Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 110908
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
308 AM CST Thu Jan 11 2018

.SHORT TERM...(Today through Saturday night)
Issued at 308 AM CST Thu Jan 11 2018

The models have come into good agreement on the synoptic details
of the upcoming winter storm. A strong cold front will move
quickly east across the lower Ohio Valley this evening. A band of
moderate to heavy precipitation will extend back into the cold air
behind the front. Several hours of sleet or freezing rain are
likely late tonight into Friday morning. The wintry precip may
extend through Friday afternoon in the Pennyrile region of west
Kentucky and southwest Indiana.

Some of the models indicate a period of snow at the tail end,
however the majority of the wintry precipitation is expected to be
sleet or freezing rain. An inch or two of sleet and snow is
forecast in most areas, along with one-tenth to one-quarter inch
of ice. Based on gfs/nam qpf, parts of se Missouri outside the
existing watch would receive less wintry precipitation. However,
the new 00z ecmwf is more impressive with qpf across all of se
Missouri. Since there is uncertainty on amounts, the Winter Storm
Watch will be expanded west across the remainder of se Missouri
and allowed to continue across the remainder of the area. There
will definitely be impacts to travel late tonight through Friday
night, but the magnitude of the impacts will depend on amounts.

Wind will also be a factor. North winds behind the front will gust
to around 30 mph Friday. Ice amounts are generally forecast to be
under the threshold considered damaging to trees and power lines.
However, any locations that manage to accumulate close to one-
quarter inch of ice will be adversely impacted by the strong
winds.

Much colder air will settle into the region late Friday night
through Saturday night. Temps will generally be in the teens and
20s. Lows in the single digits are possible Saturday night. This
cold air will obviously impede cleanup.

The only impactful weather in the near term (today and this
evening) will be some locally heavy rain ahead of the front.
Isolated thunderstorms are possible along the front, where model
mucapes are close to 500 joules/kg.

.LONG TERM...(Sunday through Wednesday)
Issued at 308 AM CST Thu Jan 11 2018

Forecast confidence is moderate to high with the typical sensible
weather details still to be worked out.

The 00Z models are in good agreement in the large-scale flow pattern
through the extended portion of the forecast. A large upper-level
trough east of the Rockies will intensify Monday through Wednesday
and then shift east Thursday, allowing the flow aloft to become
nearly zonal. At the surface, winds will briefly become southerly
Sunday night, before an Arctic cold front moves through on Monday.
The Arctic surface high will settle over the Quad State region
Wednesday and then build eastward Thursday, allowing south winds to
develop.

A minor impulse in the northerly flow aloft will bring a small
chance of light snow to mainly southeast Missouri Sunday afternoon.
This impulse will weaken as it moves through the region and the snow
is forecast to taper off quickly as it moves east the Mississippi
River Sunday evening. This occurs as a major embedded short wave
trough rotates from the Upper Midwest into the southern Great Lakes
late Sunday night and Monday. This will provide a good chance of
measurable snow as the Arctic cold front moves through our region
Monday.

There are some timing issues and the QPF is not great, but an inch
of snow is not out of the question. Temperatures may climb just
above freezing Monday ahead of the front, but the 00Z GFS indicates
that there is no other warm layer in the sounding, so it will most
likely be a pure snow event. Our high temperature forecast is likely
a bit too high, but based on some mid 30s in the south, there is
some rain/snow mix mentioned there.

The reinforcing shot of Arctic air will take temperatures down
similar to what we experienced last week. Lows in the single digits
will be common Monday night and Tuesday night along with below zero
wind chills. It appears that we will stay just above Wind Chill
Advisory levels, but KMVN may flirt with 10 below early Tuesday. If
we have some fresh snow cover temperatures could end up below zero
in some locations, and a Wind Chill Advisory may become necessary.

Wednesday may see a warming trend, but if the 00Z ECMWF is right,
that may not amount to much. It has a 527dm 500mb low near
Louisville, KY at 12Z Wednesday, which is much farther south than
the GFS and the previous ECMWF run. Regardless, the upper trough
will be lifting northeast by Thursday which will allow the flow to
relax to nearly zonal here. With the south winds temperatures may
climb above freezing, but the GFS develops some light QPF with a
weak disturbance aloft and warm advection in the low-levels. A
rain/snow mix is forecast, but it may end up as another minor snow
event.

&&

.AVIATION...
Issued at 1120 PM CST Wed Jan 10 2018

Cigs will remain MVFR or IFR with some gusts out of the south from
time to time with VFR or MVFR vsbys. There will be pockets of
drizzle overnight. Rain showers will start to become more probably
as we head toward daybreak on Thursday with the bulk of the rain
arriving by late afternoon and early evening. We will see a wind
shift between 00z to 06Z with a cold front and gusts will really
increase with the FROPA. Cold air will start to filter in at KCGI
late in the period which could cause some sleet.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Winter Storm Watch from this evening through Friday evening for
     ILZ075>078-080>094.

MO...Winter Storm Watch from this evening through Friday evening for
     MOZ112-114.

     Winter Storm Watch from this evening through Friday morning for
     MOZ076-086-087-100-107>111.

IN...Winter Storm Watch from this evening through Friday evening for
     INZ081-082-085>088.

KY...Winter Storm Watch from this evening through Friday evening for
     KYZ001>022.

&&

$$

SHORT TERM...MY
LONG TERM...DRS
AVIATION...CW



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