Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 211101 AFDALY Area Forecast Discussion National Weather Service Albany NY 701 AM EDT Thu Jun 21 2018 .SYNOPSIS... Dry and seasonable weather will continue for the remainder of the week. An approaching low pressure system will bring periods of rain and possible thunderstorms over the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 600 am, just a few lingering showers over far southern portions of Ulster, Dutchess, and Litchfield Counties as a wave of low pressure tracks eastward south of the forecast area. This activity should diminish after 12Z. Elsewhere, a frontal boundary is approaching from the north, located across central Vermont and the southern Adirondacks. Clouds will increase over far northern zones through 12Z (southern Adirondacks and Lake George region) with a light shower or two not out of the question. Between this front and the cloud cover/precip over the south, it`s a rather cool start to the day with a few patches of fog in low- lying areas. The forecast area will be under an 850 mb cold advection regime today, but this will be offset by strong diurnal heating. With a pocket of midlevel cooler air overhead, models are generating some shallow instability. There`s not likely to be enough moisture to generate showers, but there could be scattered coverage of cumulus around in the afternoon. Temps today with good mixing forecast are expected to average around normal. Tonight, a surface high will become established over Maine. This is not the most ideal spot for radiational cooling, but many areas will likely still decouple. With a dry airmass in place, expect rather cool overnight lows in the 40s to mid-50s. Some 30s are even possible over portions of the southern Adirondacks. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Friday, the high will shift eastward, resulting in a light southeasterly flow across the forecast area. This will occur as the midlevel trough over New England lifts away and the closed low over the Mid-Mississippi Valley approaches. Another dry day is expected with gradually increasing high clouds, and temperatures mainly near normal (a bit cooler than normal in the Poughkeepsie area). Friday night into Saturday, the closed low opens up and tracks across the eastern Great Lakes as it deamplifies. Deep-layer moisture will increase ahead of this system, with the GFS advertising PW values in excess of 1.5 inches by Saturday. Modest isentropic lift ahead of the wave and differential cyclonic vorticity advection are expected to produce periods of rain late Friday night into Saturday night. We may be still contending with a dry airmass Friday night, so PoPs were capped at chance levels, but enough confidence to go with likelies Saturday into Saturday night. The notable outlier is the 00Z NAM, which develops a mesoscale low tracking up the coast, with a ridge folding back into eastern New York and northern New England, keeping much of our area dry Saturday. We won`t give much credence to this solution at this time given that it`s an outlier. Showalter values go weakly negative, so have included slight chance of thunder Saturday/Saturday night. It doesn`t appear to be a total washout for the entire region for the whole day, so future forecasts may be able to refine the PoP forecast timing-wise. As for temperatures, cool easterly flow is expected to keep temps below normal. Feel that the MAV MOS is too cool though, advertising a high of 64 at KALB. Fairly mild lows Saturday night in the mid-50s to mid-60s. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... The extended forecast begins unsettled, but improving conditions are expected early next week with fair and dry weather lasting through Wednesday. Sunday-Sunday night...A weak first cold front moves through in the morning with a wind shift, but a secondary cold front will dip south/southeast from the St Lawrence River Valley. A positively tilted mid and upper level trough will be over the Northeast and Great Lakes Region poleward into eastern Canada. A short-wave moving through the long-wave trough will focus showers and scattered thunderstorms. The instability looks less this forecast cycle, but with some heating ahead of this secondary cold front and short-wave as SBCAPEs at or around 500 J/kg are possible with dewpoints in the upper 50s and 60s. PWATs will be a little above normal with values around 1.50 inches, so some locally heavy rain will be possible too. High temps will be a tad warmer than the previous day with highs in the mid 70s to lower 80s in many of the valley areas, and mid 60s to mid 70s over mtns. The front pushes south of the region Sunday night with the scattered showers/t-storms diminishing. Low-level cold advection occurs across the region in the wake of the front with lows in the 50s to lower 60s, and a few upper 40s over the Adirondack Park. Monday to Monday Night...The latest 00Z GFS and ECMWF, as well as several ensemble members are more aggressive moving the mid and upper level trough axis across the forecast area in the morning, and off the New England Coast by the afternoon. We kept a slight chance of showers in the morning, except a low chance over western New England. High pressure builds in quickly with drier and cooler weather with sun mixing with clouds, as highs will be in the lower to upper 70s in the lower elevations and mid 60s to lower 70s over the hills and mtns. Fair and tranquil weather is likely Mon night with comfortably humidity levels with lows in the mid 40s to mid 50s, with the sfc anticyclone near the Northeast. Tuesday into Wednesday...Mid and upper level heights increase over the Northeast, as a ridge sets up east of the MS River Valley. A moderating trend in temps will occur TUE into WED with seasonal readings on TUE, but a south to southwest flow of warmer and slightly more humid air will occur by the mid week with highs in the lower to mid 80s in the lower elevations, and mid 70s to lower 80s over the hills and mtns. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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A weak cold front will move south from the St Lawrence River Valley with little low-level moisture, as high pressure will build in south of James Bay this afternoon into tonight. Some mid level clouds will decrease across the mid Hudson Valley and KPOU this morning, as a disturbance moves east. Patchy MVFR/IFR/LIFR mist/fog will decrease at KPSF prior to 13Z. VFR conditions will continue with some lingering mid and high clouds, but a trend to mostly sunny conditions is likely in the afternoon with the large Canadian anticyclone ridging in. The winds will be light to calm this morning, and then be from the north to northeast at 4-9 kts in the late morning into the afternoon, before becoming light to calm again early this evening. Outlook... Friday: No operational impact. No sig WX. Friday Night: Moderate Operational Impact. Chance of SHRA. Saturday: High Operational Impact. Likely 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. Monday: Low Operational Impact. Slight Chance of SHRA. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX.
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&& .FIRE WEATHER... Seasonable temperatures for the remainder of the week with minimum RH values falling to the 30 to 50 percent range this afternoon and 40 to 50 percent Friday afternoon. Winds today will become north-northwesterly at 6 to 12 mph, and light south to southeasterly Friday. Periods of rain will return for the weekend. && .HYDROLOGY... A dry and seasonable airmass holds through the remainder of the week. The next chance for widespread precipitation will be over the weekend. Basin-averaged precipitation totals look to be on the order of a half inch to an inch. 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...Thompson NEAR TERM...Thompson SHORT TERM...Thompson LONG TERM...Wasula AVIATION...Wasula FIRE WEATHER...Thompson HYDROLOGY...Thompson

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