Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 011835
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
135 PM CDT SUN MAY 1 2016
.SHORT TERM... (Through Late This Afternoon)
Issued at 302 AM CDT Sun May 1 2016
Patchy dense fog over northeast Missouri, west central Illinois to
dissipate and thin out towards daybreak. So main issue for today
will be the closed upper level low currently over south central
Nebraska that will finally open up and slide east across northern
Missouri. Will see scattered showers and a few thunderstorms
possible, especially along and north of I70 in Missouri and along
and east of Mississippi River in Illinois. Some of the storms will
be strong over southwestern Illinois where CAPES will be in excess
of 1500 J/kg this morning through the afternoon hours, as well as
decent low level lapse rates and some shear. Could see some small
hail and wind gusts to 45 mph with the stronger storms.
As for high temps today, with mostly cloudy skies will have a wide
variation from the upper 50s far north to the mid 70s far southeast.
.LONG TERM... (Tonight through Saturday)
Issued at 302 AM CDT Sun May 1 2016
Expect thunderstorms to be ongoing at the beginning of the forecast
period, but to be E of the CWA at 00z this evening.
Mdls are in fairly good agreement with upper trof hanging up over IA
on Mon with a s/w moving thru the area. While the bulk of the precip
shud remain S of the area, this s/w and cold temps aloft shud be
enuf to support SHRA across much of the area. Given the diurnal
nature of these SHRA, expect Mon night to be dry with isod to widely
sct SHRA again on Tues as the upper trof sinks thru the region. Some
uncertainty remains how much of the area will be see any precip, but
given the expected location of the upper trof Tues morning, have
kept PoPs confined to the srn two thirds of the CWA.
The next chance for precip is Wed as another cdfnt drops thru the
area. Mdls differ regarding how much moisture will be available as
the fnt moves thru. Will keep low PoPs going for ern portions of the
CWA where a s/w rotating around the back of the upper low may
provide enuf support for some SHRA. The remainder of the forecast is
dry as a large sfc ridge builds into the area.
Overall, temp forecast will remain aob seasonal avg. thru this week
with a sfc ridge in place as mentioned above. Wed shud be slightly
warmer with more insolation expected and wly to swly winds ahead of
the approaching cdfnt. The next warm up shud be Sat as an upper
ridge builds into the area with sfc winds becoming sly again.
.AVIATION... (For the 18z TAFs through 18z Monday Afternoon)
Issued at 106 PM CDT Sun May 1 2016
Specifics for KCOU: KCOU is far enough west that VFR conditions
should prevail for the first 0-6 hours of the valid TAF pd.
Thereafter, MVFR cigs are expected for most of the night. Ceilings
may fall to IFR late tonight, but confidence was too low to
include in the TAF attm.
Specifics for KUIN: IFR conditions are expected for at least the
next few hours. Minor improvement is possible during the late
afternoon, but cigs should fall back to IFR this evening.
Scattered rain showers are possible after 20z.
Specifics for KSTL, KSUS, KCPS: IFR and MVFR cigs extended farther
south late this morning than the models had previously predicted,
and IFR/MVFR cigs are expected to remain in place through the
afternoon based on upstream satellite imagery and METARs. Cigs
are expected to fall to IFR again tonight, likely after 06z based
on RAP and local WRF soundings in BUFKIT. Light fog is also
possible overnight. Rain showers are possible after 12z, but the
St. Louis metro area should be on the northern fringe of the rain