Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 290148
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
848 PM CDT Sat May 28 2022

.UPDATE...
Issued at 732 PM CDT Sat May 28 2022

Updated to include 00z aviation discussion below.

&&

.DISCUSSION...(This evening through Saturday)
Issued at 303 PM CDT Sat May 28 2022

KEY MESSAGES:

- Multiple rounds of thunderstorms are expected through Monday night.
  Severe weather is possible tonight and late Sunday. An outbreak of
  severe thunderstorms, including some strong tornadoes and very
  large hail, is becoming increasingly likely Monday afternoon.

- Very warm and humid this holiday weekend, then turning cooler
  again later next week.

Today/tonight... We cleared out nicely this morning behind the
morning convection, though did get some gusty winds this morning
over south central MN before the overnight LLJ weakened. With 925mb
temps exceeding 20C, we`ve seen a few sites down around Fairmont and
Redwood Falls get up near 90. We`ll stay mild through tonight as
south winds continue through the night, with most of the area
remaining in the 60s. The one exception will be up near Mora and
Mille Lacs, where they cold see a cooler airmass drop down from Lake
Superior.

From the precip perspective, we`ll be dry and capped through the
afternoon, with any activity we see this period happening late
tonight. There will be two areas to watch for convection tonight.
One will be with what is expected to be thunderstorms that develop
late this afternoon near the central Neb/SD border. These storms
will track northeast through the night, with west of a Redwood Falls
to Little Falls most likely to see the remnants of these storms.
East of the Redwood Falls to Little Falls line, the threat for
convection will come from the enhancement of the nocturnal LLJ across
the central Plains. On the nose of this, the RAP shows a pool of
higher theta-e at h85 coming up out of IA and across southern MN.
This will bring about another threat for some sunrise showers/storms,
though that potential for Sunday morning is looking much lower than
it did for this morning. From the severe threat, any activity we see
this period will be elevated, but steep mid-level lapse rates will
support a hail threat for any stronger convection we see.

Sunday... We`ll see a surface low over northeast NoDak, with a cold
front extending south to another surface low that will be developing
over south central Neb (this Neb low will become our problem
Memorial Day). For Sunday, we looked to be capped, with the risk of
storms during the day on Sunday greatest in northwest MN closer to
the surface low and north of the capping. For the MPX area, the
greatest concern severe wise is for a severe MCS to come out of Neb
and across western/central MN Sunday evening. Given the strengthening
wind fields expected, a bowing MCS posing a significant wind risk,
along with your QLCS tornadoes, looks to be our greatest risk Sunday
evening. The Day 2 convective outlook covers this threat well, with
enough uncertainty being present with the scenario actually playing
out to keep the SPC from upgrading to a Moderate risk.

Monday... This continues to be the most concerning day from a severe
weather risk perspective as that Nebraska low moves up to eastern
SD/western MN and deepens on Memorial Day. In terms of forcing,
shear, and instability, this setup has many similarities to what we
typically see in the upper MS Valley on severe weather outbreak days.
This is the one day this weekend where afternoon convection looks
possible, with all modes of severe weather possible. Looking at
hodographs on Monday, they are very, very long, but relatively
straight near the surface forcing features, so this indicates that we
should see pretty rapid upscale growth with any activity we see
develop on Monday, but it will likely be a rather chaotic setup with
lots mergers and other cell interactions going on. The severe risk
continues to look greatest over western MN, where the cold
front/surface low look to reside during peak heating, but we will see
an increasing wind risk through much of the night as one or more
lines of storms advance east with the cold front, though the risk
will be diminishing by the time you get out toward Eau Claire as
storms will be encountering lower stability as they move east,
along with your typical nocturnal stabilization of the boundary
layer.

Tuesday through next weekend... The h5 low that will help drive our
severe threat Memorial day will continue north into Canada on
Tuesday, where it will merge with another h5 low coming out of
northwest Canada. The combined h5 low that will result from this
merger will then stay more or less stationary over northern Manitoba
and northwest Ontario all the way into the weekend. This will result
in a seasonably strong zonal flow across the north central CONUS
from Tuesday into the weekend. The most notable element of this
pattern shift will be a noticeably cooler and less humid airmass
from Tuesday into next weekend. For precip chances, Tuesday
continues to trend drier, with the best chance for precip residing
over MN, where a cold mid-level trough will exist, allowing for the
possibility of some diurnally driven showers. The next chance will
come Thursday night as a weak cold front passes through the upper MS
Valley. The NBM is still dry for us Thursday night/Friday morning as
the best upper forcing will going across the upper Great Lakes, but
it wouldn`t be surprising to see some low chances eventually appear.
After that, where this boundary sets up next weekend will become the
focus for additional showers and storms, with the ECMWF/GFS showing
the potential for an overrunning precip event to develop.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 702 PM CDT Sat May 28 2022

VFR to start for all terminals with clouds increasing overnight. A
quick-hitting round of showers and weak thunderstorms will move
through generally in the 10z-14z timeframe for western MN, thus kept
in PROB30 mention. Chances less than that for southern/eastern MN TAF
sites (and not expected at all at the WI TAF sites) but some
adjustments may be needed for the 06z TAFs based on newer model
guidance coming in. MVFR ceilings then look to briefly settle in late
morning to early afternoon until a weak surface boundary lifts north,
then high MVFR to low VFR ceilings will remain in place through the
rest of the afternoon. Gusty SE winds will also commence during the
afternoon. Chances for stronger TSRA ramp up after 00z tomorrow
evening so these chances will be shown in later TAFs.

KMSP...VFR through late morning but with the first of a couple rounds
of LLWS expected to develop, which will remain through sunrise. After
daytime mixing commences and the low level jetting weakens a bit,
stronger SE surface winds will take hold and remain in place. Chances
too low at this time to include any mention of sunrise thunderstorms
moving through but will re-evaluate at the 06z TAF time. Another
round of LLWS is likely at and after sunset through Sunday evening,
but accompanying this may well be a round of thunderstorms later
Sunday evening.

/OUTLOOK FOR KMSP/
Mon...Mainly VFR. MVFR/TSRA late. Wind S 10-15G25 kts.
Tue...Chance MVFR/-SHRA. Wind W 10-15G25 bcmg NW.
Wed...VFR. Wind NW 10kts.

&&

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

$$

UPDATE...JPC
DISCUSSION...MPG
AVIATION...JPC


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