Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 161500 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 1000 AM EST Sun Dec 16 2018 .SYNOPSIS... A complex storm system over the Mid Atlantic Region approaches today bringing a wintry mixture of precipitation to eastern New York and western New England. The storm system will move northeast toward Cape Cod Sunday night that will transition all the mixed precipitation to snow. Then a strong cold front will move through on Monday with isolated to scattered snow showers and possibly a few snow squalls to be followed by blustery conditions into Tuesday. && .NEAR TERM /THROUGH TONIGHT/... Winter Weather Advisory for the southern two-thirds of the cwa into the evening hours. As of 950 AM EST, wintry mix of precip continues to gradually progress northward across the forecast area with several reports of mainly sleet or rain/sleet mix. An observer in Kingston reported almost a tenth of an inch of sleet earlier this morning. There is downsloping evident in the valleys with mainly easterly winds so it may some extra time for the column to saturate in these areas. The 12Z Albany upper air sounding showed substantial mid- level dry air between 2-12 KFt. That being said, no major changes were made to the forecast as we still expect a wintry mix to continue for much of the day with temperatures hovering within a couple degrees of freezing. Prev Disc... As of 615 AM EST...Leading edge of precipitation was crossing I84 and into southern Ulster, Dutchess and Litchfield Counties. High reflectivities and variable dual pol correlation coefficients suggest a mix of hydrometers. Metar from KPOU supports this idea with `UP` being reported within the past hour. So the wet-bulb processes are underway as with this update just minor modifications to the PoPs and hourly temperatures/dewpoints per observations and near term trends. Prev Disc...A period of clearing skies occurred earlier for the Hudson River Valley and into portions of western New England that allowed for temperatures to quickly fall back to the lower 20s across the Dacks and Lake George Saratoga Region to middle 30s south of Albany. Leading edge of the precipitation continues to exhibit some drying with its approach due to the bifurcation of the moisture plumes per the layered H2O Vapor loop. However, strong upper low impulse was clearly evident across western North Carolina as region of enhance diffluence was increasing over eastern PA. This has resulted in a blossom of regional radar reflectivity`s along and north of I80 corridor. So once we are able to saturate the column, we should begin to see the mixed precipitation evolve from south to north. Mesoscale models and hourly updated guidance continue to support a low confidence forecast with respect too the downsloping influence from the increasing magnitudes of easterlies over the Berks and Greens. Its possible the leading edge of the precip may delay even longer from reaching the Capital District and points northward (as seen in the HRRR). We will tailor back PoPs through the morning hours and blend those into the afternoon forecast. Cross sections and BUFKIT profiles support a mix of rain/sleet thanks to wet-bulb processes along with some freezing rain in spots. Per the HREF and NAM3km, seems the overall threat of pure freezing rain was reduced a bit with the 00Z guidance. So precip type remains rather low confidence as advisory looks good. As for surface temperatures, we will blend the previous forecast with the NAM MOS which points toward the cooler side of the guidance envelope. Tonight, coastal low deepens just outside of the benchmark as this system approaches eastern Cape Cod. Deformation zone moves across the region through the evening hours as thermal column cools further for wintry mixture becoming more snow. This is where the potential for some accumulating snow occurs with the higher terrain the better potential with orographic lifting. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... Monday-Monday night...A strong northern stream short-wave trough accompanied by impressive height falls approaches and follows in the heels of the southern stream complex low pressure system. Some scattered rain/snow showers are possible with the short-wave trough and associated cold front. The better chance for a few snow squalls will be northwest of the Capital Region where steeper lapse rates, colder temps, and moisture profiles line up which is also support by the experiential snow squall parameter. The greatest threat would be in the afternoon. Highs get into the upper 30s to lower 40s in the Hudson River Valley and NW CT. Temps will be in the upper 20s to mid 30s in most other locations. The winds will increase from the west to northwest at 10-20 mph late in the day with gusts 30-40 mph. Snow amounts will vary from a coating to an inch in the heavier snow showers/squalls, mainly across the higher terrain. A brief lake connection occurs Monday night in the strong cold advection as the flow veers to the northwest which would impact portions of the western Mohawk Valley, eastern Catskills and Schoharie Valley. Some upslope snow showers are possible for the north-central Taconics and southern Greens too as the Froude values are less than 0.5 . Snow amounts could range from a half an inch to a few inches. Blustery and cold conditions as forecast mixing layer heights and momentum transfer suggest we tap into the high 20 to high 30 kts of winds. Wind chills in the 10 below to teens across the region with actual air temps in the teens and lower 20s with a few single numbers of the southern Adirondacks. