Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 120509
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1109 PM CST Thu Jan 11 2018

.UPDATE...
Issued at 1109 PM CST Thu Jan 11 2018

Aviation update.

UPDATE Issued at 627 PM CST Thu Jan 11 2018

Cold front has entered our far NW counties from around
Pinckneyville IL to Greenville MO. It`s going to continue to haul
and move across the area through midnight. Staring to see glazing
up around St. Louis. Once temps go below 32F and continue to
plummet, glazing will occur quickly. Having said that, the latest
RAP, HRRR, with NAM incorporation as well, show about 2 hours of
freezing rain (glaze), perhaps 3 tops, then transitioning quickly
to sleet. Later it should turn more toward snow as it tapers down.
Rainfall rates in that 2-3 hour window, wind and other factors
will determine the amount of glaze and impacts. The amount of
glaze may be slightly less, with a little more sleet than
forecast. But in the end the negative impacts will essentially be
the same overnight. Travel will not be good, period. May make
some tweaks to the ice and sleet accumulation grids. But the
message is on track.

CN

&&

.SHORT TERM...(Tonight through Saturday)
Issued at 221 PM CST Thu Jan 11 2018

Nice new model and collaborative consensus incorporates a faster
incoming speed of the freezing airmass at the surface. This will
result in a mid evening transition in our west, overnight across
the bulk of the region, and late tonight even in our farthest
eastern and southeastern counties. The ice will then continue its
transition to snow/sleet through early Friday, with significant
ice and snow accumulations in the better/higher qpf air
along/east of the Mississippi river. WPC 20 percent outlook
increased to a 40 percent chance of quarter inch ice amounts or
better, east of the Mississippi river, where 1 to 2 inches of
snow/sleet on top of that, with the potential for higher amounts
further east, still existent. Therefore, the Watch there was
transitioned to a Warning, while the northwest most counties in
SEMO transitioned to an Advisory. We`ll see the event end from
northwest to southeast, from midday to mid evening on Friday.

.LONG TERM...(Saturday night through Thursday)
Issued at 221 PM CST Thu Jan 11 2018

Lower mid level heights and an arctic surface high in the vicinity
of the PAH forecast area will be conducive to more frigid temps over
the weekend. Some breaks in the clouds may come out Sat night in
between mid level impulses, resulting in lows ranging from the
single digits to the middle teens.

The models indicated increasing clouds Sunday from the west with
the approach of another mid level shortwave and its attendant sfc
low passing by just to the north. Despite brief warm advection Sun
afternoon and Sun night, the atmospheric column should be cold
enough for almost all snow, lingering into Monday as a cold front
sweeps rapidly through our region. A brief wintry mix may occur
near the AR/TN borders Mon afternoon. The brevity of this event
translates to an inch or less of total snowfall over most of the
region, with the possible exception of along the Wabash valley,
where another half inch may occur. Western parts of southeastern
MO may not receive any snowfall with this event. Model consensus
appeared quite good with this event, thus confidence of the
numbers was quite high. However, this will be Day 5, so the
forecast is still subject to change.

Increasing surface pressure and strong northerly winds aloft will
provide more frigid readings for the PAH forecast area into
midweek. As the parent low digs toward the eastern seaboard, some
wraparound cloudiness will be most prominent east of the MS
River. As the flow aloft relaxes Thursday, there should be a
modest rebound of temps/ dewpoints.

&&

.AVIATION...
Issued at 1109 PM CST Thu Jan 11 2018

Transition to freezing rain, sleet and snow through the night and
into Friday, with precipitation diminishing from west to east,
and ending through the afternoon and end of the day Friday, first
SEMO, then east of the MS River thereafter. Occasional MVFR, IFR
conditions expected along with strong and gusty NNW winds 15 to
30+ kts.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Winter Storm Warning until 9 PM CST Friday for ILZ075>078-
     080>094.

MO...Winter Storm Warning until 9 PM CST Friday for MOZ112-114.

     Winter Weather Advisory until noon CST Friday for MOZ076-086-087-
     100-107>111.

IN...Winter Storm Warning until 9 PM CST Friday for INZ081-082-
     085>088.

KY...Winter Storm Warning until 9 PM CST Friday for KYZ001>022.

&&

$$



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