FXUS63 KMPX 300924

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
424 AM CDT Mon Mar 30 2020

.SHORT TERM...(Today through Tuesday)
Issued at 424 AM CDT Mon Mar 30 2020

It is much more tranquil this morning than yesterday morning as
the system that brought heavy precipitation has pushed east of the
Great Lakes. Thin cirrus will eventually dissipate this morning
with abundant sunshine expected all day. A few patches of fog have
developed overnight, but these are highly localized due to the
overall dry air in place. MSP has humidity around 50 percent
early this morning.

Mid level heights will build today as the northern trough
continues eastward and the next one crosses the southern Rockies.
Temperatures rebounded more than anticipated yesterday following
the precipitation. The sun and warmer temps aloft will allow us to
reach the mid 50s to lower 60s area wide this afternoon. Forecast
soundings are very dry throughout the entire atmosphere. With
further drying in the boundary layer due to mixing processes,
humidity values will drop into the 20s and 30s. Similar
conditions are expected Tuesday except cloud cover will increase
and temps may be a degree or two cooler than today.

.LONG TERM...(Tuesday night through Sunday)
Issued at 424 AM CDT Mon Mar 30 2020

An active pattern is on tap for the long term period with several
rounds of precipitation. A trough will head east across the
northern Rockies and reach the northern Plains Tuesday. A cold
front will reach western MN by Tuesday night with a leading piece
of energy. This weak wave will bring a round of light rain to
the area through Wednesday morning. The energy will then lift
north, causing the cold front to stall somewhere over MN.
Meanwhile, another low pressure center will develop to the lee of
the Rockies over Colorado Wednesday night, reinforcing the
southeasterly flow ahead of the front and northwesterly flow
behind it. Rounds of showers are expected along the front late
week as the low becomes increasingly elongated up the baroclinic
zone. The lack of a closed low/centralized piece of energy will
prevent this front from clearing the area until late Friday when
the trough finally becomes neutrally tilted and swings northeast
through the Upper Midwest.

The specifics are still hazy and will ultimately depend on the
spatial characteristics of the front. This is normally a
dangerous set up for heavy rainfall and flash flooding, but
luckily deep moisture is lacking and will be characterized by
pwats of an inch or less. Modified continental air over the Gulf
and zonal flow of the subtropical jet across the southern U.S. are
the culprits. In addition, low level dynamics aren`t that
impressive either with an 850 mb jet of 40 kts or less.
Nevertheless, good convergence along the front should maintain
almost continuous shower activity. PoP has been raised to likely
across MN Wednesday night and Thursday morning, expanding to WI by
Thursday afternoon. Again, this will be subject to the front. It
should be noted the ECMWF is quite a bit further west with it and
most of Thursday is dry across eastern MN/western WI with
temperatures approaching 60. There could be some elevated
instability and the strong baroclinic zone led me to add a small
chance of thunder through this period.

The cold side of the front is another headache altogether. Post
frontal precip is expected Friday into Friday night. GFS, ECMWF,
and Canadian raw surface temps fall into the 20s and 30s so there
will be some concern of wintry precip. That has not been
introduced in a meaningful way yet due to uncertainty and also
the NBM is blurring the temperature gradient due to spatial
differences among all of its members. It will be easier to blend
in specific models to get a more realistic look later this week
when confidence increases. That could result in more and more
wintry precip in later forecasts.

Return flow already returns later Saturday with temperatures
rebounding Sunday. Some guidance is adverting a substantial ridge
developing early next week.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 424 AM CDT Mon Mar 30 2020

VFR conditions and light winds are expected through the period.

KMSP...No concerns.

Tue...VFR. Wind SE 5-10 kts.
Wed...MVFR/-RA likely. Wind SSE 10G20 kts.
Thu...MVFR/Chc -SHRA late. Wind SE 10-15 kts.





NWS MPX Office Area Forecast Discussion