Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
164 FXUS63 KMKX 062059 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 359 PM CDT Mon May 6 2024 .KEY MESSAGES... - Showers and thunderstorms are expected Tuesday morning. Additional showers and thunderstorms are possible in the afternoon and evening, a few of which could be strong to severe. - Small craft conditions are expected Tuesday. - Showers and thunderstorms are possible Wednesday afternoon through Thursday. && .SHORT TERM... Issued 357 PM CDT Mon May 6 2024 Tonight through Tuesday night: Quiet weather across southern Wisconsin this evening as high pressure across the upper Great Lakes continues to influence the region with overnight lows generally in the mid 50s. Attention remains on the shower and thunderstorm potential on Tuesday. A mid-level shortwave trough over the northern Great Plains will propagate eastward this evening and overnight. Strong positive vorticity advection combined with divergent flow and increasing southwesterly wind speeds at 500hPa will lead to strong synoptic scale ascent in the mid to upper levels. A mature surface low pressure center currently situated across the Great Plains associated with the upper trough will also propagate eastward overnight. The mature to decaying low and associated warm/occluded front will begin to enter southwestern Wisconsin around 5am with showers and thunderstorms expected along the boundary (80-90%). This initial line of storms are not expected to be severe. Additional development is possible behind the front as low level winds become southwesterly and strong 500hPa cold air advection steepens mid-level lapse rates to 7-8 C/km. These aspects combined with CAPE values of 1000-1500 J/kg will lead to an environment favorable for large hail. A well- mixed boundary layer identified by model forecast soundings may also lead to some gusty winds at the surface with thunderstorms that are able to develop. Overall, the severe threat for tomorrow afternoon is marginal at this time. The synoptic and mesoscale environments appear to be conducive to severe weather in afternoon, but this is dependent on the ability of cloud coverage to clear out of southern Wisconsin. Current model guidance suggests dry air in the low levels may enter southwestern Wisconsin tomorrow afternoon to help erode cloud coverage. Given this and southwesterly winds behind the front, thinking that southwestern Wisconsin is the area most likely to recover from the morning`s convection and thus most likely to see strong to severe storms. Falkinham && .LONG TERM... Issued 357 PM CDT Mon May 6 2024 Wednesday through Monday: The 500 mb low over the Central Plains should slowly shift east southeast into the area Wednesday into Thursday morning, then merge with a trough and shift to the east southeast of the area Thursday afternoon into Thursday night. Surface cyclogenesis should develop to the south of the area later Wednesday into Wednesday night per EPS/GEFS/CMC ensemble output, with the low shifting to the east of the region Thursday into Thursday night. This should keep most of the surface-based convection to the south of the area, as well as most of the severe weather risk. There could still be some elevated storms that develop later Wednesday afternoon or Wednesday night that produce small hail, as there should be at least weak elevated CAPE with decent effective layer shear. The easterly flow in the low levels later Wednesday into Wednesday night should maintain a cap to any low level air parcels. Differential CVA with the passing 500 mb low/trough and 850/700 mb frontogenesis response should bring rounds of showers and some storms mainly Wednesday night into Thursday morning, before slowly moving east Thursday afternoon and night. Ensemble QPF is generally in the 0.50 to 0.70 inch range for this period. 500 mb Cluster Analysis from ensembles shows an anomalous trough lingering over or east of the region Friday through the upcoming weekend. This should keep the area in a general northwest flow aloft for the most part, with a 500 mb trough shifting southeast through the region Saturday. A cold frontal passage may accompany this feature. Left PoPs going for chances for showers and a few thunderstorms for the Friday night into Saturday period. Temperatures should remain near seasonal normals into Saturday. Trends are more uncertain for Sunday into Monday, so left NBM PoPs and temperatures for now. Wood && .AVIATION... Issued 357 PM CDT Mon May 6 2024 VFR conditions are expected at all TAF sites through this evening. A FEW deck of diurnal cumulus has developed this afternoon across southeastern Wisconsin and is expected to dissipate as we lose heating. Overnight, an area of low pressure and associated warm front will move northeastward towards Wisconsin. MVFR to IFR ceilings/visibilities as well as showers and thunderstorms associated with the front will impact all TAF sites Tuesday morning through the early afternoon. Additional showers and thunderstorms are possible Tuesday afternoon provided cloud coverage can clear out of southern Wisconsin early enough in the afternoon. Falkinham && .MARINE... Issued 357 PM CDT Mon May 6 2024 East to northeast winds will continue across Lake Michigan this afternoon and overnight into Tuesday as high pressure continues to influence the Great Lakes region. Winds will begin to accelerate and take on a southerly component by Tuesday morning, mainly over the southern half of the lake as low pressure across the Great Plains propagates northeastward towards the Great Lakes. A Small Craft Advisory is in effect from 7am to 7pm on Tuesday due to these accelerating winds. Showers and thunderstorms will accompany the low Tuesday morning and is expected to impact Lake Michigan by the afternoon. Winds will turn southwesterly Tuesday night as the low pressure moves eastward before becoming northeasterly Wednesday afternoon as another area of low pressure propagates towards the Great Lakes region. Additional showers and thunderstorms are possible Wednesday afternoon into Thursday, mainly across the southern half of the lake as the second area of low pressure moves eastward, south of Lake Michigan. High pressure then builds in briefly on Friday. Falkinham && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645...7 AM Tuesday to 7 PM Tuesday. && $$ 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