Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 280233
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
1033 PM EDT Sat May 27 2017

.SYNOPSIS...
Rounds of convection are expected this holiday weekend, until a
cold front crosses Sunday, followed by another Monday morning.
Additional cold fronts and showers cross through mid week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 1030 PM Saturday...
Convection starting to wind down. MCS just misses us to the
south. Will have to see if BL dew points return for severe wx
potential Sunday - the MCS may ingest them causing our threat
for severe wx Sunday to be lower than currently progged.

As of 750 PM Saturday... A messy evolution to the convection
tonight which is difficult to quantify with a PoP. Some places
are just getting hammered with slow moving convection while
others are lucking out and remaining completely dry. A few
severe storms though the potential for those has greatly
decreased in the last half an hour as the area has been worked
over and cloud cover has all but stopped any additional heating.
The slow moving nature of the storms and torrential rainfall
rates warrant an elevated risk for flash flooding. So will
continue with both severe and flash flood watches for the time
being.

As of 430 PM Saturday...
Atmosphere continues to destabilize with plenty of stronger
storm beginning to develop. Issued a severe thunderstorm watch.

As of 230 PM Saturday...

Cap is finally breaking over the northern tier of counties where
the better clearing has taken place over the last couple of
hours. Still looking at a high CAPE and moderate bulk shear
environment, so expect the activity to continue on the upswing
heading into the late afternoon and evening. So far, the pace
has been more than manageable, but still have a few hours of
heating left and we have already hit the convective temperature.
Have both the hail and wind threat going forward. No changes to
the SPC slight risk for us in terms of severe.

Meanwhile, precipitable water values pushing 1.50in have
warranted the flash flood watch in place over much of the
southern portion of the CWA. Flash flood guidance values still
high, so thresholds for additional rain down in these areas is
low. Repetitive rounds of storms could easily become
troublesome.

Have tailored the POPs for a lull in the activity late this
evening and early tonight, before the front swings back
northward again as a warm front. Pre dawn convection expected to
move north through the area, and back into the slight risk area
for Sunday as the cold front passes again.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 340 PM Saturday...

During this period, models have the upper trough lifting out of
the Ohio/Tennessee valleys and becoming a closed upper low over
eastern Canada. This will finally push the frontal system out
of our area during Monday and allow high pressure with drier
air to move in later Monday and Monday night. Thus, look for
decreasing rain chances from west to east on Monday, with
temperatures returning to near normal with much lower
humidities.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 345 PM Saturday...

This period features a large upper level low over eastern
Canada with a long wave trough over the eastern United States.
This spells a cooler trend for the Ohio Valley, with
reinforcing cold front dropping across the area through mid
week. Some showers will accompany these fronts, but no heavy
rains are expected. Upper ridging and high pressure will return
for the later part of the work week with dry weather and near
normal temperatures.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 1030 PM Saturday...

Quite a substantial change to TAFs for 03Z update based on
progression of MCS. Shifted towards a mainly VFR night except
do have some concern about fog potential with low flow and
higher RH`s. Models differ on evolution of precipitation
tomorrow, but am playing it as a period of shra/tsra move
through the area during the day Sunday.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z MONDAY...

FORECAST CONFIDENCE: Medium to low.

ALTERNATE SCENARIOS: Many models are not handling convection
very well and thus many questions still exist making for a
difficult 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.

DATE                                                            SUN 05/28/17
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EDT 1HRLY       20   21   22   23   00   01   02   03   04   05   06   07
CRW CONSISTENCY  H    H    H    H    H    H    H    H    L    H    H    M
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    M    M    L
BKW CONSISTENCY  M    M    M    M    M    L    M    M    L    M    M    L
EKN CONSISTENCY  H    H    H    H    L    L    L    M    L    L    M    L
PKB CONSISTENCY  H    H    H    H    M    L    L    L    M    H    L    L
CKB CONSISTENCY  H    H    H    H    L    L    L    L    H    M    M    L

AFTER 00Z MONDAY...
None expected though clear nights and low flow may cause river
valley fog Thursday morning.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flash Flood Watch through Monday morning for WVZ005>008-
     013>016-024>027-033-034-515>520.
OH...None.
KY...Flash Flood Watch through Monday morning for KYZ102-103-105.
VA...Flash Flood Watch through Monday morning for VAZ003-004.

&&

$$
SYNOPSIS...JMV/JW/26
NEAR TERM...JW/26
SHORT TERM...JMV
LONG TERM...JMV
AVIATION...JW/26


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