textproduct: Charleston

WHAT HAS CHANGED

Lowered temperatures and raised PoPs, QPF and snowfall amounts and issued a Special Weather Statement for snow in the northeast mountains this afternoon. Several reports of 2 inches were received over the lower terrain therein, likely making roads slick, at least on bridges and overpasses. Conditions were undoubtedly worse over increasingly higher terrain. Dense fog and dense freezing fog are likely overnight tonight into Friday morning, as high pressure builds overhead tonight in the wake of the exiting system

KEY MESSAGES

-1. Moderating temperatures and dry weather return for Friday and Saturday.

-2. Potential for an impactful winter storm arrives for the end of the weekend into the start of the next work week.

-3. Remaining unsettled but turning increasingly mild the rest of next week.

DISCUSSION

KEY MESSAGE 1... High pressure building in overhead overnight tonight, in the wake of a southern stream flat wave bringing light snow accumulations in the northern mountains and rain south this afternoon, will bring clearing and light wind. This will allow for low temperatures at or below freezing across much of the area, with areas of freezing dense fog.

The fog may be slow to burn off Friday morning, but once it does, and high pressure exits, a southwest flow of milder air will take control, bringing sunshine by Friday afternoon, and progressively milder afternoons Friday and Saturday. Friday night will be clear and chilly, but with enough low level gradient flow to limit fog to the better sheltered valleys in and near the mountains.

KEY MESSAGE 3... The start of Meteorological Spring on Sunday will actually reverse the springlike weather that unfolds on Friday and Saturday, via a cold front that crosses overnight Saturday night into Sunday morning. This could bring a bit of rain changing to snow as it crosses but, more importantly, it will set the stage for colder weather to start the new week, with another southern stream flat wave passing south of the area to bring snow to northern and central portions of the area, and snow to rain across southern portions of the area. There remains uncertainty as to where these transitions may be, and how quickly they then move north on Monday. In addition, there could be a stripe of sleet and/or freezing rain in the transition zone.

The chance for precipitation decreases Monday night as the wave exits, but warm advection awaits in its wake, with a generally southerly flow between high pressure off the northeast coast, and low pressure out over the plains states.

KEY MESSAGE 3... Unsettled weather continues through the middle of next week, as waves of low pressure continue to pass. However, an evolution toward higher heights with the southern and northern jetstreams farther north in the east, and troughiness out west, will result in systems tracking farther and farther north, leading to increasingly milder weather with overnight lows rising above freezing, and eventually, increasing breaks in the rain.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

VFR conditions in the wake of a wave of low pressure exiting this afternoon will give way to areas of low stratus and fog tonight, the latter of which could become dense overnight. With temperatures at or below freezing, the dense fog will be a freezing fog.

The fog may be slow to lift and thin out Friday morning, but once it does, VFR conditions are expected for the balance of the day.

Light north to northeast surface flow becoming light and variable this afternoon becomes calm tonight, and then light southwest on Friday. Aloft, light northeast flow becomes light west to northwest with height, and with time through tonight, before becoming light southwest on Friday.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY... FORECAST CONFIDENCE: Medium to high. ALTERNATE SCENARIOS: Timing of improving conditions this afternoon, deteriorating conditions in fog and status tonight, and then improving conditions again on Friday, may vary.

EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

UTC 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04 EST 1HRLY 12 13 14 15 16 17 18 19 20 21 22 23 CRW CONSISTENCY H H H H H H H M M M H M HTS CONSISTENCY H H H H H M M M H H H H BKW CONSISTENCY M H H M H M M H M L L M EKN CONSISTENCY H M H H H H H H H H M L PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H M L M H H H H H M

AFTER 18Z FRIDAY... Increasing confidence for IFR amid a mix of precipitation types Sunday night into Monday.

RLX WATCHES/WARNINGS/ADVISORIES

WV...None. OH...None. KY...None. VA...None.