Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
432 FXUS63 KMKX 141955 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 255 PM CDT Tue May 14 2024 .KEY MESSAGES... - Light rain and overcast skies today, clearing tonight for dry conditions Wednesday. - Additional rounds of showers and storms expected to impact southern Wisconsin Thursday and into this weekend. && .SHORT TERM... Issued 255 PM CDT Tue May 14 2024 Tonight through Wednesday night: Weak 925-850mb frontogenesis and plenty of moisture in the 850-700mb level, along with deformation in the upper levels, are responsible for the lingering clouds and light showers/drizzle. Weak low pressure slowly moving across southern WI this afternoon will make its way to the Ohio River Valley while weakening tonight through Wednesday. With the slower movement of this system, the clouds are much slower to clear across southern WI this afternoon. In fact, mid level clouds may linger across southeast WI until mid Wednesday morning due to the lack of any advection of dry air. Once the clouds do clear from northwest to southeast late tonight to mid Wednesday morning, temps will increase into the lower 70s for inland areas. The onshore winds will keep lakeshore areas cooler, but warmer than today, with highs in the 60s. Cronce && .LONG TERM... Issued 255 PM CDT Tue May 14 2024 Thursday through Tuesday: A surface low pressure center will propagate into northwestern Wisconsin Thursday morning supported by a weakening 500hPa shortwave trough before moving off into Lake Superior by Thursday night. Forcing via the associated occluded front is expected to move eastward across the state throughout the day which combined with the upper trough and low level moisture advection will bring precipitation chances to southern Wisconsin (60%-70%). MUCAPE of 500-1000 J/kg and ~30kt 0-6km bulk shear suggests thunderstorm development along the boundary is possible with a generally discrete storm mode currently expected given 0-6km shear is roughly perpendicular to the front. Model soundings also depict a saturated column with PWATs of ~1.25 inches and mid-level lapse rates of ~6.5 C/km which suggest that showers and storms that develop will likely be efficient rain producers. Decreasing clouds and drier conditions are expected on Friday, but with another weak shortwave trough and PVA running across the state combined with a well-mixed boundary layer, there may be showers and perhaps a few rumbles of thunder across southern Wisconsin in the afternoon (20%-30%). A lot of uncertainty surrounds the forecast this weekend. Models are starting to come into better agreement surrounding a 500hPa shortwave trough and surface low traversing the northern Great Plains Friday night into Saturday before entering the Great Lakes region on Saturday night. Amplitude and timing of this trough are still things to monitor with coming model runs, but it is noteworthy that the long range deterministic guidance now depicts this 500hPa trough as compared to a few runs ago where there was discrepancy between if zonal or meridional flow was dominant aloft. Have stuck with NBM guidance for the weekend due to this uncertainty. However, upper level ridging and surface high pressure appear to build across Wisconsin on Monday before precipitation chances return again on Tuesday. Falkinham && .AVIATION... Issued 255 PM CDT Tue May 14 2024 MVFR ceilings between 1400 and 3000 ft are hanging on across far southern WI due to low pressure over southern Illinois. Light showers and drizzle are still ongoing across southern WI, but there is a diminishing trend. Gusty northeast winds are expected along the lakeshore into mid evening, with lighter winds for inland areas. Skies will clear from northwest to southeast very gradually, and may not clear across far southeast WI until mid Wednesday morning. Cronce && .MARINE... Issued 255 PM CDT Tue May 14 2024 Low pressure over southern IL will continue to weaken overnight as it tracks along the Ohio River Valley. Northerly winds up to 30 kt over Lake Michigan will diminish overnight, but remain northerly into Wednesday evening. Southerly winds will develop Thursday as a weak low pressure trough tracks into western WI Thursday afternoon. Scattered showers and thunderstorms are expected along the trough. Winds will become variable behind the trough passage Friday as weak high pressure builds over the Upper Great Lakes. The pattern remains unsettled for the weekend with chances for showers and thunderstorms, but no periods of elevated winds are anticipated. Cronce && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 AM Wednesday. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSMilwaukee www.twitter.com/NWSMilwaukee www.youtube.com/NWSMilwaukee