989
FXUS63 KMPX 170538
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1238 AM CDT Mon Jun 17 2024

.KEY MESSAGES...

- Showers and thunderstorms overnight, with elevated storms
  posing a risk for severe hail (1" or more).

- Scattered showers & storms over the next few days with an
  increased risk of flooding due to training storms. Exact
  amounts will vary based on orientation of training
  thunderstorms.

&&

.UPDATE...
Issued at 811 PM CDT Sun Jun 16 2024

Collaborated with neighboring offices and WPC to issue a Flood
Watch across the majority of central Minnesota along with St.
Croix, Polk, and Barron counties in western Wisconsin. This
Watch coincides with a rare Moderate Excessive Rainfall Outlook,
which indicates a rich environment for potential flash flooding
tomorrow.

At this hour the atmosphere largely remains capped, as sampled
by the 00z MPX RAOB, though there is plenty of CAPE stored
aloft. Some of the hi-res models solutions have suggest isolated
convection east of a boundary that is currently located across
eastern Minnesota. The progression of the boundary will be a
focus point over the next few hours for a few isolated to
scattered storms, mainly across western Wisconsin.

Widespread convection is then forecast to move into
southwestern Minnesota overnight, with the heaviest rain
expected across southern Minnesota. A Slight Risk for severe
weather remains in place across much of the region, as a few
instances of large hail or damaging wind gusts may accompany the
heavy rain. Any storms that "train" over one location will pose
a localized flood threat. As discussed below, the evolution of
additional convection tomorrow remains somewhat uncertain, given
that the heaviest rain will be tied to the northward advance of
a warm front. Given the notable influx in moisture, the setup
bears watching for constant regeneration/training of storms.

&&

.DISCUSSION...
Issued at 315 PM CDT Sun Jun 16 2024

Temperatures have struggled to realize the 90s so far this afternoon
due to persistent cloud cover leftover from morning showers and
storms, followed by enough strengthening of the upper level wave to
continue to produce scattered to broken ceilings of cumulus through
the afternoon. The warmest heat index as of 230pm sits in the low
90s in northern Scott County, so while the 95 threshold for the
Advisory may verify briefly, we did not end up with the heat that
was expected yesterday at this time. Despite this, the air outside
is still quite humid and is not likely to change so plan accordingly
if doing anything outdoors for the rest of the day. As we move
through the overnight hours, another round of showers and
thunderstorms is expected to develop as low to mid level warm air &
moisture advection continues with an upper level wave producing a 1-
2 PVU PV anomaly shortwave as an upper level jet sits north of the
MPX coverage area. The main player overnight will remain the low
level jet with efficient moisture transport, with another round of
late night thunder to contend with. Low level lapse rates are quite
poor, however mid to upper level lapse rates are good enough such
that a few storms could be capable of producing severe hail
overnight. There is a degree of low level helicity such that some
spinning lower level storms are also possible, however with the poor
lapse rates and large moisture content, the tornado chances remain
non-zero but also quite low. What is likely is another round of
soaking rainfall equaling an additional inch or two across much of
the area, with some isolated higher amounts depending on where the
thunderstorms set up. Coupled with last night`s rainfall, we are
quickly saturating our soils and swelling area water features such
that flooding begins to become a larger concern this week.

Tomorrow has quite a bit of uncertainty regarding what will happen
especially for the second half of the day as it depends a
considerable amount on how quickly the morning showers and storms
push across the region. CAM guidance including the SPC HREF
diminishes shower activity between roughly 13-15z, but keeps lighter
showers and storms around throughout much of the day as CAMS
continue to differ on placement and timing of further showers and
storms. Should we trend towards the first line of showers exiting
later by around 15z, it becomes less likely that we maintain an
environment for stronger storms by the afternoon. However, most
guidance continues to intensify the already blistering low level
jet, with GFS/CFS deterministic solutions favoring a significant
continued influx of low to mid level moisture and forcing. This jet
will remain the focal point for additional showers and storms with
the environment remaining static through much of Tuesday before the
jet finally pushes over the Great Lakes by Wednesday morning.
Although there are significant hydrologic concerns due to the
anomalous PWAT values and multiple rounds of showers/storms, the
positioning of the features has shifted enough over the last 12-24
hours within most of the guidance such that confidence in a specific
area seeing enough to cause widespread flooding issues is low at
this time. The main takeaway should be additional showers and storms
are likely over the coming days, but unless we see multiple rounds
training over a specific location, the flash flooding/areal flooding
concerns are uncertain at best. River flooding is a different story,
with enough rain falling over a large enough portion of the CWA that
rises in area rivers will likely result in several new or upgraded
river flood warnings over the coming days.

A pattern shift mid-week with brief surface high pressure on the
heels of the departing jet will give us a break from significant
rainfall on Wednesday alongside a couple days of cooler
temperatures, however deterministic guidance once again points to a
strengthening low level jet amidst zonal to southwest flow aloft,
once again favoring multiple rounds of scattered showers,
thunderstorms, and areas of rainfall. Uncertainty will remain high
given the scope of the short-term forecast and how that will end up
modifying the overall environment later in the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1224 AM CDT Mon Jun 17 2024

The forecast remains on track as we await the arrival and
persistence of widespread showers and storms today. A line of
convection north of the frontal boundary is currently moving
northeastward from southeastern SD, which is expected to fill
in within the next few hours. Some of these initial storms could
produce hail or strong gusts at times, but the main concern is
heavy and prolonged periods of rainfall. These threats diminish
throughout the day, but light rain could linger for some
terminals in eastern Minnesota and western Wisconsin through
late evening. Winds will gradually kick more southerly
throughout the day as the front lifts north through the region.

KMSP...Theme remains the same with rain/thunderstorms arriving
around 09/10z depending on how quickly and how far south things
develop. After a few hours of storms, more showery-like
precipitation will follow. There is still uncertainty with how
long these will stick around. Depending on coverage, it could be
more like an on and off type of system which would last until
late this evening/night.

/OUTLOOK FOR KMSP/
TUE...VFR/MVFR, TSRA/SHRA likely, chc IFR. Wind S15-20G30-35kts.
WED...VFR/MVFR, chc -TSRA/-SHRA. Wind N 5-10kts.
THU...VFR/MVFR, chc -TSRA/-SHRA. Wind NE 5-10kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Flood Watch from this afternoon through late Tuesday night for
     Anoka-Benton-Carver-Chippewa-Chisago-Dakota-Douglas-
     Hennepin-Isanti-Kanabec-Kandiyohi-McLeod-Meeker-Mille
     Lacs-Morrison-Pope-Ramsey-Renville-Scott-Sherburne-Sibley-
     Stearns-Stevens-Swift-Todd-Washington-Wright.
WI...Flood Watch from this afternoon through late Tuesday night for
     Barron-Polk-St. Croix.

&&

$$

UPDATE...Strus
DISCUSSION...TDH
AVIATION...BED