Area Forecast Discussion
Issued by NWS Charleston, WV

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201
FXUS61 KRLX 211502
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
1002 AM EST Sat Jan 21 2017

.SYNOPSIS...
Unseasonably warm through the weekend. Upper trough Sunday.
Stronger upper low Sunday night and Monday, exiting Tuesday.

&&

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

Prolonged the areas of dense fog across the Western Appalachian
Valleys for a few more hours this morning. Visible imagery
clearly shows fog entrenched in the mountain valleys this
morning and the edges have not dissipated much as of 1430Z, so
current thinking is that we will not see it lift in these areas
until about noon. Also went ahead and updated sky cover based on
latest METSAT and trends as mid and upper level clouds continue
to push northward with overrunning ahead of our next system.


As of 540 AM Saturday...

Although the last hourly updated hi res models of the HRRR and
RAP have suddenly shifted the precip shield of the upper
disturbance northward over our area later today, will not jump
on raising pops at this time. Issues are that the NAM is still
confined to the mountains, it is only one model run so far of
the HRRR and RAP, and the strong MCS along the Gulf coast with
the disturbance should help to suppress the rain shield
somewhat. Thus, little change to the current forecast.

As of 305 AM Saturday...

This period will be dominated by a warm and deep moist southwesterly
flow, well ahead of a strong upper low emerging into the Plains
states later today and tonight. One leading upper disturbance
will pass mostly south and east of the area this afternoon and
evening. Models place the northern edge of the precip shield
just touching our central and southern mountains this afternoon
and evening. Will place chance pops there for showers, while
cannot rule out a sprinkle elsewhere. In any case, any precip
will be light. A second stronger upper trough ahead of the upper
low will lift northeast toward our area later tonight, bringing
a better chance of showers into southern areas later tonight.
Even with considerable clouds today, temperatures will be quite
warm again with highs well into the 60s. Look for a very mild
night with lows dipping to just below 50 degrees.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
As of 235 AM Saturday...

Looking at a significant, long duration rain maker through the
short term with a deepening upper level low rotating
northeastward from the deep south. Two distinct waves of energy
will bring the rain. The first is an upper level trough oriented
west to east, moving northward, and the second is the parent
low. NAM showing strong low level frontogenesis Sunday night,
and good upper level support in the form of Q vector convergence
over the northeastern CWA. Right now, will handle the potential
for flooding in the HWO, but high QPF amounts over the short
term with good basin coverage could be problematic.

All of this will occur in the warm sector of the surface frontal
system associated with the upper low, so there is need to
determine the efficacy of the dynamic cooling in terms of snow
potential. Core of the upper low will need to be in close
proximity to the CWA for snow to occur, which will primarily be
in the highest elevations. Rain otherwise.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
As of 235 AM Saturday...

System exits, pulling a colder airmass into the area, but only
chances for snow will remain in the mountains. A brief recovery
to the temperatures back above normal comes Wednesday, with the
next cold front not far behind, and a wholesale airmass change
heading for the end of the week and the weekend.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
12Z Saturday thru 12Z Sunday...
As of 105 AM Saturday...

A deep moist southerly flow will prevail this period with
abundant clouds. An upper disturbance will pass mostly south
and east of the area this afternoon and evening, with another
upper disturbance approaching from the southwest by Sunday
morning.

Lack of thicker clouds across the north at 11Z, along with near
calm winds and wet ground, continues to bring IFR river valley
fog, affecting PKB, CKB ,EKN. Otherwise, ceilings are generally
of the high variety ABV 12,0000 feet. The fog will dissipate by
14Z as boundary layer winds bring to stir.

VFR ceilings around 4000 feet will be the rule by 16Z and
continue most of the afternoon with diurnal heating. However,
given all the boundary layer moisture, a temporary MVFR deck may
initially form before lifting to VFR by noon. Expect scattered
VFR showers mainly over the southern mountains this afternoon
and evening, and sprinkles elsewhere with the first upper
disturbance. After 02Z ceilings generally aoa 7000 feet with
warm advection ahead of the next system, and possible IFR fog at
EKN by 08Z. Otherwise, expect scattered showers to move into
the southern coal fields and southern mountains by 12Z Sunday
with lowering ceilings.

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

FORECAST CONFIDENCE: Low to medium.

ALTERNATE SCENARIOS: Fog dissipation early this morning and
reforming later Saturday night may vary. Showers this afternoon
may be farther north 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       15   16   17   18   19   20   21   22   23   00   01   02
EST 1HRLY       10   11   12   13   14   15   16   17   18   19   20   21
CRW CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    M
HTS CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    L
BKW CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    M
EKN CONSISTENCY  M    M    M    H    H    H    H    H    H    H    M    L
PKB CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    L
CKB CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    L

AFTER 12Z SUNDAY...
IFR will be possible again Sunday through Monday with another
system.

&&

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

&&

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



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