Area Forecast Discussion · National Weather Service Milwaukee (MKX) · issued Sunday, July 26 at 1:28 AM CDT.
Revised in 10 passages since the 7:56 PM discussion. See every revision.
Messages
Hot and humid conditions Sunday and Monday are likely. A Heat Advisory is in effect from noon to 9 PM CDT Sunday. Additional Heat Advisories may be needed Monday.
A line of storms may impact far southwestern Wisconsin early Sunday morning.
Isolated to scattered storms may develop Sunday afternoon and evening. Large hail and damaging winds would be possible with this activity. Sunday night, a line of storms with damaging winds and hail is expected to develop and progress southeastward.
Monday, a cold front will bring final chances for storms to southern Wisconsin. All hazards are possible with this activity, but confidence in exact timing and placement remains dependent on Sunday night storms.
Short Term
Currently keeping an eye on Minnesota as convection has blossomed over the central portions of the state. Rapid refresh CAMs suggest a dying MCS may clip the southwestern portions of our forecast area near daybreak on Sunday. If this were to occur, gusty winds and hail would be the main hazards.
Subsidence is then expected following this morning convection and skies should clear. Dew points are expected to rise into the mid 70s tomorrow, amid daytime highs in the low 90s. This will lead to heat indices in the 100 to 103 range over much of the area tomorrow. The weak pressure gradient will promote a lake breeze which may keep the immediate lakeshore cooler for tomorrow. A Heat Advisory has been issued for much of southern WI from Noon to 9PM today.
It looks increasing likely that storms will hold off until either the evening or overnight hours tonight into Monday. One constant among the CAMs is that an MCS will fire closer to the 500mb trough over northern WI/UP of Michigan and propagate south-southeast into central WI. However, CAMs vary regarding timing/positioning, as some have this complex further east over Lake Michigan, while others have this MCS tracking south into our forecast area around midnight. In either scenario, it does look like convection may linger through the night following the main MCS as the low level jet triggers new storms along an outflow boundary. With whatever MCS gets going, gusty winds and hail will be the main threats, as DCAPE will be near 1100 J/kg, mid level lapse rates will be near 8 C/km, and effective bulk shear will approach 70 knots. A conditional boundary interaction with the remnants of the lake breeze may lead to a sneaky QLCS tornado threat on an isolated basis, provided the boundary doesn't wash out quickly after dark.
Weak convection then may linger into Monday with some potential for storms to reinvigorate ahead of a cold front with daytime heating late Monday. Given the potential for convection and cloud cover to linger during the day, have held off on hoisting a Heat Advisory for Monday at this time until details about Monday's convection become clearer.
Long Term
Mid week looks quiet as a surface high pressure ridge builds into the upper Great Lakes region. Northeast surface flow Tuesday and Wednesday should promote more manageable dew points in the low 60s and daytime highs in the low to mid 80s. precipitation chances then return late week as a warm front lifts northward into the region and humidity mildly increases.
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