Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 170809
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
309 AM EST Thu Jan 17 2019

.SYNOPSIS...
Weak system approaches from the west to produce wintry
precipitation through Friday. Another weak system passes
Thursday with a stronger storm impacting this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 304 AM Thursday...

An area of low pressure approaches from the west, to bring
light snow over portions of southeast OH early this morning.
Good agreement among synoptic and high resolution models on the
timing of pcpn spreading west to affect the entire forecast
area. However, model consensus also suggests increasing
southerly H850 flow by 15Z Friday, which will bring warm
advection. This relatively warmer air will produce a mix of
rain and snow through noon, transitioning to all light rain for
the most part, except continuing snowing over elevations at or
above 2,500 feet through Friday morning.

While little or no accumulations can be expected across the
lowlands, 4 to 6 inches will be possible over the elevated
terrain of Pocahontas and Randolph counties, and 2 to 4 inches
over eastern Webster, eastern Nicholas, and eastern Fayette
counties. Therefore, decided to issue a Winter Weather advisory
for snow until Friday morning.

Confidence runs high per similar model solutions. Went with the
CONShort for temperatures through the period.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
As of 240 AM Thursday...

Active weather in the short term period, with a major storm
system to affect the area over the weekend. Friday will see -sn
tapering off across the region, ending as light drizzle, or even
patchy light freezing drizzle across the lowlands, with
lingering upslope snow showers across the mountains, with little
additional accumulations.

Focus then shifts to the strong storm system that will affect
the area during the Saturday through Sunday time frame. Based on
coordination with WPC, which relied mostly on the euro, looking
at a period of a wintry mix to start Saturday morning, changing
over to rain across most of the CWA by afternoon. Parts of
southeast Ohio, mainly Perry county is right on the border of a
wintry mix versus rain, and at this point, have the northern
part of the county not completely changing over to rain.
Speaking of rain, rain will be heavy at times, particularly
across NE KY, parts of southeast Ohio, and adjacent WV counties,
where thunderstorms will also be possible due to increasing
instability from cooling aloft. WPC has updated the excessive
rainfall forecast for a marginal risk across most of the CWA,
with a slight risk across much of eastern KY, parts of southeast
OH, and WV. Overall, coding up QPF amounts of 1.75 to 2 inches
of across most of the CWA, with slightly lesser amounts across
southern WV and southwest VA. With the moist conditions, cannot
rule out flooding issues anywhere at this point and will
continue to highlight the threat area wide in the hwo.

As previously stated, a wintry mix is expected at the onset of
precipitation on Saturday, and slick spots will be possible.
Precipitation will gradually change over to snow late Saturday
night into Sunday, with rather significant accumulations
possible across parts of southeast Ohio. Right now, I am coding
up warning criteria across parts of northern SE Ohio counties,
with lessor amounts near the Ohio River and south/east. Based on
coordination with surrounding offices, and the still somewhat
uncertainty in accumulations/change over timing/duration of a
change over etc, the decision was made to hold off on a winter
storm watch for now and have the day shift reevaluate.

In addition to the snow, very cold air will gradually infiltrate
the area on Sunday, along with gusty winds. This will create
reduced visibility in snow and lead to single digit to below
zero wind chills by Sunday evening across much of the CWA.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 250 AM Thursday...

Much colder air will infiltrate the region Sunday night into
Monday, with -22C air at 850mb taking hold by Monday morning.
This combined with occasional gusty winds will result in wind
chills below zero across most of the CWA, with the need for wind
chill advisories looking possible across the higher terrain
counties and parts of southeast Ohio by Monday morning.

Another system will affect the area by Tuesday night, with rain,
tapering to snow as it exits the area by mid week.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
As of 1250 AM Thursday...

Satellite imagery clearly show trapped low level stratus under
strong inversion keeping widespread MVFR ceilings. Radar images
and ground observations indicate some areas of drizzle or
freezing drizzle across the Tri state area including HTS,
extending northeast just north of CRW. Expect IFR/LIFR ceilings
and visibilities under areas of freezing drizzle mixed with
light snow. Using GLAMP and SREF probabilities suggest these
conditions will prevail through 09Z, with some minor
improvements across the northern portions of southeast OH, and
northern WV. VFR conditions across northern southeast OH and WV
could become MVFR by 12Z.

Meanwhile, an area of low pressure is expected to reach the
Ohio Valley by Thursday afternoon. As the system nears our
region on Thursday, precipitation will increase in coverage
from west to east. Snow is expected to occur as precipitation
initially arrives, but as surface temperatures warm through the
afternoon, a transition to rain is expected across parts of the
lowlands. However, expecting precipitation to remain as snow in
the mountains. Thus, flight conditions will deteriorate through
the end of the period with MVFR/IFR Cigs and Vsbys expected.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY...


FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: Brief ceiling category changes possible in
low stratus 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                         THU 01/17/19
UTC 1HRLY       08   09   10   11   12   13   14   15   16   17   18   19
EST 1HRLY       03   04   05   06   07   08   09   10   11   12   13   14
CRW CONSISTENCY  L    L    M    M    M    H    H    H    H    H    H    H
HTS CONSISTENCY  L    M    M    L    L    H    M    H    H    H    M    M
BKW CONSISTENCY  H    H    H    H    M    H    H    H    H    M    M    M
EKN CONSISTENCY  L    L    L    L    M    M    H    H    H    H    H    M
PKB CONSISTENCY  M    H    M    M    M    M    H    H    H    H    H    H
CKB CONSISTENCY  L    L    M    M    M    M    H    H    H    H    H    M

AFTER 06Z FRIDAY...
IFR/LIFR possible under rain/snow Thursday afternoon through
Thursday night. Widespread IFR may be possible this weekend with
heavy rainfall across the region.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Winter Weather Advisory from 1 PM this afternoon to 10 AM EST
     Friday for WVZ522>526.
OH...None.
KY...None.
VA...None.

&&

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


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