Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 270322
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
1022 PM CDT TUE APR 26 2016

.UPDATE...
Issued at 948 PM CDT Tue Apr 26 2016

Convection over eastern Kansas and northwest Missouri is
proceeding slowly eastward...about as expected. Looks like the
leading edges will be moving into the western fringes of our CWFA
by 06-07Z. Have made minor tweaks to the PoPs to slow the precip
accordingly. RAP is forecasting 1000-1500 J/Kg of MUCAPE along
with increasing deep layer shear...and this continues to point
toward the possibility of elevated severe storms with severe hail
being the primary threat.

Carney

&&

.SHORT TERM...  (Through Late Tonight)
Issued at 332 PM CDT Tue Apr 26 2016

Current bowing convective system over SW IL has a well established
cold pool and will continue to move east into the western OH
Valley into a large region of unstable air in advance of it. The
deep convective line with any severe threat should clear the area by
500 pm with trailing stratiform rain clearing the CWA by early
evening. A prominent outflow boundary with the convective system,
which should have completely moved through the CWA by 00z, has
largely stabilized the air mass to boundary layer based storms in
its wake. I will retain some low chance pops this evening on the
fringes of our CWA however I think the vast majority of the
evening in the wake of the present system will be dry. Current
thinking is that overnight we will see a MCS that has evolved
across the Plains early this evening, move west to east into central
and finally eastern MO in the predawn hours. Additional showers
and thunderstorms could develop late this evening and overnight
ahead of the aforementioned progressive Plains MCS in response to
the LLJ and WAA along north of the retreating outflow boundary/warm
front composite. There will be a severe threat with this overnight
activity given MUCAPE of 1000+ j/kg and increasing southwesterly
deep layer shear, but not nearly as great as the system that moved
through today.

Glass

.LONG TERM...  (Wednesday through Next Tuesday)
Issued at 332 PM CDT Tue Apr 26 2016

A little unclear how everything will pan out on Wednesday. There
will likely be ongoing convection from a decaying MCS over parts
of eastern MO in the morning that will move into IL. However it
does appear that there will be sufficient air mass recovery in the
wake of the morning convection. How much and the most favored
corridors are hard to say. Mid level lapse rates will remain steep
and heating should lead to SBCAPE of at least 1500 j/kg over parts
of central MO by early afternoon. The combination of the east-northeast
rotating short wave trof and large scale ascent, and the attendant
advancing cold front should result in thunderstorm development
along/ahead of the cold front by mid afternoon. Coverage should
then increase through the remainder of the afternoon, with storms
persisting into the evening as the front and trof progress east.
We will probably see a mixed convective mode with all severe
weather threats. Most of the activity should have moved out of the
CWA by 06z Thursday.

The trof will be lifting to the northeast on Thursday with the
cold front advancing into the OH/TN Valley region. Present
indications are that increasingly deep westerly flow in the wake
of the front will lead to good drying and little if any
precipitation.

Next round of showers and thunderstorms looks to unfold Friday
night into the weekend. First with the LLJ, WAA, and a lead
impulse Friday night/Saturday and then with another formidable
upper trof and attendant cold front Saturday night into Sunday.

Glass

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 645 PM CDT Tue Apr 26 2016

Thunderstorms have mostly moved east of the CWFA with the
exception of some continuing storms over southeast Missouri.
Another round of storms is expected late tonight...but until then
VFR flight conditions are expected. Timing and strength of the
storms is uncertain at this time...but current thinking is that
the storms will move into central Missouri after 06Z and
overspread the entire area by 11-12Z. Think conditions will
primarily be VFR, but areas of heavier rain will likely bring
visibility down to 3SM and ceilings below 3,000 FT. Lower
conditions are possible as well. Rain will clear from southeast to
northwest through the morning and the atmosphere will reset for
another round of strong storms Wednesday afternoon.

Specifics for KSTL:

Expect VFR flight conditions to prevail at Lambert this evening
and probably through most of the night. Another round of storms is
expected to move in from the southwest between 08-10Z. Once the
rain starts, it will likely continue intermittently through at
least 15-17Z. Think conditions will primarily be VFR, but
intermittent heavier rain will likely bring visibility down to
3SM and ceilings below 3,000 FT. Lower conditions are possible as
well. Rain will clear from southeast to northwest through the
morning and the atmosphere will reset for another round of strong
storms Wednesday afternoon.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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