Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 182024
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
324 PM CDT Mon Sep 18 2017

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 322 PM CDT Mon Sep 18 2017

Showers and thunderstorms have developed in advance of the warm
front and short wave. This trend should continue into the early
evening and then dissipate. Some fog possible overnight but have
questions of whether it will be widespread enough. Front gradually
lifts north Tuesday morning bringing in a light south to southwest
wind and above normal temperatures. Current forecast high
temperatures for Tuesday are above guidance so have left them.
Tuesday looks to be dry as high pressure begins to build into the
area.

JPK


.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 322 PM CDT Mon Sep 18 2017

Anomalous ridging is expected to continue to strengthen over the mid-
Mississippi Valley and Great Lakes through the end of the work week.
This will help continue the trend of well-above normal temperatures
through the extended portion of the forecast period. Warmest
period appears to be on Wednesday and Thursday with low-level
thermal ridge overhead. Quite humid air also looks to be in place
(dewpoints near 70 degrees) during this time period so it will
feel even warmer than actual air temperatures. Current expectation
is for highs on Wednesday and Thursday to be in the low to mid
90s, with peak heat index values generally of 95-100 degrees each
afternoon. Some weakening of the upper-level anticyclone should
take place beginning this weekend as it drifts eastward. This will
allow slightly "cooler" air to move into the area, but still
expecting highs well into the 80s which is still about 5-10
degrees above normal.

Precipitation chances look to be generally below normal given the
mid/upper level flow pattern. Best chances of showers and
thunderstorms currently look to be on Wednesday night across
portions of northeast Missouri in proximity to a frontal boundary
and next Monday across portions of central Missouri as another
front approaches from the west.


Gosselin


&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1110 AM CDT Mon Sep 18 2017

Warm front across southern MO will gradually lift north today and
will be the focus for showers and thunderstorms. Best time looks
to be from early afternoon until about 00z. Short range convective
models all agree on bringing a round of rain through but differ a
bit on primary placement and coverage. Will view latest radar
trends for strongest wording on the forecast. Some fog possible
overnight, especially in areas that receive rainfall.

SPECIFICS FOR KSTL: Issue will be timing on showers and
thunderstorms for the terminal. Given current trends, am leaning
toward a tempo for 20z - 22z with a VCTS before and after. Expect
overnight and Tuesday to be dry as the front lifts north. A
little fog possible overnight depending on rainfall. Some of the
short range models develop fog but there is no solid consensus.

JPK

&&

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

$$

WFO LSX



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