503
FXUS63 KMPX 011000
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
500 AM CDT Mon Jul 1 2024

.KEY MESSAGES...

- Widespread showers and thunderstorms this evening through
  Tuesday. Locally heavy rainfall possible, primarily across
  southern Minnesota & western Wisconsin.

- Thunderstorms and locally heavy rainfall likely for the 4th of
  July.

&&

.DISCUSSION...
Issued at 419 AM CDT Mon Jul 1 2024

The main forecast challenge today will be how early showers and
thunderstorms develop across the area with a wide spread in
timing still present among both high-resolution & synoptic-scale
models. Everything is in agreement with the most widespread
thunderstorms & heaviest rains occurring tonight & overnight,
with the uncertainty being how much precipitation develops this
afternoon on the nose of the strengthening low-level jet.
Strong southerly flow ramps up Monday morning & advects Gulf
moisture into the region, with precipitable water values
potentially exceeding 2" by late Monday night. This morning,
most guidance initiates a narrow band of sowers & thunderstorms
along a weak upper-level boundary across the eastern Dakotas.
Some solutions keep this convection going into western &
central Minnesota through late morning & into the afternoon.
More likely, however, is that this convection decays as it heads
east, with perhaps some light precip across far-western
Minnesota early this afternoon. More widespread showers &
thunderstorms will hold off until this evening when WAA from the
low-level jet is strongest & better forcing aloft arrives from
an approaching jetstreak. Precipitation will overspread the area
fro west to east through the night, with the most widespread
thunderstorm coverage & best chance for locally heavy rainfall
looking most likely from south-central Minnesota through
western Wisconsin. In general, rainfall amounts up to 0.5" are
expected across western & central Minnesota, with amounts in
excess of 1-2" more likely across eastern Minnesota & western
Wisconsin through Tuesday morning. Hi-res models do indicate
some swaths of 3-4" where the heaviest thunderstorms from
south-central Minnesota through western Wisconsin, so locally
higher amounts are likely and could lead to some flash flooding
concerns. Isolated hail and strong wind gusts can`t be ruled out
with the strongest storms tonight, but the severe chances look
higher across the Dakotas where the shear & instability are
higher.

A lull in the precipitation appears likely Tuesday morning with
a second wave of showers and thunderstorms expected during eh
afternoon & evening along the surface frontal boundary. Trends
over the last 24 hours have progressed this front through the
area quicker, with the best chances for thunderstorms shifting
southeastwards into southeast MN/northeast IA/southwest WI. Some
showers and thunderstorms still look likely from south-central
Minnesota through west-central Wisconsin, but the heaviest rain
and strongest thunderstorms does appear to stay south and east
of our area Tuesday. Rainfall amounts only look to be on the
order of a few tenths across our area, but will be over an inch
wherever the main band of thunderstorms develops.

Drier conditions develop midweek as the flow aloft weakens &
becomes more zonal, but another round of showers &
thunderstorms looks likely for the 4th of July & into Friday as
a broad shortwave trough develops & moves over the Upper
Midwest. It looks very likely that most of the are will see rain
Thursday, with some uncertainty still present with how much
rain & where the heaviest rain will occur. Ensemble guidance
continues to show high probabilities for rainfall amounts >1".
Our highest PoPs from the NBM ensemble continue to be centered
on the evening of the 4th, with some indications that at least
morning events could stay dry. A chance for showers and
thunderstorms continues over the weekend, but with not nearly as
strong a signal for heavy rain or strong thunderstorms.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1026 PM CDT Sun Jun 30 2024

Main issue will be the incoming precipitation expected late
Monday afternoon through Monday night. High clouds will
increase in coverage during the day Monday, with ceilings likely
by midday, gradually lowering to mid-levels Monday afternoon.
Though there may be some timing tweaks done to later TAFs,
confidence is high enough to go right to prevailing precip in
western MN prior to 00z then continuing to the rest of the TAFs
after 00z Monday evening. Ceilings will likely drop into MVFR
range around or shortly after 00z Monday evening, with
visibilities currently advertised into the MVFR range but could
easily be as low as IFR in heavier rainfall. Winds will remain
generally SE throughout this duration, with speeds remaining
under 10kts through sunrise Monday then increasing to 15-20kts
with gusts 25-30kts.

KMSP...VFR conditions to prevail through Monday afternoon, then
conditions are expected to deteriorate quickly Monday evening as
rain/thunderstorms move in from the west. Confidence remains
high enough to maintain prevailing mention for both RA and
CB/TS. Showers could move into the MSP area slightly earlier
than advertised, potentially during the afternoon push. Same
could be said for CB/TS. More tweaking in the precip timing will
be done now that precip is likely within the next 24 hrs.

/OUTLOOK FOR KMSP/
TUE...MVFR. Chance IFR SHRA/TSRA. Wind SW 10-15 kts.
WED...VFR.Wind WSW 15G25 kts.
THU...VFR. Chance MVFR SHRA/TSRA.Wind S 5-10 kts.

&&

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

&&

$$

DISCUSSION...ETA
AVIATION...JPC