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Sharp upper level shortwave trough will be departing off New England on Tuesday, with surface high pressure building into the region from the Great Lakes and Midwest. Enough of a pressure gradient will be in place to continue to allow for breezy conditions on Tuesday morning, although winds should be diminishing by afternoon and evening as the high pressure approaches from the west. Aside from some patchy morning clouds, skies will be clearing out on Tuesday and any lingering upslope snow showers should be over, allowing for dry conditions through the day. With continued chilly temps aloft in place, temps will range from the upper teens over the Adirondacks to the low 30s over the mid-Hudson Valley. Surface high pressure will be passing over the area for Tuesday night, which will allow for good radiational cooling, thanks to clear skies and light winds. Lows will be in the teens, with some single digits over the Adirondacks. High pressure will continue to allow for dry weather on Wednesday into Wednesday night with a partly to mostly clear sky. Although temps will be a little milder than Tuesday, they still will be below normal, with highs in the 30s and lows in the 20s. The next storm system will be arriving for late in the week as a digging trough over the Mississippi Valley closes off over the Deep South and allows surface low pressure to track northward across the Appalachians. Although most of Thursday should be dry with increasing clouds, precip will be arriving for Thursday evening through Thursday night and continuing into the day on Friday. Strong warm advection will allow for steady precip, and with a strong southerly flow in place, plenty of moisture will arrive out of the Gulf of Mexico and western Atlantic. Along with the plenty of moisture will be much warmer temps, both at the surface and aloft, with temps in a warm nose exceeding +5 C. Although a few sheltered spots may briefly begin as some freezing rain across the Adirondacks, most of the region will only be seeing rainfall. Any ice will be limited and fairly isolated in coverage. Temps will start out in the 30s for Thursday into Thursday evening and will be rising on Thursday night, with highs reaching into the 40s for most spots on Friday. In addition, the strong E-SE winds within the low- level jet may allow for some strong wind gusts across the typical channeled flow areas within the Taconics, southern Greens and Berkshires on Thursday night into early Friday. The steadiest rainfall will be tapering off by late Friday, although some showers will continue for Friday night into Saturday, as low pressure tracks across the eastern Great Lakes. Eventually, the storm`s cold front will pass through the region, allowing for some colder air aloft to move into the region, as the upper level low tracks across the eastern Great Lakes and into Ontario and Quebec and our region is dominated by moist cyclonic flow. Some western and high terrain areas may see rain showers change over to snow showers before ending late on Saturday, although most valley areas will only see rain showers. Temps on Saturday with range from the mid 30s over the high terrain to the mid 40s in valley areas. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... Flying conditions are currently VFR with bkn-ovc mid and high level clouds in place for KGFL/KALB/KPSF. These clouds will gradually thicken and lower over the next few hours with continued VFR conditions. Meanwhile, light precip in the form of rain and sleet has just begun at KPOU and it will gradually spread northward through the morning hours. Flying conditions have already lowered to MVFR conditions, but precip is fairly light in intensity. As it lifts northward, it will be somewhat spotty in coverage. Still, some precip should reach KPSF/KALB towards midday and by later this afternoon at KGFL. At those sites, precip should be a mix of sleet and freezing rain, although some snow or plain rain could also mix in from time to time. Flying conditions will mainly be MVFR within precip, as it will be fairly light in intensity and may not be steady. North to northeast winds for all sites will be around 5 to 10 kts through the day. By evening, precip will transition over to a snow/sleet mix and may briefly pick up in intensity, which may allow for IFR conditions for visibility for all sites. North to northwest winds will be around 5 to 10 kts. Precip should start to taper off after midnight as the storm system starts to move away from the area, and flying conditions look to be MVFR for the rest of night due to lingering low stratus. Outlook... Monday Night: Low Operational Impact. Breezy Slight Chance of SHSN. Tuesday: Low Operational Impact. Breezy NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: Low Operational Impact. Slight Chance of RA. Thursday Night: High Operational Impact. Likely RA. Friday: High Operational Impact. Likely RA. && .HYDROLOGY... No major hydro problems are expected into the mid week. Dry weather is expected into early this morning before some light mixed pcpn moves into the southern extreme of the Hydro Service Area by mid-morning. The mixed pcpn will expand across the region before transitioning back to snow tonight with light accumulations of ice and snow expected. Total QPF for this event will range from a tenth of an inch of less over the northern portion of the HSA with a half to three quarters of an inch over the Mid Hudson Valley, southeast Catskills and Litchfield Hills. Some localized one inch amounts are possible in the Housatonic Basin. Some within bank rises are possible on the main stem rivers due to some rain, mixed pcpn and snow melt, but flooding is not expected at this time (caution stage for Poughkeepsie due to the east/southeast flow and the tidal impact and for Stevenson Dam which is regulated). A strong cold front moves through on Monday with much colder air moving into the region for Tuesday, as flows will continue to lower during the early to middle portion of next week with some ice formation and build up possible on the waterways. The next chance for a widespread precipitation event arrives toward the end of this week. 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...Winter Weather Advisory until 4 AM EST Monday for CTZ001-013. NY...Winter Weather Advisory until 4 AM EST Monday for NYZ038>040- 047>054-058>061-063>066-082. Winter Weather Advisory until midnight EST tonight for NYZ041- 083-084. MA...Winter Weather Advisory until 4 AM EST Monday for MAZ001-025. VT...Winter Weather Advisory until midnight EST tonight for VTZ013>015. && $$ SYNOPSIS...BGM/Wasula NEAR TERM...BGM/JLV/Wasula SHORT TERM...BGM/Wasula LONG TERM...Frugis AVIATION...Frugis HYDROLOGY...BGM/Wasula is the U.S. government's official web portal to all federal, state and local government web resources and services.