Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 281720
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1220 PM CDT Sun Jun 28 2015

.UPDATE:
Issued at 1220 PM CDT Sun Jun 28 2015

Some adjustments to PoPs throughout the morning and into the
afternoon, as expect WAA-induced band of showers and thunderstorms
to persist and slowly weaken as it moves east. Additional
development will also occur over the CWA as increasing unstable
air over western MO advects east and interacts with rain-cooled
dome of air, while large scale ascent increases with approaching...and
strong...upper level vort max. In this NW flow regime, expect that
the intense storm development should be fairly rapid.

Truett

&&

.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 12z TAFs through 12z Monday Morning)
Issued at 539 AM CDT Sun Jun 28 2015

Fog in CPS should dissipate by 13-14Z this morning.  Showers and
thunderstorms across IA, ahead of a surface low over southwest MN
and a trailing cold front extending through western Iowa and
eastern Nebraska, may drop southeastward into UIN later this
morning. Stronger storms are expected to develop and move through
UIN this afternoon and through COU and the St Louis metro area
late this afternoon and this evening as the surface low and
trailing cold front move east southeastward through our area. The
light surface wind will become swly later this morning and gusty
this afternoon. The surface wind will veer around to a wly
direction by late tonight after the passage of the low and
trailing cold front.

Specifics for KSTL: Thunderstorms will move through STL late this
afternoon and this evening, just ahead of a cold front dropping
southeastward through our area. Mainly scattered diurnal cumulus
clouds along with a mid-high level cloud ceiling can be expected
today until the storms move into STL. The light wind will become
swly and strengthen later this morning and afternoon. The swly
surface wind will veer around to a w-nwly direction late tonight
or Monday morning after fropa.

GKS

&&

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

$$

WFO LSX





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