FXUS61 KALY 111735 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 1235 PM EST Wed Dec 11 2024 .SYNOPSIS... Multiple low pressure systems developing along a slow moving cold front will bring moderate to heavy rain today through tonight. Colder air will rush back in from the west tonight with some accumulating snow mainly west of the Hudson River Valley, as a much colder air mass builds in for Thursday into Friday with lake effect snow showers in northern Herkimer and Hamilton counties. && .NEAR TERM /THROUGH TONIGHT/... As of 12:34 PM EST...Rain has begun to filter back into the region where a previous dry slot was noted in the Mid-Hudson Valley and southwest New England as an area of low pressure surges north and east farther into the region. The cold front remains still to the west of eastern New York and western New England as of this update, but continues to slowly encroach from the west. Once again only minor updates were needed with this update to ensure consistency with latest obs and trends. All else remains unchanged with additional details in the previous discussion below. Previous Discussion...Widespread rainfall continues today through tonight before transitioning over to snow as colder air temperatures arrive behind a strong cold front. Periods of moderate to heavy rainfall this afternoon and this evening is still on track. Forecasted rainfall amounts continue to range between 1 to 3 inches through tomorrow night. A Flood Watch for this afternoon into tomorrow morning continues for western New England and Washington and Rensselaer counties in NY, please see hydro section for more details. Snowfall in the valleys are most likely to melt on pavement surfaces due to how warm we have been while hilly/mountainous terrain locations will likely stick with amounts between a coating to an inch. The low pressure system continues to move north and east through today then departing to our north by tomorrow morning. Wind gusts increase this afternoon as our low pressure system and associated cold front moves through with gusts primarily ranging between 15 and 30 mph, with gusts up to 40 mph in Litchfield county. If forecast confidence continues to increase this morning, wind headlines may be needed due to this short period of strong wind gusts. Once this system moves through, wind gusts range between 10 and 25 mph through tonight. Temperatures tomorrow morning fall to below freezing everywhere which could lead to wet pavement surfaces becoming icy. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Key Messages: - Lake Effect Snow Warning for northern Herkimer and Hamilton counties. - Cold temperatures continue through Friday. Discussion: Lake effect snow bands set up for off of Lake Ontario for Thursday into Thursday night that are currently forecasted to impact northern Herkimer and Hamilton counties, with confidence still in the greatest snowfall amounts to occur north of Route 28. The Winter Storm Watch has been upgraded to a Lake Effect Snow Warning for snowfall accumulations greater than 7 inches. In southern Herkimer counties, snowfall chances can still occur (greater than 50 percent) for lighter snowfall accumulations to between 2 and 6 inches. By Friday morning, the bands should shift further westward to decrease chances of snow for these locations. With the exception of the western Adirondacks, dry conditions are in the forecast through Friday night and cold temperatures. Highs for tomorrow are forecasted to range in the 20s for higher terrain to the upper 30s for the valleys. By Friday, there's high confidence (probabilities greater than 75 percent) for even colder high temperatures in the forecast with most locations struggling to reach above freezing (32 degrees). Low temperatures are forecasted to be in the teens with the exception of the western Adirondacks where they're forecasted to see lows in the single digits. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Key Messages: - Dry and cool start to the weekend with high pressure - Precip chances (20-50%) return for the beginning of next week Discussion: High pressure and mid-level ridging will be directly overhead to start the long term period, and should provide us a dry, albeit cool start to the weekend. By Sunday morning, that surface high will be centered across eastern New England, opening the door for several shortwaves/mid-level closed lows to move into the area. The first of these systems will arrive from the Great Lakes Sunday afternoon, which will lead to low to medium chances (20-50%) of precipitation for the area. Confidence on these chances is low at this time, as there is substantial disagreement amongst deterministic guidance on strength, timing and evolution of this initial system. Chances will persist into early next week with additional systems moving across or just near the area. Both rain and snow will be favored, with chances for the later decreasing heading further into next week. Temperatures will start off below normal with AM lows Saturday in the single digits (terrain) to mid teens (valleys) rebounding into the mid 20s (terrain) to mid 30s (valleys) by the afternoon. Values will return to near to just above normal by early next week with renewed southerly flow, with highs back into the 40s for most by Monday and Tuesday. