Issued by the National Weather Service
For Winnebago County, Illinois
EXCESSIVE HEAT WARNING UNTIL 7PM CDT SAT …EXCESSIVE HEAT WARNING IN EFFECT UNTIL 7 PM CDT SATURDAY…
THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED AN EXCESSIVE HEAT WARNING, WHICH IS IN EFFECT UNTIL 7 PM CDT SATURDAY.
THE HEAT ADVISORY IS NO LONGER IN EFFECT. * HIGH TEMPERATURES…94 TO 96 DEGREES TODAY AND SATURDAY. * MAXIMUM HEAT INDICES…110 DEGREES TODAY AND 105 TO 110 DEGREES SATURDAY.
* IMPACTS…THE CUMULATIVE EFFECTS OF TEMPERATURES AND HEAT INDEX VALUES THIS HIGH COULD LEAD TO HEAT RELATED ILLNESSES WITH PROLONGED EXPOSURE.
THOSE WITHOUT AIR CONDITIONING, ELDERLY, SMALL CHILDREN, AND PETS ARE ESPECIALLY SUSCEPTIBLE. PLAN AHEAD. HAVE A COOL PLACE TO SHELTER FROM THE HEAT. AVOID OUTDOOR ACTIVITY, ESPECIALLY STRENUOUS ONES, DURING THE PEAK HEATING TIMES OF THE DAY. PRECAUTIONARY/PREPAREDNESS ACTIONS…
TAKE EXTRA PRECAUTIONS…IF YOU WORK OR SPEND TIME OUTSIDE. WHEN POSSIBLE…RESCHEDULE STRENUOUS ACTIVITIES TO EARLY MORNING OR EVENING. KNOW THE SIGNS AND SYMPTOMS OF HEAT EXHAUSTION AND HEAT STROKE. WEAR LIGHT WEIGHT AND LOOSE FITTING CLOTHING WHEN POSSIBLE AND DRINK PLENTY OF WATER. TO REDUCE RISK DURING OUTDOOR WORK…
THE OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION RECOMMENDS SCHEDULING FREQUENT REST BREAKS IN SHADED OR AIR CONDITIONED ENVIRONMENTS. ANYONE OVERCOME BY HEAT SHOULD BE MOVED TO A COOL AND SHADED LOCATION. HEAT STROKE IS AN EMERGENCY…
CALL 9 1 1. AN EXCESSIVE HEAT WARNING MEANS THAT A PROLONGED PERIOD OF DANGEROUSLY HOT TEMPERATURES WILL OCCUR. THE COMBINATION OF HOT TEMPERATURES AND HIGH HUMIDITY WILL COMBINE TO CREATE A DANGEROUS SITUATION IN WHICH HEAT ILLNESSES ARE LIKELY. DRINK PLENTY OF FLUIDS…STAY IN AN AIR-CONDITIONED ROOM…
STAY OUT OF THE SUN… AND CHECK UP ON RELATIVES AND NEIGHBORS. YOUNG CHILDREN AND PETS SHOULD NEVER BE LEFT UNATTENDED IN VEHICLES UNDER ANY CIRCUMSTANCES.
THIS IS ESPECIALLY TRUE DURING WARM OR HOT WEATHER WHEN CAR INTERIORS CAN REACH LETHAL TEMPERATURES IN A MATTER OF MINUTES
Heat and humidity will be the big story on Wednesday prior to the possible PM thunderstorms and marginal severe risk ahead of a cold front. This will particularly be the case along and south of I-80, where peak heat index values of 100 to 105 degrees are forecast. Keep heat safety in mind if you plan to spend prolonged time outdoors on Wednesday.
Coverage of thunderstorms today could be somewhat low. However, any storms that develop will have the potential to become strong to severe with a threat for large hail (possibly to the size of golf balls) and damaging wind gusts (up to 60-70 mph). Conditions will rapidly improve from west-to-east through the mid-late evening hours as a cold front sweeps through the region.
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…
Severe thunderstorms are possible Wednesday into Wednesday night
across portions of the Upper Midwest into the Great Lakes region and
middle Mississippi Valley.
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
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.
I first want to thank everyone for sending in your storm photos. THANK YOU! I am still in the process of going through them all, so if I have not posted yours yet, I soon will 🙂
Cassie C. sent us these photos of a tree falling down onto a vehicle just feet from her and several people attending a birthday party at Big Hill Park in Beloit. She said ” We were at a birthday party today and one of the HUGE trees fell down on another guest’s car just feet away from us as we were loading up to leave. Thank goodness nobody was hurt. I’ll never forget the sound of a tree crashing to the ground and shattering a Suburban.”
Below are some photos that our fans have sent us, THANK YOU!
Showers and thunderstorms are likely to move across the area this afternoon and some of these storms may be severe. Large hail and damaging winds would be the primary severe threats. Heavy rainfall will also likely accompany these storms, and this could result in some risk of flash flooding if multiple storms track over the same areas. Make sure to have multiple ways of receiving watches and or warnings should they be issued later today.
Strong to possibly severe thunderstorms are likely to move across the area this afternoon. A rough timeline of the most likely windows for storms and severe weather is shown in this graphic. Be sure to check back for updates to this forecast and have multiple ways available to receive weather alerts should severe weather threaten!
Two rounds of storms are likely on Saturday. The first round is likely to come through the northern suburbs between 7 AM and 11 AM. Widespread severe weather is not expected with this round, but the stronger of these storms may produce some small hail. The second round of storms is expected to come through the area during the afternoon/early evening and may contain some severe storms with damaging winds, large hail, and possibly a tornado or two.
