Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 210503
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1203 AM CDT Sat Apr 21 2018

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 243 PM CDT Fri Apr 20 2018

After an unseasonably cold and frosty early morning, temperatures
have quickly warmed into the lower 60s across much of the region.
This rapid warming was due to plenty of solar insolation along
with a very dry atmosphere with very low relative humidity. Lows
tonight will be warmer than the previous night, albeit still a
little below normal. The cloud cover will increase on Saturday
well ahead of an upper level low and associated surface low over
the central Plains, but it appears that any precipitation will
remain west of the forecast area with the lower levels of the
atmosphere still relatively dry. Even though there will be more
cloud cover on Saturday, high temperatures should be similar to
Friday.

GKS

.LONG TERM...  (Saturday Night through Next Friday)
Issued at 243 PM CDT Fri Apr 20 2018

The upper level low and associated surface low will drop
southeastward through the southern Plains and pass well south of
the forecast area on Sunday, moving through AR with showers moving
into southeast MO Saturday night and into southwest IL on Sunday.
The northern fringes of the precipitation shield will move
through the Interstate 70 corridor, although the better QPF will
still be confined to southeast MO and southwest IL. There is still
some uncertainty as to how quickly the upper level low will
depart our region, but with the typical slow nature of these
weather systems showers will likely linger across southeast MO and
southwest IL Sunday night and Monday. There should be a break in
the threat for rain Monday night and Tuesday, but then a northern
stream upper level trough and associated cold front will drop
southeastward through the forecast area with showers Tuesday night
and Wednesday. The operational GFS model is a little stronger and
quicker with the progression of the upper level trough and cold
front compared to the slower and weaker solution of the ECMWF. The
models then bring a deepening upper level trough and another cold
front through our area with showers Thursday night into Friday.
This upper level troughing and successive cold fronts will keep
the temperatures from getting too warm with the tendency to
remain at or at least slightly below normal for late April.

GKS

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1153 PM CDT Fri Apr 20 2018

VFR and dry thru the TAF period. Winds, ely to esely, will pick up
again mid Sat morning with gusts remaining under 20 kts. A low
pressure system will approach the region and perhaps bring showers
to KCOU around the end of the TAF period, but better chances are
beyond the TAF period.


Tilly

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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