Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 271747
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1247 PM CDT Sat Jun 27 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 310 AM CDT Sat Jun 27 2015

Have added slight chance for thunderstorms this afternoon based on
that there was upstream convection today, and forecast soundings
show that atmosphere will become unstable again today.  Both the NAM
and GFS show a upper shortwave trough moving across the area during
the midday hours with the GFS developing some QPF over the area
during the afternoon.  Even the HRRR supports this idea with it
breaking out isolated convection during the afternoon over most of
the CWA.  This convection will die out quickly this evening with the
loss of daytime heating.  Temperatures today will remain below
normal even with mixing up to 850mb.

.LONG TERM: (Sunday through Friday)
Issued at 310 AM CDT Sat Jun 27 2015

(Sunday and Monday)

A second, stronger trough will drop down in northwest upper flow on
Sunday night.  There will be additional thunderstorms develop ahead
of it on Sunday as the atmosphere becomes unstable with MLCAPES in
the 1000-2000 J/kg range. A few isolated severe thunderstorms should
be possible over the area Sunday into Sunday evening and deep layer
shear of around 40kts. The trough will move off to the southeast
by Monday, though the atmosphere will still be unstable behind the
front today. Will keep a slight chance of showers and thunderstorms
over part of the forecast area on Monday.

Temperatures these two days look slightly warmer as mixing will be
up into the 800-850mb range.

(Tuesday through Friday)

Upper pattern will remain amplified during this period with large
upper high in the western CONUS and mean trough in the east.   This
will keep a meandering frontal boundary close to our area during
mid-late week.  Temperatures will remain below normal.

Britt

&&

.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1213 PM CDT Sat Jun 27 2015

Nly flow will continue for terminals this afternoon. CU field is
expected to continue to develop with much of the area becoming BKN
this afternoon. Isod to widely sct SHRA are expected to develop
this afternoon, but have not put in TAF attm due to low chance of
impacting a terminal. Otherwise, cu will dissipate this evening
leaving much of tonight clear. FG development is possible with
light and vrb winds. Winds will become swly Sun morning ahead of
an approaching system. Precip may reach UIN shortly before 18z
Sun, but have kept out of TAF attm due to low confidence in
timing.

Specifics for KSTL: Nly winds will persist this afternoon with cu
field expected to become BKN for much of this afternoon. Isod to
widely sct SHRA are expected to develop this afternoon. CU
expected to dissipate early this eve leaving overnight clear.
Winds will become swly Sun morning ahead of an approaching system.
Precip may reach terminal before 00z Mon, but have kept out of TAF
for now.

Tilly

&&

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

$$

WFO LSX





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