Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated aviation 
National Weather Service Saint Louis MO
1138 am CDT Wednesday Jul 27 2016

Short term... (through late this afternoon)
issued at 312 am CDT Wed Jul 27 2016

Despite some mid-high level cloudiness, fog has developed
overnight across portions of southeast MO and southwest Illinois due to
high surface dewpoints and calm winds. The fog was especially
dense in the familiar area. Scattered showers and thunderstorms are
expected to develop again later this morning and this afternoon,
mainly across southeast MO and southwest Illinois with the St. Louis
Metro area on the northern fringe of most of the convection. This
activity will be associated with an old, weak frontal boundary
that has become stationary. High temperatures today will be
similar to yesterdays highs, and close to seasonal normals.


Long term... (tonight through tuesday)
issued at 312 am CDT Wed Jul 27 2016

Relatively active pattern will continue for late July as
shortwaves carve out an upper level trough over the central US and
another weak, subtle cold front drops slowly southeastward through
our area Thursday and Thursday night. Will include chance pops
across most of the forecast area through the remainder of the work
week. The NAM model has a strong shortwave and associated surface
low moving eastward through MO and Illinois on Friday and Friday night.
It appears a little too strong with these features and prefer the
weaker solutions and lower quantitative precipitation forecast of the other models. The cloud
cover and precipitation should keep high temperatures to values
just below normal for Friday and Saturday. The chance of
convection should finally lessen, while the temperatures rise by the
start of the next work week as both the GFS and European model (ecmwf) models
depict a 595 decameter 500 mb high building over MO by Monday
night, along with mainly southerly or southwesterly surface winds.



Aviation... (for the 18z tafs through 18z Thursday afternoon)
issued at 1131 am CDT Wed Jul 27 2016

Weak northwest flow aloft with a stalled frontal boundary to the
south will create a typical mess of a Summer forecast. Scattered
showers and thundertorms could pop up almost anywhere. A weak vort
Max along with some moisture convergenct has caused a few small
storms to form over west central Illinois. Uin may just be a bit
north of this area but will consider a vcty. These features should
cause more scattered storms to form over east central MO into
southern Illinois this afternoon, but as usual timing and location
is like throwing darts. A vcty will cover and then amend as they
form. As the stalled front to the south slowly begins to lift
north, showers and storm may become more numerous for much of the

Specifics for kstl: with a weak wave moving across northern MO
into Illinois would expect scattered showers and storms to form this
afternoon. A vcty will cover until they form and they amend
accordingly. Storms should wane overnight with more forming
Thursday as the frontal boundary to the south begins lifting



Lsx watches/warnings/advisories...


Weather forecast office lsx

National Weather Service Glossary of Abbreviations