Area Forecast Discussion
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FXUS63 KLSX 051822

122 PM CDT MON OCT 5 2015

Issued at 1251 PM CDT Mon Oct 5 2015

Adjusted sky grids to account for ongoing trends with the eroding
stratus from E-W. Bumped temps up a few degrees across sthrn IL
due to lack of cloud cover. Expect stratus to continue to dsspt
this aftn. Otherwise fcst looks in good shape.



.SHORT TERM:  (Through Late This Afternoon)
Issued at 317 AM CDT Mon Oct 5 2015

Look for decreasing low clouds this morning but a gradual increase
in mid/high clouds by afternoon. The lack of extensive stratus
should lead to warmer afternoon high temperatures across the region
today compared to yesterday. Winds will remain out of the north or
northeast due to the influence of a ridge axis to the north.


.LONG TERM:  (Tonight through Sunday)
Issued at 317 AM CDT Mon Oct 5 2015

Still appears tranquil weather will persist for the CWA heading
into midweek as weak ridging holds over the central CONUS. The
primary forecast question through Wednesday is temperature
specifics. AMS will be quite mild for early October with 850MB
temps roughly between +10 to +13C, but models are indicating
several waves of cloudiness...first from moisture streaming north
from Mexico, then with additional moisture advecting east from
the Plains.

Not certain as to the exact extent of this cloudiness, but models do
seem to agree that it will not be the insolation-killing low
cloudiness that made for a very chilly Sunday afternoon along and
west of the Mississippi River, but rather cloudiness of the mid
and high level variety. Given the extent of cloudiness suggested
by forecast soundings for Tuesday I`ve trimmed back temps a bit to
reflect roughly a 15-20 degree warmup from early morning
lows...which puts them in line with conditional climatology values
with a mid cloud deck for early October. Clouds should be less
extensive on Wednesday, and this should allow highs to push into
the 75-80 degree range.

After nearly a week of stalled weather features over the eastern two-
thirds of the CONUS, the GFS, ECMWF, and GEM all remain in fairly
good agreement that the upper air pattern will become much more
progressive during the latter half of the week.

A strong shortwave in the westerlies will dip southeast and push
through the mid and upper Mississippi Valley on Thursday and
Thursday night, bringing a threat of showers and thunderstorms to
the entire forecast area.  However, by Friday the GFS has the
shortwave trof east of the area, while the ECMWF and GEM slow the
movement of this feature over the mid-Mississippi Valley.  Based on
this, will maintain some PoPs over at least the southeast half of
the CWA on Friday.  Temperatures will remain very mild on Thursday,
with a noticeable cool down in the wake of the front on Friday.

Ridging is then expected to build back into the central U.S. over
the weekend as shortwave continues to dig into the eastern part of
the country.  Temps over our area should rebound in response,
with highs well in the 70s once again by Sunday.



.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1251 PM CDT Mon Oct 5 2015

The region is void of any real atmospheric features so the trapped
low level moisture is not going anywhere anytime soon. The IFR
stratus has been slow to dsspt this morning with most sites finally
bcmng MVFR early this aftn. The E to W trend of the roding stratus
should continue thru the aftn and am optimistic that most if not
all sites will be VFR by 21Z. The thinking is that the existing
stratus late this aftn will have an impact on redvlpmnt overnight
along the edges. So depending how far W the ern edge can erode
this aftn will help determine what areas see VFR/MVFR CIGs/VSBYs
again tonight.

Specifics for KSTL:

Stratus finally dssptd with the 18Z ob...though there may be a few
short prds of MVFR CIGs prior to 20Z as the last of the stratus
burns off. The proximity of the reminder of the stratus by late
this aftn will play a role in whether IFR/MVFR stratus redvlps
tonight or not and it is too early to know where the ern edge will
end up. In areas where the stratus does not redvlp...fog is a
potential but mid/high clouds may limit dvlpmnt of IFR/MVFR VSBYs.





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