Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 191356
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
756 AM CST Sun Feb 19 2017

.UPDATE...
Issued at 751 AM CST Sun Feb 19 2017

The fog has become very thick over southeast Missouri, the Lakes
and Purchase areas of Kentucky, and south of the ridge in southern
Illinois. It will likely take more than an hour for conditions to
improve. Therefore, have extended the Advisory til 17Z for these
areas, as well as along and to the west of I-57 through southern
Illinois. Elsewhere, conditions have already improved, so the
Advisory has been cancelled.

UPDATE Issued at 558 AM CST Sun Feb 19 2017

The Dense Fog Advisory continues.

The AVIATION section has been updated for the 12Z TAF issuance.

&&

.SHORT TERM...(Today through Tuesday night)
Issued at 339 AM CST Sun Feb 19 2017

There is a nice tug of war going on between the southwest winds/low
ceilings and the dense fog. Southeast Missouri and west Kentucky
should see the worst fog and should take the longest to burn off.
Will let the Dense Fog Advisory stand as is with the primary
forecast package this morning, but could see an extension in time
for some locations later this morning.

An upper ridge will build over the region through early Monday, as
surface high pressure builds east of the area. This will set the
stage for a complicated upper trough that is forecast to move
through the region Monday night and Tuesday. This trough is
comprised of a closed low moving east through Texas and then to
the northern Gulf Coast, while a faster moving northern stream
trough pushes through the Great Lakes.

It looks like our area could get caught between these two
systems, with some potential for little if any precipitation.
However, the consensus brings a rather narrow band of showers
eastward through the region Monday night into Tuesday. Given the
uncertainty, will keep PoPs at chance or lower levels. Monday is
trending drier, but will keep a slight chance in western portions
of southeast Missouri in the afternoon. Likewise will keep a
slight chance in the far east Tuesday evening. Also removed most
of the thunderstorms from the forecast. The exception was a slight
chance over the Ozark Foothills Monday evening, but not very
confident in this either. The max storm total QPF is now well
under a quarter inch.

As for temperatures, trended downward for highs today in the east
due to concerns for lingering fog and low clouds. It will still be
well above normal, but some areas may not reach 70. 70-75 is
forecast for Monday, but clouds will be on the increase, so won`t
be surprised if we are a bit too warm, especially in the west. If
skies can clear the west by Tuesday afternoon, west and northwest
areas could climb well into the 70s again. Went a bit above
consensus in these areas.

.LONG TERM...(Wednesday through Saturday)
Issued at 339 AM CST Sun Feb 19 2017

By 12Z Wednesday, a cut off low will be in the Gulf of Mexico and
the main upper trough will be east of our area. Zonal flow will
commence early in the period and eventually become southwesterly as
our next system moves into the Rockies.

An upper level trough is forecast to move into the Rockies on
Thursday and eventually into the north central Plains Thursday
night. A strong surface low will develop in southern/southwest KS by
00Z Friday and move into southern IA/northern MO by 12Z Friday. Warm
air advection will be ongoing late Wednesday night into Thursday and
offer a chance for some showers and a warm front will likely develop
to our north which may briefly enter the area before it lifts
northward Thursday afternoon and evening. As the low level jet
strengthens over the area Thursday night, we could have some warm
sector type showers/storms. The cold front associated with this low
will cross through our region on Friday, bringing chances for
showers and even storms areawide through the day.

Model dew points are showing at least mid to upper 50s to possibly
low 60s ahead of the front on Friday, helping to generate some sfc
based CAPE, although values are low. However, wind fields are
starting to look impressive with a 100+ kt upper jet pushing into
the region on Thursday night into Friday and the 850mb jet
strengthening to 50+ kts. Sfc winds will increase Thursday night
into Friday as a result. Right now, models are not too impressive
with QPF as mid levels are forecast to be pretty dry. This may
change so we will need to watch this system closely.

Aside from possibly some lingering activity in the east during the
early/mid evening, all precipitation should be coming to an end
Friday night. High pressure quickly builds in late Friday night into
Saturday and dry but cooler weather returns for most of the weekend.
We are already watching yet another system possibly impacting us
Sunday night into Monday.

For temperatures, depending on cloud cover Wednesday and into
Thursday, we will likely see low 70s to possibly mid 70s in places
for highs. Cooler readings are likely on Friday with clouds/precip
in place. Much cooler air will infiltrate for the weekend, with
highs only in the upper 40s to lower 50s on Saturday, which is
actually near normal. We might gain a few degrees on Sunday,
remaining in the low-mid 50s. Low temperatures on Saturday night
will back back to around freezing for many locales.

&&

.AVIATION...
Issued at 558 AM CST Sun Feb 19 2017

Thick fog continues to blanket the region, including all TAF
sites. With only light winds expected, and high pressure aloft
building overhead, the fog is likely to be slow to improve, and
IFR or lower ceilings may not dissipate this afternoon. Emphasized
west Kentucky as the most likely to see the IFR or lower conditions
continue through the afternoon and worsen again tonight. Even
where clearing occurs this afternoon, there is a threat of low
clouds and/or fog redeveloping tonight. This forecast is on the
pessimistic side of guidance consensus, but could easily not be
bad enough.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Dense Fog Advisory until 11 AM CST this morning for ILZ075-080-
     081-084>086-088>094.

MO...Dense Fog Advisory until 11 AM CST this morning for MOZ076-086-
     087-100-107>112-114.

IN...None.
KY...Dense Fog Advisory until 11 AM CST this morning for KYZ001>013.

&&

$$

UPDATE...DRS
SHORT TERM...DRS
LONG TERM...CW
AVIATION...DRS


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