textproduct: Charleston

WHAT HAS CHANGED

Existing winter highlights have been allowed to expire on time with snow ending in the mountains shortly. Adjusted precipitation totals slightly downward for the southern system tonight, following a continued southward shift in the heaviest moisture axis. Added preliminary mentions of a wintry mix potential for the Sunday night and Monday timeframe as model spread remains significant regarding the temperature profile.

KEY MESSAGES

1. Rain overspreads the southern coalfields and northeast Kentucky tonight through Thursday morning. While totals have trended lower, 0.50 to 0.75 inches of rain is still expected over our extreme southern flank while totals farther north have decreased.

2. A warming trend and dry weather are expected Friday and Saturday, promoting an orderly melt of existing snow.

3. A more potent and complex weather system arrives Sunday night into Monday, with the potential for rain, snow, and a narrow band of ice.

DISCUSSION

KEY MESSAGE 1... Attention shifts to a southern stream disturbance progged to skirt the southern periphery of the area tonight. Model guidance has continued a southward trend with the QPF axis. Half to three-quarters of an inch is forecast for the far southern coalfields, with a sharp reduction to less than a tenth of an inch north of Charleston. BUFKIT profiles at KBKW show dynamic cooling may briefly lower the wet-bulb zero height to around 1000ft H900 between 06Z and 12Z Thursday. While a few wet snowflakes may mix in during peak intensity, surface temperatures in the mid-30s and a lack of deep saturation in the DGZ will preclude any lowland accumulation. Additional rainfall on the existing fresh snow pack will help to begin the ripening process, but not expecting any runoff concerns this early.

KEY MESSAGE 2... High pressure builds into the Tennessee Valley by Friday morning, resulting in isentropic descent and clearing skies. A significant warming trend will commence as H850 temperatures climb to +5C by Saturday. Highs will reach the mid-50s to low 60s in the lowlands. This orderly warmup with cool overnights in the mid 30s is favorable for a steady snowmelt without significant hydrological concerns through the first half of the weekend. Minimum RH values Saturday afternoon may dip to near 30 percent in southeast Ohio, but light winds should mitigate fire weather concerns.

KEY MESSAGE 3... A backdoor cold front Sunday morning could yield some light snow across the far north. A more potent system is progged for Sunday night into early next week. Large NBM percentile spreads highlight the uncertainty of the baroclinic zone's placement. Looking at forecast soundings, a prominent warm nose develops around H850 overrunning a sub-freezing surface. Would likely see rain south, snow farther north and a narrow band of freezing rain or sleet between them. Again, overall confidence in placement and track of this system is low this far out, but it does seem plausible that some winter weather headlines may be required. Will also need to monitor state of the snow pack and potential heavier rain placement in the south for runoff concerns.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Generally VFR conditions prevail through this evening. Winds will be westerly around 10KTs with gusts up to 20KTs through 22Z, then diminishing. Tonight, rain and lower ceilings move into southern terminals (BKW/HTS/CRW) as a southern system passes. Snow could briefly mix in for CRW/BKW with dynamic cooling before switching back over to rain.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z THURSDAY... FORECAST CONFIDENCE: High, except medium with rain and snow through today. ALTERNATE SCENARIOS: Restrictions in rain may not make it as far north as advertised tonight.

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 18 19 20 21 22 23 00 01 02 03 04 05 EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H M M M M H H H H M H EKN CONSISTENCY M M M M M M H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H M H H H H H H H H H H

AFTER 18Z THURSDAY... IFR conditions may persist across southern West Virginia and southwest Virginia through mid-morning Thursday in rain. Significant flight category restrictions and a mix of precipitation types are likely by Sunday night and Monday.

RLX WATCHES/WARNINGS/ADVISORIES

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