Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 171117 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 617 AM EST Wed Jan 17 2018 .SYNOPSIS... An upper trough and cold front will cross the area today with potential for snow across northern areas and a rain snow mix elsewhere. Clearing and cooler tonight behind the front. Dry high pressure will maintain fair weather late week into the weekend, with moderating temperatures this weekend. Moisture return expected Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Upper trough, extending from the Great Lakes SW into the lower Miss Valley, will deepen and swing east through our region through this evening. Surface frontal boundary will shift east across the region today, with an inverted surface trough shifting slowly south through our forecast area (FA). Current radar mosaic and surface obs indicating light precipitation from E TN/W NC...SW across N GA into AL. Latest high resolution models indicate precipitation to expand in coverage later today and shift east across our FA, exiting our E/NE FA early this evening. Latest model runs appear to be trending towards a little more moisture/precip amounts, and trending slightly slower with precip timing. General consensus among model thermal profiles, forecast soundings, and local tools, suggest precipitation beginning as light rain this morning, then mixing with and/or changing to snow later today, for much of our FA, less so across the southern portions. Snow forecasting is less confident when cold air is not already in place but rather is coming in concurrent with the onset of expected precipitation. Another factor reducing confidence of snow accumulations is the fact that surface temps in many areas could be above freezing when snow or mix is occurring. Decided to slightly expand the winter storm warning and winter weather advisory areas. In general, snow amounts of 2 to 4 inches will be possible northern Midlands in the warning area, with amounts ranging from a dusting to up to one inch possible elsewhere in the advisory area. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... Upper trough axis will shift over the forecast area this evening then off the coast later tonight as surface high pressure builds into the area from the east. All precipitation is expected to east of the forecast area by 00z with no additional weather expected through the short term period as a cold and dry airmass settles over the area. One concern tonight may be potential for black ice with lingering moisture on road surfaces as temperatures quickly fall below freezing in the evening. Will hold off on any statement related to this for now given other warning/advisory products in effect but an SPS may be needed after this event for this potential hazard. Temperatures will drop back into the teens and lower 20s with cold advection overnight. Winds will be up through the night as well preventing ideal radiational cooling. Did lower the temps a bit in the warning area where some snow cover is expected to remain. Mostly clear skies and light westerly surface flow with some additional downsloping flow aloft will allow temperatures to rebound a bit on Thursday with highs expected in the 40s. Airmass modification will help support slightly warmer temperatures for overnight lows on Thursday night in the 20s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The extended forecast will feature generally dry weather and a warming trend to above normal temperatures with generally zonal upper level flow. Surface high pressure will reside over the forecast area through the weekend before weakening late Sunday ahead of an approaching upper trough and cold front. Surface winds will be from the west to southwest supporting a warming trend. Precipitable water values will be below a quarter inch but slowly increase to around a half inch through Sunday. Stronger moisture advection will occur Sunday night into Monday in advance of a deep upper trough moving east across the middle of the country. An 850mb jet of 40-45 knots will bring a surge in precipitable water values over an inch across the forecast area on Monday coinciding with upper level forcing resulting in high chance pops for the forecast area. There will not be much cold air behind the cold front that crosses the region late Monday as mild temperatures continue through early next week. Highs will be in the 50s on Friday then moderate through the 60s over the weekend to possibly some highs around 70 on Monday just ahead of the front. Overnight lows will be cold Friday night in the 20s but moderate warmer in the 30s to 40s Saturday and Sunday night, before falling back into the 30s early next week. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... Radar mosaic and surface obs indicate light precipitation just to our north and west, along and behind a cold front, and ahead of a strong upper disturbance. As this system progresses across our FA today, we are expecting additional precipitation and associated restrictions to develop. Precipitation could start out as rain but change to a rain/snow mix and possibly to all snow, with VSBYS and CIGS deteriorating accordingly. Will indicate conditions lowering to IFR. Expect improving conditions late this afternoon at AGS/DNL, and early this evening elsewhere. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected Wednesday night through Sunday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...Winter Weather Advisory until 7 PM EST this evening for GAZ040- 063>065. SC...Winter Weather Advisory until 7 PM EST this evening for SCZ018- 025>031. Winter Storm Warning until 7 PM EST this evening for SCZ015- 016-020>022. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.