Nelson, Minnesota Weather Forecast Discussion

437
FXUS63 KMPX 221902
AFDMPX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
202 PM CDT Mon Sep 22 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 /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1213 PM CDT Mon Sep 22 2025
IFR/MVFR stratus has stubbornly persisted this morning. However,
obs and satellite imagery do show signs of clouds lifting and
breaking apart, such that VFR should return at all terminals by
late afternoon. CAMs have trended farther south and east with
this afternoon`s precipitation, so have removed the PROB30
mention for -SHRA. VFR expected into tonight before fog and low
stratus redevelops for Tuesday morning. IFR to LIFR look most
likely for south-central MN into west-central WI as cigs fall to
near 500 feet and visibilities reduce in fog. Have gone most
aggressive with fog (1/2sm visibilities) at RWF and STC where
greatest fog occurred this morning. Conditions should improve to
MVFR/VFR by late Tuesday morning. Northeasterly winds become
light/calm overnight before increasing to near 5 knots Tuesday
morning.
KMSP...Recent obs have shown improvement in cigs with VFR
likely quickly into the TAF period. Amendments may be needed to
catch up with the trend. Expecting IFR stratus to develop again
Tuesday morning before once again improving to VFR by late
morning. North-northeasterly winds near 5 knots throughout the
period.
/OUTLOOK FOR KMSP/
WED...VFR. Wind NE 5-10 kts.
THU...VFR. Wind NW 5-10 kts.
FRI...VFR. Wind SW 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Dense Fog Advisory from midnight tonight to 10 AM CDT Tuesday
     for Kanabec-Mille Lacs-Morrison-Todd.
WI...None.
&&
$$
DISCUSSION...Dunleavy
AVIATION...CTG

NWS MPX Office Area Forecast Discussion