Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280821
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
321 AM CDT Sun Jun 28 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 312 AM CDT Sun Jun 28 2015

Area of showers and thunderstorms over northern Iowa will continue
to move southeast this morning and may affect areas north of I-70
as it will be supported by continued low level moisture convergence
per latest runs of the RAP. Then still expect thunderstorms to
move southeast across the area today as shortwave trough currently
over Minnesota and the eastern Dakotas will dip down into the CWA
by 06Z this evening. This will cause strong ascent to move into
the area during the afternoon and evening hours. Thunderstorms
should develop ahead of cold front this afternoon over northeast
Missouri and west central Illinois and move southeast to near I-70
by this evening. These thunderstorms will move out of the eastern
and southern parts of the CWA between 06-12Z tonight when the
upper trough and the low level forcing shifts out of the CWA. This
scenario is backed up by the latest 00Z run of NMM-HRRR. A few
severe thunderstorms still look possible today as MLCAPES will be
in the 1000-2000 J/kg range this afternoon and this evening with
0-6km shear values near 40kts favoring organized multicells and
some supercells.

Temperatures will be warmer today ahead of the cold front with
mixing up to near 800mb.

.LONG TERM: (Monday through Saturday)
Issued at 312 AM CDT Sun Jun 28 2015

(Monday and Tuesday)

Still looks like there will be a few isolated thunderstorms
redevelop on Monday over parts of northeast Missouri into west
central and south central Illinois as the atmosphere becomes
unstable once again with another weak shortwave trough moving across
the area. Will continue with the chance PoPs on Tuesday and
Tuesday night as atmosphere will be even more unstable with
another, more notable trough moving through the area in
northwesterly flow aloft.

Highs will be well continue to be in the 80s has mixing will be in
the 800-850mb range.

(Wednesday through Saturday)

There will continued to be an amplified upper pattern over the CONUS
with a series of shortwaves digging southward into Missouri and
Illinois during the period which will keep a chance of showers and
thunderstorm going during this period. Wavy front will be over the
area which will help be a focus for storm development. Rain
chances and 850mb temperatures around 15C favor below normal
temperatures.

Britt

&&

.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1147 PM CDT Sat Jun 27 2015

Specifics for KCOU, KUIN: Light winds and clear skies will
continue to promote light radiational fog across the region
overnight. Winds will continue to back ahead of an approaching low
pressure system, eventually becoming southwesterly and gusting to
around 20kts after 16z. Scattered SH/TS could affect KUIN before
18z, but precipitation chances at all TAF sites are higher after
21z because of favorable diurnal heating.

Specifics for KSTL, KSUS, KCPS: Light winds and clear skies will
continue to promote light radiational fog across the region
overnight, especially at KSUS where moderate rainfall earlier this
evening greatly increased the low-level moisture compared to
nearby TAF sites. T-Td spreads were high enough at KSTL at TAF
issuance to preclude a fog mention attm. Winds will continue
backing overnight ahead of an approaching low pressure system.
Expect scattered SH/TS to affect St. Louis metro area TAF sites
later this afternoon and into the evening.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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