Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 160449
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1149 PM CDT Mon Sep 15 2014
Issued at 545 PM CDT Mon Sep 15 2014
Quick update to the forecast this evening to account for area of
drizzle that has developed in the wake of the front.
.SHORT TERM: (Through Late Tonight)
Issued at 258 PM CDT Mon Sep 15 2014
Focus tonight will be RA/DZ and FG development.
Sfc low and fnt are slowly moving thru the region this afternoon.
Mdls are in good agreement with this system pulling out of the
region this eve. Behind the fnt, low clouds and DZ linger with an
isod shower. Will keep slight chance PoPs for portions of the CWA
this evening, then mention DZ and FG overnight. Mdls suggest nrn
portions of the CWA will clear out this eve allowing temps to
quickly drop and FG to potentially form. Uncertainty remains how
low vsbys will drop as nly winds will help advect dry air into the
region. Have added patchy FG for areas along and N of a line from
KJEF to KPPQ. Elsewhere, will leave mention of DZ with low clouds
lingering thru the night and based on upstream obs. This line,
between FG and DZ, may need to be moved as the evening progresses.
.LONG TERM: (Tuesday through Next Monday)
Issued at 258 PM CDT Mon Sep 15 2014
(Tuesday through Thursday)
Some patchy fog and drizzle will persist through mid morning Tuesday
before mixing kicks in and skies begin to clear. Then expect
dry weather the rest of the day and on Tuesday night as we will lie
under neutral or subsident motion under northwesterly flow aloft.
Still expect scattered showers and thunderstorms Wednesday and
Wednesday night over central and southeast Missouri as the
GFS/NAM/ECMWF are all in good agreement that a weak shortwave will
move southeast across Missouri late in the day. This system will
have some corresponding low level moisture convergence to support
it. Have left Thursday dry as upper ridge will be building into the
area from the west.
High temperatures are mainly a blend of MOS guidance which are
supported by mixing down 900mb temperatures. Low temperatures
follow the agreeable MOS guidance.
(Friday through Monday)
Still expect temperatures to warm up to near normal on Friday and
Saturday as both the GFS and ECMWF are still progging 850mb
temperatures to reach the mid teens Celsius. Friday still looks dry
before ascent increases ahead of a trough that will move through the
area over the weekend. There is less agreement today than yesterday
with the details of the operational GFS and ECMWF regarding the
speed and depth of this upper trough. Either way, it still appears
that a there will be a chance of showers and thunderstorms over the
area Saturday into Sunday as the attendant cold front moves across
the area. By next Monday, the ECMWF is showing colder air working
into the area behind a deeper upper air trough than the GFS. Will
lean toward climatology for temperatures behind the front for early
.AVIATION: (For the 06z TAFs through 06z Tuesday Night)
Issued at 1123 PM CDT Mon Sep 15 2014
MVFR Ceilings will continue to clear slowly from the north. Where
the sky becomes clear tonight, expect fog develop. Unsure how
dense the fog will be, but low end MVFR/IFR is certainly possible.
Further south across central and east central Missouri as well as
southwest Illinois and southeast Missouri, expect MVFR cigs to
prevail for the rest of the night...and likely lowering to IFR
ceilings in places along and south of the I-70 corridor. Low end
MVFR and IFR cigs will prevail until sunrise when ceilings should
lift and scatter by mid-late morning.
Specifics for KSTL:
Expect MVFR ceilings to lower to IFR before sunrise Tuesday
morning. Latest thinking is that the ceilings won`t be as low as
previously forecast, but still AOB 900FT. The timing of the
lowering is still uncertain as well, but feel it should be down to
IFR by 09Z-10Z. Ceilings should lift and scatter by mid-late
morning Tuesday with VFR conditions to prevail after.