Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 270247
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
947 PM CDT Wed Oct 26 2016
Issued at 942 PM CDT Wed Oct 26 2016
Cold front as of 0200 UTC was roughly along a KJEF to KPPQ line.
This front will continue to slide southeast and clear the CWA
around 0900 UTC. Along/ahead of this boundary...isolated showers
and sprinkles are possible. Winds behind the front will sharply
turn from the southwest to the north/northwest. Main change to the
previous forecast was to up cloud cover quite a bit overnight
tonight and into early Thursday morning. Widespread stratus
currently extends into southern Canada and as far west as the
Missouri River near the IA/NE border. 950-850 hPa winds are out of
the NNW so advection will be very slow from west to east over the
next 12-18 hours. Stratus should breakup by mid/late morning
holding off the longest on the IL side of the Mississippi River.
Other change from the previous forecast was to slightly boost
overnight lows up 1-3 degrees due to the aforementioned stratus.
.SHORT TERM... (Through Late Thursday Afternoon)
Issued at 340 PM CDT Wed Oct 26 2016
Mesoscale vort center which has triggered showers and isolated
thunderstorms this afternoon will move east of the CWA by around 00Z
ending the threat of additional storms. Behind that feature...a cold
front will move through the CWA during the evening and reach the St.
Louis metro by around 06Z. There may be a few light showers along
the front...however insufficient CAPE should preclude additional
thunder. Winds will become northwest behind the front with a low
stratus deck moving in as well. Stratus will gradually clear from
west to east during the late morning and afternoon on Thursday.
Temperatures will be near seasonal normals on Thursday...with highs
in the low to mid 60s.
.LONG TERM... (Thursday Night through Next Wednesday)
Issued at 340 PM CDT Wed Oct 26 2016
The current weather pattern indicates a warm and dry fcst thru early
Thursday night thru Friday
SW upper flow in place Thu night gradually becomes zonal Fri as a
chunk of energy is ejected from the West Coast trough. The short wave
comes onshore across the Pac NW Thu PM and then traverses the
US/Canadian border Fri. At the SFC...SFC ridge is already E of the
CWA by Thu night allowing return flow to be well established on Fri.
Thu night should be seasonable warm with lows temps 5-10 degrees
above avg due to a mild air mass in place and the sthrly flow. This
will set the stage for a warm Fri. Deep S/SW flow and 850 temps in
the mid/upper teens are basic ingredients to a warm day but the key
is how deep mixing will be. The NAM/Local WRF and SREF all indicate
mixing heights sloping from approx 925mb across sthrn IL to 875mb
across cntrl MO...but the GFS is considerably higher except across
sthrn IL. This should lead to highs ranging from near 70 for sthrn IL
to low and potentially mid 80s for cntrl MO. Another short wave is
kicked out of the base of the West Coast trough Fri.
Friday night thru Sunday night
Sthrly flow will keep up Fri night as the initial short wave slides
SE into the Grt Lks. This feature will drag a cold front into the
nthrn FA Sat mrng. Since the short wave is fcst to pass well N of
the FA...the bndry doesn`t have a whole lot of drive to push it S so
it is expected to slowly sinks S thru the day reaching along or just
N of I70 by Sat night. FROPA appears to be dry attm. The next short
wave approaches the region late Sat night into Sun mrng. The vort
assocd with this feature generates a bit of precip but the bulk of
this activity remains NE of the CWA as the short wave passes by.
This feature helps push the bndry a little farther S by Sun
evng...taking it S of the MO Rvr. The bulk of the West Coast trough
comes onshore Sun...as a result... upper level ridging begins to
work into the area Sun PM. Solutions for the wknd have shifted
considerably over the past several days so I would think there will
continue to be addtnl adjustments as guidance tries to fine tune the
Sat should be another warm day...esp for locations that remain S of
the bndry thru a good portion of the aftn. 850mb temps remain in the
mid/upper teens and would expect maybe even a little better
mixing out ahead of the advancing cold front which should lead to
another day with widespread 70s with a few lower 80s. Even with a
bndry that is expected to be S of the majority of the CWA by Sun
aftn...Sun is expected to be another day with above avg temps with
highs in the upper 60s to mid 70s from N to S...at the same time
being possibly the coolest day thru the middle of next week.
Monday thru Wed
Upper flow turns SWrly in advance of the main short wave. The wknd
cold front will lift back north as a warm from reestablishing deep
sthrly flow thru the day setting the stage for yet another day with
much above normal temps. 850mb temps are once again in the mid/upper
teens...though the 850 thermal ridge is centered N of the FA. The GFS
and ECMWF have timing differences with the main short wave energy.
The GFS is about 6-12 hrs faster than the ECMWF. The GFS drags a
cold front thru the CWA Mon night whereas the ECMWF has the cold
front entering the nthrn CWA Tue mrng. The ECMWF solution stalls the
bndry approx along I70 Tue PM and then washes the front out
overnight. Regardless of the solution...it would appear that the
pattern of dry FROPAs will continue. Depending on the eventual
timing of the Tue cold front...Tue could be another warm day for at
least a portion of the area. A SFC ridge passes N of the area Tue
into Wed allowing return flow to begin again by late Tue night. Wed
could very well be yet another day of aoa normal temps.
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 640 PM CDT Wed Oct 26 2016
Area of scattered showers had moved well to the south and east of
the terminals. Actual cold front will be moving through KUIN any
minute...KCOU by mid evening and the metro terminals toward
midnight. While I cannot rule out an isolated shower or a few
sprinkles for areas along/ahead of this front...coverage looks
much too low to mention in the TAFs. Main story overnight will be
on stratus. Upstream stratus extends into southern Canada.
Advection will be more from the NNW to SSE overnight tonight so
thinking that once the stratus moves in (bases likely between 1000
and 1500 feet AGL)...it will stick around until Thursday
morning. For KUIN and the metro TAFs...it could very well be late
morning. Conditions...once they start to improve...will go to VFR
fast as stratus breaks up toward midday with a mostly clear sky
expected by Thursday afternoon.
SPECIFICS FOR KSTL:
While a few sprinkles and possibly an isolated shower are possible
this evening...probability affecting the terminal too low to
mention in the TAF. Cold front should arrive around 0600 UTC with
winds becoming northwesterly thereafter. Prefrontal round of MVFR
ceilings looks likely this eveing. Could be a bit of a break
mid/late evening...but widespread stratus with bases between 1000
and 1500 feet AGL should overspread the area later on tonight.
This area of stratus should be persistent overnight and into mid
Thursday morning at least. Could be at least a brief period of IFR
ceilings so maintained TEMPO for very late tonight. By mid/late
morning...do expect stratus to break up and eventually dissipate
by midday with VFR conditions expected for Thursday afternoon and
Issued at 340 PM CDT Wed Oct 26 2016
With an upcoming stretch of unseasonable warmth expected over the
weekend, here is a list of record high temperatures thru the weekend.
Although there are no record high temperatures in the forecast just
yet, stay tuned to the forecast as that could change over the next
STL COU UIN
Fri10/28 85/1927 85/1927 85/1927
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 51 64 52 81 / 20 0 0 0
Quincy 46 61 50 77 / 10 0 0 0
Columbia 48 66 52 80 / 10 0 0 0
Jefferson City 49 67 52 81 / 20 0 0 0
Salem 51 61 47 75 / 20 0 0 0
Farmington 54 67 49 76 / 30 0 0 0