Area Forecast Discussion
Issued by NWS St. Louis, MO

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411
FXUS63 KLSX 192325
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
625 PM CDT Thu Apr 19 2018

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 325 PM CDT Thu Apr 19 2018

A strong ridge of high pressure centered over southern MN and
northern IA will move eastward. The cloudiness across parts of
east central and southeast MO and southwest IL will dissipate by
early evening. The northerly surface winds will also become light
this evening. This along with relatively low surface dew points
for April will lead to good radiational cooling tonight.
Unseasonably cold low temperatures are forecast tonight, about 10
to 15 degrees below normal. Will continue the Freeze Warning for
late tonight and early Friday morning for a small part of
southwest IL where lows will be just below the freezing mark, and
the Frost Advisory for much of central and southeast MO and
southwest IL where the growing season has begun and conditions
will be very favorable for frost formation. Will see warmer
temperatures by Friday afternoon, only slightly below normal as
an upper level ridge builds over the central US, while the surface
wind becomes east-southeasterly on the backside of the retreating
surface ridge.

GKS

.LONG TERM...  (Friday Night through Next Thursday)
Issued at 325 PM CDT Thu Apr 19 2018

An upper level low and associated surface low will pass well
south of our forecast area later this weekend, moving eastward
through AR. The models have recently trended further north with
this low pressure system. It still appears that southeast MO and
southwest IL will get the brunt of the showers, on the northern
periphery of the precipitation shield, but there will likely be
some light rain extending as far north as the I-70 corridor
beginning late Saturday night. Due to the slow moving nature of
the upper level low at least light patchy rain or a few lingering
showers will persist into Monday across southeast MO and southwest
IL. There will 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 region
and bring showers to most of the forecast area Tuesday night and
Wednesday.

GKS

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 616 PM CDT Thu Apr 19 2018

Sfc ridge currently centered over srn MN will move east tonight.
As it does, winds will diminish with sunset and veer overnight to
become ely to esely and increase, but expected to remain to below
10 kts. VFR conditions expected thru the TAF period with only few
to sct CI expected across the region.


Tilly

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Frost Advisory from 1 AM to 9 AM CDT Friday for Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
     Montgomery MO-Osage MO-Reynolds MO-Saint Charles MO-Saint
     Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
     Genevieve MO-Warren MO-Washington MO.

IL...Frost Advisory from 1 AM to 9 AM CDT Friday for Bond IL-Calhoun
     IL-Clinton IL-Jersey IL-Madison IL-Monroe IL-Randolph IL-
     Saint Clair IL-Washington IL.

     Freeze Warning from 1 AM to 9 AM CDT Friday for Fayette IL-
     Marion IL.

&&

$$

WFO LSX



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