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ILSNOW

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    5/15(northern half) & 5/16(southern half of subforum) Severe Wx Threats

    in Lakes/Ohio Valley

    Posted

    Chicago NWS Izzi update 

    Strong instability and strong and strengthening shear profiles
will favor supercell development along the dryline this
afternoon. Orthogonal nature of the shear vector orientation
with respect to the boundary suggests that storms could break
off the boundary and potentially remain discrete/semi-descrete
supercells as they move across the CWA. Primary threat should be
large, potentially destructive hail up to 3" in diameter.
Locally damaging downburst winds are also a threat.
    • 100% 3

    4/2-4/3 Potential Major Severe WX Outbreak

    in Lakes/Ohio Valley

    Posted

    Great read from Izzi 

    The forecast shear profiles are very concerning Wed afternoon
and evening with 40-50kt of south-southwesterly flow at 925 mb
veering to southwesterly at over 100kt at 500mb. This results in
very long and exceptionally favorable hodographs for
supercells. Very large, cyclonically curved hodographs in the
0-1km layer with mostly streamwise vorticity also would favor
the potential for tornadoes, especially given the low LCLs.

While the shear profiles are extreme, there remains considerable
uncertainty. First, does the forecast magnitude of instability
actually materialize as modeled tomorrow afternoon. Second,
convergence looks rather weak along the front and it is unclear
if it will be enough for convective initiation, assuming
sufficient instability. Finally, guidance generally has our CWA
in the convergent, right exit region of the strong upper level
jet.

Ultimately, there are many potential scenarios where we end up
with only weak, non-severe convection in the late
afternoon/early evening or no convection at all. Unfortunately,
given sufficient instability and intense convection develops,
the potential would exist for fast moving tornadic supercells,
with the potential for strong tornadoes.
    • Like 3

    March 14-15 Severe Weather Outbreak

    in Lakes/Ohio Valley

    Posted

    From storm prediction center  

     The northern portion of this convection will be oriented more orthogonal to the ejecting
 mid-level jet, and current expectations are for quick upscale growth
 into a fast northeastward-moving band, posing a risk for widespread
 severe/damaging winds as this activity moves into IA and towards the
 MO/IA/IL border region. Given the strength of the low/mid-level flow
 and presence of steep lapse rates aloft, along with a well-mixed
boundary layer, intense thunderstorm straight-line gusts peaking
locally in the 80-100 mph range are possible with the stronger
cores/inflections in the band as it matures and moves across parts
 of the mid MS Valley, and eventually into the southwestern Great
 Lakes this evening through tonight.
    • Like 4

    March 2025 General Discussion

    in Lakes/Ohio Valley

    Posted

    Chicago NWS 

     
    While the strength of this system is expected to begin a
weakening trend as it encounters more confluent mid-level flow
across the western Great Lakes on Friday, there is concern that
the snow could still fall at moderate to heavy rates at times
(up to an inch per hour) during the day. This occurs as a band
rather potent 850 to 700 mb frontogenesis looks to set up right
across northern IL during the late morning and afternoon. Model
cross sections across this tightening baroclinic zone depict a
rather classic frontogenetical response, with forced ascent
right into a layer characterized by negative Theta-E lapse rates
(convectively unstable) through the DGZ. This suggests that
some narrow heaver bands of snow will certainly be possible,
with the most favored location for this being areas from I-80
northward late in the morning through the afternoon.

Surface temperatures are expected to remain near freezing across
far northern IL during the snowfall into Friday afternoon.
Accordingly, this raises questions as to the extent of road
snow accumulations and hence if any real travel impacts other
than reduced visibilities will materialize. Current thinking is
that most areas will only see some slushy accumulations on area
roads, but in an areas that happen to fall under one of the
more intense narrow bands, the snow may fall at a high enough
rate to result in some snow covered roads and possible travel
impacts. Unfortunately, however, the exact locations in which
these narrow intense snow bands setup are very difficult to
pinpoint with any degree of skill this far out. At this time,
the most favored area for these bands of heavy snow resides
north of I-80 in northern IL.

The precipitation will come to an end by early Friday evening.
Total snow accumulations of 2 to 3 inches (locally higher) look
favorable north of I-80. Farther south, (south of I-80) warmer
temperatures will limit accumulations, and may even result in
any lingering precipitation falling as rain in the afternoon.

     

     

     

    • Like 1

    2/14-2/15 Potential Major Winter Storm

    in Lakes/Ohio Valley

    Posted

    earlier this week the "pattern" had changed to a more active one and we were looking at 3 possible snowstorms (Thursday, this weekend and mid week) and even pro mets were talking about the high possibility of 10+ inches here in Chicago from the first 2 storms, we all know it didnt happen for a variety of reasons and the upcoming 3rd snow storm will hit our friends in Kansas and Missouri  (again).  Have you noticed that we NEVER get a good bust in our area (there is no way the mid week KS/MO storm moves north because of a 1050 high pressure).

    So basically our 7 days of winter (snow) are done and now we can look forward to dry weather and below zero wind chills at night till it warms up and rains in early March.

     

    2/12 Winter Storm

    in Lakes/Ohio Valley

    Posted

    ouch

    and Milwaukee just went WSW for Racine: 

    WINTER STORM WARNING IN EFFECT FROM NOON WEDNESDAY TO 3 AM CST
THURSDAY...

* WHAT...Heavy snow expected. Total snow accumulations between 6 and
  9 inches. Lake effect snow may bring locally higher totals.

    snku_acc-imp.us_mw.png

    • Haha 3
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