Arlington Heights, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

564
FXUS63 KLOT 240933
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
333 AM CST Sun Nov 24 2024

.KEY MESSAGES...

- Above normal temperatures today and Monday with highs in the 50s.

- Cold front to bring a period of rain showers and drizzle
  tonight through Monday.

- Potential for travel impacts in the region from accumulating
  snow in the Tuesday night to Thanksgiving Day period appears
  to be increasing.

- Below normal temperatures will prevail Monday night through
  Thursday, followed by much below normal (true mid-winter cold)
  Friday-Saturday and beyond.

&&

.DISCUSSION...
Issued at 333 AM CST Sun Nov 24 2024

Through Monday Night:

Another gloomy morning is ahead as pesky low-level moisture
remains trapped beneath a subtle ridge overhead. While there has
been signs that the low stratus is gradually advancing
eastward, a deck of mid-level clouds has moved in aloft and
looks to persist through this afternoon. So expect at least
mostly cloudy skies today but a few pockets of sunshine may be
briefly seen especially across our far south and southwestern
counties where some scattering may occur. Despite the cloud
cover, temperatures this afternoon are still expected to reach
into the above normal category for late November with highs in
the low to mid-50s.

Heading into tonight, the subtle shortwave trough over the
Sierras is expected to be ejecting into the central Plains and
lead to the development of a weak surface low as it does so.
This surface low is then forecast to lift through northern IL
late tonight into Monday morning resulting in a period of
showers and drizzle. Since temperatures overnight should remain
nearly stationary in the mid to upper 40s, the showers and
drizzle will remain in a liquid state and thus should pose no
significant threat aside from minor visibility reductions. As
the low lifts into Lower MI Monday afternoon it will drag a cold
front across the area resulting in a period of true showers
especially across far northeast IL and northwest IN.

Showers will quickly taper behind the front late Monday
afternoon and evening as colder and drier air filters in.
However, winds will quickly increase with northwest gusts in the
20-25 mph range likely Monday afternoon and overnight.
Temperatures will also be cooling behind the front resulting in
lows in the mid to upper 20s by Tuesday morning. Though, the dry
air will finally break us out of the clouds heading into the
day on Tuesday.

Yack


Tuesday through Saturday:

Focus in the extended period remains the potential for snow-
related impacts during the busy Thanksgiving holiday travel
period with true mid-winter cold also arriving over the
extended holiday weekend.

After what has been a fairly prolonged cloudy stretch, the sun
may manage to make a brief appearance Tuesday morning, with
fairly decent ensemble agreement in a drop in cloud coverage
before increasing again later in the day. Continued cold air
advection into the area in the wake of Monday`s cold front will
still likely hinder temperatures from warming out of the 30s.

Heading into Tuesday night, there remains a signal for a
preceding warm advective and frontogenetically forced band of
snow overnight (mainly after midnight) into Wednesday morning.
The GFS and NAM are also beginning to pick up on this signal,
which the ECMWF has shown the past few model runs. The exact
placement of this feature remains somewhat in flux, but felt
comfortable maintaining 20-30% chances for snow during this
period.

Over the past 24-hours there has been a gradual increase in
confidence toward winter-related travel impacts occurring
somewhere in the region Wednesday into Thursday. However, models
continue to struggle with how amplified the upper jet becomes
during this period (related to the handling of potential phasing
of waves over the Central Plains) which has significant
implications for the system track and intensity and accordingly
whether additional snowfall related impacts occur here locally.
It does appear that the percentage of ensembles keeping the area
dry has decreased (a less amplified pattern and further south
storm track). Additionally a cluster of ensemble members
continues to depict a potentially higher end outcome (shifting
the ensemble mean above the 50th percentile). With all this
said, confidence in the details for this system remains low.

Thursday night through the upcoming weekend continues to look
like a favorable lake effect snow set-up oriented into northwest
Indiana/western Lower Michigan as much colder air advects over
a still relatively warm lake (currently in the upper 40s).
Speaking of the cold, forecast highs over the upcoming weekend
are only in the 20s with wind chills in the teens and single
digits! Something to keep in mind for the those returning from
Thanksgiving travels!

Petr

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1100 PM CST Sat Nov 23 2024

Key Messages:

- MVFR to IFR cigs and VFR to MVFR vsby reductions tonight

- Winds become southeasterly Sunday morning

- Showers and drizzle arrive late Sunday evening and overnight
  with another round of MVFR to IFR cigs

While effectively obscured by high cloud cover, regional surface
observations indicate the back edge of the MVFR to high IFR
stratus deck continues to make northward progress out of central
Illinois. Extrapolating this progression results in the back
edge getting close to ORD/MDW towards 9-10z. While redevelopment
of lower stratus remains possible on the SW flanks of the cloud
shield, have not seen this occurring readily in surface
observations. As a result, have moved the previous prevailing
IFR group into TEMPO groups. If redevelopment does not occur
overnight, VFR cigs may ultimately prevail late tonight into
Sunday morning. Some vsby reductions-- into the 4-6 SM range--
appear plausible at all the terminals into Sunday morning, but
the thick high cloud cover should temper the dense fog threat.

Winds will turn southeasterly through Sunday morning with VFR
conditions expected through the afternoon and early evening
hours. The next disturbance will approach the region Sunday
night, resulting in an expansion of VFR and eventually MVFR to
IFR cigs Sunday night. Expecting showers or drizzle to develop
towards about 06z Monday, and have added a mention into the ORD,
MDW, and RFD sites with the latest TAF issuance.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago