Scientific Forecaster Discussion
fxus63 kmpx 250634
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
134 am CDT Mon Sep 25 2017
Short term...(this evening through monday)
issued at 304 PM CDT sun Sep 24 2017
Widely scattered showers and isolated thunderstorms will continue
to pop up this afternoon ahead of the cold front over the eastern
Dakotas, where boundary layer heating has resulted in 3-hour
MLCAPE increases of 100-200 j/kg over western Minnesota. This
activity will be possible through sunset. A few stronger storms
cannot be ruled out during this time with a damaging wind threat
given 40-50 knot 850-500 mb flow. Overall, however, the severe
potential is low. The concern for large hail is lower given
relatively poor mid level lapse rates.
After sunset the concentration turns to the main area of Post-
frontal precipitation that will advance eastward across the area
overnight and Monday. Have included 70-80 percent precip chances
as the front meanders across the area. This event should provide a
good soaking given precipitable water values are forecast to
increase to around 1.75 inches by 12z Monday, coming close to
setting a record high precipitable water value for the date.
With the bulk of the area socked in with clouds and precip behind
the front on Monday, most areas will see highs in the 50s and 60s,
with the exception of Wisconsin where 70s will be common.
Long term...(monday night through sunday)
issued at 304 PM CDT sun Sep 24 2017
Things continue to look similar to how they've looked the past
several days. In the big picture, the western upper trough will lift
northeast and work its way across our area through midweek. Ridging
will re-build across the west during that time, with northwest flow
setting up over our area for the second half of the week. The
western ridge will then flatten as it shifts east toward our area
over the upcoming weekend. The numerical guidance is in fairly good
agreement on this overall scenario, with no notable differences
until the tail end of the period.
The frontal boundary will continue to push east tomorrow night
through Tuesday, eventually taking lingering precipitation with it
and out of the eastern portion of the area by Tuesday evening. This
timing could be slightly delayed if the surface wave which develops
along the front on Tuesday winds up stronger than currently
indicated. High pressure will build in from the west and provide
cool and dry weather Tuesday night through Wednesday night. But, a
cold front will drop in from the north on Thursday, with an
accompanying chance for showers. A stronger surface high will build
southeast from Canada behind this front, with seasonably cool and
dry weather Thursday night through Saturday evening. The details are
a bit Muddy after that, but the GFS and European model (ecmwf) both suggest another
frontal boundary and associated shortwave trough will move toward
the area on Sunday, bringing another chance for precipitation.
Aviation...(for the 06z tafs through 06z Monday night)
issued at 131 am CDT Mon Sep 25 2017
Ceilings have already lowered to IFR in west central Minnesota. Ceilings
across the rest of central and southern Minnesota and far western WI
will also lower to IFR or low MVFR tonight, spreading west to
east, then persisting for much of Monday. There will be rain with
a chance of thunder moving through as well.
Kmsp...low clouds will persist most of Monday with the slow
moving pattern. Rainfall will be steadiest in the morning.
/Outlook for kmsp/
Tue...chc MVFR/thunderstorms and rain early. Winds northwest 5-10 kts.
Wed...VFR. Winds west-northwest 5-10 kts.
Thu...VFR. Winds west 5 kts.