Temperature at the airport is currently 37 degrees. As cold frontal boundary crosses the region this afternoon, low level cold air advection will move in between 600ft and 2500ft. This region will be the focus for a period of freezing rain and sleet tonight. Surface temperatures will range between 27 mainly north of Keene and above 1000ft to 34 in southern Cheshire County between midnight and 5am. 1000-850mb thicknesses will begin decreasing by 6pm this evening, and will likely be under 1310m by midnight. 850-700mb thicknesses will stay above 5500m for the duration of the event. Considering an elevated warm layer up to 2000m thick with maximum temperature of 6C, this will be a mainly freezing rain event Keene and southward. North of Keene, it is possibly that sleet will be the main precipitation type. Warm air advection associated with low pressure moving through NY state will raise temperatures above freezing Keene and southward by 6am with the rest of the county by 7am. Some locations above 1000ft could maintain a mix of rain and freezing rain through 8am.
Precipitation will fall heavily especially after 3am. Water equivalents over .5" are possible between midnight and 6am. Sleet accumulation north of Keene and in the higher elevations will be around a half inch, while downtown Keene will likely not see any sleet accumulation. Ice accretion up to a quarter inch is still possibly in a few locations mainly above 1500ft, with a glaze possibly even in downtown Keene.
--- Snowday Outlook ---
The main issue is how long surfaces temperatures remain below freezing Wednesday morning. The recent trend is to have WAA bring temperatures above freezing before 4am. This could allow most roads to be ice free by 6am. However, considering the persistent precipitation, as well as abundant snow cover, temperatures at the immediate surface may stick around freezing a little longer. This suggests a good possibility for a delay.
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A significant nor'easter, the first of Gulf origins this winter, will affect the east coast Thursday through Sunday. Many uncertainties with this storm, most of which revolve around the final track. Top on the list is precipitation type, timing, and axis of heaviest accumulations. One possibility with this storm, as shown on the 18z GFS is a classic flash freeze. So far the 18z GFS model run is the only one to go this far, but the possibility exists nonetheless. One thing that is certain is that this storm will be loaded with moisture from the Gulf. PWATs could rise up to 1.5" across SNE which is very impressive for a near winter temperature profile. However, there also could be a fairly sharp northern cut off in accumulations. As for timing, there remains some large discrepencies, however it appears likely that the height of the storm will revolve around Friday Night.
For snowday potential, if and only if the timing for the storm quickens would there be a potential for less than 6 hours 37 minutes to the schoolday Friday.
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