-- Discussion containing changed information from previous version are highlighted. --
795
FXUS63 KDVN 210554
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1254 AM CDT Fri Jun 21 2024

.KEY MESSAGES...

- A chance for isolated storms this afternoon and evening. Severe
  weather not anticipated. Locally heavy rainfall possible.

- Hot and humid Friday and especially Saturday.

- A chance for severe thunderstorms Saturday and Saturday night.

&&

.UPDATE...
Issued at 610 PM CDT Thu Jun 20 2024

Slow moving, but loosely organized storms along a line are
gradually lifting northward this evening, and in this waa
regime, this should continue tonight. Some spotty heavy amounts
around 2 inches are likely, but most locations will remain dry,
thus, am sticking with the scattered / chc pops for tonight. I
will slightly enhance the Highway 30 corridor to 60% through 8
PM.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 241 PM CDT Thu Jun 20 2024

Tonight...Light sfc flow with several embedded boundaries seen on
sfc observations and RADAR loops. Afternoon heating has made for
2000+ J/kg MUCAPEs, and with convective temps of mid to upper 80s,
weak ridge-riding vort aloft, the buoyancy will be allowed to
translate into isolated to widely sctrd showers and thunderstorms
through mid evening. While widespread severe storms not expected
with weak shear and lapse rates, can`t rule out pop and drop
isolated downburst winds doing some shenanigans here or there. Also
an environment favorable for non-supercell funnels. PWATs remain very
high from 1.8 to 2 inches acrs the area, thus any more substantial
cell will be very heavy rainer`s as they drift by. After some cloud
thinning and evening storms fade, ongoing light sfc wind flow and
juiced sfc DPTs there may be some patchy fog in spots, especially
along any lingering boundary. Will place patchy fog wording in the
north for now. Low temps in the upper 60s to low 70s for most of the
area.

Friday...High pressure aloft will look to bump up acrs the
southeastern CWA, while periphery thermal ribbon-storm track
setting up around this feature from the northern plains over to the
Great Lakes, keeping the brunt of the MCS storm track northwest and
north of the local area possibly into Sat morning. But lingering
boundary north of I-80 or even Hwy 30, or possibly outflow from
convective activity to the north or northwest, may be enough to bump
up buoyancy-driven isolated storms in these areas Friday afternoon.
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 should not warrant a heat advisory. 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 or
limited CU.  Friday night, a low chance of upstream MCS activity to
bleed down toward the northwestern CWA late night or just before
dawn Saturday morning.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 241 PM CDT Thu Jun 20 2024

Saturday and Sunday...A hot and more humid airmass Saturday with
highs in the low to mid 90s. Of course any cloud or convective
debris lingering out of Friday night or coming in the form of
initially decaying storms from upstream in the morning may make
temps warm up potential tricky in some locations. Sfc DPTs may hang
closer to 70 thus making heat indices push the upper 90s or near
100. Synoptic flow ensembles still keep the same signal of a
vigorous northern stream short wave digging against the upper ridge
and heat dome, with an associated sfc cold front acrs the region on
Saturday. Stronger forcing/shear breaking the EML and plowing into
high CAPEs likley will spark strong to severe, heavy rain producing
storms later Saturday and into Saturday night. It`s still early but
currently indicated CAPE and shear profiles would support damaging
winds, large hail and isolated tornadoes. In the wake of the
Saturday cool front and storms, incoming upper MO RVR Valley ridging
and northwest flow may make for a dry, not quite as hot and less
humid Sunday. Still looking like the best day of the weekend. Sunday
night still under the influence of the sfc high and we may have low
temps cool well down in the 60s by Monday morning.

Monday through Wednesday...Latest run medium range ensembles and
upper jet patterns 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 possibly subject to occasional convective systems. Thus may be
a unsettled stretch this period especially Tue or Tue night. But one
change in the latest runs was being more bullish in pumping up the
Rockies upper ridge out west, resulting in more of a southward surge
in LLVL ridging dumping down the upper to mid MS RVR Valley and
western GRT LKS, for a cooler and dry reprieve from the early week
warmth/storms.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
-- Changed Discussion --
Issued at 1254 AM CDT Fri Jun 21 2024

Largely VFR conditions are anticipated through the TAF period.
Early this morning, we will mainly be focused on DBQ, where an
IFR stratus deck has developed, evident on the GOES-East nighttime
micro satellite imagery showing the southern extent of this low
stratus along the Highway 20 corridor. It is uncertain just how
persistent that low stratus will linger at DBQ, but the
majority of the model guidance has it staying around 500 ft
through the early morning hours. Some MVFR fog is also possible
there as well for a time this morning. Some isolated storms are
possible this afternoon and evening.
-- End Changed Discussion --

&&

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

&&

$$

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