Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 200556 AFDALY Area Forecast Discussion National Weather Service Albany NY 1256 AM EST Tue Feb 20 2018 .SYNOPSIS... Unseasonably to possibly record warm weather will be around Tuesday and Wednesday in the wake of a warm frontal passage. After some showers this evening into tonight, little to no precipitation is expected for much of the area into midweek except for over the southern Adirondacks. The combination of snowmelt and rainfall may lead to some minor flooding over the higher terrain north and west of Albany. A cold front will cool temperatures down by Thursday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Flood Watch in effect tonight through Thursday morning for northern Herkimer, Hamilton, and northern Warren Counties... As of 1245 AM EST...Radar showing areas of rain continuing to track east through our region, mainly along and north of I90. So, just some minor adjustments to the timing of the expansion of the area of rain through the overnight. Some minor adjustments to temperatures based on current data and trends as well. Previous AFD has a few more details and is below... A very amplified flow is over the CONUS with a strong anticyclone in place over the southwest Atlantic, and a full- latitude trough pushing into the Intermountain West. A strengthening low level jet is resulting in isentropic lift which is gradually saturating the dry column noted on the 12Z KALY sounding. Will continue with categorical PoPs nearly area- wide through 00Z. The moisture plume is impressive with PWATs around 1 inch over the majority of the forecast area by 00Z. Have increased QPF a bit over the favored southwesterly flow higher terrain of the western Mohawk Valley/southern Adirondacks/southern Vermont (see hydro section below). Temperatures aloft above freezing support rain as the dominant P-type. Some wet bulbing has cooled temps a bit with the onset of the precipitation, but it appears that surface wetbulb temps above freezing will greatly limit any icing threat, and the current forecast has no mention of ice. Tonight, chances of rain will diminish south to north, becoming confined to areas mainly north of the Mohawk Valley after 06Z. This will occur as low to mid-level winds veer, minimizing isentropic lift, and with some drier midlevel air arriving. Some areas of fog or light showers/drizzle cannot be ruled out with southerly flow allowing for low-level moisture advection to continue. Temperatures should stay steady or rise somewhat overnight, solidly in the 40s in most areas by daybreak Tuesday.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/... Tuesday into Wednesday, the massive upper ridge centered off the southeast US coast will expand into the Northeast, with a large area of +2 to +3 SD H500 heights over much of the eastern CONUS. At lower levels, the warm front and attendant isentropic lift will continue to push mainly north of the forecast area, mainly confining rainfall to portions of the southern Adirondacks. With the influx of low-level moisture, we could see areas of fog or perhaps drizzle early in the day outside of the area of steadier rainfall in the Adirondacks. Temperatures are a tricky call. The potential for unseasonable warmth is there with H925 temps of 10-12C (also +2 to +3 SD), but it will be heavily dependent on whether any low clouds can scour out. The NAM keeps these low clouds around along with an easterly wind component up the Hudson Valley, and is nearly 10F cooler than the GFS which mixes deeper with a southwesterly flow. Sided a bit more toward the warmer side for favored downslope areas with a fairly strong SW flow at 925 mb, but would not be surprised to see large spatial variation in temperatures. Very mild Tuesday night as the forecast area remains solidly in the warm sector with an elongated area of low pressure along the approaching baroclinic zone well off to our west. Patchy fog is possible, especially across areas with snowpack as dewpoints approach 50F. On Wednesday, the upper trough deamplifies as it pushes east, resulting in gradual height falls locally. This will push a cold front through the forecast area during the evening hours, but with little upper support, expect nothing more than a broken band of showers. Have better confidence in widespread very warm to possibly record high temperatures with the warm air in place and winds in the low levels veering southwesterly. Feel that mixing potential is better Wednesday compared with Tuesday, and sided more toward the warmer MAV MOS rather than the overly cool MET MOS. This has the potential to put us not only in record high territory, but possibly near all-time February record highs (which were set just last year at Albany, Glens Falls, and Poughkeepsie). One factor that could short-circuit the record warmth is if the front and associated cloud cover end up being a bit quicker than currently anticipated. A quick drop in temperatures is expected behind the front Wednesday night. The degree of cooling is still uncertain, with some guidance suggesting the northern half of the forecast area falling below freezing by sunrise Thursday. Current forecast calls for lows in the mid-20s to upper 30s. Mainly rain is expected with the weakening band of showers, although some snow could mix in across the higher terrain. See our Hydro and Climate sections with more details... && .LONG TERM /THURSDAY THROUGH MONDAY/... Unsettled pattern setting up Thursday through Monday. Pieces of upper energy track quickly within west southwest upper flow. There are timing differences in sources of guidance and ensembles as the boundary layer baroclinic zone oscillates north and south in response to the advance and exit of each upper impulse and zone of enhanced moisture and forcing. First, on Thursday, as a cold front settles south of our region, there are hints of one last piece of upper energy that tracks through our region, which could support a brief