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969
FXUS63 KDVN 192320
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
620 PM CDT Wed Jun 19 2024

.KEY MESSAGES...

- Isolated to Scattered storms this afternoon and evening with a
  Marginal Risk (Level 1 of 5) of severe weather.

- After a brief reprieve, trending hotter again Friday and
  especially Saturday. Storms may feed on this heat energy
  Saturday or Saturday night.

&&

.UPDATE...
-- Changed Discussion --
Issued at 612 PM CDT Wed Jun 19 2024

As of 6 PM, the front remains positioned from near Quincy IL, to
just east of the QCA, to near Freeport. Isolated showers and
very isolated thunderstorms have formed along it this afternoon,
but have not become organized in any way. A weak MCV, or other
PWAT heavy feature continues to slowly move towards our
southwest, and could enhance coverage of showers/storms tonight
along and north of this front. Models are highly varied on
whether they convect this area, or bring light rains. We have
just a small cap to overcome through lift, around 883mb per the
00z sounding just sent up, and there`s big questions on whether
that prevents activity from becoming more widespread tonight.
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&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 250 PM CDT Wed Jun 19 2024

Tonight...Slow moving northeast-to-southwest front seen on sfc
observations and MSAS draped from southwest WI, the northwestern DVN
CWA, down acrs northeast MO and trailing acrs eastern KS ATTM. To
the lee of that, a lead boundary oriented the same way and probably
enhanced by differential heating was seen on RADAR and satellite
crossing the MS RVR. Aloft, there was low amplitude upper ridging
edging acrs the southeastern CWA off eastern CONUS upper ridge
complex, with water vapor imagery and upper air analysis showing
mainly channeled vorticity on the northwestern flank of this feature
acrs central IA into northwest MO. Trying to see an approaching MCV,
unless it is subtle and maybe acrs northeastern KS, it may edge acrs
the western CWA later this evening. So these lift features will
continue to work on local 1000-2000 J/kg MUCAPEs to produce isolated
to widely sctrd convection acrs the CWA this late afternoon into
evening especially along the boundaries. Also will monitor the
approaching showers and storms currently acrs north central MO and
see if they can maintain as they advect northward. some post
frontal more stratiform looking light precip Effective shear profiles
and marginal at best mid level lapse rates limit the severe
potential, and if we got any thing it would probably be in the form
of an isolated downburst wind. A PWAT feed of at least 1.8 inches
would also support locally heavy rainfall in swaths of storm
movement paths.

The southwesterlies with vorts or weak MCV/s will continue acrs the
area overnight, and will have to continue to carry POPs over night
for sctrd showers and storms continuing especially along lingering
LLVL boundaries. Low temps in the mid 60s in the northwest, to the
low 70s southeast.

Thursday...Another day of high buoyancy(CAPEs of 1500-2500 J/kg) but
weak shear, marginal lapse rates, and lack of deep forcing
precluding much of any severe storm threat.  Areas more favored for
isolated to sctrd storm development will look to be along and north
of I-80 and especially Hwy 30 and north Thu afternoon and evening.
This area further away from mid level ridging acrs the southeast,
and closer to ongoing weak S/W shuttle flow north of the ridge from
acrs the Dakotas, MN and into WI. Also these northern areas may have
more lingering boundaries laying out more west-to-east for some
focus. Cloud cover somewhat uncertain as well and will look to be
variable. High temps again a challenge but will range them from the
low to mid 80s in the north, to the low 90s south. Heat index`s in
the mid to upper 90s in the south.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 250 PM CDT Wed Jun 19 2024

Friday...Ongoing thermal ridge looks to amplify somewhat overhead
and keep the area under a suppressing EML. Latest ensemble indicated
mid level steering flow patterns suggest a partial ring of fire
pattern setting up around this feature from the northern plains over
to the Great Lakes, keeping the MCS storm track northwest and north
of the local area possibly into Sat morning. Thermal profiles
support highs in the upper 80s to low 90s, but sfc DPTs are still
looking to mix out in the mid to upper 60s, thus the lower humidity
may not warrant a heat advisory this day. But with the somewhat
reduced humidity, there may be a better chance for ambient temps to
reach the mid 90s in some locations with full sun.

Saturday and Sunday...A hot and more humid airmass Saturday with
highs in the low to mid 90s. Sfc DPTs may hang closer to 70 thus
making heat indices push the upper 90s or near 100. A northern
stream short wave digging against the upper ridge with an associated
sfc cold front acrs the region may spark strong, heavy rain
producing storms late Saturday or Sat night. It`s still early but
currently indicated CAPE and shear profiles would support some
severe storms. In the wake of the cool front and storms, incoming
upper MO RVR Valley ridging and northwest flow could make for a dry,
not quite as hot and less humid Sunday. Best day of the weekend.
Low temps well down in the 60s for Sunday night.

Monday and Tuesday...Currently progged upper jet pattern on the
medium range ensembles suggest broad upper ridge amplification
acrs the Rockies and western CONUS early next week. Resultant
northwesterly steering flow acrs the upper MS RVR Valley into
the GRT LKS may place the DVN CWA close to the ridge-riding
short wave storm track thus occasional convective systems. AS
the upstream upper ridge tries to squeeze eastward acrs the mid
CONUS, the unsettled pattern acrs the upper Midwest may linger
well into next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
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Issued at 612 PM CDT Wed Jun 19 2024

A front is draped along a line from Freeport IL, to near Moline
IL, to near Quincy IL this evening. Some MVFR cigs have built in
on the west side of that front this evening, but should not
lower further until overnight, when somewhat more widespread
showers and storms are possible. These appear most likely over
northeast Iowa, but will be watched in all locations for a tempo
group tonight. CID and DBQ will be in a Prob30 for the late
night and early morning hours Thursday for both MVFR Cigs and
thunderstorms.

A lull is expected through the sunrise to afternoon hours
Thursday before more scattered activity forms again.

Winds will become light this evening, and remain variable with
the front nearby.
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&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

UPDATE...Ervin
SHORT TERM...12
LONG TERM...12
AVIATION...Ervin