Scientific Forecaster Discussion
fxus63 kmpx 232000
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
300 PM CDT Sat Sep 23 2017
Short term...(this evening through sunday)
issued at 300 PM CDT Sat Sep 23 2017
The cold front stretches from near Redwood Falls, Minnesota to Ely, Minnesota
this afternoon, as witnessed by a 30-degree temperature spread
from west to east across the area (upper 50s in the west to upper
80s east). Showers and thunderstorms will continue generating
along the front over west/southwest Minnesota this afternoon and early
eve. Expect the bulk of the activity to stay west of a New Ulm to
Mora line, although a few "popcorn" showers will be possible as
far east as areas surrounding the I-35 corridor. A few storms
could pulse up to produce large hail and damaging winds, although given
the anafrontal nature of the convection (stronger lift on the
cool side of the front), most activity will be elevated with less
of a severe threat. As storms continue to train over western Minnesota
we will also need to monitor the heavy rainfall potential, given
precipitable water values are nearing 200 percent of normal for
this time of the year.
By Sunday morning, the front looks to retreat back into the
eastern Dakotas. This will make for another warm and humid day
across the eastern half of the forecast area, with cooler temps
and continued precip chances across the far west closer to the
Long term...(sunday night through saturday)
issued at 300 PM CDT Sat Sep 23 2017
The upper trough that has been over the western US for much of the
past week will start to move eastward tomorrow, and will slowly push
across our area during the first half of the week. A very pronounced
ridge will develop over the west during the second half of the week,
with northwest flow over our area as the upper trough re-amplifies
to our east. The medium range guidance is in decent agreement on
this overall evolution of things, with the typical differences in
some of the details, particularly during the second half of the
week. This is all in fairly good agreement with the going forecast,
so only minimal changes were needed to blend with the latest
numerical guidance consensus.
The frontal boundary stalled to our west will finally start to move
east tomorrow night as the western upper trough starts to push east.
This will bring shower/thunderstorm chances eastward across the
central and eastern portion of the forecast area from Sunday night
through Monday night. The upper trough isn't going to move too
quickly, so the surface front will also be slow to move, keeping
chances for precipitation going across the eastern portion of the
area through Tuesday. High pressure will then build into the area
with seasonably cool but dry conditions Tuesday night through
Wednesday night. It still appears we'll see a bit of a backdoor
front and reinforcing shot of cold air on Thursday, which could
bring some showers with it. This will be followed by the arrival of
Stout Canadian high pressure, will will build across the region
Friday through Saturday, with cool but dry weather.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1248 am CDT Sat Sep 23 2017
IFR/MVFR cigs will primarily affect the far northwest part of the
taf area (kaxn), although fleeting broken ceilings around 3kft or
just under will be possible slightly farther east and south
(kstc/krwf/kmkt) during the afternoon. Rain showers/ts chances are
expected to stay confined to kaxn as well. As the front wobbles
back into the eastern Dakotas overnight, precipitation and low
cigs retreat back west as well. This will mean kaxn will mostly
likely be precip-free after 05z, with VFR cigs arriving by early
Sunday. Other sites should therefore stay dry tonight with VFR
conditions. With the front back over the Dakotas, southerly winds
are expected to return for Sunday, with gusts into the upper teens
to lower 20s (knots). Showers and thunderstorm chances will inch
into the western portion of the area again on Sunday p.M.
expecting precip and MVFR cigs to stay to the west and northwest
of msp through the period.
/Outlook for kmsp/
Mon...MVFR/tsra. Winds S 5-10 kts.
Tue...chc MVFR/thunderstorms and rain early. Winds northwest 5-10 kts.
Wed...VFR. Winds west 5-10 kts.