Sunrise 5:35 AM   Sunset 7:54 PM Moonrise 5:06 AM   Moonset 7:48 PM

  Print   HELP   Reset   Save   Recall  New

LMZ744 Expires:202405072115;;796687 Fzus53 Klot 071833 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 133 pm cdt Tue may 7 2024
for waters within five nautical miles of shore on lake michigan
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the waves, along with the average height of the highest 10 percent of the waves which will occasionally be encountered.
lmz743>745-072115- calumet harbor il to gary in-gary to burns harbor in- burns harbor to michigan city in- 133 pm cdt Tue may 7 2024
.tornado watch in effect until 8 pm cdt this evening - .
Rest of today - South winds 15 to 20 kt becoming southwest. Numerous showers and Thunderstorms. Waves 1 to 3 ft. Tonight - Southwest winds 10 to 15 kt. Slight chance of showers and Thunderstorms in the early evening. Waves 1 to 2 ft. Wednesday - Southwest winds 5 to 10 kt becoming east in the early afternoon and then northeast 10 to 15 kt late. Slight chance of showers and Thunderstorms in the afternoon. Waves around 1 ft. Wednesday night - Northeast winds 10 to 20 kt. Showers and slight chance of Thunderstorms in the evening, then showers likely and a chance of Thunderstorms overnight. Waves 1 to 3 ft.

LMZ700
No data

FXUS63 KLOT 071800 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 100 PM CDT Tue May 7 2024

KEY MESSAGES

- Thunderstorms expected this morning, which may produce gusty winds and/or small hail.

- A second round of scattered thunderstorms is likely this afternoon, with the highest confidence east and southeast of the I-55 corridor. A few of these afternoon storms could become severe with large hail and damaging winds as the primary hazards.

- Another round of storms may develop late Wednesday, some of which could be strong to severe, mainly south of I-80 into central IL/IN.

MESOSCALE UPDATE
Issued at 1259 PM CDT Tue May 7 2024

We're closely monitoring for an increased severe weather threat within the CWA through the mid to late afternoon. The area of greatest concern is across northwest Indiana where there is a more distinct tornado threat. The threat for damaging hail has also increased further northwest in the CWA, encompassing much of if not the entire Chicago metro area. Our window of severe weather potential is approximately from 1-5PM CDT.

17-18z analysis indicated a deep occluding surface low across the ND/SD border, its warm front lifting into southern Wisconsin, and its cold front back across eastern Iowa. A seasonably warm and moist air mass has developed across the warm sector, with temperatures in the 70s and dew points in the mid 60s, except across our far northwest (upper 60s) and the northeast IL shore (50s and 60s due to onshore winds).

Elevated convection is ongoing across northwest Illinois, where a hail and gusty wind threat is present. This area will continue to be monitored for severe hail up to 1" or so in diameter. A warning was recently issued for Ogle County.

The main focus for the more appreciable severe threat will be spurred by strong large scale ascent (mid-level PVA and height falls and upper jet support) and cold frontal convergence. Given already weak and eroding MLCINH, isolated cells across west central IL at the top half of the noon hour may be the beginnings of the anticipated convection ahead of the cold frontal zone.

While surface winds had been backed, we're seeing an anticipated veering to southwesterly taking place across northern and central Illinois. Effective bulk shear of 60+ kt, steepening mid-level lapse rates, sizable CAPE in the hail growth zone, and straightening hodographs with decreased low level shear present a favorable setup for splitting supercells with damaging hail as their main threat, some of which could be significant.
As such, in the 1630z SPC outlook update, severe hail probs have been spread farther northwest, and include the potential for 2"+ stones.

Near and east of I-57 in eastern Illinois and particularly across northwest Indiana is the area most likely to have a ~2-3 hour overlap of more backed southerly breezy southerly surface winds, strong low level shear with decent low-level hodograph curvature, 100-150 J/kg of 0-3 km MLCAPE, and aforementioned very strong deep layer bulk shear and steepening mid-level lapse rates. Supercells in this corridor certainly could be supportive of all hazards, including tornadoes. Given the shorter residence time of the most favorable parameter space, confidence in significant (EF-2+) tornado occurrence within the CWA is on the lower side and appears more favored just east and southeast of the CWA, though given the conditional sig-tor potential, SPC's 10% hatched tornado probs appear appropriate.

Farther north and west, certainly can't rule out a brief tornado threat, though the shortening and straightening hodographs seem to be a key limiting factor. The cold front passage this afternoon will quickly end the severe threat by 5 PM CDT or so.

