Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Twin Cities/Chanhassen Minnesota
644 am CDT sun may 28 2017
Short term...(today and tonight)
issued at 357 am CDT sun may 28 2017
Showers have developed across western WI overnight ahead of the
cold front passing through. These showers will push east by dawn
with a period of dry weather this morning across the County Warning Area. As
temperatures rise into the mid to upper 60s by late this morning,
some weak surface-based cape will develop within the cyclonic
flow of the upper low centered just south of Hudson Bay. This
should allow for scattered showers and thunderstorms to develop,
most numerous north of I-94, and persist until diurnal instability
diminishes this evening. With seasonably cold thicknesses in
place, some of the more vigorous storms could contain hail, but
severe weather risk will be minimal due to such meager instability.
Steep low level lapse rates and cold air advection will bring a
windy day as well. Winds are beginning to gust into the 20-25 mph
range across western Minnesota, even early this morning. Forecast
soundings show good potential to gust to 25-30 mph area wide this
afternoon before boundary layer stabilization this evening leads
to a quick drop off in gusts.
Long term...(monday through saturday)
issued at 357 am CDT sun may 28 2017
The long term can be broken down into 3 parts. The first is cool,
showery weather on Monday with a few afternoon showers possible
again on Tuesday. The second it dry weather for Wednesday the third
is a chance for showers and thunderstorms on Thursday and Friday as
warmer, more seasonable air moves across the region.
On Monday an area of upper level vorticity will spin across the
Great Lakes region, and drive cool, Canadian air across the upper
Midwest. The forcing associated with the wave, together with the
unstable air generated by the Reservoir of cold air aloft will lead
to some afternoon rain showers on Monday, with a few lingering into
Tuesday afternoon as well. A few of the stronger cores could produce
some pea-size hail. Northwest wind will gust near 25 mph on Monday,
and near 15 mph on Tuesday.
Wednesday will be dry as a surface high pressure centers itself
across the region. The upper level ridge axis associated with this
surface high is narrow, meaning that as it moves east expect
southerly flow to return quickly so that by Wednesday night should
see a warm front lifting up from the southwest. The GFS/Gem 28.00
are in good agreement with an mesoscale convective system developing and moving along this
boundary on Thursday. The European model (ecmwf) is less aggressive.
Confidence beyond this period is low. There will be an upper level
wave dropping down from Canada, and depending on the timing this
could lead to a return of cooler, drier air for Friday and Saturday
as shown in the GFS/Gem, or else if it is quicker like the European model (ecmwf)
indicates, then more zonal flow may set up across the region and
bring warmer more humid air with chances for showers and
Aviation...(for the 12z tafs through 12z Monday morning)
issued at 644 am CDT sun may 28 2017
VFR conditions until late tonight when MVFR cigs may start
dropping south into central Minnesota. Scattered showers and a few storms
will form across much of the region this afternoon, with the
highest coverage likely in the vicinity of axn and stc. Left it
out elsewhere for now due to coverage concerns. West winds will
ramp up this morning, with gusts around 25 kt this afternoon.
Kmsp...best risk for showers and storms will be north this
afternoon, but a few cells could drift south toward the terminal.
/Outlook for kmsp/
Mon...VFR. Chc -shra. Wind northwest 10-20 kts.
Tue...VFR. Wind northwest 10-20 kts.
Wed...VFR. Wind northwest 5-10 kts.