Comfrey, Minnesota Weather Forecast Discussion

891
FXUS63 KMPX 141939
AFDMPX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
239 PM CDT Sun Sep 14 2025
.KEY MESSAGES...
- Occasional chances for showers and thunderstorms throughout
  the week, with the most active period to be Wednesday through
  Friday.
- Warm and humid conditions continue through Wednesday, then
  cooling off to near normal.
&&
.DISCUSSION...
Issued at 237 PM CDT Sun Sep 14 2025
h5 analysis this afternoon shows a rather blocky pattern over the
CONUS, with a blocking high over Michigan, with couple of negatively
tilted troughs over the western half of the country, one over
Oregon/Washington and the other near the CO/Neb border. With that CO
wave, there`s a deep plume of moisture coming out of Mexico and
extending up into the Dakotas and the Canadian Prairies. For us, it
is the trough coming out of CO that will cause headaches for much of
the upcoming week as it becomes cut-off from the main flow within
the central North American ridge and slowly meanders across the
north central CONUS.
For today, that blocking high over Michigan has helped to keep the
moisture shunted to the west. In addition, it has kept our surface
winds more southeasterly, which has checked up the forward progress
of the warm front some, with it roughly along I-94 down into the
Cities, then down along the MS River from there. Eventually, this
plume of moisture will start coming into MN, though we`re likely
looking at after 21z before showers make inroads into western MN.
Through the night, we`ll see southerly winds at h85 through h5 work
east across MN and into western WI. Usually, a LLJ on the order 30-
35 kts would be a good source of lift for precipitation development
thanks to the WAA associated with it. However, when looking at the
h85-h7 layer, the temperature advection within these southerly winds
is either neutral or even cold. Given the lack of WAA and its
associated lift, deterministic, ensemble, and hi-res models are all
over the board with if/where we see showers through the night. Given
this uncertainty, basically capped PoPs at 30-40% through the night
and Monday morning, with the highest PoPs following the path of
enhanced h85 and h7 winds and the moisture feed associated with it.
This looks to be the type of setup where within this moisture plume,
we see isolated to scattered showers come and go through the night
and Monday morning wherever we happen to get some mesoscale
convergence within the southerly flow. Given the small scale nature
of the forcing, confidence on when/where we`ll see precip is low.
SPC still has a Marginal Risk over far western MN and this still
looks plausible, as any stronger convection we see out there will
have the potential to mix down some of the stronger winds we have in
that h85-h5 layer. Needless to say though, we aren`t anticipating
anything widespread.
For Monday and Tuesday, the models are trending drier for the MPX
area as the h5 low slowly spins over the Dakotas. We`ll have ample
moisture (PWAT over 1.5") for generating precip, but we look to be
missing the forcing component for getting any widespread
precipitation. Some diurnal showers will be possible both days, but
in general, these two days look hot and and humid for mid-September
standards, with highs remaining in the 80s and dewpoints in the 60s
to low 70s.
More active weather looks to finally set in on Wednesday as the cut-
off mid-level low begins moving into western MN. This looks like a
rather broad and nebulous upper trough that will be working across
the upper MS Valley into next weekend. Though by no means a washout
at any point, we should see several periods of showers from
Wednesday into next weekend as weak vorticity features and diurnal
destabilization provide the forcing to get showers going. Given the
weak forcing, confidence on precip is relatively low in any period
(though chances look best during the late afternoon and evenings),
which the NBM covers well with its prolonged period of 30-50 PoPs
Wednesday through Friday. PoPs do start coming down over the
weekend, but those lower PoPs will be defendant on how long it takes
for an incoming Pacific jet to move far enough east to start pushing
this upper trough out of the upper MS Valley. Besides the rain
chances, all the cloud cover and rain will help hold temperatures
down, with highs expected to be back near normal (in the 70s) from
Wednesday on, though lows will remain above normal through this
period.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1224 PM CDT Sun Sep 14 2025
MVFR/IFR cigs are hanging on across W WI, but will scattered our
shortly after start of TAF period. VFR throughout the remainder
of the TAF period for all sites with scattered to broken high
clouds through the period. Some CAMs try to develop a line of
isolated storms overnight. Confidence remains highest across
western MN where PROB30s have been maintained at our western
sites. Will opt to add in additional PROB30 in future
updates if confidence increases.
KMSP...HRRR tries to bring a line of isolated -SHRA/-TSRA
through the MSP around 12z Monday morning. Forecast confidence
in coverage is low so I opted to keep out any mention in the
TAF.
/OUTLOOK FOR KMSP/
TUE...VFR, chc MVFR/-TSRA pm. Wind S 5-10kts.
WED...MVFR/SHRA/-TSRA. Wind S 5-10kts.
THU...MVFR/SHRA/-TSRA. Wind SE 5-10kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
DISCUSSION...MPG
AVIATION...BPH

NWS MPX Office Area Forecast Discussion