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fxus63 kmpx 261059 
afdmpx

Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
559 am CDT Wed Jun 26 2019

Update...
issued at 558 am CDT Wed Jun 26 2019

Updated to include 12z aviation discussion below.

&&

Short term...(today through thursday)
issued at 345 am CDT Wed Jun 26 2019

Surface analysis early this morning shows a wavy frontal boundary
extending east from northern Colorado and northern NE through southern Iowa
then northeast into southeast WI. Nondescript pressure patterns
sit to the north and south of this boundary, although one evident
low pressure center meanders over central South Dakota. Aloft, one
trough sits over the western Continental U.S. Coast and another over eastern
Canada into New England, with the north-central Continental U.S. Within
generally zonal flow.

And the day progresses today through tonight, the western Continental U.S.
Trough will dig deeper and become more pronounced. With the
eastern Continental U.S. Remaining relatively in place, this will push a
more ridge- like pattern into the central Continental U.S.. in addition, it
will also allow the surface front to gradually move its way
northward through tonight. A few isolated showers/thunderstorms
may try to drift into Minnesota near the front but moving into a ridge,
any activity is expected to dissipate during the day today.
However, what the ridge and northward movement of the front will
do is start a trend of increasing heat and humidity into MN/WI.
Instability near and to the south of the front will push MLCAPES
to the 2500-3500 j/kg range this evening through tonight. However,
the kicker feature will be an arriving low level jet in the vicinity of
enhanced isentropic lift on the leading edge of the warm front. In
line with what multiple cams are advertising (but, interestingly,
not so much at all on the gfs), discrete cells to storm clusters
are likely to develop during the early morning hours Thursday.
Still a highly conditional nature to storm development, but storms
could evolve into strong/severe cells with large hail and/or
damaging winds. Fairly wide swath of slight risk that Storm Prediction Center has
delineated for the swody1, mainly south of the I- 94 corridor, so
it is a little tough to pin down details any more than what's
currently out there. Will need to see how models evolve this
situation during the day today before being able to nudge pops
into the likely category for any particular portion of the weather forecast office mpx
coverage area.

Once any activity gets going tonight, it will potentially continue
into the first half of Thursday, which along the lines of severe
potential makes sense that the entire coverage area is within a
marginal risk in the swody2. Again, the highly conditional nature
of this event and the location of multiple features (i.E. The
surface front, the llj, concentration of instability, outflow
boundaries) will determine what portions of the coverage area will
have the best shot at seeing storms, let alone those of strong to
severe strength. Similarly, have also capped pops in the chance
range.

As for the aforementioned heat/humidity, highs will reach the low-
mid 80s both today and Thursday with the initial reaches of the
warmer air to the south into southern MN/WI. However, with the
temperatures essentially the same both days, the difference will
be the dewpoints. Dewpoints today will generally run from the mid
50s to the lower 60s. The humidity will take a leap on Thursday as
dewpoints climb to the mid 60s to around 70, making for heat
index values on Thursday into the upper 80s to near 90. This will
be just a small taste of what is to come later in the week and the
weekend.

Long term...(thursday night through tuesday)
issued at 345 am CDT Wed Jun 26 2019

The main concern during the long term period is the first heat
wave of the season, developing Friday and lasting through the
weekend. Convection is also an issue early and again late in the
weekend into early next week.

Thursday night should see the main convective threat exit to the
east. Then the upper ridge builds into the area with 500 mb
heights rising above 590 dam by Saturday. This should bring in
the mid level cap over the region and should hold through
Saturday. Dewpoints are forecast to rise to the lower 70s and with
temperatures in the low-mid 90s, heat indices rise to around 100
in the afternoon. Dewpoints may not rise into the lower 70s
across most of the region Friday, but heat indices will still
peak out in the mid 90s. Models diverge on how quickly the ridge
builds in with the European model (ecmwf) a bit slower and generates some
convection on the edge of the cap Saturday/Saturday night. Will
need to watch this potential with very unstable airmass building
across the area.

The upper ridge breaks down some Sunday night or Monday and this
looks like the best chance for thunderstorms with a cold front
dropping southeast over the area. This should break the heat wave
with temperatures returning to the 80s into midweek. The front
may stall close to the Minnesota/Iowa border so we will be
susceptible to periodic thunderstorm chances with any impulses
moving through the more westerly upper flow.

&&

Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 558 am CDT Wed Jun 26 2019

All sites start out as VFR and have kept all sites as VFR
throughout this taf set. Convection crossing from South Dakota into southern
Minnesota this morning is expected to dissipate and not cause issues for
any taf sites. That said, will monitor and make amendments as
necessary. The bigger concern is tonight with convection expected
to develop sometime from the early morning hours Thursday into as
late as early afternoon. Timing differences among the models along
with a highly conditional nature of the convection plus low
confidence in determining location prevents mention of ts/cumulonimbus at
this point. Will need to see how the models resolve their
differences before later taf packages can include precip.

Kmsp...same overall idea. Low confidence in timing/location of
precipitation spells maintaining a dry msp taf at this point.
Winds will be light overall, generally backing from SW to southeast
through tonight.

/Outlook for kmsp/
Thu...VFR. Chc MVFR/tsra. Winds south-southeast 5-10 kts.
Fri...VFR. Winds south-southeast 5-10 kts.
Sat...VFR. Winds S 5-10g15 kts.

&&

Mpx watches/warnings/advisories...
WI...none.
Minnesota...none.
&&

$$

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