Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 140800
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
300 AM CDT Mon Jul 14 2014
.SHORT TERM: (Through Tonight)
Issued at 226 AM CDT Mon Jul 14 2014
Focus this period will be precip chances as well as the svr threat
associated with these storms.
Mdls are in relatively good agreement with a cdfnt pushing thru the
CWA today. The NAM is slightly slower than other guidance, but only
by a couple of hours. This fnt will reinforce a weaker baroclinic
zone that is shifting S of the CWA early this morning.
This zone is expected to continue to produce TSRA S of the CWA
during the day. The cdfnt is currently progd to reach the MO/IA
border around 12z this morning. By 18z, the fnt is progd to be
near a PPQ to MBY line before pushing S of the CWA by 03z. While
isod SHRA may accompany this fnt this morning, believe the greater
coverage will hold off until around Noon today. Mdls prog K index
values around 40 C along and ahead of the fnt. This, coupled with
the timing of the fnt, shud limit the svr threat in the CWA.
However, mdls prog around 1500 J/kg SBCAPE along and ahead of the
fnt, which may support isod near svr storms.
Focus tonight will be temps as the fnt continues to push S of the
area with high pressure building into the region. Clouds shud clear
out quickly with winds diminishing. With such cool dewpoints, have
trended twd the cooler guidance.
.LONG TERM: (Tuesday through Sunday)
Issued at 230 AM CDT Mon Jul 14 2014
(Tuesday through Wednesday)
Focus thru this period will be temps. Mdls are in rather good
agreement thru the period. A large sfc ridge is progd to build
into the region tonight behind the cdfnt mentioned above. Mdls
agree with 805 mb temps in the 8 C to 10 C degree range thru Wed
which shud keep highs in the low to mid 70s. The cool dewpoints
with this sfc ridge will allow lows to drop well into the 50s and
perhaps into the 40s in some spots.
(Thursday through Sunday)
Mdl solns quickly diverge at the beginning of this period. Mdl
mass fields do not differ much until the GFS develops an upper low
late Thurs into Fri. Believe this is a result of the convection
developed on Wed and Thurs across the Plains. Also believe at
least the nrn portions of this convection is due to convective
feedback. With the GFS soln as an outlier and the ECMWF/GEM in
rather good agreement, have trended away from the GFS soln.
Overall, not much change from the prev forecast with temps well
below avg until Sun.
.AVIATION: (For the 06z TAFs through 06z Monday Night)
Issued at 1131 PM CDT Sun Jul 13 2014
Existing precip should be east of the terminals by 6Z. This precip
is expected to aid in fog formation overnight. The light winds and
recent rainfall will combine with a moist air mass to allow fog to
form late tonight after the clouds begin to clear. If the clouds
clear out sooner than expected...then the fog could be more dense
than currently expected. Any fog that forms should dsspt quickly
after sunrise. Attention then turns to a secondary cold front that
will drop through the region on Monday. There are some very isld
cells along the front across IA as of 0430Z. Models indicate fairly
decent coverage along the bndry by aftn...though think this may be
overdone. Given uncertainty in coverage...have held onto the VC
groups during the late morning into the aftn. Other than early
morning fog...terminals have a VFR fcst for the remainder of the prd
with winds aob 12kts.
Specifics for KSTL:
Sctrd TSTMs from this evng should be east of the terminal by 6Z.
There may be some high end MVFR fog that forms prior to sunrise
due to recent rainfall...light winds and a moist air mass. A
secondary cold front pushes thru during the aftn bringing another
chance for TSTMs. Given uncertainties with coverage...opted to
hold onto the VCTS group. Other than the possible MVFR fog early
Monday morning...the remainder of the fcst should be VFR with
winds aob 12kts.
.PRELIMINARY POINT TEMPS/POPS:
Saint Louis 87 57 76 56 / 50 10 0 0
Quincy 79 51 72 50 / 40 5 0 0
Columbia 84 53 74 52 / 50 5 0 0
Jefferson City 85 55 75 54 / 50 10 0 0
Salem 86 55 74 53 / 50 20 0 0
Farmington 86 55 74 53 / 50 40 0 0