Isanti, Minnesota Weather Forecast Discussion

774
FXUS63 KMPX 230634
AFDMPX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
134 AM CDT Tue Sep 23 2025
.KEY MESSAGES...
- Dense Fog Advisory for portions of central MN tonight through
  early Tuesday.
- Another round of showers and storms is expected along and
  south of the I-90 corridor this afternoon and evening.
- Quiet weather for the rest of the week with temperatures in
  the 70s.
&&
.DISCUSSION...
Issued at 200 PM CDT Mon Sep 22 2025
An upper-level trough situated over Lake Superior will prog
slowly to the northeast over the next several hours. A surface
low was located over southern MN with a stationary boundary
extending over to central Lake Superior and a cold front
trailing behind down through Nebraska. These features are
expected to track to the east- southeast through this afternoon.
Another round of showers and thunderstorms looks most probable
to redevelop across extreme southern and southeastern MN this
afternoon and evening. Based off of latest cams, isolated CI
looks to occur as early as 2 or 3 PM this afternoon with
development trailing down along the surface boundary to the
southwest into northwestern IA. The SPC does have this region in
a marginal (level 1 of 5) risk for severe thunderstorms as the
convective environment does look to advertise lapse rates around
7 deg/km and MLCAPE values 1000-2000 J/kg. However, the best
support for the strongest storms has seen a noticeable
southeastward shift over the last few runs of the hi-Res
guidance, thus the overall trend in PoPs appears to have nudged
southward over the MN/IA border. In order to keep mentionable
PoPs within southern MN, we deviated from the NBM slightly by
maintaining a blend of the previous forecast which kept a
mention of slight PoPs across southern MN. For any storm that
does manage to become severe would pose mainly a large hail and
damaging wind threat. But again, the best likelihood of these
threats look to be focused across northern Iowa.
Flow aloft veers to northerly with some minor deviations to
northwest/northeast over the rest of the week, alongside weak
surface high pressure bringing general subsidence across the
region. Fair weather cu can still be anticipated daily as dew
points remain in the 50s as mixing remains favorable. Which will
also maintain chances for overnight fog as temperatures fall to
dew points with efficient radiation cooling and a lack of
surface winds under high pressure. The fog will be the most
dense earlier in the week behind the showers, especially
tonight. Visibilities will likely fall below one quarter mile
across north-central MN where a Dense Fog Advisory is in effect
from midnight tonight through 10 AM Tuesday. Depending on fog
development trends overnight, its likely the advisory may need
to be extended in coverage farther south across west- central
MN. Drying conditions will continue throughout the week which
will gradually suppress the fog coverage a bit more each night.
As mentioned in the previous discussion, it looks to be a fairly
warm but overall quiet end to September, with predictability
lower as we head into October due to a lack of longer scale
indicators. For now, enjoy the warm weather while it lasts as
October also brings the autumnal equinox, marking the trend of
rapidly losing daylight as we slide closer to the winter months.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 107 AM CDT Tue Sep 23 2025
Only issue will be low/stratus fog thru sunrise. IR satellite
clearly shows a swath of low stratus sliding SW from Lake
Michigan, thus making the northern and eastern TAF sites most
susceptible to flight category restrictions, down to LIFR as
times. Because of weak low-to-mid flow, the low stratus may hang
on until late morning, followed by VFR conditions into the
afternoon and evening. Early-on thinking is similar conditions
may well develop again tonight into Wednesday morning given the
continued weak NE flow which will again bring low level moisture
in from Lake Michigan under the nightly inversion.
KMSP...Main window for reduced conditions looks to be from about
11z on through the remainder of the morning push, with potential
for ceilings as low as 300ft at times. Will monitor conditions
and AMD as needed but confidence is high on at least low stratus
if not ground fog and visibility restrictions.
/OUTLOOK FOR KMSP/
THU...VFR. Wind W 5-10 kts.
FRI...VFR. Wind S 5-10 kts.
SAT...VFR. Wind NW 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Dense Fog Advisory until 10 AM CDT this morning for Kanabec-
     Mille Lacs-Morrison-Todd.
WI...None.
&&
$$
DISCUSSION...Dunleavy
AVIATION...JPC

NWS MPX Office Area Forecast Discussion