Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 031104 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 704 AM EDT Wed Jun 3 2020 .SYNOPSIS... A warm front will initially bring some spotty showers this morning, then a low pressure system and a cold front will bring showers and some thunderstorms especially south of the Capital District in the afternoon. High pressure will briefly build in tonight into Thursday, as temperatures will trend above normal. A warmer and more humid air mass will be over the region on Friday with a threat of afternoon scattered showers or isolated thunderstorms late in the day into the overnight period ahead of another cold front. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 638 AM EDT...A warm front continues to be south and west of most of the forecast area early this morning. Isolated showers are across the Schoharie Valley and eastern Catskills. The KENX radar is fairly quiet. The mid and upper level flow continues to be nearly zonal. As a low pressure system will approach from southeast Ontario for the early afternoon with a cold front. The question will be if the warm front makes it through the entire forecast area. The low level forcing with the boundary looks weak, but with the low-level moisture in place with dewpts rising into the 50s and lower 60s will allow some spotty light showers to be possible especially from the Capital Region north. This is supported by the latest NAM/GFS/ECMWF/CMC and we kept slight and low chance PoPs in these areas. The 09Z 3-km HRRR is drier with some light showers northeast of Albany. Plenty of low stratus and clouds will be over the region, though some intermittent breaks with some sunshine are possible from Albany south and east in the late morning into the afternoon, where a mini warm sector sets up. A strong short-wave in the west/northwest aloft and the cold front will focus a mesoscale convective system /MCS/ in the late morning moving southeast from Lake Erie/western NY and northwest PA. This potential MCS or complex of showers and thunderstorms may graze or impact the southern most zones of the forecast area or roughly the I-84 corridor south. The majority of the guidance keeps it barely south, though the latest GFS and the 3-km NAM, last few runs of the 3-km HRRR are a little further north into Ulster/Dutchess and Litchfield Counties. The better instability, steeper mid-level lapse rates and strongest model updraft helicity values are further south across PA and NJ with the majority of the guidance. The 00Z HREFS have has some mean SBCAPE values of 750-1000+ J/kg near the I-84 corridor with 0-6 km shear values of 40-45 kts. The Day 1 Marginal Risk for this small area looks good, and we will keep mention in the HWO with our forecast area on the northern end of this MCS. We did mention a period of gusty winds/small hail and heavy rainfall especially 16Z-22Z /noon-6 pm/ in those areas. Damaging winds and large hail would be the severe threats It looks like these areas may get briefly in a stratiform region of the MCS prior to the late pm. The last few runs of the 3-km HRRR show some discrete convective cells popping north of the MCS we widened the potential for isolated severe cell there. Further north, a few thunderstorms may occur up to the Capital Region, Berkshires, northern Catskills and southern VT, but limited SBCAPE of 200-500 J/kg should limit updrafts from getting taller, and we did not even include thunderstorms in the northern most zones due to the lack of sfc heating and instability. The cold front tracks eastward during the afternoon with some isolated to scattered showers and limited forcing. The initial wind shift will likely be with the prefrontal trough, as the wave moves across northern New England. We had to lower temps slightly due to clouds possibly limiting sfc heating, despite H850 temps getting to +10C to +14C. Highs were favored with a blend of the GFS/NAM MOS guidance with mid 60s to lower 70s over the higher terrain, and mid and upper 70s in the valleys and over the southern Berkshires and NW CT. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... Tonight...The cold front moves across the region with very weak low-level cold advection. The isolated to scattered showers should end around midnight over the northern zones. Some patchy fog may form, if the skies clear. We did not add it to the forecast yet. Lows will be mainly in the 50s to around 60, though some upper 40s are possible in the Adirondack Park. Thursday...The mid and upper level flow remains quasi-zonal. A piece of northern stream energy may increase the clouds a bit over the northern zones and across the higher terrain. The 06Z NAM tries to develop a few showers near the southern Adirondacks. We kept it dry with a weak sfc high building in from the Great Lakes Region. Partly to mostly sunny skies with good mixing will allow temps rise about 5 to 7 degrees above normal with upper 70s to lower 80s in the valleys (a few mid 80s in the mid Hudson Valley), and upper 60s to mid 70s over mtns. Thu night...A weak sfc wave and a warm front will move across eastern Pa and NJ. Low-level moisture will increase from the south and west. Weak thermal advection occurs which will allow a few showers to move into the southeast Catskills, mid Hudson Valley and NW CT. We kept some slight and low chance PoPs in the forecast. Otherwise, it should be dry with an increase of some clouds from the south and west. Lows will be in the 50s to lower 60s. Fri-Fri night...The biggest change for Friday is the slower progression of the cold front. The latest trends are for the frontal passage to be more in the night time period for the forecast area. Heat and humidity will increase with sfc dewpts rising into the mid 50s to lower/mid 60s. H850 temps increase to +1 to +2 STD DEVs above normal based on the 00Z GEFS. Some scattered showers are possible during the morning south and east of Albany with the wave passing to the south. Some clearing is possible later with partly sunny skies and highs in the mid and upper 80s in the valleys, and mid 70s to lower 80s over the higher terrain. Some pop-up showers or isolated thunderstorms are possible in the late afternoon ahead of the cold front. The upper trough upstream begins to amplify which should help the cold front move across the region Friday night with scattered showers and isolated thunderstorms. We are not expecting these to be severe at this time, as the latest SPC DAY 3 graphic has general thunderstorms. && .LONG TERM /SATURDAY THROUGH TUESDAY/... After a muggy and very warm Friday, a positively