Dry conditions will remain through the evening. Hazy skies are possible tonight as a result of smoke from ongoing fires in southern Canada.
Storms are likely along and ahead of a cold front on Saturday.
Strong to severe storms will be possible.
Conditions will turn dry and cooler behind the cold front for Sunday.
Monday and Tuesday look to be dry and mild, with increasing rain chances late Tuesday.
A Flash Flood Watch has been issued for portions of north central Illinois for tonight. This watch could need to be expanded eastward to include portions of the Chicago metro area if forecast confidence continues to increase.
Have multiple ways to receive warnings if any are issued for your area. Do not drive onto flooded roadways- Turn Around, Don’t Drown!
Note: Clear off your sewer drains, so the water can flow freely and not cause any flooding.
A Tornado Watch has been issued until midnight for Winnebago, Lee, Ogle, LaSalle, Grundy and Livingston counties. Have multiple ways to receive warnings if any are issued for your area and a plan to access safe shelter if needed
URGENT – IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 236
NWS Storm Prediction Center Norman OK
625 PM CDT Fri May 24 2019
The NWS Storm Prediction Center has issued a
* Tornado Watchfor portions of
Northern and central Illinois
Far northeast Missouri
* Effective this Friday night from 625 PM until Midnight CDT.
* Primary threats include…
A few tornadoes possible
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 65 mph possible
SUMMARY…A few supercells should develop along a residual boundary
from eastern Iowa into west-central Illinois. This activity should
spread east-northeast in northern Illinois through late evening.
The tornado watch area is approximately along and 85 statute miles
north and south of a line from 45 miles north northwest of
Burlington IA to 40 miles north northeast of Bloomington IL. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU6).
REMEMBER…A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.
553 PM CDT
The weather forecast over the next 12+ hours remains fairly
complicated, and uncertainties abound mainly due to the weak
nature of large-scale forcing for ascent. While a threat for
strong to severe thunderstorms certainly exists this evening and
into the nighttime hours, how this threat materializes remains
tied to mainly subtle mesoscale processes and subtle waves of
synoptic ascent which are both difficult to diagnose and pinpoint
with much certainty.
Surface analysis late this afternoon depicts a northwest to
southeast arcing warm front–reinforced by this morning’s
convection which laid out an outflow boundary–likely just
entering portions of La Salle, Livingston, and Ford Counties.
Dewpoints immediately to the south of this boundary jump into the
70s with breezy south to south-southwesterly winds, and this
seems to be demarcated pretty well by an area of bubbling Cumulus
and HCRs which are steadily building northward. Recent RAP
soundings and SPC mesoanalysis reveal that this is a relatively
high-quality warm sector, with mean mixing ratios pushing 16 g/kg
and decent moisture through a fairly deep layer (up to 700 mb). An
earlier tornadic supercell, which was riding along the northern
extent of this warm frontal boundary, quickly dissipated a few
hours ago as it approached Bloomington, likely as it encountered a
pocket of warmer air aloft with 700 mb temperatures analyzed at
+9 to +10C. This is indicative of lingering capping, which has
thus far suppressed any additional convective initiation attempts
in the warm sector. Recent GOES-16 visible satellite loops reveal
some towering Cu development taking place across West Central
Illinois, however, where capping is lower due to cooler
Farther to our west, an additional area of bubbling cumulus has
been noted across central and eastern Iowa, although recent radar
trends suggest incipient updrafts are struggling to develop.
Large scale forcing for ascent is not strong here, but modest
mid-level height falls (20-40 m/12 hours) are noted in recent
analyses nosing into far northwestern Iowa at the leading edge of
a very subtle shortwave. It’s possible some lingering mesoscale
subsidence is still in place across eastern Iowa in the wake of
this morning’s MCS, tempering additional robust convective
development at this juncture, but conditions do appear favorable
for robust updraft development over the next few hours.
With this all laid out, it does appear there may be two favored
corridors for potential convective development over the next few
hours: /1/ near and south of the incoming warm front and /2/
across eastern Iowa. All modes of severe weather would be possible
across our area, including the threat for a few tornadoes. Deep
layer shear in excess of 50 kts will support rotating storms and
supercell structures and sizable CAPE in the hail growth zone
will foster large hail development, potentially to the size of
golf balls or even larger with some analogs supporting 2″+ hail
not out of the question.
Recent runs of the HRRR have been a bit concerning, developing
robust storms near the incoming warm front and into the I-80
corridor. Locally backed surface flow would support a tornadic
potential with these storms as they interact with the front and
gain access to considerable streamwise vorticity. Think it looks
too aggressive based on latest satellite trends, but we will need
to keep our eyes peeled for development near and south of I-80
during the 8 to 11 PM time frame. The other area of convection–to
our west in eastern Iowa–may attempt to develop into our western
counties later this evening, likely after 10 PM or so. A tornado
threat will continue here, although CAM guidance indicates some
propensity for storms to congeal into clusters which may
eventually deliver more of a damaging wind and hail threat as this
second area of activity pushes eastward into the overnight hours.
Finally, a flash flood potential does exist this evening and
overnight, although the spatial breadth and magnitude of this
threat still is uncertain due to the mesoscale processes involved.
Current thinking is that the Flash Flood Watch captures the
favored corridor well, and no immediate changes are planned.
As of 1 PM: We are monitoring for severe storms this afternoon across the area this afternoon. Best timing for the severe storms could start as early as mid afternoon and continue into the evening hours. Keep a close watch on the forecast for later watches and warnings.