714
FXUS63 KLOT 140837
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
337 AM CDT Mon Apr 14 2025
.KEY MESSAGES...
- Breezy/windy conditions are expected today through Tuesday,
with a locally elevated risk of brush fire spread (mainly
south of Interstate 80) this afternoon.
- A wetter/stormier weather pattern is expected to become
established over the Midwest late this week through early next
week.
&&
.DISCUSSION...
Issued at 337 AM CDT Mon Apr 14 2025
Through Tuesday:
A weak surface low embedded within a cold front currently
across the western CWA will track eastward through the morning.
Meanwhile, a low-amplitude wave over Nebraska will become
increasingly sheared as it crosses central Illinois through late
morning. Some associated mid-level showers will encounter a dry
sub-cloud layer that should limit precip from reaching the
surface, though widely isolated light showers or sprinkles are
possible mid to late morning south of a Pontiac to Valparaiso
line.
Modest CAA and pressure rises combined with diurnal mixing into
30 to 40 knot flow across a developing subsidence inversion
will result in W/WNW winds gusting 35 mph or higher late morning
through the afternoon. With RH values falling to or below 40%,
the gusty winds could increase the spread of any brush fires.
Otherwise, skies will be partly cloudy with passing upper-level
clouds through the day and shallow diurnal cumulus in the
afternoon. Expect temps to rise to around 60 north and the mid
60s south.
A subtle mid-level disturbance over southeast Alberta and
embedded trough axis shifting southward from Manitoba early this
morning will phase across the Upper Mississippi River Valley
late this afternoon. A developing 90 knot mid-level jet nosing
into an area of steepening low to mid-level lapse rates and a
marginally favorable moisture regime will likely yield at least
some isolated showers and a few storms across Iowa this
afternoon. This activity will begin to wane after sunset as it
nears the Mississippi River, but the decaying showers could
generate gusty surface winds west of the Chicago metro mid-
evening.
A resurgence of CAA behind the passing wave in the evening will
likely result in a pop of wind for several hours late tonight
into Tuesday morning amid a strengthening pressure gradient over
the area. Would not be surprised to see frequent NW gusts over
30 mph and a few gusts to 40 mph during this time. Meanwhile,
widely isolated showers with sufficiently deep stratocumulus
blanketing the area will continue overnight. Cannot fully rule
out a few wet snow flakes mixing in toward sunrise closer to the
Wisconsin state line. Clouds will be slow to erode from the
west through the day Tuesday, with temps struggling to rise to
50 for northeast Illinois and northwest Indiana.
Kluber
Tuesday Night through Sunday:
A meridionally elongated region of surface high pressure will
settle into the region Tuesday night into Wednesday, causing
winds to lighten and skies to clear out overnight into Wednesday
morning within a relatively dry air mass. Thus, between the
cold air advection off of modestly breezy northwesterly winds
during the evening and more optimal radiational cooling
conditions materializing later overnight, temperatures appear
poised to bottom out in the 30s (and possibly even the upper
20s) across most of our forecast area Wednesday morning. This
would include near to below freezing temperatures pretty much
everywhere outside of the footprint of Chicago`s urban heat
island.
With the region of surface high pressure more or less centered
along our longitude, Wednesday should be a quiet day weather-
wise with ample sunshine allowing temperatures to rebound to
more seasonable readings in the mid 50s to low 60s. Our lake-
adjacent locales look to be an exception to this as weak onshore
flow and/or the development of a bona fide lake breeze should
keep locations near the lakeshore several degrees cooler
compared to locations farther inland.
The synoptic pattern evolution for the latter half of the week
into the weekend remains quite convoluted owing to the
involvement of multiple upper-level disturbances undergoing
complex interactions with one another. In spite of this,
ensemble guidance has continued to throw more support behind
the general idea of upper-level ridging becoming established
over the eastern CONUS late in the week while upper-level
troughing (and likely an eventual cut-off low) sets up over the
western CONUS. As this occurs, a northern stream trough should
trek eastward across Canada, inducing a surface low beneath it
that should serve as the northern terminus of an elongated
frontal zone tucked between the eastern CONUS ridge and western
CONUS trough. Multiple surface low pressure centers may end up
spawning along this frontal zone Thursday into Friday, helping
to draw warmth and moisture northward into the central/northern
Plains and Midwest as an EML plume originating from the
southern Rocky Mountains and Sierra Madre is commensurately
pulled poleward along the frontal zone. The net result of all
this will be a rainier/stormier weather pattern across the Great
Plains and into the Midwest from late this week through early
next week.
For us here locally, it will mean warming temperatures into
Friday, when well above normal highs in the 70s and possibly
even low 80s may be observed. It will also likely mean that
there will be multiple opportunities for showers and storms to
be observed in the area between Thursday and Monday. Of those
days, at least Friday appears to be a day when we might need to
be on the lookout for potential severe weather as that is when
the pre-frontal instability plume will likely end up being
positioned over our forecast area amidst strong deep-layer
shear. However, numerous question marks remain pertaining to the
strength and track of any nearby surface lows, the timing of
the better upper-level forcing support, and the degree of
capping at the base of the EML, among other things. Accordingly,
confidence in the finer-scale details of this potential severe
weather threat and the extent to which it may materialize here
remains low at this time.
Ogorek
&&
.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 108 AM CDT Mon Apr 14 2025
Key Messages:
- West-northwesterly wind shift to occur behind cold front
prior to daybreak.
- Gusty westerly winds beginning after sunrise and continuing
through the remainder of the TAF period.
- Chance for light rain showers late Monday night/early Tuesday
morning.
A cold front will track across the area from west to east
roughly between 0900Z and 1100Z. Winds are favored to shift to
a direction between 300 and 320 degrees immediately behind the
front, but should settle into more of a 270-290 degree direction
soon afterwards and largely maintain that direction through
pretty much the remainder of the TAF period. After sunrise,
winds should start gusting to around 25 kts or so before picking
up slightly going into this afternoon, when gusts of 30-35 kts
should become more commonplace. Continued cold air advection and
strengthening low-level wind fields should then allow for gusts
near and in excess of 30 kts to continue with some regularity
through Monday night.
A brief period of sprinkles couldn`t be ruled out later this
morning, but it appears more likely that all post-frontal
precipitation will just remain as virga as it passes over the
terminals. A better chance for rain showers will come late
Monday night/early Tuesday morning. It appears that the
coverage of these showers will be scattered at best, and it`s
possible that most of these showers may end up passing to the
northeast of our TAF sites, but felt that there was enough of a
chance for some raindrops to be seen at ORD and MDW to warrant
the introduction of a PROB30 group for -SHRA at the tail end of
their respective TAFs. MVFR ceilings could accompany these
showers, but VFR conditions are otherwise expected to prevail
throughout the TAF period.
Ogorek
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 8 AM this morning to 7 PM CDT
Tuesday for Winthrop Harbor IL to Gary IN.
Small Craft Advisory from noon today to 7 PM CDT Tuesday for
Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.
&&
$$
Visit us at weather.gov/chicago