Area Forecast Discussion
000
FXUS63 KLSX 262319
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
619 PM CDT Mon Sep 26 2022
.SHORT TERM... (Through Late Tuesday Night)
Issued at 236 PM CDT Mon Sep 26 2022
Dry, tranquil, mostly sunny fall weather is in store again for
Tuesday.
The upper-level flow pattern will change little through Tuesday from
today, with an upper-level longwave trough over the eastern Great
Lakes, Ontario, and Quebec and ridge across the Rocky Mountains.
These features will contribute to maintenance of deep northwesterly
flow across the Midwest. Although weak low-level WAA between today
and Tuesday across central and southeastern MO could support
slightly warmer high temps across that area, Tuesday`s high temps
will otherwise be very similar to today and in the mid-60s to mid-
70s F with near full insolation.
Through Tuesday night, the upper-level flow pattern will begin to
become more progressive with eastward propagation of the downstream
longwave trough and upstream ridge, inducing mid-level height
rises/large-scale subsidence across the Midwest amid still-present
northwesterly flow upon approach of the ridge. This subsidence will
facilitate the arrival of a strengthening, increasingly anomalous
(central MSLP exceeding 99th percentile of climatology) surface/low-
level anticyclone to the upper Midwest and Great Lakes. The
associated MSLP rises and positioning of the anticyclone is
anticipated to push a weak, dry backdoor cold front through the CWA
Tuesday night, cooling 850-hPa temps into the mid-single digits C.
Pfahler
.LONG TERM... (Wednesday through Next Monday)
Issued at 236 PM CDT Mon Sep 26 2022
Dry, tranquil, mostly sunny fall weather is highly favored to
continue through this week into the upcoming weekend with Wednesday
likely the coolest day. Some patchy frost will be possible across
northeastern MO Wednesday morning, perhaps Thursday morning as well.
Thereafter, a slow warming trend will occur into the upcoming
weekend.
The arrival of the cool airmass, nearby anticyclone to the
northeast, and mostly clear skies may enable efficient radiational
cooling to take place into Wednesday morning as well as Thursday
morning. Low temps these mornings could fall into the upper 30s F in
some areas north of I-70 and isolated low-lying locations along and
south. Some readings in the mid-30s F are even possible in localized
portions of northeastern MO. NBM probabilities of low temps less
than or equal to 36 F Wednesday and Thursday mornings are highest in
northeastern MO at around 50 to 40 percent at Kirksville, MO and
around 30 percent at Mexico, MO. Therefore, the greatest potential
for patchy frost exists in portions of northeastern MO Wednesday and
Thursday mornings.
Thursday through Friday, the upper-level ridge is progged to
continue eastward from the Mid/Upper Mississippi River Valley to the
East Coast. Simultaneously, model guidance depict an interruption of
TC Ian`s northward advancement through the northeastern Gulf of
Mexico as it initially encounters the ridge, before making landfall
somewhere along the west coast of FL. Thereafter, TC Ian`s most
likely track takes it inland of the Southeast as it continues
generally northward Friday into Sunday. Model guidance consensus is
a track well east of the CWA, but at least some indirect impact may
be felt. Currently this impact still appears to be a prolonged, slow
retreat of the southwest branch of the surface/low-level anticyclone
across the Midwest from the peripheral subsiding circulations of TC
Ian. As a result, low-level flow should be weak along with any temp
advection, leaving only repeated days of considerable insolation and
large-scale subsidence to gradually modify the airmass in place and
moderate temps Thursday through Sunday to average and above average.
NBM interquartile ranges, even at this relatively longer lead time,
are around 5 F or less, bolstering confidence in this slow warm up.
Pfahler
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 618 PM CDT Mon Sep 26 2022
Gusty conditions will diminish after sunset. Tomorrow, gusts will
pick back up for KUIN and the St. Louis metropolitan terminals.
These gusts will be less than those of today, primarily under 20
kts. Otherwise, dry, VFR conditions will prevail through the TAF
period.
Jaja
&&
.FIRE WEATHER...
Issued at 236 PM CDT Mon Sep 26 2022
Northwesterly winds sustained at 10 to 18 mph and occasionally
gusting to 20 to 30 mph will continue through the remainder of the
afternoon, coincident with minimum RH fluctuating between around 30
and 20 percent. Despite live, green fuels still present across the
area, some stressed vegetation may exist across portions of central
and southeastern MO from antecedent largely dry conditions with
continued curing from persisting dry, breezy conditions. Therefore,
elevated fire weather conditions will continue primarily across
central and southeastern MO into early evening before winds quickly
slacken and RH increases.
Pfahler
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 51 72 45 66 / 0 0 0 0
Quincy 46 68 39 62 / 0 0 0 0
Columbia 48 75 43 66 / 0 0 0 0
Jefferson City 47 76 44 67 / 0 0 0 0
Salem 44 70 39 65 / 0 0 0 0
Farmington 46 73 39 66 / 0 0 0 0
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
NWS LSX Office Area Forecast Discussion
