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Office: DVN
FXUS63 KDVN 072331
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
631 PM CDT Mon Jul 7 2025

.KEY MESSAGES...

- A few periods of showers and storms remain in the forecast,
  mainly for this afternoon through Tuesday, and again Thursday
  night through Friday. Severe weather potential remains low at
  this time.

- Seasonal temperatures and humidity levels will continue this
  week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 219 PM CDT Mon Jul 7 2025

Isolated to scattered showers and storms have developed early this
afternoon, mainly along and just east of the Highway 218 corridor.
So far, thunderstorms have remain isolated and haven't reached
severe levels, but lightning and a brief heavy downpour remain the
main hazards with these. A weak mid-level shortwave has helped to
spark off this activity. Otherwise, partly to mostly sunny skies
will be common elsewhere.

Late tonight through Tuesday looks to be more active as a more
robust mid-level trough and attendant cold front approaches the
area. We will have to watch the current activity over South Dakota
as that is expected to eventually approach our region late tonight,
albeit in a decaying fashion. Other than some locally heavy rainfall
and gusty winds, strong to severe storms are not anticipated.
Chances of showers/storms are around 20-40%.

Tuesday will have relatively higher chances (40-60%) of storms,
especially in the afternoon. Analysis of the convective parameter
space indicates ample instability, with MLCAPE values around 1000-
2000 J/kg, but with very weak deep-layer shear once again. Low-level
lapse rates appear to be somewhat steep - around 6.5 to 7.5 C/km -
coupled with higher PWAT values (1.7 to 2.0 inches). With this said,
although SPC has kept our region out of any convective outlooks (we
remain on the northern cusp of a Marginal Risk to the south), there
appears to be some support for some locally gusty winds in any
storms that develop. Temperatures will be a little cooler due to
more cloud cover, with most areas reaching the low to mid 80s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 219 PM CDT Mon Jul 7 2025

Tuesday night through Thursday: we should enter a period of largely
dry conditions, thanks to an upper-level ridge building across the
central Plains region. This should help keep any mid-level impulses
at bay for a time. Seasonal conditions should continue these days,
with highs warming to the middle to upper 80s for both Wednesday and
Thursday, along with seasonal humidity.

Thursday night and Friday: the next mid-level shortwave sweeps
through the area during this time, leading to another round of
showers and storms potential across the area (40-60% chances).
Unlike the last few rounds of strong to severe storms, Friday looks
to have stronger deep-layer shear and stronger flow in place, along
with abundant instability. The various extended machine learning
output continues to highlight the potential for at least isolated
strong to severe storms, so something to keep an eye on as we get
closer to the end of the week.

An early look at the upcoming weekend indicates a slight cooldown
for Saturday in the wake of Friday's fropa, with highs in the lower
80s for most, and perhaps some lingering shower and storm chances
Saturday morning. Sunday appears likely to remain dry, with
continued seasonal temperatures.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 624 PM CDT Mon Jul 7 2025

Outside of any shower or storm, light winds and VFR conditions
are expected at all TAF sites. More widespread storms are
possible tonight across the area with the best time being just
before daybreak. Later in the period, more afternoon storms are
possible as well.

