heavy rain will train/repeatedly impact some areas, enhancing chances for flooding. Embedded convection will also increase rainfall rates. To add insult to injury, southwest flow typically upslopes the south facing slopes of the southern Adirondacks and parts of the Mohawk Valley, exasperating rainfall rates. Given theses factors, we and BTV collaborated with WPC and a slight risk was introduced in the Day 2 excessive rainfall for the southern Adirondacks and western Mohawk Valley with a marginal for the rest of eastern NY and western New England. Latest QPF amounts range 1 to 2 inches for areas mainly north and west of the Capital District with 0.50 - 1 for the rest of eastern NY and western New England. But, locally higher amounts are possible depending on where any areas of rain can train or repeatedly impact. Heavy rain exits into New England by the pre-dawn hours Saturday night as the sfc boundary finally tracks eastward through our area. While Sunday starts off dry, it will still be very humid as dew points remain in the upper 60s to low 70s with a period of morning sun generating instability. As the trough axis associated with our incoming potent shortwave pushes west to east through our area late Sun morning into the early afternoon, the boundary will result in renewed scattered areas of rain and thunderstorms. Since the boundary will not reach the mid-Hudson Valley and western New England until Sunday afternoon, there likely will be more time for the environment here to destabilized within this highly sheared environment to support strong to even severe thunderstorms. SPC introduced a slight risk for severe weather for these areas with damaging winds the main hazard from severe thunderstorms. There is a marginal risk for severe weather across the rest of eastern NY into southern VT but given the earlier arrival time of the trough axis, there is more uncertainty on how much destabilization can occur. Areas south/east of the Capital District have a higher chance to destabilize enough than north/west. Otherwise, it will turn quite warm on Sunday thanks to increased sunshine with the air mass ahead of the trough axis featuring 850hPa isotherms +15C to +18C. Highs should reach into the mid to upper 80s and with dew points still in the 60s, it will fee closer to 90 in the Hudson Valley with near Heat Advisory criteria (heat index ~95F) in the mid-Hudson Valley. Behind the trough axis and renewed showers/storms, westerly winds turn quite breezy/gusty as a large area of high pressure in the Midwest builds eastward, tightening the sfc pressure gradient. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Cold front should move south/east of region Sunday evening with perhaps some lingering showers/thunderstorms across the mid Hudson Valley and NW CT. Upper level trough then slowly shifts across and east of the region Monday, however lingering cold air aloft could promote isolated showers across the southern Adirondacks, southern VT and Berkshires, especially through early afternoon. Otherwise, high pressure building in from the Great Lakes should bring generally fair weather Monday night through Tuesday night. It may be breezy Monday with a relatively tight low level pressure gradient across the region. High pressure then shifts off the eastern seaboard Wednesday, with a cold front approaching from the west late Wednesday, and then tracking across the region Wednesday night into Thursday. Some showers/thunderstorms will be possible with this system late Wednesday through Thursday, although exact timing details and areal coverage remain uncertain. Temperatures will initially be slightly below normal Sunday night through Monday night, with lows in the 40s to lower 50s, and Monday highs mainly in the 70s for valley areas 60s across higher terrain. Near seasonable temperatures expected Tuesday with highs 80-85 in valleys and 75-80 across higher terrain. Above normal temperatures then expected Wednesday into Thursday, with highs 85-90 in valleys and upper 70s/lower 80s across higher terrain areas. Increasing humidity levels could allow heat indices to approach the mid 90s within the mid Hudson Valley, especially on Thursday. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... Through 12Z/Sat...VFR conditions are expected through at least 08Z/Sat with just occasional patchy high/mid level clouds. Some lower clouds and isolated showers may approach KGFL and KALB after 10Z/Sat with brief MVFR Vsbys/Cigs possible. MVFR Cigs may also develop at KPOU toward 12Z/Sat. North to northwest winds 4-8 KT this morning will become north to northeast at 5-10 KT by mid morning, shifting into the east to southeast at similar speeds this afternoon. Winds will become light/variable around/shortly after sunset, however will remain southeast to south and increase to 8-12 KT at KALB with some gusts of 15-20 KT possible after 03Z/Sat. Outlook... Saturday Night: High Operational Impact. Breezy. Definite RA...TSRA. Sunday: Moderate Operational Impact. Breezy. Likely SHRA...TSRA. Sunday Night: No Operational Impact. NO SIG WX. Monday: Low Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Low Operational Impact. Isolated SHRA...TSRA. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Speciale NEAR TERM...Speciale SHORT TERM...Speciale LONG TERM...KL AVIATION...KL