Rochester, Minnesota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

716
FXUS63 KARX 151721
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1221 PM CDT Fri May 15 2026

.KEY MESSAGES...

- Widespread shower and storm potential increases this
  afternoon and evening (50 to 75%). There is a threat for
  severe weather to occur with some of these storms with large
  hail and damaging winds being the primary threats, especially
  along and south of I-90.

- More active pattern this weekend into early next week with
  periodic shower and storm chances. Sunday and Monday exhibit
  highest severe storm risk.

- Temperatures across much of the forecast area warm up into the
  80s from today through Monday.

&&

.DISCUSSION...
Issued at 150 AM CDT Fri May 15 2026

Today-Saturday: Warmer with Periodic Showers and Storms

A shortwave continues to make its way through the Upper Midwest
early this morning. Accompanying it is a band of light to at times
moderate rain. Rainfall amounts up to 0.1" will be possible. This
rain is expected to be done between 3 and 5AM. After this wave exits
the region, southwest flow  in the low levels advects warm and moist
air into the Upper Midwest. High temperatures for today are in the
low to mid 80s, however the soundings for the afternoon show
potential for good mixing which may result in temperatures
approaching the 90F mark. During the afternoon, a cold front
intensifies across western Wisconsin, southern Minnesota, and
central Iowa. Something that recent CAM runs have shown and most of
them are showing it, is a trend of 60+ dewpoints right along the
cold front. This is tricky as if we do over mix then that would
lower your dewpoints, but with warm and moist air entering the CWA,
this is certainly a possibility. As the cold front moves into
southeast Minnesota and northeast Iowa, compared to earlier runs of
CAMs, the more recent runs are producing convection towards the
early evening hours. MUCAPE gets into the 1500 to 2000 J/kg range
and the 0-1km and 0-3km shear increases during the evening with the
0-1km shear increasing to the 20 to 30kt range and the 0-3km shear
increasing to the 25 to 35 kt range. Accompanying elongated
hodographs indicate supercellular storm mode will be initially
possible before becoming linear along the frontal boundary. The
severe storm signal increased in most recent high resolution
model runs (15.00Z). The 12Z CSU probs for wind and hail
increased for our CWA and the hail threat has a 15% probability
over the area. Accompanying risk from the Storm Prediction
Center grazes an Enhanced in parts of northeast Iowa and
southwest Wisconsin with a Slight risk slightly farther
northeast.

Zonal flow continues for Saturday, persisting mid 80 degree
daytime high temperatures for much of the area. The cold front
that caused the showers and storms from today pushes into
eastern Iowa and northern Illinois during the morning. This
boundary become quasi-stationary during the day and trends northward
through the evening. The northern extent of said boundary will
determine local precipitation potential. The area with the best
chance at seeing precipitation is along and south of I-90
during the evening and early overnight. Compared to today`s
shower and storm potential, Saturday is more questionable.
Guidance differs on if and where precipitation occurs. There are
quite a few models that suggest no precipitation during the
day.

Sunday-Tuesday: Strong to Severe Storm Potential with Continued
Warmer Temperatures

By Sunday morning, a shortwave pushes into the Upper Midwest which
in turn pushes the quasi-stationary boundary further north. Further
aloft, a trough continues to deepen across the Rockies. Moisture
transport increases during the morning and early afternoon as a wave
of precipitation moves into the Upper Midwest. During the afternoon
and evening instability builds back in with warm and moist air
filtering in. Deep-layer shear is not very strong in our area but
the low to mid-level shear is around 25 to 45 kts (0-3km shear).
With relatively weak low-level lapse rates (up to 6C/km) but strong
mid-level lapse rates (7.5 to 8.5 C/km), storms that develop during
the afternoon and evening would mostly pose a hail and wind threat.
AI NWP guidance and CSU ML guidance continues to suggest a favorable
severe weather environment with medium probabilities (30 to 45%) for
severe weather to occur.

Monday looks to be the best day for strong to severe storm potential
based on the trough over the Rockies becoming negatively tilted as
it moves towards the northern Plains and the Upper Midwest. Ample
moisture and strong southwest flow will increase instability and
warm temperatures up into the mid 80s once again. There remains
quite a bit of uncertainty with how Monday could go regarding the
cold frontal passage. The deterministic models of the GFS and ECMWF
continue to shift closer together with the GFS slowing down the
frontal passage and ECMWF speeding up the frontal passage. Previous
runs had 24 hour differences in the frontal passage which would
impact the severe weather potential for Monday. The 00Z GFS
continues to show a negatively tilted trough with the frontal
passage occurring Monday evening. This would be favorable for severe
weather to occur and both AI NWP and CSU-ML guidance continue to
suggest another favorable for severe weather to occur. The 18Z ECMWF
has the frontal passage occurring about 12 hours after the GFS which
would mean that any severe weather potential would be focused on any
shortwave perturbation or mesoscale feature. One thing to note is
that the GEFS continues to show a high probability (85 to 100%) for
at least 1000 J/kg of SBCAPE occurring on Monday afternoon and
evening across the CWA indicating that the GEFS has high confidence
in quite a bit of instability occurring.

Not only is there a severe risk early next week, with multiple
rounds of storms there is also a heavy rainfall risk. PWATs for
early next week are in the 90th to 97th percentiles based on the
latest NAEFS with values roughly in the 1.25 to 1.50" range. LREF
probabilities for at least 0.5" occurring in a 24 hour period ending
Monday morning are between 35 and 65% and another period ending
Tuesday morning between 30 and 50%. The footprint for at least 1" of
rain in those same 24 hour periods also increased with values of 15
to 30% possible for each period.

Overall the next few days offer multiple chances for severe weather
to occur so make sure to pay attention to forecast updates over the
next 4 to 5 days as we enter an active pattern.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1221 PM CDT Fri May 15 2026

Main taf concerns are thunderstorm chances this evening at both
RST/LSE taf sites. Convection is expected to develop late this
afternoon/evening and move across the area this evening. Timing
of convection at both taf looks to be 23z today to 04z Saturday.
There could be a brief period of MVFR/IFR conditions under the
heavier showers/storms. Have introduced a tempo for this brief
period potential. By 05z Saturday convection will move east of
the taf sites and VFR conditions are expected to prevail after
05z Saturday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Cecava
AVIATION...DTJ