Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 241650
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1150 AM CDT SUN APR 24 2016
.SHORT TERM... (Through Late This Afternoon)
Issued at 355 AM CDT Sun Apr 24 2016
The sfc ridge is expected to build further ewd today, allowing sly
winds across the region. An upper ridge is expected to remain in
place today, which will keep precip W of the CWA.
The light FG across ern portions of the CWA shud dissipate by mid-
morning. This area shud also see the most cloud cover, but is still
expected to be only sct coverage. However, high clouds shud cover
the region. Believe these clouds, other than those lower over ern
CWA, will have little impact on temps today. Have trended aoa the
warmer guidance across the region.
.LONG TERM... (Tonight through Saturday)
Issued at 355 AM CDT Sun Apr 24 2016
An omega block will dominate Canada and the northern CONUS thru this
week, with upper longwave TROFs on the west and east coasts and the
RIDGE component over the Plains. A series of strong Pacific storms
will run just south of this blocking pattern, 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. Model
progs show that each successive storm system will track a bit
further south than its predecessor.
The first storm system will track to our north late tonight and into
Monday, and will be just a glancing blow to our region as a result,
with what forms mostly upstream initially to our northwest working
its way in late tonight as it weakens with a possible low level
boundary setting up for additional development further southeast
during the day on Monday.
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
rain. Severe storm chances up until this point look to be low.
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 late Tuesday night into Wednesday
morning. This should result in elevated storms, with hail as their
primary severe threat during that time.
Heading into Wednesday afternoon and evening, it will depend heavily
on how far north the front gets. Models continue to skiddishly
track the frontal boundary a tad further south than where they were
progging it 24hrs prior, but the bottom line still remains nearly
the same for now, with a strong shear and unstable environment with
a low level boundary for severe storm formation potential, including
Things dry out briefly for late in the work week before the third
storm system approaches from the west for the upcoming weekend and
rain chances ramp up again. But with this storm system expected to
track the furthest south, this next episode of rain could very well
be mostly showers with imbedded storms if this track holds, with any
severe potential remaining well to the south.
Otherwise, the default RIDGE setup in our part of the CONUS will
ensure that temps remain at or above average throughout the period.
.AVIATION... (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1113 AM CDT Sun Apr 24 2016
Just few-scattered diurnal cumulus clouds this afternoon, and
some high level clouds this evening. An upper level low now over
southwest SD and an associated surface low over central SD will
move eastward through the northern Plains tonight and into the
Great Lakes region on Monday. It appears that most of the
convection associated with this storm system will remain north of
the taf sites, although could not rule out a few showers or storms
late tonight and Monday morning impacting UIN and COU. For now
will leave precipitation out of the tafs as the probability is
quite low and the timing still uncertain. Will get some low-mid
level clouds moving into the taf sites late tonight and Monday
morning as a low level jet brings increasing low level moisture
into the area. There may be a brief period of MVFR cigs Monday
morning in UIN or COU. Southerly surface winds, gusty at times
this afternoon and again late Monday morning, will become more
southwesterly Monday morning.
Specifics for KSTL: Few-sct diurnal cumulus clouds this afternoon,
high level clouds tonight, then VFR low-mid level cloudiness on
Monday. There may be a few showers/storms on Monday, mainly during
the afternoon, but will leave the STL taf dry for now as the
probability is quite low and the timing uncertain. Southerly
surface wind will increase to around 13-15 kts this afternoon and
become gusty. The southerly wind will weaken a little this
evening, then become more southwesterly Monday morning as well as
strengthen and become gusty again by late Monday morning.