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... Band of light rain with embedded pockets of moderate rain is tracking from central NY into eastern NY and western New England. This band of rain is producing MVFR ceilings and visibilities across the region, including all TAF sites with some localized IFR at KALB and KPSF. Although, KPOU has some periods of VFR. As the steadier rain affects the TAF sites this afternoon into early this evening, indicating varying intervals of MVFR and IFR conditions at all TAF sites. The rain will end as a brief mix of rain and snow this evening around midnight through about 07Z. Then dry weather moves in as the cold air continues to spread through the region. Dry weather is expected through Thursday morning. Winds will be east to southeast at 10 Kt or less through this afternoon, with LLWS indicated due to winds being 19040kt at about 2000 feet. The LLWS will end between 00Z-03Z as the strong winds aloft shift east of our region. Surface winds will shift to west and west southwest by about 03Z-05Z and increase to 10 to 15 Kt with gusts around 20 Kt. The gusty west to west southwest winds will continue through Thursday morning. Outlook... Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: Low Operational Impact. Slight Chance of SN. Sunday: Moderate Operational Impact. Chance of RA...SN. Sunday Night: Moderate Operational Impact. Chance of RA...SN. Monday: Moderate Operational Impact. Chance of RA. && .HYDROLOGY... Key Message: - Flood Watch in effect 1 pm Wednesday to 7 am Thursday for Rensselaer and Washington Counties in NY and all of western New England. Multiple low pressure systems along a slow moving cold front will bring an extended period of rainfall during the daytime before winding down and changing to snow this evening. Rainfall amounts expected to range from 1.0 to 2.5 inches across the Hydro Service Area (HSA), with some higher amounts around 3" across south/southeast-facing mountain slopes. The rain will be heavy at times, especially in the afternoon to early evening. Most of the HSA is in D1 (Moderate Drought) to D2 (Severe Drought) currently based on the latest US Drought Monitor. The widespread rainfall will be beneficial for drought conditions, but there will likely also be some impactful hydro issues. The heavy rainfall, some convection with intense rainfall rates combined with snow melt, is expected to cause some minor to moderate flooding on main stem rivers and even isolated flash flooding. A Flood Watch is in effect for all of western New England and Rensselaer and Washington Counties in eastern NY. Ponding of water on roads, urban/poor drainage and river flooding may occur in some locations due to the runoff and some snow melt. WPC Day 1 Excessive Rainfall Outlook has eastern NY in a Marginal Risk and western New England in a Slight Risk for the potential of exceeding the flash flood guidance. Latest NERFC forecast hydrographs are indicating minor to moderate flooding along some main stem rivers, including Hoosic at Williamstown(moderate) and Eagle Bridge(minor), Walloomsac at Bennington(moderate), and Mettawee at Granville(minor). There is lower than normal confidence in the amount of runoff due to snow melt, so the magnitude of river flooding will continue to be assessed. Rivers may keep rising for a time after the transition to snow with colder temps Thursday morning. Colder air quickly moves back in tonight turning any remaining rain to snow, and slowing down runoff. Be sure to check the National Water Prediction Service (NWPS) on our webpage for more details on river and lake observations and forecasts. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Flood Watch through Thursday morning for CTZ001-013. NY...Flood Watch through Thursday morning for NYZ043-053-054-084. Lake Effect Snow Warning from 1 AM Thursday to 7 AM EST Friday for NYZ032-033. MA...Flood Watch through Thursday morning for MAZ001-025. VT...Flood Watch through Thursday morning for VTZ013>015. && $$ SYNOPSIS...JPV/Webb NEAR TERM...Gant/Webb SHORT TERM...Webb LONG TERM...Speck AVIATION...NAS HYDROLOGY...Speck