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Gibbs



Office: LOT FXUS63 KLOT 080531 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1231 AM CDT Tue Jul 8 2025 .KEY MESSAGES... - Dangerous swimming conditions continue at Lake Michigan beaches, but improving late this evening. - Chance (30-50%) for scattered showers and thunderstorms on Tuesday across primarily northern and central IL. - Low shower/storm chances continue on Wednesday. Better chances return Friday/Friday night. && .DISCUSSION... Issued at 226 PM CDT Mon Jul 7 2025 Tonight: Expect partly cloudy skies and quiet conditions with seasonable overnight lows in the lower to mid 60s outside of Chicago and upper 60s in the city. The Beach Hazards Statement is set to expire at 7pm for Illinois beaches and 9pm for Indiana beaches, which looks reasonable per web cams and observations as of this writing. There could be some patchy fog tonight near/south of the Kankakee River overnight. Castro Tuesday through Monday: Forecast evolution for Tuesday remains a bit unclear, with some timing differences in the handling of low-amplitude disturbances noted in today's guidance. At the surface, a moist axis which is currently displaced west of the Mississippi River will slosh eastward into the region as low-level southwesterly flow returns. Aloft, several vorticity maxima will be in the vicinity as a more notable shortwave translates well to our north across the Minnesota Arrowhead Region. Have expanded some 20-30 percent PoPs a bit farther east across the region Tuesday morning as very modest ascent within a moistening airmass could yield clusters of showers and a few storms. Through the rest of the day, upper 60s/near 70 degree dewpoints are forecast to return, and most guidance commensurately suggests capping will erode through the late-morning and afternoon, even with muted insolation and the potential for pockets of morning showers/storms tied to a 700 mb wave in the region. While surface convergence isn't strongly defined tomorrow, the presence of a moist/destabilizing airmass and presence of several disturbances aloft suggests mid-range chance PoPs remain appropriate to cover the potential for afternoon and early-evening shower and thunderstorms. Mid-upper flow looks fairly weak, so storms should remain disorganized and posing primarily a locally heavy rain and gusty wind threat. Some potential that activity festers a bit through Tuesday evening, but should see a gradual diminishing trend as drier low-mid level air spreads in from the north. Through the day on Wednesday, forecast soundings look like they become increasingly capped across the northwest half of the region as a subsidence inversion pushes eastward. Deeper boundary layer moisture is evident with south and east extent through the area, however, resulting in more limited capping. A lack of defined upper-level features suggests that any diurnally-driven activity may remain more sparse in coverage, and tied generally to surface boundaries. Speaking of boundaries (on Wednesday): today's guidance is starting to hit the wind response on the lake a bit harder as a backdoor front drops down the lake, which conceptually fits the set up of a near 1020 mb high pushing east across the UP of Michigan. Gusty northerly wind response is not ubiquitous in the model guidance today, but did boost winds a bit on the lake, and will need to keep an eye on this window for a period of moderate or greater swim risk. Thursday could end up being largely dry in the wake of the aforementioned front. The surface high won't build across the entire area, and lingering moisture could hold on in our far southern locales, enough to justify hanging onto some very low (15%) PoPs south of the Kankakee River vicinity, but even these could end up being a bit too high. On Friday-Saturday, forecast confidence begins to diminish as a fairly sharp shortwave trough slicing across the Northern Plains starts to interact with remnant MCVs/vorticity clusters. Deterministic GFS continues to advertise some severe weather threat across northwest Illinois but currently remains a bit of a south and east outlier across the guidance suite. Carlaw && .AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 1231 AM CDT Tue Jul 8 2025 Forecast concerns include... Chance of thunderstorms this afternoon. Low chance for showers through mid morning. Potential for fog early Wednesday morning. Current isolated showers across northwest IL are expected to dissipate over the next few hours before reaching the Chicago terminals, though an isolated shower will remain possible. A few showers across southeast MN/western WI may continue to fester through the overnight hours, bringing a chance for showers to RFD after daybreak. If these were to materialize, they may persist north of the terminals through the mid/late morning hours. There remains a chance of thunderstorms for all of the terminals this afternoon, though coverage remains uncertain and maintained prob mention for now. A large complex of thunderstorms is moving southeast across southwest IA into northern MO. How these storms evolve over the next 12 hours, will impact storm trends locally this afternoon. The most favored areas appear