Castro

DISCUSSION
Issued at 344 AM CDT Tue May 7 2024

Through Wednesday Evening:

Early morning Midwest radar mosaic depicts an extensive north- south linear MCS propagating east-northeast across eastern IA/MO. This MCS, associated with a potent negative-tilt mid- level short wave and surface cold front spreading east from the mid/upper Missouri Valley, will continue to push into northern IL and the WFO LOT forecast area after 5 am. The surface cold front was in the process catching up to a warm front stretching from IA into central IL, which should allow storms to become slightly elevated farther east into IL, which along with the gradual diurnal decrease in low-level instability should result in a slow weakening trend as it moves into our area. Despite these trends, localized sub-severe gusty surface winds up to 50 mph will likely still be possible across our western cwa as this line arrives. While a few isolated to widely scattered cells may develop ahead of the line within increasing warm advection flow, the main line of storms should reach the Chicago metro area around 7-8 am.

The convective outflow/cold pool footprint from these morning storms will stabilize low levels through midday, with some question remaining regarding location/extent of diurnal destabilization across the forecast area this afternoon.
Kinematics certainly favor the potential for strong to severe storms, with the mid-level short wave trough steepening mid- level lapse rates and a 75+ kt mid-level jet spreading across the area. Guidance continues to indicate the bulk of morning convection clearing the area around noon, with around 1000 J/kg of MLCAPE developing by early afternoon. CAMs depict at least widely scattered to scattered thunderstorm redevelopment early- mid afternoon, though location and evolution is of somewhat low confidence. Severe storms are possible area-wide this afternoon with all hazards possible, though areas east/southeast of the I-55 corridor look to have a higher overall and higher tornado threat better low-level instability and stronger shear as the mid-level jet spreads east. The window for greatest severe threat is roughly from 1-2 pm through about 5 pm, with storms becoming more isolated thereafter. Coverage may be a bit better across northwest IL and along the IL/WI border late in the afternoon.

Generally quiet weather is expected tonight into Wednesday morning, as the mid-level short wave lifts northeast of the area and short wave mid-level ridging develops overhead. Breezy southwest winds later today will diminish overnight, as weak surface high pressure slides across the area.

Another round of showers and thunderstorms is expected to develop Wednesday afternoon into Wednesday night, as the next short wave approaches the area. A surface low pressure wave is expected to develop along the cold/stationary front which will trail across the southern Plains in association with this wave, which will then propagate northeast into the mid-Mississippi Valley by Wednesday evening. Renewed warm advection return flow will help push the front north across central IL/IN as a warm front during the period, with showers and thunderstorms developing northeast into the forecast area during the afternoon. Details remain somewhat unclear with the track of the surface wave and frontal position by Wednesday evening, with various guidance showing quite a bit of spread. A more northerly low/warm front track into our southern cwa would likely present a greater severe weather threat.

Ratzer

Late Wednesday Night through Monday:

A mid-level trough extending southwest across Quebec and southern Ontario will phase with a mid-level low over the Missouri Valley Wednesday night. As the phasing wave crosses the area on Thursday, a residual low to mid-level TROWAL combined with PWATs around 1" and a deep layer favoring warm rain processes supports the potential for a low-end localized band of heavy rain (1-2") across portions of northern Illinois into southern Wisconsin late Wednesday night into Thursday. Outside of this band, scattered diurnally enhanced showers and perhaps a few storms are expected.

After a quick-moving ridge yields dry and seasonable temps on Friday, another upper-level low is progged to cross the western Great Lakes on Saturday. Anomalously cold mid-level temps shifting across the area through the day will yield scattered showers and storms, with some stronger cores likely producing locally strong wind gusts. Diverging solutions by early next week with regards to handling of the departure of Saturday's upper low and a building ridge to the west greatly diminishes the forecast by early next week.

Kluber

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
Issued at 1259 PM CDT Tue May 7 2024

Key Aviation Messages:

- Scattered TSRA, possibly locally severe this afternoon - SE winds shifting SW and gusting over 20 knots around 19Z

Satellite analysis depicts MVFR clouds growing in depth to become more concerning for thunderstorm expansion across NE Illinois in the 18z-19z hour and then expanding into NW Indiana after 19z or so. The storms in around Chicago and points westward do pose a threat for hail along with winds in excess of 35 kt. The main window for storms will continue until about 23-0z, longest in NW Indiana, with the main window for the Chicago terminals through 2230z.

VFR conditions will return behind the storms this evening, with initially breezy SW winds easing overnight. Winds will shift southeasterly and then easterly through the late morning into the afternoon Wednesday. Another batch of precipitation will shift toward NE Illinois later in the day. Confidence in thunder toward the tail end of the 30 hr TAF is still below 30 percent.

KMD

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...None.

toggle option: (graph/table)

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Northern Indiana, IN,