Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 231131

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
631 AM CDT Mon Jul 23 2018

Issued at 623 AM CDT Mon Jul 23 2018

Updated to include 12z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 232 AM CDT Mon Jul 23 2018

Surface analysis early this morning shows a north-south oriented
cold front in the far eastern Dakotas, associated with a low
pressure center over central Manitoba province. High pressure over
the Northern Plains helping nudge the front eastward. Aloft,
zonal flow prevails from the Pacific NW into the Great Lakes,
south of a H5 low atop the aforementioned surface low while a dome
of high pressure resides over the Four Corners region. This
scenario will portray the surface front steadily moving eastward
across the WFO MPX coverage area today with isolated to widely
scattered showers and possibly a few thunderstorms. The main low-
level focusing mechanism will be the cold front, as such the
precipitation will be limited to the vicinity of the cold front.
Very weak support aloft combined with only modest instability
(MUCAPEs in the 500-1000 j/kg range) will mean that any
thunderstorms will be rather weak and isolated, thus mitigating
any strong/severe threat. Not looking for much in the way of QPF
either as PWATs are only in the 1.25-1.50 inch range with poor
coverage and progressive precipitation. In essence, just a few
passing showers with possibly a few embedded thunderstorms today
into this evening with clearing skies tonight through tomorrow

Mild temperatures will persist today with the zonal flow bringing
in no change in airmass. Will again look for highs in the upper
70s to lower 80s.

.LONG TERM...(Tuesday through Sunday)
Issued at 232 AM CDT Mon Jul 23 2018

The main feature across North America for this week will be the
large upper low and longwave trough across southern Canada. An
expansive ridge will also be in place across the southwestern
CONUS with the main jet (albeit weak) across the northern plains
at the start of the period.

A secondary shortwave embedded in the longwave trough across
southern Canada will pivot southeast around the main upper low,
Tuesday night into Wednesday, eventually moving through the MN/WI
with an associated cold front at the surface.  This front will have
a stronger thermal gradient and greater low level convergence, in
addition to upper level support from the upper level shortwave/vort
max and upper jet in the area.  Instability along the front will be
rather limited, so while scattered thunderstorms appear possible.
The guidance has come into better agreement with the timing of this
front, which will mainly move through Wednesday afternoon and

Adjusted wind speeds upward from the previous forecast as blended
guidance timing differences appeared to wash out the realistic
potential for winds behind the front Wednesday and on Thursday.
Widespread 10-20 MPH winds are expected both days after the fropa.
After this front moves through, we expect to see continued
northwesterly flow into the weekend with the main upper jet
dropping south of our area. We could see a few diurnally driven
showers from Thursday through the weekend as the main upper low
sags southward toward the northern Great Lakes, placing our region
in a favorable cyclonic flow pattern with steepening lapse rates
thanks to the cold air advection aloft.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 623 AM CDT Mon Jul 23 2018

A cold front will steadily sweep from west to east across the area
today. This will bring an increase in cloud cover along with the
potential for isolated -SHRA for mainly eastern MN into western
WI. Not looking for any significant impacts and will maintain VFR
conditions after any morning fog burns off. Chances for TS are too
low for mention at this point but the chances are non-zero so they
cannot be completely discounted. Best timing looks to be during
the afternoon hours with clearing starting this evening behind the
front and continuing through tomorrow morning. Winds will
eventually settle on NW in the 5-10 kt range by this evening.

KMSP...VFR conditions expected throughout this TAF set but there
is a small chance (about 30%) of having showers move through the
area early-to-mid afternoon. Any precip is expected to be light
with rainfall amounts possibly a few hundredths, at best.

Tue...VFR. Wind NW 5-10 kts.
Wed...Chc MVFR/-SHRA/-TSRA. Wind W bcmg NW 10G20 kts.
Thu...Chc MVFR cigs. Wind NW 10G20 kts.




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