Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 232024
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
324 PM CDT Thu Apr 23 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 321 PM CDT Thu Apr 23 2015

A large surface high currently centered through eastern MO was
responsible for a dry conditions and pleasant temperatures across
the region today. This high will retreat eastward tonight. The
lightest winds and least clouds will be this evening and this will
also be the period of greatest temperature drop. Overnight
progression of the upstream upper trof and ridge and veering of the
Great Plains LLJ will result in the onset of low-mid level warm
advection as well as the east and northeast transport of moisture.
While the highest quality moisture will remain well to our west
through 12z Friday, the warm advection associated lift, increase in
mid level moisture, and advection of steeper mid level lapse rates
into the area will result in a chance of showers and thunderstorms
into portions of central and eastern MO late tonight into the
predawn hours. At least a few of the CAM are showing scattered
showers after 09z. The new forecast continues with pops in the 20-30
percent range but expands them slightly to the east.

Glass

.LONG TERM:  (Friday through Next Thursday)
Issued at 321 PM CDT Thu Apr 23 2015

Still seeing timing and placement issues between the 12z NAM and GFS
especially with warm front that will be over region. No matter what
feel that elevated convection will continue to increase in coverage
and spread east across forecast area on Friday on nose of low level
jet. With the cloud cover and precipitation, highs will only be in
the upper 50s to mid 60s.

Then Friday night, will see system begin to lift and slide east
across Missouri. Best chances of rain will be along and north of
I-70 with possible MCS developing and sliding east. Could see some
strong to severe storms with this wave, but will have better chances
during the day on Saturday as main cold front slides through. CAPE
in excess of 1000 J/kg expected with decent convergence along and
ahead of low, with best chances of severe weather over southeast
Missouri and southern Illinois. As for rainfall amounts, could see
up to an inch of rain mainly along and north of I-70 with higher
amounts possible Friday through Saturday night. Will see wide range
of temps on Saturday with highs in the upper 50s far north to the
mid 70s far south.

System to exit Saturday night with precipitation tapering off from
west to east. Then dry weather to persist through first part of next
week. Extended models are now a bit further south with next system,
so chances of rain a bit less, so just have slight chance pops
Tuesday through Wednesday, before dry and near normal temps return
next Thursday.

Byrd
&&

.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1228 PM CDT Thu Apr 23 2015

VFR flight conditions are expected today and tonight with surface high
pressure resulting in light winds, and a slow increase in mid
clouds later this afternoon into tonight. Some light showers could
impact KCOU before 12z but if these do occur they shouldn`t impose
any flight restrictions. A better threat of showers and some
thunderstorms will occur after 12z at KCOU as precipitation over
western MO moves eastward on Friday morning. This in now reflected
in the new TAF. Any impacts to the remainder of the terminals will
be near or after 18z Friday.

Specifics for KSTL:

VFR flight conditions are expected today and tonight with surface high
pressure resulting in light winds, and a slow increase in mid clouds
beginning this evening. Present indications are that any threat of
precipitation more than sprinkles will be after 18z Friday.

Glass
&&

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

$$
WFO LSX




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