Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
000
FXUS63 KLSX 142015
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
315 PM CDT Thu Sep 14 2017

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 312 PM CDT Thu Sep 14 2017

With upper ridge overhead and south winds at surface, will have
dry and warmer weather for the last part of the work week. Skies to
remain clear tonight through Friday. So, lows will be in the upper
50s to mid 60s tonight with highs on Friday between 85 and 90
degrees, about 10 degrees above normal for this time of year. As for
any possible fog late tonight, should not be a problem as there was
plenty of mixing during the day today to dry out the lower levels.

Byrd

.LONG TERM...  (Friday Night through Next Thursday)
Issued at 312 PM CDT Thu Sep 14 2017

The remainder of the seven day forecast period will be marked by
above average temperatures and periodic thunderstorm chances.

Heights aloft will be on the rise Friday night into Saturday as the
upper ridge builds through the mid MS Valley in response to a
migratory upper trof moving from the Great Basin/Northern Rockies
into the northern and central Plains region. This along with veering
south-southwesterly lower tropospheric flow will contribute to
tranquil but seasonably warm conditions. As the upper trof moves
across the upper MS Valley Saturday night it will result in weak
height falls aloft across northern parts of the CWA, and will be
the impetus for a cold front advancing into northern sections of
the CWA. Increasing low level moisture and instability will aid in
scattered shower and thunderstorm development/maintenance along
and ahead of the front Saturday night/Sunday morning. I guess if
there is any question, it is just how far south this front will
sag into the CWA through Sunday night. Given the lack of strong
post-frontal high pressure and southwest flow aloft, I tend to
lean towards a solution which largely keeps the front north of
I-70, and then retreats the front back northward and out of the
CWA by early Monday evening. I would think that the highest
precipitation chances then would reside along and north of the
front however the ECMWF is quite bullish with extensive QPF well
south.

From Tuesday into Thursday there is a good amount of variance in
model solutions that lead to lower than normal confidence. One thing
that can be said is that above average temps should persist through
the week. Low confidence revolves around two things - the ECMWF
seems to want to generate QPF every period, and also the GFS is more
progressive than the ECMWF with the large scale western trof and mid-
week lead short wave. At this point the forecast reflects the
anticipated seasonably warm temps, along with POPS in numerous
forecast periods.

Glass

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1242 PM CDT Thu Sep 14 2017

Upper ridge to remain over the region with VFR conditions and
light southeast to southwest winds through the forecast period.

SPECIFICS FOR KSTL:
Upper ridge to remain over the region with VFR conditions and
light southeast to south winds through the forecast period.

Byrd

&&

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

$$

WFO LSX



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.