NWS Forecast Discussion

FXUS63 KMPX 211805

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
105 PM CDT Wed Aug 21 2019

Updated for 18Z aviation discussion below.


.SHORT TERM...(Today through Thursday)
Issued at 347 AM CDT Wed Aug 21 2019

Fair and mild will describe the short term forecast period, as
surface high pressure drifts south from Canada.

In the meantime, a few showers may graze the southwest part of the
of forecast area this morning as a mid-level trough pivots through.
Otherwise, weak cold air advection will yield highs in the 70s over
the next couple days, with more comfortable dewpoints in the mid 40s
to lower 50s. Nighttime conditions will be conducive to opening
up the windows, with lows in the upper 40s to mid 50s. Any fog
concerns would most likely be restricted to river valleys.

.LONG TERM...(Thursday night through Tuesday)
Issued at 347 AM CDT Wed Aug 21 2019

The trend in the long term period has been to slow down the
arrival of the an upper trough and surface cold front this
weekend, and that trend continued with the latest guidance.

This period begins with very pleasant conditions thanks to a large
area of high pressure extending south across the Upper Midwest
from southern Canada and upper level ridging in leaning in from
our west. Thursday night will be cool under clear skies and with
the dry airmass in place. Overnight lows will likely fall into the
40s across central MN and parts of western WI, with low 50s
elsewhere. The center of the strengthening surface high will move
due south across Ontario toward Lake Superior by Friday, keeping
the very pleasant conditions in place locally through Friday.

The main change for this weekend was to continue holding the pops
off until later in the weekend. The models are in good agreement
that the upper ridge and the surface high will hold more firmly
through the day on Saturday, which now looks to be dry with
partly cloudy skies and temperatures warming up to near 80 as
southerly wind develops.

The anticipated upper wave will push east across the Dakotas
Saturday, so have pops slowly spreading east Saturday night across
western MN, finally reaching the MN/WI border midday Sunday.
However if this trend continues, the arrival could be even later.
As of now, the best chance of precipitation is from Sunday (west)
to Monday morning (east). Modest instability along with PWAT
values increasing to over 1.5" will lead to thunderstorms with
potentially efficient rain producers. There are some timing
differences for the frontal passage, but still looks to occur on
Tuesday which will be followed by cooler and drier air once again.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1258 PM CDT Wed Aug 21 2019

VFR conditions through the period with northwest winds around 10
kts this afternoon becoming diminishing after sunset. Mid/high
clouds will depart to the south with a few cu developing this
afternoon. Winds become NE tomorrow morning at 5-10 kts, with a
VFR cu field developing by late morning.

KMSP...No concerns.

Fri...VFR. Wind SE 5-10 kts.
Sat...VFR. Wind SE 10G20 kts.
Sun...MVFR/IFR possible. PM -TSRA likely. Wind S 10G20 kts.





NWS MPX Office Area Forecast Discussion

Script by Ken True @Saratoga-Weather.org