Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 201838

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
138 PM CDT Sat Jul 20 2019

Issued at 129 PM CDT Sat Jul 20 2019

Updated for the 18Z aviation discussion below.


.SHORT TERM...(Today through Sunday)
Issued at 413 AM CDT Sat Jul 20 2019

The main forecast concern in the short term period is the showers
and thunderstorms forecast to move through the Minnesota and western
Wisconsin today.

As of early this morning, a surface low was noted across eastern
Colorado with the frontal boundary we`ve been dealing with for
days in place across northern Iowa. North of the front across
southern MN and western WI, dew points have fallen into the mid to
upper 60s and temperatures have cooled into the upper 60s to
lower 70s. Meanwhile, an MCS was progressing eastward across South
Dakota, and will eventually move across our local area today with
additional thunderstorm development out ahead of the MCS north of
the front.

The strongest instability has shifted south of with the front
itself, but up to 3,000 J/kg of MUCAPE will be in place across
southern MN which could lead to strong elevated storms with
isolated large hail. The main issue will be heavy rainfall and
lightning. The strongest forcing, including 600-700mb Fgen will
shift nearly due east across southern MN and western WI today.
There have been some differences in the model guidance on exactly
how far north or south the main slug of precipitation will go. The
HRRR is one of the more northern solutions while the global
models tend to point to far southern MN along the Iowa border.
Leaned toward the northern solution as CAMs have been consistently
showing this from run to run. From mid morning through mid
afternoon, expect showers and thunderstorms to work east across
southern MN and western WI, with a narrow 1-2" swath of rainfall
(and possibly locally higher amounts)expected.

Skies will clear from west to east this evening as reinforcing dry
northerly flow pushes in with pressure rises from the north. Sunday
will start out clear and dry, but a quick moving shortwave trough
will approach from the west by afternoon, introducing some chances
of precipitation to the forecast.

.LONG TERM...(Sunday night through Friday)
Issued at 413 AM CDT Sat Jul 20 2019

A pattern change is on the horizon in the long term, as the large
scale flow transitions to ridging over the Intermountain west and
troughing over the eastern CONUS. Overall this will mean dry and
mild weather for the forecast area, with the exception of possibly
the entry into and out of the pattern.

Sunday will be one of those days, in which we should see overall
dry weather, but a few stray showers can`t be ruled out given
fleeting northwest flow aloft. After that, we see several days
with mostly sunny skies and high temps moderating from the 70s to
low/mid 80s.

On Friday the western ridge flattens, which looks to bring back
northwest flow to the region. Both GFS and ECMWF models bring a
weak front across the area as a shortwave trough pivots over
northwest Ontario. Therefore the Friday night - Saturday time
frame would be the next decent opportunity for organized shower
and thunderstorm activity.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 129 PM CDT Sat Jul 20 2019

Thunderstorms have generally pushed south and east of all
terminals and will remain as such through this afternoon. VFR
conditions expected to prevail throughout. Clearing skies will
then follow tonight and remain through tomorrow. Winds will
eventually settle on an easterly direction with winds in the
15G25kt area this afternoon then go light/variable late tonight
through tomorrow.

KMSP...Improving conditions expected.

Mon...VFR. Wind N 5 kts.
Tue...VFR. Wind NW 5 kts.
Wed...VFR. Wind SW 5 kts.




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