Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 161142
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
642 AM EST Tue Jan 16 2018

.SYNOPSIS...
A cold front passes through the region today, with an anafront
snow event developing. Arctic high pressure crosses Wednesday
and Thursday. Southwest flow of milder air this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 640 AM Tuesday...

Increased snow amounts in the mountains a but later today and
tonight, to better fine tune the upslope effects. Forecast
otherwise on track with strong advisory snow setting up across
the area first thing this morning.

As of 315 AM Friday...

Anafront precipitation event takes place today into tonight, in
the wake of a cold front crossing the area today. The front was
just entering the middle Ohio Valley early this morning. Areas
of light snow were near and behind the front, but a more
definitive band was zipping northeastward along the front, into
northeastern KY.

The front aloft was well behind the surface front, with the
positively tilted upper level short wave trough even farther
behind and parallel to it, reflecting the tilted baroclinic
zone. This is further reinforced by the upper level jetstream,
up to 130 kts, right over the area today through much of
tonight, easing slowly eastward with time.

The latest model trends were to slow the system onset, and,
even more so, its exodus, hence lengthening the duration of the
event, and snow totals. Snow ratios increase to around 20 to 1
today, in the deep layer moisture and very cold air mass.
However, snow amounts, while reflecting a strong advisory event
throughout the area now, still fall short of 12 and 24 hours
warning criteria for strategic time ranges.

Advisories are left in place as are, all in effect already
except Pocahontas county, which kicks in at 10 AM this morning.
The advisories begin expiring in interior southeast Ohio 9 AM
this morning, and lastly in the mountains at 11 AM Wednesday.

In the cold advection, temperatures fall this morning before
leveling out this afternoon, and then fall tonight. MOS and
near term guidance had a good handle on the baroclinic zone,
with lows tonight in the single digits to around ten above.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 315 AM Friday...

Light snow showers will be winding down at the beginning of the
period, with cold temperatures expected on Wednesday as upper trough
sags south into the region. Gusty winds will be common Wednesday
into Thursday, as high pressure gradually tries to nudge into
region. This combined with the cold temperatures will likely produce
wind chill advisory criteria Wednesday night into Thursday across
the higher terrain counties. Will continue to highlight in the HWO.
There could be a few light snow showers or flurries as times
Wednesday across the higher terrain in northwesterly flow, but no
additional accumulations are expected.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 315 AM Friday...

High pressure with moderating temperatures at the end of the work
week. Warm frontal boundary will lift north across the area over the
weekend, with light rain showers across the area. Cold front comes
through on Monday with rain changing over to light snow. At this
point, moisture is limited once enough cold air is in place for snow
changeover.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
As of 640 AM Tuesday...

In the wake of a cold front crossing the area this morning into
early this afternoon, a band of anafront, or behind the front,
snow will lead to IFR conditions.

IFR snow was already impacting most locations, and will reach
BKW 15-16Z.

The snow will later today in the middle Ohio valley, and tonight
in the mountains, with improvement to MVFR and then VFR
visibility 18-22Z this afternoon along the Ohio River, 21-00Z
late today CRW and CKB, and 00Z-05Z tonight in the mountains.

MVFR stratocu will linger a few hours longer, especially in and
near the mountains, with VFR conditions along the Ohio River
tonight.

Light southwest surface flow will continue to shift to northwest
across the remainder of the area this morning and early this
afternoon, as the front crosses. Flow aloft will remain
moderate southwest today, and then become light southwest
tonight, with the front aloft well behind the surface front, a
characteristic of anafronts. Flow aloft will finally become
light northwest overnight tonight.

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

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of MVFR to IFR in snow may vary
today into tonight.

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               TUE 01/16/18
UTC 1HRLY       10   11   12   13   14   15   16   17   18   19   20   21
EST 1HRLY       05   06   07   08   09   10   11   12   13   14   15   16
CRW CONSISTENCY  H    H    H    H    M    M    M    M    M    L    L    L
HTS CONSISTENCY  L    L    M    M    L    L    M    M    L    L    L    L
BKW CONSISTENCY  H    H    H    H    L    L    H    H    L    L    L    L
EKN CONSISTENCY  M    M    M    M    M    M    L    H    M    L    L    L
PKB CONSISTENCY  M    M    M    M    M    M    L    L    L    L    L    L
CKB CONSISTENCY  L    L    L    M    L    L    L    L    L    L    L    L

AFTER 12Z WEDNESDAY...
IFR in snow at times lingering into Wednesday in the mountains.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Winter Weather Advisory from 10 AM this morning to 6 AM EST
     Wednesday for WVZ523-524.
     Winter Weather Advisory until 6 PM EST this evening for
     WVZ005>011-013>020-027>032-039-040.
     Winter Weather Advisory until 6 AM EST Wednesday for
     WVZ520>522-525-526.
     Winter Weather Advisory until midnight EST tonight for
     WVZ024>026-033-034-515>519.
OH...Winter Weather Advisory until 6 PM EST this evening for OHZ076-
     085>087.
     Winter Weather Advisory until 9 AM EST this morning for OHZ066-
     067-075-083-084.
KY...Winter Weather Advisory until 6 PM EST this evening for
     KYZ101>103-105.
VA...Winter Weather Advisory until midnight EST tonight for VAZ003-
     004.

&&

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



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