501
FXUS63 KDVN 131933
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
233 PM CDT Thu Jun 13 2024

.KEY MESSAGES...

- Well above normal temperatures next week will bring hot and
  humid conditions to the area. Heat indices will be in the 95
  to 100 range.

- An active weather pattern will develop across the Midwest with
  organized storms running around the edge of the heat dome.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 231 PM CDT Thu Jun 13 2024

18z DVN sounding still shows a small cap inhibiting convection but
this will erode quickly with convection initiation occurring between
3 and 6 PM.

Of interest is the PWAT of 1.50 in the sounding. This is essentially
at the 90% percentile in climatology. Thus storms that develop will
be very efficient in generating high rainfall rates. Additionally,
precip loading of downdrafts raises the specter of wet microbursts.

Thus through 6 PM very rapid development of storms will occur along
or just ahead of the front from southern Iowa to east northeast of
the QC metro area.

Initially, the primary risk will be the potential for hail that is
at least golfball size. Precipitation loading in the storm
downdrafts suggests the potential for wet microbursts with wind
gusts over 75 mph.

Very short term models have more cloud cover in them than what is
being observed by satellite but their overall trend points to storms
growing upscale into a broken line across southeast Iowa into west
central Illinois by early evening. Once this occurs, storm
interactions raises the possibility of meso vortices developing and
the potential for brief spin up tornadoes.

The overall severe risk should be done by 10-11 PM with the decaying
convection exiting the area by 2 AM. The very late night hours will
be dry with dropping humidity levels.

On Friday, slightly cooler but much less humid conditions will be
seen across the area. Temperatures will still average above normal.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 231 PM CDT Thu Jun 13 2024

Friday night
Assessment...high confidence

Quiet conditions will be seen across the area as high pressure
quickly moves across the Midwest.

Saturday through Thursday
Assessment...high confidence on hot and humid conditions. Low
confidence on rain chances.

While there is a near daily risk of rain, much of the area has a
high probability of remaining dry.

A prolonged period of hot and humid conditions will build into the
Midwest. Peak daytime heat index values of 95 to 100 are expected
with overnight head index values only dropping into the mid 70s.

The higher uncertainty is where will the organized thunderstorm
track develop. If it develops north of the area, dry conditions will
be seen. If it is over the area then periodic rounds of storms can
be expected.

The global models vary on their respective solutions, deterministic
and ensemble wise. From a thermodynamic perspective, the favorable
temperature gradients at H85 and H7 (19-23 and 9-13 C respectively)
remain over or close to the area. Thus the prospects of seeing
periodic organized thunderstorm complexes is reasonably good.

The one time period that appears to have a higher probability of
remaining dry looks to be Monday night into Tuesday. No discernible
upper level disturbances can be found in the flow aloft.

Otherwise, there is a small risk (20-30 percent) of thunderstorms
Saturday through Monday for areas north of I-80.

Tuesday night through Thursday there is a weak signal of an upper
level disturbance moving through in the flow aloft that may bring a
risk of rain to the entire area. However, overall coverage during
this time period will remain at 20 to 30 percent.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1239 PM CDT Thu Jun 13 2024

Cold front runs from far southwest Wisconsin back into southwest
Iowa. A warm layer aloft is preventing convection from
initiating but rapid TSRA development is likely from southern
Iowa into west central Illinois 20z/13 to 00z/14. Outside of
TSRA VFR conditions will be seen with high density altitudes
ahead of the cold front. IFR conditions are likely in TSRA with
wind gusts over 40 knots. After 04z/14 conditions will improve
back to VFR as storms exit the area and high pressure builds in.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...08