Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1244 PM CDT Sun Oct 6 2024
KEY MESSAGES...
- Very elevated fire danger today due to gusty winds and dry
conditions.
- Dry weather continues through the week, with temperatures
trending above average.
&&
DISCUSSION...
Issued at 252 AM CDT Sun Oct 6 2024
Through Monday:
Recent surface analysis shows a cold front stretching from the
central Upper Peninsula of MI southward across southeastern WI
and northwestern IL which will continue to race across northern
IL and northwest IN this morning. Ahead of the front, gusty
southwest winds will persist with gusts in the 25 to 35 mph
range. While gusts are expected to diminish immediately behind
the front for a period towards daybreak, gusty northwest winds
will return by midday with gusts once again in the 25 to 30 mph
range for the rest of the afternoon.
These gusty winds in combination with the dry conditions behind
the front (dew points in the low to mid-30s) will set up
favorable conditions for very elevated fire danger this
afternoon, especially for areas along and south of I-80 where RH
values should dip into the 20-25% range. Since fuel moistures
are currently in the 9-12% range it appears that we will be just
above local Red Flag Warning criteria, however; a Special
Weather Statement (SPS) will be issued for the entire forecast
area through this afternoon for the elevated fire danger.
Therefore, any planned burning should be postponed until
conditions improve and extra caution should be used when
discarding any burning materials (such as cigarettes) today.
Otherwise, expect temperatures this afternoon to be more in the
seasonable category with highs in the upper 60s to mid-70s.
Heading into tonight, winds are expected to subside as a
surface high moves into the Midwest. While this will lower the
fire danger, dry conditions are still expected to prevail
through the day on Monday with minimum RH values generally in
the 25-30% range. So continue to be cautious with any planned
burning.
The combination of light winds and clear skies under the high
will also set up conditions for strong radiational cooling
tonight and allow temperatures to dip into the upper 30s and
lower 40s areawide. These cool and calm conditions may also lead
to the development of some patchy frost late tonight
particularly across northwestern IL where the coldest
temperatures and lightest winds are forecast. Any frost that
does materialize will diminish Monday morning as temperatures
rebound into the middle 60s by Monday afternoon with otherwise
sunny skies.
Yack
Monday Night through Saturday:
At the start of the period, medium range guidance continues to
be in good agreement in depicting a closed upper low centered
over southern Quebec, within a larger scale upper trough over
much of northeastern North America. While a series of low-
amplitude short waves are indicated wrapping south-southeast
through the western periphery of this circulation, their impacts
are expected to remain well off to the east and northeast of
the forecast area. Eventually, an upper level ridge extending
from the desert southwest into the northern Plains and eastern
Canadian Prairie Provinces is progged to shift east mid-week,
nudging the northeastern NOAM trough further to the east. This
results in rising heights indicative of increasing subsidence
across the upper Midwest and western Lakes Wednesday into
Thursday, allowing surface high pressure to build across the
western and central Lakes region.
Locally, this portends continued dry and gradually warming
weather conditions into mid-week, tempered only by daily lake
breezes near Lake Michigan. Daytime temperatures are expected to
moderate from the lower 70s (upper 60s/near 70 along the lake)
Tuesday, to the low to mid/upper 70s (warmest west) by Thursday,
under largely cloudless skies. Nighttime lows may dip into the
upper 30s in our typically coolest spots Monday night, and
generally in the 40s elsewhere (upper 40s/low 50s in the core of
the Chicago urban region).
Models remain in excellent agreement in tracking a mid-level
short wave trough and associated jet streak along/just north of
the U.S./Canadian border region Thursday into Friday, flattening
the upper ridge across the upper Midwest and northern Lakes.
This initially enhances west-southwesterly low-level warm
advection into the upper Mississippi Valley and northern Great
Lakes, around the northwest periphery of the departing surface
high drifting east of our area. The warm advection axis is
progged to eventually shift south across IA/WI and northern IL
Friday and Saturday, with ensemble mean 850 mb temperatures
warming to +15/16C by Saturday. This looks to further warm
surface temps into the upper 70s and lower 80s Friday and
Saturday, well-above average heading into mid- October.
Ratzer
&&
AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1237 PM CDT Sun Oct 6 2024
- Gusty WNW winds 25-30 kts will continue through the afternoon.
Winds gusting 25-30 kts will continue through the afternoon from
the west to northwest with a more prevalent northwest direction
setting up with time. Winds will then diminish slowly this
evening, with lingering gusts especially at our warmer Chicago
urban airports. Winds will eventually settle to 10 kts or less
from the northwest after midnight and persist into Monday
morning and likely Monday afternoon as well.
Otherwise, a very dry airmass will be in place with VFR
conditions expected through the period under nearly cloudless
skies.
MDB/Ratzer
&&
FIRE WEATHER...
Issued at 252 AM CDT Sun Oct 6 2024
While temperatures today will be around 10 degrees cooler than
yesterday, dewpoints are expected to settle into the low to
mid-30s which will result in afternoon relative humidities in
the 20 to 30 percent range. The driest conditions/lowest RH
values will occur south of about I-80. Gusty winds from the west
to west-northwest will develop quickly through the morning,
peaking towards midday and early afternoon in the 25 to 30 mph
range. At this time, sustained 20-foot winds are forecast to
come in just under formal Red Flag criteria, and 10-hr fuel
moisture values may only briefly tag 8 percent. As a result,
have refrained from issuing a Red Flag Warning on this shift,
but will issue a Special Weather Statement and continue to
highlight a heightened fire danger in our graphical messaging
suite. Winds will diminish rapidly near sunset.
Yack/Carlaw
&&
LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 7 AM CDT Monday for the IL
nearshore waters.
Small Craft Advisory until 10 AM CDT Monday for Calumet Harbor
to Gary IN.
Small Craft Advisory until 4 PM CDT Monday for Gary to Burns
Harbor IN-Burns Harbor to Michigan City IN.
&&
$$
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