Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 230815
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
315 AM CDT Thu Oct 23 2014
.SHORT TERM: (Through This Afternoon)
Issued at 313 AM CDT Thu Oct 23 2014
Broad N-S band of showers and isolated thunderstorms ahead of plains
shortwave currently stretch from western IA, through nw MO, into se
KS, and the primary forecast question for today is how far east this
rain will get. Strong ridging with very dry low level air remains
locked in place from the Great Lakes to the Ohio Valley by storm
system working its way up the east coast, and this will certainly
inhibit any substantial increase in lower tropospheric moisture.
Believe that the combination of shortwave energy, moisture
advection, and isentropic ascent will cause upstream showers to work
work into our far nw counties this morning, with this precip then
struggling eastward during the day and "withering on the vine" from
central MO into west central IL during the afternoon hours as
shortwave outruns the limited low level moisture return and
encounters much drier air. Still working on fine-tuning the
details, but at this time planning to limit any mention of precip to
areas northwest of a Cuba-St Louis-Hillsboro line, with highest PoPs
just east of Kirksville.
.LONG TERM: (Tonight through Wednesday)
Issued at 313 AM CDT Thu Oct 23 2014
(Tonight through Saturday)
With no precip anticipated, focus thru this period will be temps.
Mdls are in good agreement with upper trof moving E of the region
overnight and swly flow at the sfc returning ahead of the next
cdfnt. This cdfnt is progd to push thru Sat morning, which may
require adjustments to temps on Sat with future updates.
With clouds expected to clear late tonight, have trended twd the
cooler guidance for tonight. With the thermal ridge advecting into
the region for Fri, have trended twd the warmer guidance. Similar
trends for Fri night with swly flow continuing overnight. Sat has
some forecast challenge with fropa expected in the morning. With
full insolation expected, have trended twd the warmer guidance even
with a nwly flow.
(Sunday through Wednesday)
Focus turns to precip chances on Tues.
23/00z mdls are in generally good agreement thru Tues morning, tho
the GEM is faster with the upper trof ejecting into the Plains. Have
focused PoPs on Mon night and Tues when the ECMWF/GFS have come into
better agreement. However, the 00z solns are somewhat different from
the prev 12z solns. Therefore, have still kept PoPs on the lower
side for now until a persistent signal is given.
.AVIATION: (For the 06z TAFs through 06z Thursday Night)
Issued at 1103 PM CDT Wed Oct 22 2014
Surface ridge extending from MI southwest through southeast MO
will shift slowly southeastward this period. An upper level
disturbance and associated weakening cool front/surface trough
will move eastward through the region on Thursday. Most of the
precipitation associated with this feature will be n-nw of the taf
sites, although UIN may receive a brief shower late Thursday
morning or early afternoon. For now will include mainly mid-high
level cloudiness in the tafs for Thursday. The NAM MOS guidance
appears a little overdone on its low level cloud forecast. Could
not rule out a little fog in SUS and CPS late tonight with only a
little cirrus cloudiness and calm surface wind. E-sely surface
winds will veer around to a sly direction Thursday morning.
Specifics for KSTL: Mid-high level cloudiness will advect into the
STL area on Thursday. Any significant rain should remain n-nw of
STL. A light e-sely surface wind late tonight will gradually veer
around to a sly direction Thursday morning, and eventually to a
swly direction Thursday night.
.PRELIMINARY POINT TEMPS/POPS:
Saint Louis 65 52 74 58 / 10 5 0 0
Quincy 63 50 72 53 / 20 10 0 0
Columbia 67 51 75 56 / 20 5 0 0
Jefferson City 69 51 77 55 / 20 5 0 0
Salem 65 49 71 54 / 10 10 0 0
Farmington 64 46 73 54 / 10 5 0 0