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Area forecast discussion...updated aviation 
National Weather Service St Louis MO
642 am CDT Tuesday Sep 1 2015

Short term: (through late this afternoon)
issued at 330 am CDT Tuesday Sep 1 2015

Primary concern for today is thunderstorm chances throughout the
day. Short range guidance continues to want to break out isolated
to widely scattered convection this morning along a line from near
West Plains Missouri to Salem Illinois. This is in the vicinity of
a middle-upper level vorticity chain stretching up from East Texas
through Arkansas and southeast Missouri into Indiana. Rap shows
some weak low level warm advection and moisture convergence under
the vorticity chain through middle morning and latest infrared Sat-pics show what
looks like Alto-cumulus breaking out in the vicinity of the
aforementioned line. Indeed...surface observation show developing ceilings
between 8000-10,000 feet and an isolated cell has recently popped up
on radar in central Illinois. Should see this activity continue to
percolate through middle morning before waning. Think there will be
some redevelopment this afternoon in the vicinity of that vorticity chain
where the middle level capping and upper level subsidence will be
weakest. Coverage will likely be widely scattered at best. With
relatively stagnant pattern in place, expect highs to be similar to
yesterday's...perhaps a degree or two warmer.


Long term: (tonight through monday)
issued at 355 am CDT Tuesday Sep 1 2015

Expect any thunderstorms that develop this afternoon to quickly
dissipate early this evening as we lose daytime heating. While the
shear axis/vorticity chain in the middle and upper levels will still be
in the vicinity of the area tonight and Wednesday, it looks like it
will be weakening with time as well as dipping further south across
far southeast Missouri, northeast Arkansas, Tennessee, and Kentucky.
I can't totally rule out an isolated shower or thunderstorm
tonight into wednesay, but think precipitation chances are low enough in
our County warning forecast area to keep probability of precipitation below mentionable levels at this time.

The rest of the forecast at least through the weekend looks pretty
uneventful. Late Summer-like pattern with strong ridging through
the depth of the troposphere should keep the area hot and dry
through the weekend. Highs look to be in the low to middle 90s with
lows generally in the low to middle 70s. Dewpoint temperatures should
stay in the upper 60s to low 70s across the area though the period.
While this will feel warm and humid, current thinking is that heat
headlines will not be needed. A pattern shift with some cooler
temperatures may be in the forecast next week, but GFS and European model (ecmwf)
aren't exactly in good agreement on this. Regardless...the shift
(if it occurs) will likely be toward the middle of the week; so have
kept warm temperatures going through Monday.



Aviation: (for the 12z tafs through 12z Wednesday morning)
issued at 628 am CDT Tuesday Sep 1 2015

So far this morning...visibilitiy restrictions in fog has been
fairly limited. Have maintained a mention of brief MVFR visibilities
for the next hour or so at kcou, KUIN, and ksus where observed
visibilities and close T/dew point spreads still suggest some fog potential.
Otherwise...with little change in air mass aviation weather trends
for this valid period should mimic those of the past 24
hours...namely a few middle deck clouds this morning giving way to a
scattered cumulus field (with bases at or above 4kft) by midday...with these
clouds dissipating during the early evening. Much like yesterday
we will be monitoring convective trends for possible inclusion in
tafs in Nowcast updates...however believe threat of convection at
any one location will be even less than yesterday, as shear axis
is a bit further S and east. Given limited fog this morning...have
held off including any visibility restrictions tonight.

Specifics for kstl: VFR conditions expected. A few middle clouds
this morning...then scattered cumulus with bases at or above 4kft developing
during the heat of the day, with these diurnally driven clouds
then dissipating early this evening. No ts mentioned in the very minimal threat of convection for this
afternoon will be a bit further S and east than yesterday.



Preliminary point temperatures/pops:
Saint Louis 91 78 92 78 / 10 10 5 5
Quincy 90 70 91 70 / 5 5 5 5
Columbia 90 69 91 69 / 10 10 5 5
Jefferson City 91 69 92 70 / 10 10 5 5
Salem 89 71 90 70 / 20 10 10 5
Farmington 88 68 91 69 / 20 20 10 5


Lsx watches/warnings/advisories:


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