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RyanDe680

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    Winter Storm? Jan 18-19th, 2019

    in Lakes/Ohio Valley

    Posted

    LOT update:

      

    .UPDATE...
1038 AM CST

In summary, no significant changes to the message for this event
this morning. One element we did alter was the mid-late afternoon
snow potential, confining the highest likelihood of commute
impacts to I-90 and north.

Will have more in the afternoon discussion overall, but will
briefly describe some observational trends tied to onset time and
evolution into the evening. The well-defined northern stream mid-
level wave across southeast South Dakota has been mainly moving
due east, a little further north than guidance indicated last
night. This will start to trend more east-southeast as a gradual
phasing with the southern stream low begins to occur. The active
baroclinic zone draped from the Minnesota/Iowa border region into
southwest Wisconsin this morning is gradually filling in with
snow, some heavy. As this has filled in it has slowed its northern
progress. Extrapolating its current development would bring it
into the northern CWA this afternoon, and more so the far northern
CWA (I-90 and north) as it becomes robust around sunset. High-
resolution guidance generally supports this. There may be a period
mid-afternoon where further south of that does still see snow,
but the stronger frontogenesis (f-gen) and vertical circulation
for appreciable snow looks to be more focused in the far north.

As broader synoptic forcing overspreads the region this evening,
snow should spread from west to east across the area. F-gen
signatures become somewhat transient, but there remains
indications of that as the systems gradually phase in the broad
northern precipitation shield over the area. General snowfall
forecast amounts still look good. Some parts of the I-88 corridor
have been lowered just slightly because of the aforementioned
mid-late afternoon expectations.

While could justify backing up the start time of some of the
warning counties along I-88 that begin at 3 pm, the northern
parts of these counties, including Cook, could certainly still
get into the f-gen driven more moderate snow. So have left as is.

    Winter Storm? Jan 18-19th, 2019

    in Lakes/Ohio Valley

    Posted

    LOT

      

    As indicated above, just getting a quick look at the new 00Z NAM
guidance. Fairly similar to previous runs, and continues to
highlight areas along/north of the I-88 corridor across far
northern IL for the greatest snowfall potential with similar
timing going into Friday night. Perhaps a slight (half county)
shift southward with the main frontogentically-forced QPF axis
Friday evening, though basically little change to current
forecast. In collaboration with surrounding offices have made no
changes to going headlines at this time. Midnight shift will have
full suite of 00Z guidance available for possible upgrades.
    • Thanks 1

    Winter Storm? Jan 18-19th, 2019

    in Lakes/Ohio Valley

    Posted

    Ther euro seems to have continued the trend of making this significant.  Going out on a limb saying that plays out and shifts north.  If the system digs SW and moves NE or ENE and negatively tilts, all bets are off then when it comes to amounts   

    I dread the bitter cold to follow.  

    • Like 3
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