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FXUS63 KMPX 261205 AFDMPX

Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 705 AM CDT Fri Apr 26 2024

KEY MESSAGES

- Widespread rain and gusty winds will be the theme today. Heaviest rainfall rates will be with late afternoon/evening activity.

- Marginal risk remains in place along I-90, where a cluster or two of elevated convection may pose a hail threat.

- Saturday is looking dry and mild, before another storm system brings widespread rain and t-storms for Sunday.

- Generally warmer in the extended forecast, which will likely persist into the start of May. Unsettled pattern brings additional shower chances for the middle and end of next week.

DISCUSSION
Issued at 310 AM CDT Fri Apr 26 2024

Temperatures are relatively mild across the region at this hour (50s in western/central Minnesota) thanks to breezy southeasterly flow.
All localities are currently dry, however that trend will not be the story for the majority of the day. A mature surface low spinning over the central Great Plains will pinwheel to the northeast through the day, resulting in widespread rain chances for all of south central Minnesota and western Wisconsin. The initial precipitation shield has lifted as far north as Sioux Falls and guidance is in excellent agreement that this activity will continue to push northeast through the morning hours. CAMs illustrate a few hours of rain at each location as the the initial round moves through, followed by a dry period before more wet weather develops.
Significant differences exist with regards to the arrival time of additional rain/storm chances for the second half of the day, however the general thinking is that any rain/storms that develop later on will produce more efficient rainfall rates due to the strengthening LLJ and proximity to the surface low (thus greater forcing). While there is plenty of shear available, guidance depicts an atmosphere that will be starved of much in the way of instability this evening, so most locations should not expect much more than gusty showers and perhaps a few rumbles of thunder. With that said, we'll have to keep an eye on the situation in southern Minnesota (along I-90) this evening, where the SPC has maintained a Marginal Risk for an isolated damaging wind/hail threat. It appears hail would serve as the more likely hazard of the two given steep mid- level lapse rates (~7.5 deg/km) and skinny CAPE profiles (MUCAPE ~500 J/kg). The severe weather risk is greater to the south in Iowa, however the current thinking is that any convection that can persist northward into southern Minnesota will likely be in a weakening phase given the expected lack of instability.

Rain chances will come to an end by daybreak Saturday, as the surface low tracks through western Minnesota. Saturday should be "nice" per the standards set by the next 3-day stretch, as mostly dry weather is expected. Highs will range from the 50s in west central Minnesota to the mid to upper 60s in southeast Minnesota and western Wisconsin. Sure, it will be mostly cloudy, but if you are looking fresh air Saturday will be the day for you.

Another strong storm system will move into the Upper Midwest for the second half of the weekend. Widespread rain is expected to arrive as early as Saturday night and will continue through Sunday morning.
We'll have to monitor upcoming trends, as a break in the rainfall action through midday Sunday could spell trouble with regards to a severe weather threat. SPC's Day 3 outlook features a Marginal Risk across southeast Minnesota and portions of western Wisconsin and the overall "high-end" potential of the threat will be tied to how far north or east the surface low tracks. If the low takes a southerly track (currently favored) the severe weather threat will be largely suppressed. On the flip-side, a more northerly track (represented in some model solutions), could mean the arrival of "juicy" unstable air, capable of fueling stronger storms. Combine the idea of stronger instability with the ~50kts of 0-6km bulk shear and the pieces are there for stronger storms to the southeast of the advancing surface low. To reiterate, much of our thinking this morning is that instability will be on the lower side, but there are a few scenarios that could result in a more favorable setup for severe weather from Rochester, MN to Eau Claire, WI come Sunday afternoon.

Putting it all together, the upcoming forecast could be characterized as a bit of soaker with 1-2" of rain expected areawide. Roughly a half inch to inch of rain will be possible during the course of each "round", with the higher end 3-day totals coming from locations that experience convectively driven showers and storms.

Looking ahead, guidance has come into better agreement with additional rain chances in the Tuesday PM/Wednesday AM time period, though enough spread still exists that broad 30-40% PoPs from the NBM seem reasonable. Blended guidance features highs in the 60s for much of next week, followed by another round of potential wet weather heading into next weekend.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
Issued at 652 AM CDT Fri Apr 26 2024

Dry air has really done a number on the progression of the rain and lower cigs into the region and continued to push the arrival of those back by an hour or two. In fact, current HRRR trends would say this band of rain moving across MN now doesn't even make it to western WI. There's low confidence on timing precip across the area through tonight, with multiple rounds of showers expected and little agreement in the models on when/where these indivicual rounds will develop. In general though, we expected a lull in precip coverage around 18z as this current rain fizzles out. Redevelopment around 21z, with multiple waves of precip then coming through the night, with the heaviest precip and best chance at TS coming between 2z and 8z.
Breezy southeast winds are expected through the day, but they will settle down some overnight as the surface low moves up through western MN.

KMSP...Frontal passage looks to happen Saturday morning, with cross southwest winds expected to start the day that will transition to a WSW direction at the end of the TAF. Best TS chances will come with the redevelopment of showers around 21z, the TS chances will then continue through 8z as the dryline begins to shut down precip.

/OUTLOOK FOR KMSP/ SAT...MVFR. -SHRA likely late night. Chc IFR/TS overnight. Wind SW 15G25 kts becoming NW.
SUN...MVFR/-SHRA, chance IFR/TS. Wind ENE 10-15G25 kts.
MON...MVFR/-SHRA early, then VFR. Wind W 15G25 kts.

MPX WATCHES/WARNINGS/ADVISORIES
MN...None.
WI...None.

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