Rockford Scanner™: Warmer With A Slight Chance of Severe Weather




 

It will be bit warmer today, but mainly dry. Some showers and a few non-severe thunderstorms are possible overnight into early Wednesday, along with increasing humidity. The heat and humidity should reach the lakefront Wednesday after morning clouds dissipate. Expect another round of thunderstorms on Wednesday later afternoon and evening, some of which may be severe. Cooler and drier conditions will return to end the work week

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEDNESDAY INTO
WEDNESDAY NIGHT ACROSS PARTS OF THE UPPER MIDWEST AND GREAT LAKES REGION INTO MIDDLE MISSISSIPPI VALLEY…

…SUMMARY…
Severe thunderstorms are possible Wednesday into Wednesday night
across portions of the Upper Midwest into the Great Lakes region and
middle Mississippi Valley.

…Synopsis…
A prominent mid-level subtropical high center appears likely to
undergo further strengthening/expansion over the southern Rockies
and surrounding areas of the Colorado Valley, Great Basin and
central and southern Plains during this period. Around the northern
periphery of this feature, anticyclonic mid-latitude westerlies
across the Pacific Northwest through the Montana international
border area and northern Plains may broaden, in the wake of one
amplified short wave trough forecast to progress east and southeast
of the Upper Midwest/upper Great Lakes region. Another short wave
digging across northern portions of Alberta, Saskatchewan and
Manitoba may contribute to the suppression of the ridging.

A modest surface cyclone may accompany the lead trough, with a
relatively well-defined cold front forecast to advance southeastward
into the lower Ohio/Middle Mississippi Valley region and south
central Plains by 12Z Thursday. It still appears that a corridor of
moderate to strong boundary layer destabilization ahead of the front
will provide the primary focus for possible severe thunderstorm
development Wednesday through Wednesday night.

…Upper Midwest/Great Lakes into middle Mississippi Valley…
Models indicate that the larger-scale short wave trough will be
comprised of several fairly significant smaller-scale perturbations,
with lingering spread evident within the model output concerning
their evolution. This contributes to at least some uncertainty
concerning convective evolution for this period, and it remains
unclear what impact the relatively cool waters of Lake Michigan may
have.

It does still appear that one impulse will pivot across Wisconsin
toward the upper peninsula of Michigan and Lake Michigan during the
day Wednesday. As it does, the strongest southwesterly mid/upper
flow is forecast to nose northeastward across this region and
contribute to strong deep-layer shear supportive of supercells. It
remains more unclear whether low-level wind fields will be strong
enough to contribute to sufficiently large low-level hodographs
supportive of tornadic potential, but any appreciable risk for
tornadoes during this period may become focused across northeastern
Wisconsin into the upper peninsula of Michigan.

Otherwise, gradually evolving and organizing clusters of storms
posing a risk for potentially damaging wind gusts, and some risk for
severe hail, appears the primary concern, southward across northern
Illinois, parts of eastern Iowa and northeastern Missouri. This
will be aided by inflow of air characterized by moderate to large
CAPE (2000-3000+ J/kg), and perhaps forcing for ascent and
strengthening lower/mid tropospheric flow (30-40+ kt at 700 mb) with
another smaller-scale impulse digging southeastward toward the lower
Ohio Valley through Wednesday night.

Farther north, models indicate that boundary-layer destabilization
associated with low-level moisture advection may allow for upstream
storms to re-intensify while spreading eastward into and across
lower Michigan Wednesday evening.

…MAXIMUM RISK BY HAZARD…
Tornado: 5% – Slight
Wind: 15% – Slight
Hail: 15% – Slight