• Currently

    Reported at Cahokia / St. Louis, St. Louis Downtown-Parks Airport, IL
    9:53 AM CST SUN SEP 24 2017
  • 88°F31°C
  • Clear
    Clear
  • Feels Like:90°F32°CDew Point:66°F19°CHumidity:49% Winds:VRB 3 mph 5 kph
    Pressure:30.06 in1018 hPaVisibility:10.00 miles16090.00 meters
  • Area Forecast Discussion

531 AM CDT Sun Sep 24 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 335 AM CDT Sun Sep 24 2017

The persistent upper level ridge has shifted northeastward early
this morning and was now centered over the OH Valley region.  Our
forecast area continues to be on the western periphery of a large
surface ridge centered over the OH Valley region. Weather conditions
today and tonight will be close to persistence with only subtle
differences.  With the upper level ridge further northeast of the
forecast area, we will likely have a little more diurnal cumulus
clouds this afternoon with a better possibility of isolated
afternoon convection. The most likely area for afternoon
convection should be across southeast MO, eastern Ozarks where
there will be a little more favorable low-mid level moisture and
instability. For now will just include mainly slight chance pops
for showers and thunderstorms across central and southeast MO this
afternoon. Highs today will be well above seasonal normals and
similar to yesterday, maybe a degree or two cooler. Will be close
to record highs for STL and possibly also UIN as well.

GKS

.LONG TERM...  (Monday through Saturday)
Issued at 335 AM CDT Sun Sep 24 2017

The synoptic pattern at the start of the long term period will
continue to feature a very amplified regime, with a deep trough
across the western CONUS and a downstream ridge located over the
central/eastern United States. The trough will attempt to shift to
the east through the period, but the strength of the ridge will help
to deamplify it and deflect it more into the north-central CONUS.
The end result will be a fairly benign long term period.

The approach of the trough will help to push a surface cold front
into the region Tuesday and especially into Wednesday.  Just enough
moisture return ahead of this boundary may be enough to kick off a
shower/storm Monday into Tuesday mainly over central MO.  However,
think most areas remain dry with continued hot temperatures as highs
remain in the upper 80s/low 90s.

The front should pass through the area by Wednesday afternoon.
Several factors will be working against any precip along the front
which include limited convergence, a lack of upper-level forcing for
ascent (the front will be running into the upper-level ridge), and
fairly meager deep-layer moisture with southeastward extent.
Therefore, have kept the Wednesday forecast dry.

The passage of the front will usher in much cooler temperatures by
the end of the week. Highs Thursday through Saturday will only climb
into the 70s. Overnight lows will become rather chilly by Friday
night as a secondary front ushers in readings in the 40s/low 50s!

KD

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 459 AM CDT Sun Sep 24 2017

A persistent surface ridge extended from the OH Valley region
west into eastern MO. Scattered diurnal cumulus clouds can be
expected this afternoon with isolated showers possible. Will keep
the tafs dry for now with coverage expected to be very spotty, and
the best potential for convection likely south of the taf sites.
Southeast surface wind will continue through the period with
speeds only up to about 7-8 kts this afternoon. There will be some
light fog in SUS early this morning, and possibly also again
early Monday morning as well.

SPECIFICS FOR KSTL: A persistent surface ridge extended from the
OH Valley region west into eastern MO. Scattered diurnal cumulus
clouds can be expected this afternoon with isolated showers
possible. Will keep the STL taf dry for now with coverage
expected to be very spotty, and the best potential for convection
likely south of the STL area. Southeast surface wind will
continue through the period with speeds only up to about 7-8 kts
this afternoon.

GKS

&&

.CLIMATE...
Record Max Temperatures Through Tuesday

              KSTL  KCOU  KUIN
Sept 24     94 (1891)   95 (1891)   94 (1935)
Sept 25     92 (1900)   94 (1891)   93 (1920)
Sept 26     94 (1897)   96 (1897)   91 (1956)

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX