Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 211358
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
958 AM EDT Fri Apr 21 2017

.SYNOPSIS...
Cold front sags south through this afternoon then lifts back
north late Friday night/Saturday. System exits Sunday
night/Monday. Dry early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Friday...

Front is moving through the forecast area this morning with most
precipitation occurring over northeastern zones. Band should
exit CWA shortly. Then short term models hint at weak shortwave
entering southern coalfields later this afternoon as it rides
along the boundary. This wave, along with some weak diurnal
heating should help trigger more shower development today over
southern zones. Made some minor adjustments based on latest
HiRes short term model data, but overall the idea remains the
same. Temp diurnal trend should remain generally flat today and
this covered well with inherited forecast.


As of 315 AM Friday...

Cold front at 07Z gradually entering central Ohio. Progged to enter
southeast Ohio by 09Z, Ohio River area around 12Z, and to the east
of the higher terrain by 18Z. Several waves moving through the area,
will create showers and thunderstorms at times, particularly across
southern/eastern zones, where greater moisture will exist. Some
partial clearing is expected today, mainly across parts of southeast
Ohio, with a mostly cloudy day expected elsewhere. The threat for
heavy downpours with any storms will continue today, with a high
moisture content atmosphere in place, and pw values around 1.2
inches across the south, generally less than an inch across the
north. There is the possibility of a storm across the far south
today being on the strong side with wind and hail the primary
threat, however, thinking chances are rather low/limited due to
overall lack of strong dynamics and expected cloud cover.

Overnight, showers and thunderstorms are expected to continue, but
there is lots of uncertainty in terms of the timing/location of this
as models vary on timing and track of individual waves. For now,
kept higher pops across southern zones, with proximity to frontal
boundary and higher moisture.

The biggest concern during the near term period, is the threat of
heavy rain across southern zones. WPC has southern WV and southwest
VA highlighted in a marginal threat for excessive rainfall. The nam
indicates an axis of heavier precipitation setting up across
southern zones later today and tonight, which the other models do
not indicate. For now, will allow the day shift to evaluate/monitor
the situation and issue any water headlines as necessary.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
As of 420 AM Friday...

This will be a wet period, as low pressure tracks south of the
area. It is progged to move from northern Arkansas Saturday
morning eastward, across Tennessee Saturday, and then more
slowly across the Carolinas Saturday night through Monday night,
as it occludes and becomes stacked through the mid and upper
levels by Monday morning.

Models show 4 to more than six inches rainfall over the central
Appalachians through Monday morning, which makes sense given an
upper level low tracking slowly south of there. The GFS was the
one showing in excessive of six inches, and the outlier there.
Otherwise, the models are converging on a solution of three to
three and a half inches for roughly the southern third of the
forecast area, and at least two inches for the southeast half.
The latter is dependent on the exact track of the system and the
sharpness / consistency of the northern edge of the heavier
rainfall, which comes in several waves.

Highlighted the HWO for potentially excessive rainfall through
this weekend, and have heavy rain in the grids where PoPs are
categorical, roughly the southeast half Saturday and Saturday
night.

There is a gradual shift southeastward in the rainfall Sunday
through Monday, as the system gradually pulls away from the
area. Question is how long low level moisture lingers in the
southeast half of the area on Monday, and whether low clouds /
fog become an issue in the light and variable flow in the wake
of the wet system Monday night.

Temperatures close to central guidance, except went a little
lower Sunday afternoon, which should not be much warmer than
Saturday. This wet weekend will also feature highs much lower
than recent days and, in fact, break a string of 13 consecutive
days with highs in the 70s and 80s at Charleston.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 420 AM Friday...

Weak high pressure crosses Tuesday. A cold front approaches
Wednesday, but then retreats northward, as a warm front
Wednesday night, as its driving upper level trough lifts out,
and upper level ridging builds. This opens the door to warmer
weather, even a summer preview, toward the end of the work week.
Central guidance temperatures accepted, climbing well above
normal by Friday.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
As of 622 AM Friday...

A cold front, with scattered showers and isolated thunderstorms,
will gradually sag south into the region through early
afternoon, with additional waves, creating more widespread
showers and thunderstorms after 15Z, mainly across southwest
Virginia and southern West Virginia, with brief MVFR conditions.

Behind the front, expecting widespread MVFR conditions to
develop, generally 12Z-17Z before some improvement to VFR most
locations, although areas of mvfr cigs may still linger,
particularly along and south of a line from kckb to kcrw.

Additional rounds of showers and thunderstorms, with widespread
mvfr and local ifr conditions developing after 09Z.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SATURDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: More widespread mvfr and ifr conditions may
occur than currently 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       12   13   14   15   16   17   18   19   20   21   22   23
EDT 1HRLY       08   09   10   11   12   13   14   15   16   17   18   19
CRW CONSISTENCY  M    H    H    H    M    M    M    M    H    H    H    M
HTS CONSISTENCY  H    H    H    H    M    M    H    H    H    H    H    M
BKW CONSISTENCY  H    M    M    M    M    M    M    M    M    M    M    L
EKN CONSISTENCY  H    M    M    M    L    H    M    H    H    H    H    M
PKB CONSISTENCY  H    L    M    M    M    H    H    H    H    H    H    M
CKB CONSISTENCY  H    H    H    H    M    M    H    H    H    H    H    M

AFTER 12Z SATURDAY...
IFR possible Saturday into Sunday with another wave of low pressure.

&&

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

&&

$$
SYNOPSIS...TRM/SL
NEAR TERM...KMC/SL
SHORT TERM...TRM
LONG TERM...TRM
AVIATION...SL



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