333
FXUS63 KLOT 112004
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
304 PM CDT Wed Sep 11 2024

.KEY MESSAGES...

- Summer-like warmth to continue through at least Thursday.

- Persistent dry weather will maintain a heightened threat for
  grass and brush fire starts especially on Thursday.

- Chances for showers late Friday through Monday as the remnants
  of Hurricane Francine move by, though potential for
  meaningful rainfall continues to look low.

&&

.DISCUSSION...
Issued at 304 PM CDT Wed Sep 11 2024

Through Thursday night...

Our stretch of summer-like warmth will continue through
Thursday as a broad area of high pressure continues to reside
over the eastern CONUS and Great Lakes. High temperatures on
Thursday will once again top out in the mid to upper 80s
areawide, however; the combination of onshore winds and a lake
breeze will result in slightly cooler readings along the
lakeshore. These temperatures in combination with the antecedent
dry conditions will maintain a heightened threat for grass and
brush fire starts through the day on Thursday. Thus anyone
conducting outdoor burns should exercise caution.

Otherwise, expect skies to remain generally cloud free for
tonight through Thursday before cloud cover increase Thursday
night as the cirrus from now Hurricane Francine drifts
overhead. Some low concentrations of wildfire smoke aloft will
maintain a slight haze to the sky tonight into Thursday morning.
Regardless, temperatures tonight should still be able to cool
into the low to mid-50s (lower 60s in Chicago), but more modest
lows are expected Thursday night (readings in the upper 50s to
mid-60s) due to increasing clouds.

Friday through Wednesday...

The main forecast concern for the upcoming weekend continues to
be the chances for showers associated with the remnants of now
Hurricane Francine. Francine is still expected to make landfall
along the LA Gulf Coast tonight and then track into the Mid-
Mississippi Valley on Friday as a decaying tropical depression.
At the same time, the broad ridge (high pressure) over the
eastern CONUS is expected to develop into a closed high and
pivot over the eastern Great Lakes over the weekend. In doing
so, the upper high should cutoff the remnants of Francine from
the upper trough forecast to pivot through the Mountain west and
northern Plains over the weekend.

What this means for us is that the bulk of Francine`s moisture
should become trapped along the Ohio and Tennessee River vallies
and struggle to make much progress into northern IL and
northwest IN. While this solution is conveyed nearly identically
amongst all ensemble and deterministic guidance, there
continues to be some indications that a subtle ribbons of
moisture may be able to creep into the western half to third of
our forecast area (roughly areas along and west of a Rockford to
Paxton line) during the late Friday through Monday timeframe.
Since the better dynamics and resultant forcing should remain
closer to Francine`s remains to our south, coverage of showers
associated with the moisture plumes continues to be a point of
uncertainty. Therefore, have decided to maintain a slight chance
(20-30%) mention for showers areawide during this period for
now but suspect that many locations (especially those east of
the aforementioned line) will remain dry. Nevertheless, any
rainfall that occurs does not look to be sufficient enough to
provide much, if any, relief to the prevailing dry conditions.

Heading into the early part of next week, what is left of
Francine is progged to shift east into the mid-Atlantic region
as another upper-ridge builds across the central CONUS. While it
does look like we may hang on to some residual moisture with
this ridge, dry conditions are still forecast through at least
the middle part of next week. Though, temperatures do look to
moderate some with readings more into the lower to mid-80s this
weekend through midweek.

Yack

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1228 PM CDT Wed Sep 11 2024

Light southwest winds in the 5-8 kt range this afternoon will
become light southeast to at times variable this evening and
overnight. Winds then prevail easterly by late Thursday
morning/early afternoon around 8-10 kt.

A layer of smoke aloft remains overhead with increasing high
cloud coverage expected during the day on Thursday.

Petr

&&

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

&&

$$

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