Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 250828
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
428 AM EDT Mon May 25 2020

.SYNOPSIS...
Hazy, very warm, and humid for much of this week as summer-
like upper level ridge builds into the region. Cold front late
week. Canadian high pressure builds in next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 200 AM Monday...

Upper level heights build slightly today as dirty ridge axis
remains just east of the forecast area. Lingering low level
theta e axis located along the western fringes of the area will
serve as the primary focus for diurnally driven convection
today along with some orographically enhanced activity on light
southeast flow, though confidence there is low given a bit more
in the way of dry air and somewhat stable air on the eastern
slopes. Given the very light flow and lack of shear, pulse
convection will be the rule with slow moving downpours and weak
downbursts...possibly resulting in localized high water across
northeast KY and perhaps down the Tug Fork basin. Elsewhere, I
only have an isolated mention and dependent on any outflow
boundary from the convection across far western zones.

Temperatures will remain above normal making for a hot and
somewhat muggy Memorial Day.

Any convective activity will quickly wane with sunset, leaving
just some convective debris clouds to contend with. River valley
fog will once again be in the cards but dependent on extent of
high clouds.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 425 AM Munday...

Upper level ridging to start Tuesday morning, moves off the east
coast, giving way to way to deep layer southeast flow Tuesday,
and the southerly flow Wednesday. This brings increasing deep
layer moisture into the area. However, the veering of the flow
will play a role in the timing of timing of this increase.

While the richer moisture associated with a wave coming up
through the Carolinas, with PW values of two inches or higher,
will stay east of the area, values can get as high as 1.8 inches
either overnight Wednesday night, or sometime on Thursday, in a
broad area of increasingly moist air, well out ahead of a cold
front extending from the upper Great Lakes to the central
Plains states by Thursday morning.

Tuesday will be a very warm and relatively quiet day, with
showers and thunderstorms limited to the diurnal variety and to
western and southern portions of the forecast area, aligned with
increasing moisture and instability associated with the
increasing deep layer southeast flow there.

For Wednesday, increased moisture encroaches from all quadrants
except the north. However, while showers and thunderstorms will
still be mainly diurnally driven for western and southern
portions of the area, at least showers can persist over the
mountains overnight, depending upon the proximity of the wave to
the east.

Central guidance temperatures similar to previous values and
generally accepted, remaining above normal through the period,
especially early on.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 425 AM Monday...

A progressive northern stream amplifies late this week, with a
trough flattening and kicking out the ridge in the east, and a
new ridge building over the west-central U.S., behind the
deepening trough. The trough will amplify enough to drive a
cold front southeastward toward the area Thursday and Friday. A
broad area of increasing moisture ahead of the front, with PW
values generally in the 1.4 to 1.8 inch range much of the time.

Showers and thunderstorms are most likely across eastern
portions of the area on Thursday, with coverage depending upon
the proximity of a wave moving north, east of the Appalachians.
Thursday night, that wave moves on, while the cold front
approaches from the northwest. This shifts the likelihood of
thunderstorms to the middle Ohio valley by Friday morning, and
then throughout the area during the day Friday.

The amplifying northern stream trough drives the front through
the area Friday night into Saturday, with the decrease in
precipitation coverage from northwest to southeast somewhat
accelerated by the loss of diurnal heating Friday night.

High pressure of Canadian origin then brings cooler and drier
weather for the balance of the weekend, and into early next
week.

Central guidance reflects above normal temperatures to start,
dropping to or even a bit below normal next weekend.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
As of 220 AM Monday...

Convective debris clouds will continue to make for a challenging
fog forecast through the remainder of the overnight hours.
Current thinking is IFR or worse fog will be limited to
EKN/CKB/PKB with MVFR at HTS/CRW. Convection today will
primarily be confined to eastern KY and southern OH, with just a
period of VCTS at HTS in the TAFs at this juncture.

Generally weak SSWrly sfc winds through the period, except more
SErly at KBKW.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z TUESDAY...

FORECAST CONFIDENCE: Medium on extent of fog through 12Z, high
thereafter.

ALTERNATE SCENARIOS: Fog coverage may vary through 12Z,
depending on timing scattering of convective debris.

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.

DATE                              MON 05/25/20
UTC 1HRLY       06   07   08   09   10   11   12   13   14   15   16   17
EDT 1HRLY       02   03   04   05   06   07   08   09   10   11   12   13
CRW CONSISTENCY  H    H    H    L    L    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  L    M    M    M    M    M    M    M    H    H    H    H
PKB CONSISTENCY  H    H    M    M    M    M    H    H    H    H    H    H
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H

AFTER 06Z TUESDAY...
IFR at times in showers and thunderstorms Thursday through
Friday.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...TRM/30
NEAR TERM...30
SHORT TERM...MEK
LONG TERM...MEK
AVIATION...30


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