Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 281813
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
113 PM EST Tue Feb 28 2017

.SYNOPSIS...
An upper disturbance brings showers and possibly a thunderstorm
today. Strong cold front passes Wednesday. Reinforcing
trough/front Thursday night. High pressure for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 110 PM Tuesday.

Forecast is generally on track. Generally leaning toward an
SREF-like PoP for tonight and Wednesday given near term model
differences on evolution of convective clusters.

As of 1130 AM Tuesday...

Issued Flash Flood Watch for northern and central portions of
the area through Wednesday in coordination with northern and
western neighbors. Rainfall from repetitive rounds of
convection may start to become excessive by tonight. Portions of
the watch area have FFG values down near one inch per hour,
1.25 in 3 and 1.5 in 6. PW values are progged to approach 1.4
inches by Wednesday morning, which is every bit as high as it
gets in this area this time of year.

As of 940 AM Tuesday...

Adjusted PoPs higher/faster to better account for MCS moving
into the area. Thunder has reached western portions of the area
and cloud tops on this morning warm advection feature have not
yet begun to warm. Also lowered temperatures today in the rain
cooled area over the middle Ohio Valley.

As of 6 AM Tuesday...

Adjusted pops faster in the west this morning per latest radar
trends. Do not think thunder will make it this far east early
this morning, as deeper instability is lacking. Main batch of
showers and possibly thunder still to come across later in the
day.

As of 3 AM Tuesday...

Within a broad and vigorous southwest flow aloft, models key in
on an upper level disturbance moving over a warm and
increasingly moist atmosphere today. This brings a widespread
band of rain showers today, mainly from later this morning
through this afternoon. Deep instability is still lacking with
this feature, so have only a slight chance for thunder.
Nevertheless, rainfall amounts from a quarter of an inch up to
as much as three quarters of an inch in spots can be expected.
Temperatures will be much above normal in the low level
southerly flow, despite the clouds and showers.

For tonight, expect a break in the rain before another upper
disturbance comes our way later tonight. This will initiate
more showers, and a better chance of thunderstorms as the
atmosphere further destabilizes. However, the chance for any
severe thunderstorms will mainly come just after this period as
better parameters will then be in place. With a southerly flow
and clouds, temperatures will be on the mild side tonight.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 240 AM Tuesday...

Will mostly likely have a squall line in progress pushing
towards the Ohio Valley at the break point from the near term
forecast. Have multiple ingredients in place for a severe setup.
Very dynamic situation with strong shear profiles pushing 90kts
0-6km values with falling heights aloft from the approaching
trough. Strong surface front in place from a deepening center of
low pressure. Still have 10C dewpoints to work with at 850mb and
near 60F dewpoints at the surface which may increase slightly
with some pooling ahead of the front. SPC has the risk
increased to enhanced across the bulk of the CWA. Damaging wind
threat exists, and cannot discount hail given the colder air
aloft. Also have potential issues with excessive rainfall as
given the PWAT values well over an inch.

Behind the front, will turn sharply colder as the moisture
exits. Lingering precipitation will transition to rain/snow mix
and all snow in the higher elevations. Have a storm total snow
grid in place, but only minor accumulation well under an inch
are expected.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 240 AM Monday...

Reinforcing cold front/upper trough combo passes Thursday night,
but will only keep the cold air in place for so long. Some light
snow at night will accompany the system. Rebounds to above
normal values expected Saturday, increasing through the Monday
time frame with strong 850mb ridging returning with high
pressure settling in at the surface.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
As of 110 PM Tuesday...

The first in a series of rounds of showers and thunderstorms was
bringing deteriorating conditions, mainly to MVFR but
occasional IFR visibility. This round will move out this
evening, followed by patchy overnight MVFR stratocu and mist.
There should be enough wind to keep the boundary layer stirred
up, so fog and stratus should not become widespread.

The next round of showers and thunderstorms will arrive early
Wednesday morning. There is too much uncertainty to time the
clusters of showers and Thunderstorms on Wednesday other than it
is likely to be active much of the time. Thunderstorms
Wednesday, even early on, can bring very strong to even
damaging winds. Any heavy thunderstorm can easily bring IFR
conditions.

Light south to southeast surface flow will increase tonight,
and become rather gusty out of the southwest overnight into
Wednesday. Wind gusts on Wednesday could reach 40 kts beneath
strong southwest flow aloft.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: There may be more IFR in rain this
afternoon and again late overnight into Wednesday.

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       18   19   20   21   22   23   00   01   02   03   04   05
EST 1HRLY       13   14   15   16   17   18   19   20   21   22   23   00
CRW CONSISTENCY  M    M    M    L    L    H    H    M    M    M    M    L
HTS CONSISTENCY  M    M    H    M    H    M    H    H    M    L    M    L
BKW CONSISTENCY  H    H    M    H    M    M    L    M    H    M    H    L
EKN CONSISTENCY  H    H    M    M    M    M    M    M    H    H    M    L
PKB CONSISTENCY  H    H    L    M    H    H    M    M    H    H    M    L
CKB CONSISTENCY  L    M    M    M    M    H    M    H    H    M    M    L

AFTER 18Z WEDNESDAY...
No widespread IFR conditions are expected at this time.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flash Flood Watch through Wednesday evening for WVZ005>011-
     013>020-027>032-039-040-519>522-525-526.
OH...Flash Flood Watch through Wednesday evening for OHZ066-067-075-
     076-083>087.
KY...Flash Flood Watch through Wednesday evening for KYZ101>103-105.
VA...None.

&&

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


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