textproduct: Charleston

WHAT HAS CHANGED

12Z Aviation Forecast Discussion update.

230 AM update... The dry, pleasant weather of this week gives way to unsettled weather associated with a system this weekend, followed by a more summerlike regime next week, with mainly diurnal driven convection amid dirty mid/upper-level ridging.

KEY MESSAGES

- 1) High pressure maintains dry weather through the balance of work week, and into the weekend, with a warming trend as ridging aloft crosses.

- 2) A system encroaches from the north Saturday afternoon and night, and drifts slowly southward through the area through Sunday, with the likelihood for showers and chance for thunderstorms.

- 3) The system leaves the area in a very warm to hot, and somewhat messy, weather pattern for the upcoming work week, with dirty ridging providing the chance for mainly afternoon and evening showers and thunderstorms amid the slowly building heat.

DISCUSSION

KEY MESSAGE 1...

High pressure remains overhead for the balance of the work week week, before yielding to light low level southwest flow heading into the weekend. This continues the dry, mostly sunny weather and warming trend for the next two days, as mid/upper-level ridging crosses. Lowland high temperatures will gradually climb over the next two days, reaching the upper 80s for highs for Friday and Saturday.

With the mainly clear sky and light and variable to calm low level flow associated with the high, river valley fog will remain possible each morning before sunrise.

KEY MESSAGE 2...

The mid/upper-level ridge yields to a mid/upper-level short wave trough, which drives a surface cold front toward the area Saturday and Saturday night, but then pushes it only sluggishly into the area Sunday and Sunday night, as mid-upper level high pressure builds quickly in the wake of the exiting short wave trough.

While the exact coverage and strength of showers and thunderstorms, expected rainfall amounts, and timing remain uncertain, increasing integrated moisture and modest increase in effective layer flow/shear could lead to strong, heavy thunderstorms late Saturday afternoon into Saturday evening north, and then spreading south for Sunday afternoon.

KEY MESSAGE 3...

There is uncertainty as to how far south the front pushes for the beginning of the next work week, but either way, mid/upper- level ridging will reduce coverage of showers and thunderstorms while relegating activity to the diurnal heating cycle, and the associated light deep layer flow will reduce the strength of storms outside localized downbursts.

With offshore troughing, and central to eastern U.S. ridging bisected by a weak trough axis near or just west of the middle Ohio Valley, the diurnal chance for showers and thunderstorms continues, but there may be a gradient in integrated moisture content, with precipitable water values lowering east but remaining high west. The predictability in terms of the heavier downpour and downburst threat being highest west is low at this forecast projection, but the forecast does carry the chance for diurnal thunderstorms mainly across western portions of the forecast area through midweek next week.

Central guidance reflects above normal temperatures during the next work week, perhaps a bit more so on lows versus highs amid the dirty ridging.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Outside of some late night/early morning river valley fog, mainly over southern West Virginia and southwest Virginia, expect VFR conditions with lights winds.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY... FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: Fog formation could affect EKN late 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 17 18 19 20 21 22 23 00 01 02 03 04 EDT 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 H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H

AFTER 18Z FRIDAY... IFR conditions locally in showers and thunderstorms at times late Saturday through Sunday.

RLX WATCHES/WARNINGS/ADVISORIES

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