Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

006
FXUS63 KDVN 142344
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
544 PM CST Thu Nov 14 2024

.KEY MESSAGES...

- Areas of fog are possible across the southwest portion of the
  outlook area late tonight into Friday morning and could become
  locally dense.

- Quiet and warmer weather through Saturday.

- Active weather Sunday through the end of next week with a
  major change in the weather patten. Please the climate section
  below.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 139 PM CST Thu Nov 14 2024

The main forecast problem in the short term is whether clouds
will move out of the area or lingering through Friday. A closed
500 MB trough over the area is forecast to move into the Mid
Atlantic states as 500 ridging builds into the area at the
surface and aloft. Bufkit soundings show a strong subsidence
inversion across the area through the period which would keep
clouds in place across the area. In addition, HREF and SREF
probabilities show a high probability of the clouds lingering
through the period. In collaboration with neighboring offices
have decided to raise low temperatures by a couple of degrees
resulting in low temperatures in the mid 30s west of a Cedar
Rapids to Kahoka Missouri line with upper 30s to around 40
degrees along and east of the Mississippi River. Lowered high
temperatures slightly on Friday but still widespread
temperatures in the mid 50s.

A second question is whether or not we will see dense fog
development tonight. The HRRR and HREF show the possibility of
fog developing across the area mainly southwest of a Fairfield
to Keokuk to Quincy Illinois line. Think that any fog
development will be tied to whether or not we see clearing and
have left the mention of fog out of the forecast for now. If
clouds do push to the east, any areas that see clearing will
have to monitored for the potential of dense fog late tonight.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 139 PM CST Thu Nov 14 2024

During the long term period the weather pattern will go through
a large scale pattern change especially during the mid to later
parts of next week.

Friday night into Saturday shows a highly amplified ridge
across the area as a deep trough moves across the Inter Mountain
West. A shortwave moving from Idaho into Wyoming is forecast to
break off from this trough and move eastward across the
Northern Plains and Upper Midwest Saturday into Sunday. At this
time, this storm systems looks like it lacks moisture and
chances have been limited to areas along and south of
Interstate 80. Chances of rain showers range from 20 to 50
percent with the highest chances in far northeast Missouri and
adjacent areas of Iowa and Illinois. There is a low chance for
thunderstorms and they were left out of the forecast.

In the wake of the Sunday into Sunday storm system, the flow
aloft will become more southwesterly as a closed 500 MB low in
the southwest begins to eject into the Plains for the start of
next week. The most recent runs of the operational GFS and
ECMWF as well as the GEFS and ECMWF Ensemble have come into
better agreement of this upper level low lifting northeastward
into the Upper Midwest and then merging with another shortwave
moving eastward across the northern US resulting in a large
closed low over the central US through next Wednesday. This will
bring the chance for several rounds of showers and possible
storms before a cold front moves across the area late Tuesday.
At this time, rainfall amounts look light. In addition to
chances for rain, a strong pressure gradient is forecast to be
in place across the area and is expected to bring breezy to
windy conditions across the area on Tuesday and Wednesday. At
this time, the NBM is showing a 20 to 30 percent chance of wind
gusts over 30 MPH on Tuesday and Wednesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 535 PM CST Thu Nov 14 2024

Latest satellite imagery showed a large area of low stratus
over eastern Iowa and northwest Illinois. The clouds/moisture
is trapped beneath a low-level inversion and will take a while
to mix out, so anticipate MVFR ceilings to persist into tonight.
As high pressure continues to build in, the stratus deck should
begin to gradually break up and we can anticipate a return to
VFR late tonight into early Friday morning from west to east.

&&

.CLIMATE...
Issued at 230 AM CST Thu Nov 14 2024

As mentioned in the key messages, a major pattern change will
occur the week of November 17th to a more active and much colder
than normal regime. This colder than normal regime potentially
may remain across the area until the end of November.

The anomalous cut off low that develops in the Rockies will
slowly move into the mid-CONUS early next week as a longwave
trof begins to develop over the eastern CONUS. Energy topping
the weak west coast ridge will drop into the developing longwave
trof and deepen it.

As the longwave trof deepens, the NAO mean is progged to go
strongly negative with most GEFS members remaining negative
through the end of the month. The AO mean is progged to go
slightly negative with most members remaining negative through
the end of November as well.

Based on data from the GEFS and ECMWF-EPS, the core of the cold
air (with the largest negative anomalies) is progged to move
across the Midwest the weekend of November 22-25. Although still
below normal, there are indications of temperatures beginning
to moderate toward the holiday and holiday weekend at the end of
November.

Although details are not known this far out, the coming pattern
change brings the prospects of clipper-type systems. Origin
points could be from the Alberta or Saskatchewan Provinces of
Canada. If sufficient cold air is present then precipitation
could very well be in the form of snow at times. However, the
ground is extremely warm so any snow would melt on contact.

&&

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

&&

$$

SHORT TERM...Cousins
LONG TERM...Cousins
AVIATION...Uttech
CLIMATE...08