Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 171821

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
121 PM CDT Mon Apr 17 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 333 AM CDT Mon Apr 17 2017

Sfc fnt will remain south of the CWA today and much of tonight. Sfc
winds will be ely today, becoming sely tonight with the fnt lifting
thru the region late tonight into Tues morning. With the sfc ridge
building into the region today and cloud cover remaining over the
srn portions of the CWA, have trended twd the cooler guidance across
the srn third to half of the CWA. Further north, have trended twd
the warmer guidance despite the ely flow, due to what shud be a
mostly clear day across that region.

Mdls hint at a slight increase in TSRA this morning across srn
portions of the CWA due to a brief increase in the LLJ over the area
and a back-building ULJ to help with deeper lift. Expect the precip
to be moving out of the CWA around Noon today and tonight shud
remain dry.

With winds becoming more sly tonight and with clouds moving back nwd
into the region, temps tonight will be tricky. With fewer clouds
across the area earlier this evening, may see temps drop somewhat
quickly. Then, with increased sly winds and the return of clouds,
temps may level out or even rise slightly. The end result is temps
trended twd the warmer guidance across the region.


.LONG TERM...  (Tuesday through Sunday)
Issued at 333 AM CDT Mon Apr 17 2017

Active week to continue to across the forecast area. On Tuesday,
weak surface ridge to slide off to the east allowing southerly winds
to return once again. In the meantime, next system tries to approach
region, but has a tough time doing so. Boundary to remain parked
just to the north of the forecast area with several rounds of
scattered showers and storms north of I-70 corridor through

Some uncertainty with the timing and strength of main system with
extended models. For now more intense upper level shortwave to slide
through Wednesday night and Thursday, finally pushing the frontal
boundary through forecast area by late in the day on Thursday. So
will see our best chances of showers and storms during this period.
Another issue is severe weather chances with this system Wednesday
afternoon and evening. Position of warm front is hard to pin down,
but decent mid level lapse rates, storm relative helicity and
instability with majority of models. So isolated strong to severe
storms possible over northeast MO, west central IL, so will mention
in HWO.

This will also be the warmest period, with highs in the mid to upper
70s on Tuesday and upper 70s to mid 80s on Wednesday.

Beyond Thursday, slightly cooler than normal temperatures expected
with boundary stalled out just south of the Missouri/Arkansas
border, with low chance pops for our far southern counties through
the end of the work week.

Then boundary begins to lift northward through forecast area as next
system moves in from the southwest. Will see precipitation chances
increase across rest of forecast area for the weekend.



.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1236 PM CDT Mon Apr 17 2017

Lingering showers and ceilings below 10,000 ft are moving slowly
southeast and out of the area. Expect VFR flight conditions with a
slowly clearing sky this afternoon and tonight for much of the
area. MVFR cigs are likely to develop late tonight over the
eastern Ozarks and into far southwest Illinois and could linger
into late morning on Tuesday.


VFR flight conditions are expected to prevail at Lambert through
Tuesday afternoon. MVFR ceilings are expected to develop over
southeast Missouri late tonight and persist into Tuesday
morning...but current indications are that they will stay well
south of the terminal.





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