Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 231221
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
621 AM CST Fri Jan 23 2015
.SHORT TERM: (Through Late This Afternoon)
Issued at 240 AM CST Fri Jan 23 2015
A low pressure system moving through the southern CONUS will have
very little effect on today`s weather except for an increase in high
level clouds across the southern CWA. Highs in the 40s will be above
average for mid to late January.
.LONG TERM: (Tonight through Thursday)
Issued at 240 AM CST Fri Jan 23 2015
A storm system centered over western TX, yet having influence well
to its east across much of the deep South, is expected to move to
the east over the next 24 hours and not have much of an impact for
our region. As a result, quiet wx is forecast for tonight.
Intermittent periods of clouds and not a particularly strong cold
front later will yield min temps above normal for this time of year,
with mid-upper 20s.
In this storm system`s wake beginning later tonight, we will see a
resumption of the familiar winter pattern of NW flow and this is
expected to last thru Tuesday of next week. There is really only
one system of any note during this period, and that is a strong
clipper system that has been discussed at length for several days
now. This clipper system is still on track to impact our region
primarily on Sunday. Model diffs continue to exist on the track and
structure, with the NAM the biggest outlier, and least reliable on
Day 3. The EC and GFS solutions are greatly preferred here. They
feature an initial strong disturbance that cuts into northwest MO
thru dawn Sunday, with the energy then splitting in two: the
northern portion tracking almost due east to Cincinnati, OH by early
Sunday evening, and the southern portion continuing to dig
southeastward to Memphis, TN. The initial phase thru dawn on Sunday
has a unified broadscale lift to it across the entire region at some
point, but with all of the moisture of any note on the very backside
of the region of lift. What should be anticipated from this is a
brief shot of pcpn for most locations but will struggle to measure.
Have broad-brushed low PoPs for virtually the entire forecast area.
Pcpn-types are expected to be liquid for this with boundary layer
temps too warm, not being helped out at all from SW winds at the
time. By Sunday daytime, the split in the system will result in the
high PoP/accumulating snow region to extend well to our
northeast--from Chicago, IL to northern OH--with once again a
broad-brushed region of low PoPs extending well to the south where
an invigorated broadscale lift region during mainly the morning and
midday hours will largely be cancelled out by moisture loss.
Boundary layer temps will once again preclude snow in the low PoP
region over us, with only spotty light rain expected. The system
should be gone and well east by nightfall Sunday. Prefer GFS QPF
with a hundredth or two only with EC too high on its values.
A weak front late Monday may result in a threat for light pcpn, but
prefer to wait for another model iteration before adding any
mention, otherwise dry until the middle of next week.
Temps will be primarily a tug of war between above normal and a
return to seasonable values with what few cold air intrusions there
An even milder period looks on tap for Wednesday and Thursday next
week with an upper level ridge building overhead and S-SW flow at
.AVIATION: (For the 12z TAFs through 12z Saturday Morning)
Issued at 537 AM CST Fri Jan 23 2015
Specifics for KUIN: MVFR stratus in place should eventually advect
eastward today, leaving VFR conditions for most of the afternoon
and evening. Some lower clouds may accompany a cold front when it
moves through after 24/06z.
Specifics for KCOU: MVFR stratus has locally cleared out near KCOU
however a lingering batch was located upstream. It may produce
MVFR conditions at KCOU at times until it starts to dissipate.
Thereafter, expect a prolonged period of VFR conditions until a
cold front arrives late tonight after 24/09z. Some lower clouds
may accompany the front.
Specifics for KSTL, KCPS, KSUS: Back edge of MVFR stratus has
been making slow progress eastward, but new westward development
over south central MO does raise some doubts about how quickly the
stratus will clear out. Once it does clear out, though, expect
several hours of VFR conditions before low-end VFR or high-end
MVFR cigs arrive with a cold front after 24/10z.