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WHAT HAS CHANGED

Winter Storm Watches have been UPGRADED to Winter Storm Warnings for the following areas: Eastern mountains and western foothills of WV for snow accumulations of 5 to 12 inches expected, and portions of southern, central, and northern WV for snow accumulations of 2 to 5 inches expected.

Confidence is increasing for the formation of heavy snowbands over SE OH, NE KY, and most parts of WV late tonight into Sunday.

Critical Travel Hazard: Flash Freeze late tonight into Monday night.

KEY MESSAGES

- 1) A system brings colder weather and an opportunity for accumulating snow late tonight through Monday. Hazardous travel conditions likely.

- 2) Plunging temperatures will sweep across the entire region, rapidly freezing any lingering wet surfaces tonight into Monday. Expect dangerous, icy travel conditions anywhere, even in areas that received lesser snowfall amounts.

- 3) Additional precipitation chances arrive with a couple of mid to late week systems.

DISCUSSION

KEY MESSAGE 1...

A low pressure system passes by to the south tonight, tracking east off the Carolinas coast, while an upper trough shifts into the area on Sunday. Precipitation should begin with rain this evening, transitioning into a mix of rain and snow tonight, and into all snow by Sunday morning. Meanwhile, an upper level trough ushers in much colder air into the local region Sunday into Monday. Although the developing coastal low begins to pull away from the area Sunday night into Monday, moisture transported into the area under northwest flow from off the Great Lakes should allow snow to continue through Monday.

Gusty northwest flow and good Great Lakes moisture connection will allow for snowbands to develop over the lowlands later tonight, and then squeeze moisture against the mountains Sunday through Monday evening to produce significant upslope snow accumulations, up to 15 inches at the highest peaks. Travel will be difficult to impossible over these areas. Upslope snow should wind down once the upper trough departs to the east early Tuesday morning.

WPC snowband probability tracker suggests a signal for snowbands formation across central and eastern West Virginia sunday thorugh Sunday night. Intense bursts of heavy snow in a short period of time are possible. Gusty winds leading to blowing snow and visibility rapidly falling to less than one-quarter mile may be possible. Wind gusts up to 45 mph are expected.

Probabilities for 4+ inches of snow have increased to near 100% across the higher elevations of the northeast mountains. Similarly, the probabilities for these areas exceeding 6 and 8 inches have increased to 80% and 60%, respectively. Across central WV, there is a 55% probability of exceeding 4 inches of snow. However, the official expected snowfall totals by Monday evening are 5 to 12 inches across the northeast mountains, 4 to 5 inches across the western foothills, and 2 to 4 inches across central WV and Kanawha Metro Area. These accumulations will result in a moderate to high threat for hazardous, snow-covered roads and broader travel disruptions during this period.

KEY MESSAGE 2... An upper-level trough will usher much colder air into the local region from Sunday into Monday. Under northwest flow, strong cold air advection (CAA) is expected to drive H850 temperatures down from 0C to -10C by Sunday night. This sharp temperature drop will likely cause a FLASH FREEZE of any lingering surface moisture, resulting in dangerous, icy travel conditions across the entire forecast area, even at locations that receive lesser snow amounts. Be aware of black ice formation. Bridges and underpasses freeze much faster than regular roads and become treacherous first.

KEY MESSAGE 3... Precipitation chances return mid-to-late week as a pair of systems cross the region. Forecast models show good consensus on the first system tracking to our north on Wednesday.

A second system is slated for Thursday into Friday, though significant uncertainty remains regarding its exact track and timing. Mild temperatures should favor rain as the primary precipitation type, though a wintry mix cannot be ruled out across the northeast mountains and portions of SE Ohio.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Widespread VFR conditions will continue through this evening under a brief surface high pressure. Ceilings will deteriorate to MVFR/IFR overnight tonight as precipitation in the form of rain spreads east across the area. Rain will quickly transition to all snow overnight as strong CAA arrives.

Expect IFR/LIFR conditions under snowbands at most terminals tonight and Sunday. Have coded these conditions using TEMPO and PROB30 groups in TAFs.

West to northwest winds should be light for the majority of the TAF period.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SUNDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Onset time of precipitation and associated restrictions may vary from the forecast.

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 19 20 21 22 23 00 01 02 03 04 05 06 EST 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY H H H H H H H H L L H H HTS CONSISTENCY H H H H H H H M L L H H BKW CONSISTENCY H H H H H H H H L L H H EKN CONSISTENCY H H H H H H H H H H L H PKB CONSISTENCY H H H H H H H H L L H H CKB CONSISTENCY H H H H H H H H H H M H

AFTER 18Z SUNDAY... IFR conditions possible in snow and low ceilings, particularly across the mountains Sunday and Monday.

RLX WATCHES/WARNINGS/ADVISORIES

WV...Winter Storm Warning from 1 AM Sunday to 1 AM EST Tuesday for WVZ008-013>020-024>034-039-040-515>526. OH...None. KY...None. VA...None.