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.
&&
$$
DISCUSSION...Strus
AVIATION...MPG