Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 250518
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1218 AM CDT Wed Apr 25 2018

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 352 PM CDT Tue Apr 24 2018

A pair of storm systems currently are grabbing our attention.  The
first, centered over the central portion of the Bluegrass State, was
our weather-maker the past couple of days and is still maintaining
some influence over our way, with clouds slow to clear out this
afternoon.  The second storm system was over South Dakota and
western Nebraska slowly heading our way in an overall northwest flow
pattern.  This storm system was generating a solid swath of pcpn
over much of central-eastern Nebraska and into northern Kansas.
Temperatures range from the lower 60s where clouds and the first
storm system hold sway in southern IL, and into the low-mid 70s in
central MO where clouds have cleared.

Storm system #1 will continue to move away and should carry its
clouds with it out of our region, with the last set to exit this
evening in our eastern counties in southern IL.  Right on its heels
will be cloudiness from storm system #2 that will result in any
mostly clear skies being short lived tonight, with increasing
cloudiness overnight.  The position of storm system #2 to the KS/NE
border will be such that it should keep any system generated rain to
our west thru early Wednesday morning.  Min temps will be very
dependent on how much clearing can be seen, but stuck close to MOS
with its middle of the road reasonable values in the upper 40s and
lower 50s, which is close to climatological lows for this time of
year.  A longer period of clearing would mandate a dropping of these
temps, while more rapid cloud onset would keep temps in the 50s for
all areas.

The expected track of storm system #2 southeastward to near the
intersection of MO/AR/KS/OK by late Wednesday afternoon should keep
the best lift largely to our west and southwest during the day, thus
limiting PoPs to chance category or less for our forecast area
except for areas roughly SW from COU-FAM where PoPs were boosted to
likely category.  Realized rain should be a solid area and just a
matter of where the northeast gradient sets up with respect to our
region.  Either way, there should be plenty of clouds across our
region and with northerly winds continuing, this will limit temp
rises and have low-balled MOS at most sites, keeping forecast maxes
mainly in the mid 60s.

TES

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 352 PM CDT Tue Apr 24 2018

A trough with an attendant cold front will begin pushing through the
forecast area on Wednesday night into Thursday. The best accent and
moisture will be over southeast Missouri and southwestern Illinois
on Wednesday night into Thursday closer to the upper low pressure
system as it passes southwest of the forecast area. The highest pops
will be closest to the low pressure system with scattered pops
possible up to the interstate 70 corridor on Wednesday night into
Thursday. A significant pattern change still appears on tap to
beginning on Friday over the CONUS. A trough will begin to build
over the western third of the country with an area of high pressure
building over much of the central US on Saturday. High pressure over
the middle of the country is expected to slowly shift east by
Saturday night. Winds will turn to the south by Saturday night
allowing for the warmup to commence notably on Sunday into Monday.
The GFS and operational ECMWF ensembles are continuing to trending
higher with each run for Sunday through mid week, but will not get
too carried away raising temperatures. A series of shortwaves will
move over the forecast area ahead a storm system on Tuesday
afternoon with showers and thunderstorms possible.

Kelly

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1153 PM CDT Tue Apr 24 2018

Not much change from the prev TAFs. Upper low currently over the
Plains will move SE thru Wed. This system will spread VFR clouds
across the region. Also expect showers with this system, but the
bulk of the precip shud remain just west and then move south of
KCOU. Have kept mention of VCSH. Otherwise, expect cigs to remain
VFR with other sites remaining dry.

SPECIFICS FOR KSTL: VFR and dry thru the period. Some of the
latest guidance suggests showers developing Wed afternoon in the
area, but have kept out mention due to low confidence.

Tilly

&&

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

$$

WFO LSX



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