Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 231153
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
653 AM CDT SAT APR 23 2016
.SHORT TERM... (Through Late This Afternoon)
Issued at 350 AM CDT Sat Apr 23 2016
Focus today will be clouds and temps.
Sfc ridge will continue to drift ewd today, allowing sly winds to
return to wrn portions of the CWA. Winds elsewhere are expected to
remain sely to ely.
The area of clouds currently just E of the CWA shud remain E.
However, some clouds may drift into ern portions of the CWA mainly
this morning until the ridge pushes them out of the area.
A secondary ridge axis over nrn portions of the CWA is expected to
be the focus for FG/stratus this morning. There is still uncertainty
regarding how widespread any FG will be, as well as any stratus. The
additional moisture within the bndy layer across this region shud
allow for at least sct clouds this morning, dissipating thru the
All of this leads to a rather complex temp forecast for today. For
ern portions of the CWA, have kept temps cooler where the ridge axis
will remain in place longer. Areas under this ridge yesterday saw
temps in the upper 60s, however, believe there will be less cloud
cover today. Believe the warmer temps will build into wrn portions
of the CWA where winds will become sly as well as the thermal ridge
building into this area. Have gone with trends close to a blend of
the RAP and local 4km WRF, which has been a good mix in these
setups. Did trend slightly cooler than this blend across nrn
portions of the CWA where more questions exist regarding cloud cover
.LONG TERM... (Tonight through Friday)
Issued at 350 AM CDT Sat Apr 23 2016
An upper level longwave RIDGE axis will persist over the Plains
thru much of next week, with upper longwave TROFs on the west and
east coasts. A series of strong Pacific storms will run thru this
RIDGE, being dropped off from the west coast TROF and being picked
up by the east coast TROF a few days later, with an overall track to
the E-NE thru our region. It would seem that each successive storm
system will track a bit further south than its predecessor.
The first storm system is slated to track to our north late Sunday
and into Monday, and will be mostly a glancing blow to our region as
a result, with what forms mostly upstream initially to our northwest
as it is thrown in our direction and largely weakens as it moves in.
This convection may also create additional boundaries during Monday
afternoon and early evening to maintain the threat for showers and
In the wake of this first storm system, a cold front will drop down
late Monday night into Tuesday and will maintain a low chance for
The second Pacific storm system will be more of a direct hit as it
will initially correspond well with the surface frontal boundary
buckling north as a warm front Wednesday morning. This should
result in elevated storms with hail as their primary threat during
Heading into Wednesday afternoon and evening, it will depend heavily
on how far north the front gets. Models have been trending with
less northward progress from 24hrs ago, but anywhere to the south of
it will have plenty of instability and moisture as well as strong
shear for more surface-based storms which will have a good potential
for some severe.
The rain potential lingers into Thursday if the cold front slows
enough to not make it thru until this day.
Friday should be a dry day, finally, but it appears only briefly
until yet another storm system approaches from the west in time for
the following weekend.
Otherwise, the longwave RIDGE setup will ensure that temps remain at
or above average throughout the period.
.AVIATION... (For the 12z TAFs through 12z Sunday Morning)
Issued at 640 AM CDT Sat Apr 23 2016
Sfc ridge is expected to push ewd today with winds eventually
becoming sely. The lingering FG this morning is expected to
dissipate quickly this morning. Some uncertainty regarding the
area of stratus over ern IA into far nern MO. This stratus may
develop far enuf sewd to impact UIN this morning. However, with
the sun rising and the slow pace the stratus is moving, do not
currently expect it to impact the terminal. Expect winds to
continue to veer this evening, with a LLJ creating LLWS concerns
at COU/UIN tonight.
Specifics for KSTL: VFR and dry conditions expected thru the TAF