Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

140
FXUS63 KDVN 140438
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1138 PM CDT Sun Apr 13 2025

...Updated for 06z Aviation...

.KEY MESSAGES...

- Breezy/Windy conditions through Tuesday with elevated fire risk
  area-wide Mon/Tue).

- Lower end (20-40%) shower chances for the area Monday
  evening. Better chances (50-60%) for rain arrive mid-late
  week.

- Cooler weather midweek with the potential for near freezing
  lows and frost for some next Tuesday night - Wednesday
  morning.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 153 PM CDT Sun Apr 13 2025

As of 1 PM, a cold front is sweeping east through Iowa,
positioned west of I-35. A wave of low pressure is found along
the front in northern Iowa, and along and north of that low`s
path, there has been showers and storms today, with dry weather
to the south and east. High cloud cover delayed the warm up into
the 70s through the lunch hour, but is now underway over all
but the northern CWA, thus highs in the upper 60s north to upper
70s/near 80 south remain on track today. Winds are breezy, but
most gusts today have been in the 25-30mph range, outside of a
couple observations here and there reaching 35 mph.

Though more windy weather is on the way later tonight, and
especially Monday, this evening should actually see light winds and
mild/warm temperatures. This should be a great evening to fire up
the grill, but that all ends late tonight, when the cold front
arrives, with a period of gusty winds of 30 to possibly 40 mph from
the northwest. Temperatures will fall, but not abruptly, and with a
well mixed late night, with lows of 45 northwest to lower 50s
southeast expected. A post frontal FGEN band with some mid level
instability remains possible in the south towards morning, and
though NBM has dropped the pops to near zero, I`ll maintain the
slight chance for showers, but not advertise this as any hazard.

Monday, winds will be already going by daybreak from the northwest.
The CAA is not too aggressive through the morning, so some sunshine
and mixing will allow for highs to reach the upper 50s north to
lower 60s central and south.  Wind gusts with a deeply mixed
sounding, (inverted-V profile), continue to support 30 to 35+ kt
gusts, especially late in the morning and early afternoon. For now,
this appears the main message in graphics, but not an advisory day,
though it`s still worth considering tonight if data supports it.
GFDI values remain forecast in the "very high" range, mainly
northwest of Fairfield IA to Freeport IL.

The coldest air aloft is set to arrive Monday evening, with a pool
of -5C at 850mb moving over the area. Guidance continues to suggest
some saturation at the top of the mixed layer as this occurs
Monday evening, with some scattered showers moving southeast
through the CWA. Thunder would be possible if this was during
the afternoon hours, but it does look like most of this will be
after dark and CAPE values are waning considerably, with the
main forcing from mid level lapse rates remaining steep.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 153 PM CDT Sun Apr 13 2025

The process of deeply mixed CAA will generally continue into
Tuesday, with another deeply mixed windy cool day forecast.
Winds again appear likely to reach the 30-40 mph range during
the late morning and afternoon, bringing yet again another risk
for fires spreading out of control. Highs in the 50s will feel
quite brisk Tuesday!

High pressure building in Tuesday night and Wednesday morning will
lead to chilly conditions. Frost and freezing temperatures are
possible, especially north of I-80 where NBM probabilities for lows
<32F are 40-50%.

Beyond, the pattern looks to turn unsettled/active for the latter
half of the week through next weekend, as the flow aloft shifts from
the southwest. An undulating surface boundary in/near the area will
lead to periodic modest rain chances (40-60%) along with an ebb and
flow in temperatures. Any rain doesn`t look to be too heavy with NBM
probabilities for >0.75 inch over 72 hr period ending 12z Saturday
at just 10-20%. Severe weather potential is uncertain, although
having said that a few machine learning applications do show some
lower end severe probabilities potentially Thursday/Friday. The main
thing to watch for next weekend and into the early part of the
following week is the eventual track/ strength/timing of a
potentially stronger system, which could bring with it some better
risk for heavier qpf and strong storms. Lots of uncertainty though
that far out, but just something to keep tabs on in the days ahead.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1130 PM CDT Sun Apr 13 2025

A cold front will continue to push through the terminals early
in the period. In the wake, a brief bout of NW gusts 20-30+ kt
can be expected before diminishing prior to daybreak. Upper
level energy will traverse the southern half of the area Monday
morning accompanied by sprinkles and a few showers, mainly near
MLI and BRL. Meanwhile, further north a disturbance moving into
the Upper Midwest will slosh some lower clouds down into
northern parts of the area by mid-morning, with a brief bout of
MVFR CIGs possible at DBQ and CID before lifting to VFR and
scattering Monday afternoon. A secondary disturbance approaching
from the northwest late in the day will bring the potential for
scattered shra and isolated tsra to the terminals late
afternoon and evening. Some of these could enhance wind gusts to
35-45 kt, otherwise prevailing gusts outside of the convection
will be up to 25 kt from the northwest.

&&

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

&&

$$

SHORT TERM...Ervin
LONG TERM...Ervin/McClure
AVIATION...McClure