Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

612
FXUS63 KDVN 152340
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
640 PM CDT Thu May 15 2025

.KEY MESSAGES...

- A conditional threat for severe storms (level 2 of 5) remains
  this afternoon and early evening across northwest and north
  central Illinois.

- Humid and breezy conditions today with near record highs,
  with most locations hitting the upper 80s to lower 90s.

- Strong southwest winds are forecast on Friday, potentially
  peaking 40 - 45+ mph.

- Active weather returns early next week, with widespread
  beneficial rain likely.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 110 PM CDT Thu May 15 2025

The forecast remains on track today with hot and humid conditions
ahead of a cold front which is currently approaching the far
western portion of the outlook area. A potent, negatively
tilted trough will swing through the Upper Midwest today, and
an unseasonably strong surface low (~980mb) nearly vertically
stacked with the upper-low will shift through eastern South
Dakota into far southeast North Dakota into this evening. This
system will push a cold front through eastern Iowa and northwest
Illinois through the mid to late afternoon, marking a SSE to
WSW wind shift and significant drop in low-level moisture with
dewpoints falling from the upper 60s/near 70 F down into the
50s. Ahead of the front, diurnal BL mixing will aid in pushing
temperatures to near record highs as very warm air at 850mb
(near 20 C) is adiabatically mixed down to the surface. This
will yield highs in the low 90s for counties along and east of
the Mississippi River.

SPC has maintained a Slight Risk (level 2 of 5) for severe
storms in the counties east and northeast of the Quad Cities,
with a small area of an Enhanced Risk (level 3 of 5) in eastern
Stephenson County. A Marginal Risk (level 1 of 5) extends back
to the west toward the Quad Cities.

While the forecast environment is favorable for severe storms
this afternoon due to high instability with MLCAPE of 2500+
J/kg and sufficient deep layer shear for storm organization,
CAMs have continued to show relatively low areal coverage,
although with a wide variance in solutions. The HRRR continues
to be one of the least aggressive with CI in our outlook area,
holding off development until either near or east of our eastern
border. Other CAMs such as the NSSL/ARW/NAMnest develop
scattered storms along and just east of the Mississippi River
between 3 to 5 PM. And this is likely the worst case scenario
for today -- scattered strong to severe storms impacting the
eastern tier or two of counties during the late afternoon/early
evening, before the activity quickly shifts to the east. The
other possible scenario is for the area of low-level convergence
along and slightly downstream of the surface front to progress
far enough to the east through the afternoon that CI is
primarily focused east of the outlook area during the late
afternoon to early evening. As mentioned, the environmental
setup is there to support severe storms, so any convection that
does develop could quickly become severe with large hail and
damaging winds the primary threats, and an isolated tornado
secondary. Dry conditions are expected overnight with lows in
the 60s and 50s.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 110 PM CDT Thu May 15 2025

Friday: Warm and windy conditions are expected with a much drier
post-frontal air mass in place. The strong area of low pressure
will remain positioned across west-central MN to southeast ND
which will keep a tight pressure gradient over eastern Iowa and
northwest Illinois. Strong, gusty SW to WSW winds are forecast
locally with peak values around 45 mph possible and a Wind
Advisory may eventually be needed.

Low-level moisture will be much lower than on Thursday, but
with dewpoints in the mid 40s to lower 50s there may be enough
instability during the afternoon to lead to high-based isolated
showers and storms, which could locally enhance the winds to 50+
mph. Forecast soundings display MUCAPE of 500+ J/kg and DCAPE
near 1200 J/kg. On a separate note, since significant green-up
of vegetation and area grasses has already occurred this spring
the fire weather threat should be muted. Nonetheless, given the
strong gusty winds, dry conditions, and low afternoon humidity
between 20-30%, burning is discouraged on Friday.

Saturday - Sunday: Seasonable weather is forecast for the
upcoming weekend with highs in the 60s across the north and 70s
elsewhere. It will be breezy on Saturday with NW winds gusting
around 30 mph. No precipitation is expected through Sunday
evening.

Next Week: Models are in good agreement on an active weather
pattern setting up for the early to middle portion of next week
with periods of widespread rainfall likely. NBM highs are in
the 60s and 70s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 640 PM CDT Thu May 15 2025

VFR and dry conditions are expected throughout the TAF period.
Gusty southwest winds early this evening will quickly diminish
with sunset, leading to a clear night with much lighter winds.
There should be a brief period of low-level wind shear late
tonight for CID and DBQ as a 30 to 40 knot low-level jet
strengthens for a time. Expect another windy day Friday, with
southwest winds gusting in excess of 30 knots for most
locations. There is a low (less than 20%) chance of showers and
perhaps a thunderstorm Friday afternoon, but confidence is too
low to include in the TAFs.

&&

.CLIMATE...
Issued at 220 PM CDT Wed May 14 2025

Record High Temperatures:

May 15:
KBRL: 93 / 1944
KCID: 94 / 1941
KDBQ: 90 / 1944
KMLI: 91 / 1941

Record Warm Low Temperatures:

May 15:
KDBQ: 67 / 2001
KMLI: 69 / 2001

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...Uttech
AVIATION...Schultz
CLIMATE...Gross