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Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
602 PM CDT sun Aug 18 2019

Update...
issued at 551 PM CDT sun Aug 18 2019

Updated to include 00z aviation discussion below.

&&

Short term...(this evening through Monday night)
issued at 338 PM CDT sun Aug 18 2019

Clearing skies this afternoon as high pressure builds into the
region behind a departing cold front. Gusty northwest winds around
20 mph this afternoon will diminish after sunset, but still remain
around 5 kts overnight. This continued advection of dry air into
the area should mitigate any widespread fog concerns overnight,
despite the wet ground and clear skies. Still could see some
patchy fog across west-central Wisconsin where winds will be
lighter, as well as the typical culprits near bodies of water and
in low-lying areas. A comfortable night is expected temperature-
wise, with lows in the upper 40s to mid 50s.

Tomorrow looks like a fantastic late Summer day with plenty of
sunshine and highs reaching near 80. Dewpoints will begin rising
into the mid-60s across western Minnesota as southerly winds
develop out ahead of the next front, but muggy conditions should
hold off elsewhere until Monday night. Models continue to be
inconsistent in handling the front moving across the area Tuesday,
as well as the strength of the shortwave skirting the
Minnesota/Iowa border. Guidance has trended towards the bulk of
any precipitation either during the day on Tuesday or remaining
mostly dry, but the 12z European model (ecmwf) has come in much stronger with the
shortwave and generates widespread thunderstorms along the front
overnight Monday. Have added low chance pops across western
Minnesota early Monday morning to account for this potential early
onset of precipitation.

Long term...(tuesday through sunday)
issued at 338 PM CDT sun Aug 18 2019

The weather during the extended will be your typical fare as we
head toward the end of August. Best chances for rain look to
come Tuesday and again Friday/Saturday with the passage of a
couple of weak waves. Temperatures will be near normal as well,
with no significant heat expected.

We start this period with the passage of a cold front Tuesday.
Models, which had been trending drier with this front for US the
last couple of days have started creating a little bit more quantitative precipitation forecast
down this way, at least with the 12z runs of the ECMWF, GFS, and
Canadian. The best forcing and upper jet support is still expected
to be up along the international border, but we'll have the
better moisture and instability down here. The main question is
will we have enough forcing to overcome the fairly Stout capping
in the form of either a shortwave or low level jet. We stayed with nbm pops
for now, which were just 20s/30s for eastern Minnesota into WI. If we
were to get something to go, given lapse rates, instability, and
shear, an at least conditional severe risk would exist. Another
area of some uncertainty for Tuesday is highs. Nbm gave US low-mid
80s for highs on Tuesday, which will only happen if one, the
front comes through late in the afternoon and two, it comes
through dry with little cloud cover.

Behind the front, we will get a couple of absolutely perfect
Summer days Wednesday and Thursday. With mixing, we should see
dewpoints drop into the 40s for most of the area on Wednesday,
with highs both days in the low to mid 70s with mainly sunny
skies. Given the extent of dry air with high pressure moving in
Wednesday night, we should have no problem getting some lows down
into the upper 40s Thursday morning into central Minnesota.

Thursday night into Friday, a strong h5 low will be tracking
across northern Saskatchewan and Manitoba. This will send a cold
front into the upper MS valley region on Friday, but being so far
removed from the forcing, we will be at the south end of this
front, with it likely washing out or getting hung up across the
region over the weekend. This is why we have low pops from Friday
through the weekend at this point. Right now, but chance for rain
looks to come Friday into Saturday as the boundary initially moves
into the area. There really isn't any forcing to help push this
boundary out of the area until early next week. With this boundary
moving in, we will see humidity levels increase for the weekend,
though the brunt of the heat looks to remain to our southwest, so
we'll likely just see highs creep back up into the 80s, with any
90s remaining likely southwest of the Missouri River.

&&

Aviation...(for the 00z tafs through 00z Monday evening)
issued at 551 PM CDT sun Aug 18 2019

Solid VFR conditions with only few high cirrus, if any, clouds
through tomorrow afternoon. Gusty northwest winds early this evening will
settle down to less than 5 kts and back to southerly overnight
through tomorrow then pick up to around 10 kt tomorrow afternoon.

Kmsp...no additional concerns.

/Outlook for kmsp/
Tue...VFR. Chc a.M. -Tsra/MVFR. Wind S 5-10 kts becoming northwest.
Wed...VFR. Wind northwest 10-15 kts.
Thu...VFR. Wind variable 5 kts or less.

&&

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

$$

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