Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 260919
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
319 AM 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 06z TAFs through 06z Monday Night)
Issued at 1132 PM CST Sun Jan 25 2015
Lingering MVFR SC deck to persist across most of taf sites through
mid morning before scattering out. There is a hole in the mvfr
deck that has made its way into KUIN but should see that fill back
in by 08z Monday. Then next frontal boundary to move through and lower
cigs back down to mvfr for tafs along and east of Mississippi
river, while KCOU to remain vfr. As for winds, to persist from the
north, then back to the southwest to south ahead of next front.
Frontal boundary to move through KCOU by 22z Monday, KUIN by 23z
Monday and metro area by 01z Tuesday. It will be a dry frontal
passage with winds veering to the northwest.
Specifics for KSTL:
Lingering MVFR SC deck to persist across metro area through midday
before lifting and scattering out. Then next frontal boundary to
move through and lower cigs back down to mvfr by 01z Tuesday. As
for winds, to persist from the north, then back to the south ahead
of next front. Frontal passage will be a dry one with winds
veering to the northwest.
.PRELIMINARY POINT TEMPS/POPS:
Saint Louis 43 33 44 29 / 20 5 0 0
Quincy 42 30 39 27 / 30 5 0 0
Columbia 51 31 46 31 / 5 0 0 0
Jefferson City 52 31 47 31 / 5 0 0 0
Salem 36 31 40 27 / 20 10 0 0
Farmington 45 33 46 27 / 10 0 0 0