Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
909 FXUS63 KMKX 200923 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 423 AM CDT Mon May 20 2024 .KEY MESSAGES... - Unsettled Monday and Tuesday with several rounds of rain/storms. - Risk 2 out of 5 for severe thunderstorms exists today primarily over the southeastern corner of our CWA at this time. The main threats are gusty winds and hail. - While there remains uncertainty on the exact specifics of the severe weather threat Tuesday, there remains a higher chance (risk 3 out of 5) for severe weather on Tuesday with all modes of severe weather (large hail, damaging winds, and tornadoes) possible. Overnight storms Monday into Tuesday and how they track/evolve over IA/IL will impact the development and environment Tuesday afternoon and evening. && .SHORT TERM... Issued 423 AM CDT Mon May 20 2024 Today through Tuesday night: Early this morning a band of rain/storms is moving through southern Wisconsin. This initial band of showers is expected to be on the weaker side and will continue to diminish/weaken as it traverses east away from the LLJ and shortwave trough. This line of showers is currently supporting this thought process well as it has been very outflow dominate over the last few hours. Behind this band, further up stream, is the MCV feature that brings our concern for severe weather today. The lull between the ongoing rain the MCV will be a big determining factor in how much sfc instability we will have. The MCV is currently being supported by the LLJ and shortwave trough approaching the state. The best chances for strong to severe storms late this morning into the afternoon will likely be across southeastern and eastern Wisconsin where conditions are currently dry. The ongoing line is likely to weaken significantly early this morning. This should keep the environment primed for when the MCV rolls through. Overall the biggest threat from any stronger storms will be hail. Can`t rule out some gusty winds, but thats gunna be more likely from towering storms that fall apart quickly than anything else. Tuesday brings the next chance for rain and storms as the next upper level shortwave moves through. This next system will be more robust than the previous provide southern Wisconsin with a greater chance for severe weather. There are two "rounds" of rain/storms expected Tuesday, one along the warm front and a second along the cold front. The cold front will be the main driver for our severe potential. Overall the environmental setup will have decent moisture, great low level instability and some upper level synoptic support. 0-3km shear will be high and hodographs are taking on that nice curved feature. This allows all storm modes to be possible with the main hazard concerns being winds and tornadoes. Tornadic potential at this point leans toward the short-lived quick spin up type. Now the bigger issues with the amount of synoptic support with this shortwave and the warm front. Uncertainty in how far north the warm front will move north and the timing this will occur are the biggest factors. If these two "rounds" run together then it would be hard for the environment to recover and it would reduce the severe potential. On the other hand, if the warm front surges northward with a significant break between it and that cold front. Then the door opens up for more supercellular like behavior along and ahead of the cold front. Behind the front, quieter weather is expected to return. Patterson && .LONG TERM... Issued 423 AM CDT Mon May 20 2024 Wednesday through Sunday: The cold front and dry slot will be clear of southern WI by Wednesday morning, per the majority of models and ensembles. There may be a few strato-cu showers toward central WI with any wrap- around precip from the exiting upper low. Otherwise, expect gusty westerly winds and cooler temperatures around 70. Thursday through Sunday high temps will also be in the lower to mid 70s, with lows in the lower 50s, much more seasonal for this time of year. The next chance for showers and thunderstorms will arrive Friday afternoon or night to kick off Memorial Day Weekend. This is associated with an upper low tracking across southern Canada and remnant vorticity advection over southern WI. As the case has been lately, the GFS goes crazy with the QPF and also brings the front through WI earlier than the ECMWF (by at least 12 hours). The low level jet, warm air advection, and a weak shortwave justify our small chances for showers and storms Fri evening. One more shortwave digging through the Plains is expected to swing across WI on Saturday. The ECMWF came in with a similar idea to the GFS for the 00z run. While there is still plenty of time to work out the details, the risk of showers and storms sometime Saturday-Sat nt is there. Weak ridging moves in Sunday, so precip chances are much lower for that period. Cronce && .AVIATION... Issued 423 AM CDT Mon May 20 2024 VFR to IFR conditions are expected throughout the period. Lower ceilings and visibilities are expected with the multiple rounds of rain and thunderstorms this morning through Tuesday. The first round moving through early this morning will likely have VFR ceilings around 8 kft with visibilites of 2-4 SM with the moderate to heavy rainfall. Rain will likely persist into the afternoon before beginning to wane today. The is a chance for some gusty winds and small hail with thunderstorms late this morning. Overnight tonight there should be a lull in the rain/ storms between the two systems. With low level moisture high, there is a small chance for some patchy fog to develop but chances are low as skies are expected to remain overcast and winds should be high enough to prevent development. Sheltered low lying areas would likely have the best chance. Tuesday will bring the next round(s) of rainfall. One round along the warm front and a second with the passage of the cold front. There is uncertainty how much of a break there will be between these rounds. Southeast to southwest winds are expected throughout the period with breezy winds expected Tuesday. Patterson && .MARINE... Issued 423 AM CDT Mon May 20 2024 Light and variable winds over Lake Michigan will continue early this morning before shifting to southeasterly. Winds will become southwest to westerly by this afternoon as a weak low pressure system traverses the Great Lakes Region. Monday night into Tuesday southeast winds return as another stronger low pressure system advances from the Central Plains. This low pressure system will deepen as it moves into the Great Lakes Region causing southerly winds to increase. A Small Craft Advisory will likely be needed Tuesday night into Wednesday for the breezy southwest winds. Patterson && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && $$ 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