Scientific Forecaster Discussion
fxus63 kmpx 220401
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1101 PM CDT Sat Jul 21 2018
Short term...(this evening through sunday)
issued at 345 PM CDT Sat Jul 21 2018
This afternoon, the upper Midwest was caught between an anomalous
upper low across the Great Lakes-Ohio Valley, and an upper ridge
over the High Plains of Montana and western North Dakota. Deep
layer moisture has been abundant in the eastern 1/4 of mpx
forecast area of west central Wisconsin due to the persistent
wrap around of the moisture associated with the upper low. Mid
level lapse rates are weak in this area of west central Wisconsin,
but at least enough to generate a few diurnally driven showers or
storms through the early evening. Elsewhere over the upper
Midwest, very dry mid levels will keep this area dry through
The persistent north/northeast flow in the boundary layer will also
lead to an increase in boundary layer moisture across Wisconsin
later tonight. This may lead to low stratus/fog building across the
area toward sunrise. Sunday will mostly sunny and dry with an
increasing southeast wind in western Minnesota in advance of a cold
front moving across the Dakotas.
Long term...(sunday night through saturday)
issued at 345 PM CDT Sat Jul 21 2018
The pattern will be characterized by an upper high in the
southwest that slowly retrogrades, leading to a broad upper low
and trough across central and eastern Canada and into the U.S. By
mid and late week.
Aforementioned ridge over the High Plains will shift eastward, and
it should extend across Minnesota tomorrow evening. An upper low
in western Canada will follow, bringing broad ascent later Sunday
night and Monday in the wake of the ridge. Moisture will be
abundant, evidenced by the storms developing at this time from
Saskatchewan into Wyoming and Colorado. Thus have maintained the
chance of storms late Sunday night and Monday across the area.
Models are in decent agreement with moving the trough past Minnesota/WI
later Monday, so Monday night and Tuesday should be dry.
As the Canadian upper low heads for the Great Lakes region
Thursday, the next trough will approach Tuesday evening. Cooler
air will begin filtering in with northwest flow. Temps aloft drop
quite a bit, and this is a pattern typical of scattered showers
with a few afternoon/evening thunderstorms as well. Highs
Thursday look to be the coolest of the upcoming period, when the
upper low is the closest to MN/WI. But even as it moves away into
eastern Canada Friday, there should still be some northwest flow
and cool enough temps aloft to help promote more showers on Friday
afternoon/evening. And again on Saturday. Certainly a pre-fall
Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1101 PM CDT Sat Jul 21 2018
Main change from 00z tafs is stratus in WI is not looking to make
it as far west in WI, which means eau will remain in the clear. It
will be VFR through the night, with only a small threat of br/fg
at axn/stc/rwf, but potential is too low to include in the tafs.
With high pressure passing off to the north Sunday, we'll have
light east winds and a few-sct cu field between 3k and 5k feet.
During the afternoon, thunderstorms will develop along a cold
front in nodak and will be heading toward axn by the end of the
taf period. A few of the cams show ts reaching axn as early as 3z,
but that thunder will be on a decreasing trend, so will wait until
confidence increases on ts evolution into Minnesota before brining any
mention in to the taf.
Kmsp...at the end of the period, a few of the cams are indicating
showers may be in the area, with the hrrr being the most
aggressive with showing showers in the area as early as 8z. This
looks overdone when looking at forcing/instability forecasts, so
have kept msp dry and would be surprised if msp saw anything at
all with this front coming through on Monday.
/Outlook for kmsp/
Mon...VFR. Slight chc -tsra. Wind vrbl bcmg northwest 5-10 kts.
Tue...VFR. Wind west 5 kts.
Wed...VFR. Slight chc -tsra. Wind west bcmg northwest 10g20 kts.