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Area forecast discussion 
National Weather Service St Louis MO
330 am CDT Monday Aug 31 2015

Short term: (through late this afternoon)
issued at 326 am CDT Monday Aug 31 2015

Threat of convection remains the primary question mark for todays
forecast. Model guidance over the last few days has not offered any
clear answers to this question...and unfortunately the signals in
this mornings guidance isn't much more definitive.

Overnight water vapor imagery indicates middle level shear axis parked
from the arklatex region into the lower Great Lakes...with the
animation of the imagery indicating a weak circulation center has
worked its way NE from western Arkansas to just east of Uno by 08z.
Meanwhile...subtle drying over S Illinois suggests some very weak
shortwave migrating SW through stl area on the north side of the shear
axis. Obviously this is a fairly chaotic upper air pattern, and since
features are fairly weak models are having a tough time resolving
sensible weather trends.

However...almost all guidance...including the hi-res explicit
output...suggests some threat of convection over southeast sections
of the County Warning Area today. While current radar data indicates no precipitation
in/near our area would not be surprised to see some sunrise surprise
over the next few hours ahead of upper low as it spins its way into
southern Illinois (which seems to be a trend hinted at by much of the hi-
res guidance)...with additional spotty storms attempting to flair up
during the heat of the afternoon in the vicinity of the shear axis.
For now have primary focus of afternoon development over S Illinois and southeast
MO in the vicinity of the aforementioned shear axis.

Slow moving storms could once again pose a threat of spotty heavy
downpours...similar to the storm that produced 2.57" @ kfam on
Sunday afternoon/evening.

Highs today should be similar to those of yesterday.


Long term: (tonight through sunday)
issued at 326 am CDT Monday Aug 31 2015

Even though shear axis will shift further southeast, could still see
some isolated activity this evening, but confidence is low so kept
mention out for now. Day crew will need to keep an eye out.
Otherwise, warmer weather is expected through the rest of the
forecast period with highs in the upper 80s to low 90s and overnight
lows in the upper 60s to low 70s.

As we get into the Holiday weekend, upper level ridge begins to
weaken allowing next weather system to move closer to forecast area.
Will see an increase in low level moisture and instability by Sunday
so kept slight chance probability of precipitation in for portions of the forecast area.


Aviation: (for the 06z tafs through 06z Monday night)
issued at 1107 PM CDT sun Aug 30 2015

Weak surface front/trough from central to northeast MO will drift
around and dissipate by Monday afternoon. Widely scattered
thunderstorms popped up late Sunday afternoon and have died after
sunset. Quite a bit of fog formed overnight Saturday night across
central to northeast MO/west central Illinois. Atmosphere is not much
different so see no reason why it will not form again. However,
temperature/dew point spread at uin is several degrees more tonight than
last night. Thus fog may be slower to form. Will back off a bit
from the previous forecast for cou and uin. Sus could be an issue
tonight as it has 6sm br at 73/72. The met MOS guidance has also
back off on the expected visibility. Otherwise the forecast will
stay VFR with light southerly winds Monday.

Specifics for kstl: widely scatters thunderstorms have pretty much
dissipated except for a storm near the Monroe/St. Clair County,
but it is dying. VFR forecast with light southerly winds.


Lsx watches/warnings/advisories:

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