tilted trough will approach the Northeast from southern Canada on Saturday. Guidance has waffled on its arrival time with the latest 00 UTC guidance maintaining the delayed onset trend. Now, it looks like the strongest height falls do indeed hold off until towards 12 UTC Saturday which is when the main cold front looks to push through eastern NY/western New England. This is a bit atypical since we usually see cold frontal passages in the afternoon but the global guidance shows the front pushing through in the morning and early afternoon with northwest flow in place by the end of the day. Given the ongoing timing uncertainties, we show chance POPS for both Saturday morning and afternoon but placed slightly higher POPs for areas near and south of I-90 where dew points still near 60 combined with a few hours of daytime heating ahead of the front could contribute to a region of enhanced instability and thunderstorm activity. Otherwise, temperatures should end up slightly above normal reaching into the upper 70s to near 80 since we probably will not see an air mass change just yet. The positively tilted upper level trough swings into the region Saturday night, clearing us of the humid air mass with cold air advection ensuing in the northwest flow. The trough is slow to exit on Sunday and with guidance showing some mid-level moisture within its upper level cold pool, we expect partly to mostly cloudy skies with even potential for a few isolated showers in western New England, which should be closer to the cold pool. While the 500mb cold pool ranges between -15C to -18C, we did not include any thunder mention at this time but it will be something to monitor. Temperatures will be cooler and less humid Sunday given this set-up and because of the potential for few on/off showers and increased cloud coverage, we went slightly cooler than the blended guidance and only show highs in the low to mid 70s. This matched up well with the 50 percentile of the ensemble MOS guidance output which was slightly cooler than the operational run. The ECMWF continues to suggest that the trough strengthens as it digs into New England Sunday night and becomes neutrally tilted which would enhance the cold air advection overnight. The GFS and CMC do not show as sharp of a feature and keep it more broad. With clearing skies and Canadian air infiltrating the region thanks to breezy northwest winds, we show overnight lows falling into the 40s to near 50 but if the ECWMF is correct, temperatures may trend cooler. Upper level ridging from the Central CONUS builds into the Northeast Monday and Tuesday, keeping a mainly dry forecast with seasonable temperatures. The next warm front looks to cross into our region mid- week which could lead to another day or two of above normal temperatures. While the ridge axis looks to move overhead mid-week, it`s worth mentioning that some members of the global guidance show a potent cut-off low exiting the Rockies and steering the remnants of Cristobal towards the Great Lakes/Southern Canada mid to late next week. Still much too early to know the details but it`s something to keep an eye on. For the latest information on Cristobal, visit www.hurricanes.gov. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... MVFR ceilings continue at ALB and PSF with VFR conditions at POU and GFL. Expecting currently ceilings to persist through 15-16 UTC with potential for a passing shower as a warm front remains stalled nearby. A decaying MCS in western NY will progress eastward this morning with a few leftover showers possible at PSF, POU and ALB. We did not include thunder for this period but we will monitor conditions. Once these showers exit, ceilings should improve to 4- 5kft and could even break for sun. Winds could also shift to the southwest and become a bit breezy (sustained 5-10kts, gusts to 20mph). A cold front sagging southward through the TAF sits this afternoon could lead to a few scattered showers. Thunderstorms, some potentially strong to severe, are possible at POU and we included a TEMPO group to illustrate this potential. Any storm could produce damaging winds and heavy downpours. PSF and ALB may also see thunderstorms but we did not include at this time since confidence is lower in these areas. Once the front exits this evening, skies could partially clear and any areas that had showers could see fog quickly develop. We included MVFR visibilities developing after 03 UTC at POU, GFL and PSF. Outlook... Thursday Night: No Operational Impact. NO SIG WX. Friday: Moderate Operational Impact. Chance of SHRA...TSRA. Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Saturday: Moderate Operational Impact. Chance of SHRA. Saturday Night: No Operational Impact. NO SIG WX. Sunday: High Operational Impact. NO SIG WX. && .FIRE WEATHER... A warm front will initially bring some spotty showers this morning, then a low pressure system and a cold front will bring showers and some thunderstorms especially south of the Capital District in the afternoon. High pressure will briefly build in tonight into Thursday. A warmer and more humid air mass will be over the region on Friday with a threat of afternoon scattered showers or isolated thunderstorms late in the day. The RH values will only lower to 55 to 70 percent this afternoon, and then increase close to 100 percent Thursday morning. The RH values will drop to 35 to 45 percent Thursday afternoon. The winds will begin south to southeast at 5 to 10 mph this morning, and then shift to the southwest to west at 10 to 20 mph in the afternoon. The winds will become light tonight at less than 10 mph from the west. Expect west winds of 5 to 15 mph on Thursday. && .HYDROLOGY... Widespread hydrologic issues are not expected on the main stem rivers the next several days. A cold front and low pressure system will bring some scattered showers and isolated to scattered thunderstorms. A complex of thunderstorms may produce the heaviest rainfall in the southeast Catskills, mid Hudson Valley and NW CT. Some brief heavy downpours are possible, especially south of Albany. Basin average QPF is expected to remain less than half an inch. Dry weather returns Thursday, with a chance of showers and isolated thunderstorms Friday afternoon into Friday night. Some showers may linger on Saturday before drier weather returns for the 2nd half of 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...Wasula NEAR TERM...Wasula SHORT TERM...Wasula LONG TERM...Speciale AVIATION...Speciale FIRE WEATHER...Wasula HYDROLOGY...Thompson/Wasula

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