Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 192314

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
614 PM CDT Mon Jun 19 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 323 PM CDT Mon Jun 19 2017

Scattered showers continue across southeast MN and west central WI
late this afternoon, with even a lightning strike or two at times.
This activity will diminish after sunset, with clearing skies for
this evening. Another fairly potent wave in the mid levels arrives
late tonight. This should bring another round of scattered to
numerous showers and a few storms between midnight and mid morning
Tuesday. Highest coverage will be across central/eastern MN and
western WI. Drier air will follow for Tuesday afternoon with
clearing skies again.

.LONG TERM...(Tuesday night through Monday)
Issued at 323 PM CDT Mon Jun 19 2017

In the big picture, we`ll see the eastern lift out over the next two
days, but a healthy shortwave trough moving through our area in the
Wednesday-Thursday time frame looks to help reload the eastern
trough by the weekend, with northwest flow re-establishing itself
over our area with unseasonably chilly temperatures for the weekend.
The guidance, deterministic and ensemble, is in fairly good
agreement on that overall scenario and evolution of large scale
features, so didn`t see much reason to stray too far from a
consensus approach with the forecast. The main item of
interest/concern continues to be the system that will affect the
area Wednesday and Wednesday night. Until then, things will be
relatively quiet. We`ll see a weak surface ridge build into the area
Tuesday night, helping to end any lingering shower activity.
However, a shortwave ridge will begin to approach from the Northern
Plains by Wednesday morning, with return flow and the 850 mb theta-e
ridge getting into the western part of the area after 12Z. We should
see some elevated convection as this works into the area, which
should shift north of us during the morning. However, the guidance
shows enough disagreement for there to still be quite a bit of
uncertainty as to where lingering convection will be and where it
will persist on Wednesday morning and early afternoon. This
complicates things for where/when we`ll see new convection fire
during the late afternoon/evening as the cold front works east
across the area.

But, with it looking likely that there will be some convection over
the region, there will certainly be some risk of severe weather
given decent instability and more than sufficient shear expected.
MLCAPE values in the warm sector look to be from 1000-2000 J/Kg, and
0-6 km bulk shear is forecast to be AOA 50 kt across much of the
area. Lower layer (0-3 km) bulk shear is also forecast to be quite
strong (with some differences amongst the guidance) with values AOA
35 kt. Expected storm motion looks to be somewhat parallel to
forecast 0-3 km shear, which could favor bowing segments and a wind
threat. However, 0-1 km bulk shear looks to be AOA 25 kt and
somewhat perpendicular to anticipated storm motion, which would
potentially favor low-level streamwise vorticity ingestion which
would favor stronger longer-lived low-level mesocyclones. It`s a bit
too far out to have a ton of confidence in these details, but there
is enough of a signal to continue to keep an eye on things, and
anticipate all three severe weather threats at this point in time
should storms develop in the favorable zone from southern Minnesota
southward ahead of the cold front in the late afternoon into evening

We should see precipitation mostly exit the area by Thursday
morning. We`ll see a secondary cold front bring in much cooler air
starting Friday, then lingering through the weekend. With the cold
pool aloft that means we`ll have a chance of diurnal showers and a
few thunderstorms each day, with some nighttime continuation of
activity when it`s enhanced by shortwave troughs embedded in the
northwest flow (which, at this point, is impossible to pin down the
timing of).


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 615 PM CDT Mon Jun 19 2017

Confidence is fairly high that a complex of SHRA/TSRA in eastern
North Dakota, will move southeast and affect portions of
central/southern Minnesota, and into west central Wisconsin
overnight. Although timing is easy, the intensity will be
difficult and whether there is enough instability to lead to TSRA
or heavier SHRA. At this time, will keep things simple with either
VCTS and a tempo of 6SM SHRA, or -SHRA with VCTS. Otherwise, VFR
conditions will continue with little/none of SHRA/TSRA Tuesday


Similar discussion with timing of storms/showers around 7z with
possibly a period of 6SM SHRA. Although confidence is low on
intensity and areal extent of the precipitation. After 13-15z, VFR
conditions will prevail with no more precipitation expected.


Wed...VFR. Chc -TSRA in the Aftn/Evening. Wind S 10 kts.
Thu...VFR. Chc -TSRA in the Morning. Wind WNW 5-10 kts.
Fri...VFR. Wind NW 10 kts.




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