Area Forecast Discussion
Issued by NWS St. Louis, MO

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697
FXUS63 KLSX 222335
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
635 PM CDT FRI JUL 22 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 322 PM CDT Fri Jul 22 2016

The main question for tonight is the threat of additional showers
and thunderstorms in the wake of this morning`s decaying MCS. The
outflow boundary from this mornings storms has pushed well to the
south of the CWA and extended from eastern TN across southwest MO
into far eastern KS at mid-afternoon. Although dew points have
recovered some since this morning and heating is ongoing, the air
mass has become only weakly unstable and remains capped to surface
based convection.

We will need to keep an eye on 2 areas this evening. The first is an
expanding area of storms in north central KS. Present indications
are this cluster should if anything eventually take a south-
southeast turn across eastern KS in conjunction with north-
northwesterly deep layer shear vectors and winds in the cloud-
bearing layer, a southerly LLJ providing convergence/lift on the
forward flank, and into the most unstable air residing along/west of
the outflow boundary. Another smaller area of scattered storms in
southeast IA is drifting south-southeast and I think this will
eventually dissipate. I think the best threat of storms albiet low
will occur overnight across northeast MO and west central IL, and
this is provided upstream activity develops later tonight in eastern
NE and western IA. The mid levels weren`t much of a hinderence last
night and they are cooler tonight. Low level winds /850 mb/ across
the CWA however were impacted by this mornings activity and
currently have a northerly component. The northern CWA is the only
part of the region they recover late tonight to provide a more
convergent signal and perhaps aid southeast moving convection. All
in all however the forecast confidence is low.

Glass

.LONG TERM...  (Saturday through Next Friday)
Issued at 322 PM CDT Fri Jul 22 2016

After a bit of a bust on temps on Friday due to storms and cloud
cover, Saturday to rebound back into the 90s for highs. Dewpts in
the 70s will continue to create heat indices well over 105. Same
conditions can be expected on Sunday. So no changes to heat
headlines at this time.

As for precipitation chances over the weekend, it will be
conditional on Saturday. It will depend on any development
tonight. So for now have slight chance pops early Saturday
morning over northeast MO/west central IL. Then some
isolated/scattered activity possible Saturday afternoon, though
despite decent instability, not a lot out there to trigger
activity. Then a break Saturday night with main frontal boundary
finally sinking south across region on Sunday. With such slow
movement to the front, it will not exit forecast area til midday
on Monday. Best chances of rain through this period will be Sunday
night and Monday.

Frontal boundary to stall out over far southern Missouri through the
first part of the work week. Will see just see isolated/scattered
storms along and south of I-70 through this period. Then by
Wednesday, boundary to begin lifting back north with increasing
chances of showers and storms. As for temperatures, will see highs
near normal Monday through Friday.

Byrd

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 635 PM CDT Fri Jul 22 2016

VFR conditions and light surface winds will prevail at the TAF
sites thru the valid period. Only two concerns at this time. First
is possibility of VSBY reductions in mist, but with thick CI cloud
shield currently in place, this will effectively blunt those
possibilities until that changes. The other concern is on whether
another MCS will form to our north late tonight and make a run on
our area Saturday morning but probs on that are low enough at this
time to preclude mention in the TAFs. Both concerns will be
monitored closely this evening for any changes.

TES

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Excessive Heat Warning until 8 PM CDT Sunday for Audrain MO-
     Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-
     Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln
     MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
     Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Charles MO-
     Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
     Genevieve MO-Shelby MO-Warren MO-Washington MO.

IL...Excessive Heat Warning until 8 PM CDT Sunday for Adams IL-Bond
     IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-
     Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
     Montgomery IL-Pike IL-Randolph IL-Saint Clair IL-Washington
     IL.

&&

$$

WFO LSX



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