Forecast Discussion / NWS-Twin Cities

018
FXUS63 KMPX 200521
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1221 AM CDT Tue May 20 2025

.KEY MESSAGES...

- Soaking rain spreads northeast today through Tuesday night.
  Highest chances for rain in western into southern MN while
  lowest chances are north of I-94. Severe weather is not
  expected.

- Widespread 1.5" of rain expected, with the chance for 3"+
  across south-central Minnesota.

- Drier and trending towards normal temps for the second half
  of the week.

&&

.DISCUSSION...
Issued at 323 PM CDT Mon May 19 2025

While a volatile severe weather setup impacts the central
Plains, a long duration, light to moderate soaking rainfall
will spread across our area up north. From a synoptic
perspective, this system provides a ton of lift as a negatively
tilted longwave trough enhances surface cyclogenesis over the
Plains. Widespread PWAT values on the order of 1"+ spread north
and west through tomorrow afternoon, providing ample moisture to
work with. The latest QPF amounts are mostly unchanged, with a
large portion of the region expecting at least 1.5" of rain if
not more. The corridor for the highest amounts falls along and
south of I-94, mainly owing to the fact that rain is already
starting there this afternoon AND will likely stick around
through Wednesday there as well. Some locally higher spots can
be expected wherever more convective-based showers move through.
Other thing to note is that there should be a pretty tight
gradient along the northeastern edge, where Duluth may not even
see a drop of rain and are messaging the chance for elevated
fire weather conditions across northern Minnesota.

NOAA`s Probabilistic Precipitation Portal highlights that areas
near Mankato/Saint James/New Ulm have the highest "ceiling"
with about a 15% chance of exceeding 4", however their floor is
a bit lower compared to areas further north. For example, the
highest probability for exceeding 2" of rain actually falls from
a line extending from Montrose southeast through Lake
Minnetonka and down towards Lakeville in Minnesota (roughly
80-90%). In other words, there is a scenario where the highest
rainfall is shifted a bit north, however if we do see those 3"+
amounts, it should be centered closer to Mankato.

The upper trough begins to flatten out Tuesday into Wednesday,
resulting in more of a stationary front at the surface as the
system occludes. Rainfall along this front should be quite
light, and likely on and off, but could tip the total rainfall
scale higher for a folks on Wednesday. Models continue to
struggle a bit with the placement of this front with the GFS and
NAM trending further north compared to its European and
Canadian counterparts. One thing for sure is that it will remain
cloudy, breezy, and well below normal for highs across the
region.

Speaking of winds, we have hoisted a Wind Advisory for much of
western and southern Minnesota today through 8pm. Mixing is not
quite as efficient, but the strong pressure gradient has
promoted sustained winds around 25 to 35 mph this afternoon. An
additional wind headline may be needed tomorrow depending on how
much of 45+ knot mid level winds can be mixed down.

A quieter stretch of weather can be expected to end the week as
a ridge builds in from the west. A gradual recovery to normal
highs will last through early next week until models hint at
potentially another active pattern setting up by Monday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1218 AM CDT Tue May 20 2025

Kept much of the 00z TAF intact with MVFR bcmg IFR with -RA
throughout the period. Winds will gust at 30-35kts from 060-090
throughout, dwindling below 25kt gusts by the end of the period.
There could be a gap between rounds of showers from TAF start to
12z where we briefly return to high MVFR/VFR visibility, however
showers are expected to fill in these gaps shortly after sunrise
and persist throughout the day. Expect predominantly IFR once
the showers remain continuous at 3-4sm and CIGS around 1000ft.

KMSP...Compared to the 00z TAF, any mention of TSRA has been
removed with thunder absent for the rest of this system. Did opt
to include IFR cigs as confidence in 800-1000ft CIGS is higher
than with the 00z issuance. Winds are once again the wild card,
with gusts frequent to 30-35kts with an occasional higher gust
possible.

/OUTLOOK FOR KMSP/
WED...MVFR/-SHRA early, then VFR. Wind NE 10-15kts.
THU...VFR. Wind N 10-15kts.
FRI...VFR. Wind NE 5-10kts.
&&

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

&&

$$

DISCUSSION...BED
AVIATION...TDH

NWS MPX Office Area Forecast Discussion