to be west central IL with activity possibly dissipating further to the northeast. Overall, low confidence for trends, which will need to be monitored for possible later forecast changes. After this potential precipitation, the rest of this evening into early Wednesday morning is looking mainly dry. Winds are light and variable and will become light southerly by daybreak then become southwest by mid morning with speeds increasing into the 10-12kt range. The forecast soundings suggest there may be a period in the late morning, when gusts into the 15-20kt range will be possible. Wind directions this evening are uncertain. If there are storms, winds may favor a light southeast direction. Forecast soundings also show hardly any wind aloft early Wednesday morning as weak frontal boundary sags into northern IL. This would easily support fog development. However, fog may be dependent on how widespread any precipitation becomes and the best location for fog appears to be northwest IL, which would be after the current 24 hour RFD taf period. But some fog mention may be needed with later forecasts. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago
Office: ILX FXUS63 KILX 080508 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1208 AM CDT Tue Jul 8 2025 .KEY MESSAGES... - There will be daily chances (20-50% coverage) for scattered showers and storms, particularly during the afternoon and evening hours. There is a marginal risk (level 1 of 5) for severe storms Tuesday across portions of central Illinois. - Seasonable heat and humidity will be in place the remainder of the week into this weekend with afternoon highs generally in the mid to upper 80s and dew points in the 70s. && .DISCUSSION... Issued at 211 PM CDT Mon Jul 7 2025 A weak area of high pressure is centered over the Great Lakes this afternoon with ridging extending into portions of central Illinois. This will help suppress the convective chances for the remainder of today as well as provide brief relief from the muggy conditions across the region with dew points generally running in the 60s north of I-70. Some patchy fog will be possible overnight into Tuesday morning within the weak flow, mainly over east central and southeast Illinois. Surface ridge axis will shift to our east Tuesday allowing humidity to return across central Illinois with dew points building back to around 70 degrees for most of the area. Meanwhile, a shortwave trough is progged to move across the state Tuesday afternoon/evening coinciding with peak heating and allowing scattered thunderstorms to develop. Moderately strong afternoon instability is expected to develop with MLCAPE values advertised by the GFS expected to be around 1500-2000 J/kg. Despite passage of the shortwave trough, deep layer shear will remain sub-optimal for a more organized severe weather threat. Nevertheless, a pulse severe threat will remain a concern Tuesday afternoon and evening with downburst winds the primary concern. Slow storm motions of 15-20 kt from west to east couple with PWats approaching 2 inches will contribute to a localized heavy rain threat. HREF LPMM indicates a couple very isolated pockets of heavy rain (3-5 inches) will be possible. Wednesday and Thursday will be characterized by weak upper level troughing over the Great Lakes region with weak surface ridging over much of the Midwest. Typical summer-time pop-up storms will be possible each day within the weakly forced and modestly unstable environment. Weak deep layer shear and more modest MLCAPE values peaking 750-1250 J/kg both days will keep the severe threat in check, but a brief pulse wind threat cannot be completely ruled out along with slow moving storms that will be capable of locally heavy rain. Friday and Saturday will see a more notable upper wave traverse the northern Great Plains and Upper Midwest. In response to this wave, a warm front will lift across central Illinois Friday. A low level jet developing Friday evening off to our west will allow storms to develop and grow upscale and eventually track east along the warm front into portions of Illinois late in the evening and overnight. A severe threat will likely materialize with this system, and depending on specific timing, could translate east into portions of central Illinois. A cold front sweeping across the region Saturday will result in another round of showers and storms, again with a possible attendant severe threat depending on timing and location of the synoptic front or effective cold front as determined by the remnants of the Friday night storms. Deubelbeiss && .AVIATION... (For the 06z TAFs through 06z Tuesday Night) Issued at 1208 AM CDT Tue Jul 8 2025 In the short term, quiet conditions expected aside from some patchy light fog in east central Illinois toward daybreak. Main concern will be with potential for thunderstorms in the afternoon hours. Much will depend on residual boundaries from convection currently west of the Mississippi River, but will maintain the PROB30 mentions at all sites with some timing refinements based on the 00z model guidance. Outside of the storms which will drop visibility briefly, VFR conditions will prevail. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$