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FXUS63 KMPX 251737 AFDMPX

Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1237 PM CDT Thu Apr 25 2024

KEY MESSAGES

- Friday's system brings widespread rain and gusty winds to the region. The heaviest rain expected Friday afternoon into Friday night.

- There is a Marginal severe threat for overnight convection along the I-90 corridor in southern MN.

- A break in the active weather is anticipated Saturday, with another strong system expected to bring additional widespread rain on Sunday.

- A more Summer-like warmth expected to start May, with an active weather pattern expected across the central CONUS.

DISCUSSION
Issued at 253 AM CDT Thu Apr 25 2024

Strong WAA across SoDak is helping drive the clouds and radar returns we've been seeing through the night. However, there was ample dry air on the MPX sounding last night, which has held much of these returns in the virga category and through the day today, the virga theme is expected to continue, with perhaps a brief sprinkle or two fighting its way to the ground through the morning in west central MN. The big change for today is the increasing pressure gradient and associated uptick in southeast winds. The strongest winds are expected in western MN, where sustained speeds will get up into the 20-25 kt range, just below wind advisory criteria.

Tonight, showers will spread in across the area from west to east as a better than 40 kt LLJ and its associated moisture transport move into the region. We did slow the eastward progression of the rain by a few hours as it will take time for the dry airmass to be overcome.
In fact, the HRRR doesn't really show precip crossing the MN/WI border until Friday afternoon. We will see periods of showers and occasional storms through Friday evening, but the heaviest rain is expected Friday afternoon/evening as PWATs increase to over 200% of normal (over 1") and h85 winds increase to over 50 kts. The severe risk on Friday continues to be more of an issue down toward Omaha, with the surface low and warm front expected to move across southern MN overnight Friday night. The continued Marginal Risk for severe weather from the SPC for the southern 2 or 3 tiers of counties in MN continues to look adequate to capture our limited severe storm threat during the overnight hours.

Saturday continues to offer us a breather before a stronger wave arrives on Sunday. Once again, the track of the low will be key to our severe risk, though the 25.00 ECMWF continues to paint an interesting picture for southeast MN on Sunday, with a warm front bringing low 60s dewpoints up into southeast MN during the afternoon. The main question for our severe potential on Sunday is what kind of instability can we develop behind what will be widespread WAA convection across the region Saturday night/Sunday morning. There's still a good deal uncertainty with exactly where the Sunday low tracks, but it certainly bears keeping a close eye on as we head for the weekend.

As for rainfall potential, not much has changed with either system.
A widespread 1-2" of rain expected between both systems. From an overachieving perspective, it's the second low on Sunday that will have the potential for that, especially for eastern MN and western WI where Pwats will be more in the ballpark of 1.5" with a favorable coupled upper jet structure developing as well. We could easily see a couple of swath of 2-3" with just the second system on its own from southeast MN up through western WI.

We will dry out for Monday, but we will have zonal flow in place to start the week. Models are starting to come into agreement on a westerly jet streak coming across the Dakotas on Tuesday, with the exit region of this jet streak leading to the possibility of another round of scattered showers and thunderstorms Tuesday. Model spread starts to increase dramatically toward the end of the forecast period, though there is agreement on the general idea of the flow becoming a bit more amplified by the second half of next week as another trough digs into the western CONUS.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
Issued at 1228 PM CDT Thu Apr 25 2024

High clouds and breezy southeasterly winds will continue through this evening before we see a mid level cloud deck overspread the area after 06z or so. -SHRA will move in from the southwest before sunrise across southern and western Minnesota and continue to the northeast through mid morning. Cigs/vis will be low VFR/MVFR with this first round of showers with lower clouds expected by the end of the period.

KMSP...Highest chances for -SHRA/MVFR tomorrow look to be between 12 and 15z with a break until late afternoon. Thinking that higher chances for another round of showers and a few thunderstorms lies just beyond the end of the forecast period.
Winds will remain gusty out of the southeast.

/OUTLOOK FOR KMSP/ SAT...MVFR. -SHRA likely early and overnight. Chc IFR/TS overnight. Wind SW 15-20 kts becoming NW.
SUN...MVFR/-SHRA, chance IFR/TS. Wind NE 10-15G25 kts.
MON...MVFR/-SHRA early, then VFR. Wind W 10-15kts.

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

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