period of snow and rain to our area, primarily from the Mohawk River Valley, Capital District and southern Vermont and points south. Just including chances since there is not a good consensus and we will know more as we get closer. Highs Thursday in the 30s to lower 40s but cooler if there is more organized precipitation. Thursday night should be dry but the next system will approach and begin to affect our region Friday, likely impacting our region Friday and Friday night. Depending on where the baroclinic zone and freezing line sets up, there should be a zone of mixed precipitation over our region with rain to the south, snow to the north and the mix in a broad zone in between. There are hints of possible sleet and freezing rain but because of the high degree of uncertainty in coverage of precipitation and thermal profile of the atmosphere in various regions just including rain or snow. Highs Friday in the 30s to lower 40s but potentially cooling to around freezing in many areas Friday night. Another period of reduced coverage of clouds and precipitation and potential dry weather is possible Saturday and Saturday night but keeping small chances with the uncertainties in timing of systems in the quick west southwest upper flow. Ensemble probabilities also support keeping at least chances for precipitation Saturday and Saturday night. Highs Saturday in the 40s but some upper 30s northern areas. Increased coverage of precipitation with another piece of upper energy Sunday into Monday but again, precipitation types will be determined on where the baroclinic zone sets up and where the boundary layer freezing line sets up. Indicating mostly rain chances in the day and mixed rain and snow at night. There are still some hints at some potential sleet or freezing rain but again there is a very high degree of uncertainty. Highs Sunday in the 40s with around 40 north and mid 40s south. Highs Monday in the 40s but some upper 30s north and possible near 50 south. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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A warm front will approach eastern NY and western New England from the Ohio Valley and the Mid Atlantic Region overnight. This boundary will slowly lift north and east of the region Tuesday with periods of rain and showers ending. Variable flight conditions overnight with mainly IFR conditions with respect to CIGS but visibilities have remained up. Exception to this has been KPOU where fog has become problematic. Conditions will likely improve to MVFR/VFR between 12Z-16Z Tuesday as rain ends with lingering MVFR/IFR conditions persisting the longest at KPSF. Visibilities should remain VFR through Tuesday afternoon but ceilings may vary between MVFR and VFR as the warm front will be slow to lift north, keeping clouds in the region. LLWS remains in the forecast overnight as this warm front lifts northward. The LLWS will diminish towards daybreak. The winds will lighten to less than 10 Kt overnight, and then increase from the south to southwest at 7-12 kts late Tuesday morning continuing in the afternoon. Outlook... Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Moderate Operational Impact. Breezy Chance of RA. Wednesday Night: Moderate Operational Impact. Chance of RA. Thursday: Low Operational Impact. Slight Chance of RA...SN. Thursday Night: No Operational Impact. NO SIG WX. Friday: Moderate Operational Impact. Chance of RA...SN. Friday Night: Moderate Operational Impact. Chance of RA...SN. Saturday: Moderate Operational Impact. Chance of RA.
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&& .HYDROLOGY... Temperatures will be well above normal to possibly near record high levels through Wednesday, not falling below freezing until Wednesday night at the earliest. Periods of rainfall will affect the entire forecast area through early tonight before becoming mainly confined to the southern Adirondacks through Wednesday. A cold front may bring additional light precipitation Wednesday evening. The combination of QPF of 0.50 to 1.50 inches across the southern Adirondacks, along with 1 to 3 inches of runoff from snowmelt, will lead to flooding concerns through Thursday morning. Latest forecasts have rivers rising in the upper Hudson and western Mohawk basins including the Sacandaga and Schroon Rivers. The Sacandaga at Hope is forecast to reach minor flood stage by Wednesday evening. A Flood Watch is in effect for portions of the southern Adirondacks to address flood potential. There is potential for renewed flooding near the ice jam on the upper Hudson River near Thurman. A Flood Watch was not extended into the Schenectady area at this time due to the light rainfall forecast, potential for a gradual melt of the ice with the mild temperatures, and recent reduction in ice thickness. However, the Mohawk River is likely to rise from an influx of water from upstream rainfall and snowmelt, so additional flooding concerns cannot be ruled out in the vicinity of the ice jam along the Mohawk. If confidence in flooding increases, a Flood Watch may be necessary. 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. && .CLIMATE... Record Warmth is possible TUE into WED. Feb 20th The record highs: KALB 66F set in 1930 KGFL 58F set in 1981 KPOU 63F set in 2016 Feb 21st The record highs: KALB 65F set in 1981 KGFL 65F set in 1981 KPOU 67F set in 1953 All-time February highs: KALB 74F set Feb. 24, 2017 KGFL 70F set Feb. 25, 2017 KPOU 73F set Feb. 24, 2017 RECORDS FOR KPOU DATE BACK TO 1949... HOWEVER...DATA IS MISSING FROM JANUARY 1993 - JULY 2000. && .ALY WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Flood Watch through Thursday morning for NYZ032-033-042. MA...None. VT...None.
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&& $$ SYNOPSIS...Thompson NEAR TERM...BGM/NAS/Thompson SHORT TERM...Thompson LONG TERM...NAS AVIATION...BGM/NAS HYDROLOGY...Thompson CLIMATE...NWS ALY

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