Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 261813
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1213 PM CST Mon Jan 26 2015
.SHORT TERM: (Through Late This Afternoon)
Issued at 318 AM CST Mon Jan 26 2015
Radar and satellite data at 08z indicate another clipper system over
northern MN and producing a swath of pcpn out ahead of it on its
eastern flank but also with good pcpn coverage on its southern
periphery as well. Mostly cloudy skies extend from this clipper
well to the southeast where they run up against the system that just
moved thru our region on Sunday. Some breaks in the clouds were
over the STL metro area. Temps for most areas are in the 25-30F
Model data is in good agreement on phasing of strong WAA,
frontogenesis and broadscale lift from shortwave TROF pushing thru
IA and into west-central IL this morning and working its way thru
southern IL this afternoon with its backedge near the MS river.
This should be enough for isolated to widely scattered showers and
have added 20-30 percent PoPs to the forecast. The atmosphere also
looks to support varied pcpn-types, with snow initially supported
thru midday and then the western edge of the pcpn near the MS river
transitioning to rain during the afternoon with snow likely
maintaining some presence thru the day in the far eastern CWA around
Vandalia and Salem, IL.
Most QPF amounts will struggle to measure by the very definition of
the low PoPs in the forecast, but some isolated areas in IL may be
able to accumulate a light dusting of snow.
Otherwise, temps will vary widely across the forecast area today
with readings remaining in the 30s for the Salem/Vandalia, IL areas,
but rising into the low 50s for central MO.
.LONG TERM: (Tonight through Sunday)
Issued at 318 AM CST Mon Jan 26 2015
(Tonight through Wednesday)
Mdls are in relatively good agreement thru the period. Surface fnt
associated with the approaching clipper shud be E of the CWA by 00z
this evening. Precip shud have exited the region by this eve as
well. Clouds are expected to linger thru the night as the low pulls
sewd out of the region. Expect clouds to be slow to clear out on
Tues as well. Have trended cooler thru Tues due to the clouds.
Thermal ridge extends over the region by mid-day Wed. Have raised
temps on Wed and kept temps aoa the warmer guidance. Some
uncertainty exists regarding temps thru this period as mdl solns
begin to diverge with respect to temps and sfc low placement.
(Thursday through Sunday)
Mdl solns continue to diverge thru the period. Mdls differ in timing
of the system to impact the area thru the weekend. Have kept slight
chance PoPs to account for this system. Will keep PoPs low until
solns come into better agreement.
Mdls do agree with temps being much cooler late this week behind the
system on Wed, then cooler still with the reinforcing trof late this
week. Attm, mdls agree that temps will be cold enuf so that any
precip that does occur late this week and into this weekend shud be
SN. Will continue to monitor as the system approaches.
.AVIATION: (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1135 AM CST Mon Jan 26 2015
Upper level disturbance moving southeast through the Midwest is
producing spotty areas of light snow across parts of west central
and southwest Illinois. KUIN had about 10-20 minutes of light snow
which dropped vsby to IFR very briefly. Brief periods of IFR will
be possible through the early afternoon as this area of snow moves
southeast, but for the most part MVFR ceilings will prevail along
and east of the Mississippi this afternoon with unrestricted
visibilities. Expect VFR conditions to prevail over central
Missouri at least into early evening. Should see a clearing trend
this afternoon at least up to the Mississippi river, but then
guidance brings another round of MVFR clouds down across the area
this evening. MVFR ceilings will likely hang across the area
through most if not all of Tuesday morning.
Specifics for KSTL:
MVFR ceilings will be scattering at Lambert over the next hour or
two, and VFR flight conditions are expected to prevail after that
until evening. There may be a few snow flurries in the area
through 19-20Z as well, but do not expect snow heavy enough to
affect flight conditions. Guidance brings another area of MVFR
ceilings down from Iowa along the Mississippi during the mid to
late evening hours. Looks like ceilings could fall below 2,000ft
for a short period overnight tonight, but confidence is not high
in that at this time. Ceilings between 2,000-3,000ft are expected
to prevail through Tuesday.