611
FXUS63 KMPX 180802
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
302 AM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Another round of showers and weak storms will affect primarily
southern MN this morning. Isolated showers with some rumbles of
thunder remain possible during the day.

- Another chance for rain arrives Thursday into Friday, with a few
strong storms possible.

- Quiet weather returns after Friday, with seasonal temperatures
  and only hit or miss chances for rain.

&&

.DISCUSSION...
Issued at 301 AM CDT Tue Aug 18 2026

The initial round of showers and storms that was expected as this
mid level shortwave coupled with a surface front push through the
area, and round two is the cluster of showers and storms over
eastern South Dakota. This second round is expected to move across
southern Minnesota this morning, arriving in our coverage area
closer to 5-6am and affecting the area along and south of the
Minnesota River, with the best chance for more than showers being on
the southern edge of the line that is more likely to be in Iowa. All
this to say, we do not expect to see significant or widespread
impacts from the second round, primarily some showers and maybe
rumbles of thunder that exits the area later this morning. The CAMs
all have some form of cold air northwest flow isolated showers
lingering throughout the day, and with a bit of mixed layer CAPE we
could see a few rumbles of thunder from any activity as well,
although with unidirectional northwest flow, it is unlikely that
anything more than a rumble or two results from it. The front will
fully pass through during the day and leave us with weak high
pressure by this time tomorrow morning, resulting in quiet weather
through Thursday when our next chance for showers and storms
arrives. Temperatures today and tomorrow will be in the 70s thanks
to the weak subsidence from the weak high pressure as well as the
meager CAA from the northwest flow, returning to the 80s on Thursday
as our next system arrives.

Speaking of, our next chance for rain will arrive on Thursday as a
broad area of weak forcing stretches south of a weak surface low in
central Canada, with northwesterly flow aloft continuing. The
surface low looks to move southeast towards the northern tip of Lake
Superior by 12z Friday, and as it does our area finds itself between
the weak leading warm front and sagging cold front, resulting in
chance for scattered showers and storms starting late Thursday
morning and continuing until the cold front moves through by midday
Friday. The setup is rather interesting with a narrow upper level
jet streak left exit region arriving Friday morning coupled with a
low level jet, with the low level jet also within northwest flow
which is a rather unique setup as typical nocturnal low level jet
features tend to favor southerly flow. One would think we will
struggle with moisture with this kind of setup, which is certainly a
consideration, however most of the guidance shows dew points in the
low to mid 60s with the ECMWF even suggesting upper 60s by Thursday
evening. As long as our low level advection does not contain
significant dry air, we should have enough moisture to force showers
and storms. I would expect the forecast trend as we approach to
gradually favor increasing PoPs and QPF, with ensemble probabilities
showing above 80% likelihood for at least a tenth of an inch across
most of the MPX coverage area by 7am Friday. The percentages get
lower than 30% for a half inch or more, which seems realistic given
the pattern. As the cold front arrives on Friday, one last push of
precipitation will make way for more seasonal temperatures and weak
high pressure to round out the 7 day period into early next week.
The longer range pattern continues to favor northwest flow aloft as
the ridge slides westwards, giving us potential for shortwaves to
produce precipitation, however also favoring a relatively low
confidence forecast at this time scale.

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 1219 AM CDT Tue Aug 18 2026

The start of the period will see continued -SHRA/-TSRA at
MSP/EAU with the weak storms moving across MSP moving southeast
likely to miss RNH to the south, as we await a 2nd round of
primarily -SHRA coming out of the Dakotas near the 12z time
frame. Maintained the prob30 groups inherited from the 00z TAFs
as the timing is still is consistent with latest guidance, with
instability expected to be low enough that -SHRA will prevail
over -TSRA for most of the sites. Winds will shift towards
330-360 after the precipitation wraps up, however speeds become
less than 5kts so some VRB winds are possible. We will scatter
out later in the day generally after 00z, becoming FEW/SKC by
the end of the period.

KMSP...With ongoing -TSRA at period start, went with a 0630
group to end things it is expected to be out of here before 06z
even arrives, which is simply a syntax issue that cannot be
avoided. The storms are producing a bit of lightning and some
downpours, and we have not observed any wind gusts recently,
however kept some 25kt gust potential in the prevailing line
with -TSRA that ends as soon as the storms do. Afterwards, the
2nd round still looks probable to skirt south of MSP, but will
be close enough to maintain the prob30 we have been sticking
with.

/OUTLOOK FOR KMSP/
WED...VFR. Wind NW 5-10 kts.
THU...VFR, chc PM MVFR/-SHRA. Wind SW 10-15 kts.
FRI...VFR, chc -TSRA/MVFR. Wind W 10-15kts.

&&

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

&&

$$

DISCUSSION...TDH
AVIATION...TDH