Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 191755

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
1255 PM CDT THU MAY 19 2016

Issued at 1255 PM CDT Thu May 19 2016

Forecast for today on target with max temps around 70 or in the
lower 70s with dry wx and light east winds. Clouds were the
hardest to nail down, with areas of diurnal CU clouds that are
more densely packed than others. This expected to fade late this

Taking a quick look at the next 24 hours...

Clouds from a system in southern KS are expected to increase
tonight with rain chance onset looking faster than with previous
forecast packages, with a favorable setup over western MO and
central MO being on the edge of this overnight and eastern MO and
parts of southern IL by dawn. Min temps will be higher than
persistence due to increased cloud cover, mostly in the lower

The system itself crosses thru on Friday, especially during the
afternoon hours, and with this also occurring during peak heating,
should be able to produce a new round of scattered SHRA over most
areas. Temps look similar to today with a slightly warmer airmass
being offset by more clouds and better rain chances.



.SHORT TERM...  (Through Late This Afternoon)
Issued at 255 AM CDT Thu May 19 2016

Surface ridge extends from the Great Lakes region southwest into
MO. Just scattered diurnal cumulus clouds expected late this
morning and afternoon along with some high level clouds. High
temperatures should be a few degrees warmer than yesterday and
just slightly below normal.


.LONG TERM...  (Tonight through Wednesday)
Issued at 255 AM CDT Thu May 19 2016

Upper level trough now over the southwestern US will approach our
area tonight with increasing cloudiness along with showers
spreading into portions of central and southeast MO late tonight.
There is still some uncertainty on the timing and coverage of the
precipitation tonight and Friday. The ECMWF model appears a little
bullish on its QPF tonight, while the GFS looks too skimpy both
tonight and Friday. The best QPF should be south and southeast of
our forecast area associated with a surface low moving
northeastward from the Gulf Coast states into the TN Valley
region. Will place the highest pops, albeit only chance across
southeast MO and southwest IL on Friday. With the upper level trough
moving east of the forecast area Friday night the precipitation
should shift east of the region. A shortwave will be dropping
southward through our area Saturday afternoon and night, but it
appears that moisture will be too limited for any precipitation
with continued surface ridging over our area. Warmer, more normal
temperatures typical of late May can be expected by Sunday with an
upper level ridge over our region, and as surface/low level winds
become southerly as the surface/850 mb ridge shifts east of our
area. There will be the potential for convection by Monday night
as the upper level ridge shifts east of the region, and continued
southerly flow leads to warmer temperatures and relatively high
humidities. Weak southwest flow shortwaves coupled with low-mid
level warm air advection should bring periods of convection from
Monday night through the remainder of the extended forecast



.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1255 PM CDT Thu May 19 2016

VFR conditions and light easterly surface winds are expected to
prevail at the TAF sites thru the valid period. Rain chances will
increase in COU late this evening and around dawn for STL metro
sites and UIN with approach of upper level system currently in KS
and should result in scattered showers for a period at those
sites. Activity is expected to decrease during Friday morning and
then pick up again after 17/18z as upper level system moves thru
our region to result in a new round of scattered showers Friday





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