Area Forecast Discussion
Issued by NWS Twin Cities, MN

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758
FXUS63 KMPX 290007
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
707 PM CDT Wed Jun 28 2017

.UPDATE...
Issued at 657 PM CDT Wed Jun 28 2017

Updated to include 00z aviation discussion below.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 349 PM CDT Wed Jun 28 2017

In the wake of morning convection, we saw a seasonably strong
stratospheric intrusion with the 1.5 PV surface getting down to
about 400 mb. This has shown up well on all 3 water vapor
channels. Just before 3pm, this upper feature reached the cold
front near the I-35 corridor, with storms initiating over Dakota
county. The cells that went up over Wright county over to the
north metro are on the northern edge of this PV feature and were
more elevated, at least initially. We have had great low level
shear most of the day with backed surface winds. However, as these
storms have developed, our surface winds have really started to
veer and our shear values have plummeted, to the point where in
MN, we have only weak speed shear. As a result, the storms we have
seen near the metro to this point have been more pulse in nature
and have not been able to sustain strong updrafts long enough to
get anything severe going. Effective shear values over 30 kts
reside where the SPC has a slight risk in the Day 1 outlook and
our thinking on the severe threat is pretty similar, with it being
confined to southeast MN toward central WI where the better shear
resides and the potential for better organization exists. So
we`ll have to keep an eye on this activity as it moves into this
region.

Tonight, these storms will exit our east by midnight as we lose
diurnal heat and the front continues its march into WI. The main
question for tonight is how extensive does low stratus become as
we get into the backside of the low. The NAM/RAP/HRRR all bring
it down to about the US-12 corridor. This may be a bit far south,
but did increase sky grids quite a bit across central MN into
western WI for tonight.

Thursday will feature ridging over the upper MS Valley, but
another trough will be working across the Dakotas in the
afternoon. The front working through tonight will be washing out
across IA. All of this puts the MPX area in a bit of a lull when
it comes to forcing, with thunderstorm activity through the day
Thursday expected to be mainly down in Iowa near the remnant
boundary and to the west in the Dakotas with the upper wave. Our
precip chances look to increase Thursday evening (start of the
long term) as the Dakotas trough moves into MN.

.LONG TERM...(Thursday night through Wednesday)
Issued at 349 PM CDT Wed Jun 28 2017

Expect periodic chances for showers and thunderstorms, but
overall not a complete washout for the upcoming weekend. The first
half of the weekend will be cooler and cloudy with light winds and
a few scattered showers or thunderstorms. High pressure will
briefly move in for Sunday and Monday which will dry things out
north of I- 90 and bring temperatures closer to normal. Looking
ahead, southerly flow will return early next week and set the
stage for more widespread showers and thunderstorms for the middle
to end of next week.

An upper level trough will drive a couple of cold fronts through
the region over the weekend. The synoptic forcing ahead of this
trough, together with the small, thin CAPE profiles support
scattered showers and thunderstorms on Friday, similar to what
occurred this past Saturday. Marginal CAPE and Shear profiles
limit the risk of severe weather, so at this time only expect
perhaps some small hail with a few of the stronger cells. Saturday
will have less of a chance for showers and thunderstorms, but
can`t go completely dry.

On Sunday a secondary cold front will move through the region as a
shortwave trough sweeps across the Boundary Waters to the north.
Models try to produce some precip along this front, but it seems
like the large-scale subsidence should win out, so went drier than
the model guidance for Sunday. The GFS tries to hang up a
boundary across the south with repeated chances for showers and
thunderstorms early next week, but these should be more favored
across the south near IA/IL. Looking ahead, another shortwave
trough should bring showers and thunderstorms across the Upper
Midwest for the middle/end of next week, with warmer more humid
weather to follow after that.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 657 PM CDT Wed Jun 28 2017

Convection has exited the terminals to the east so will not expect
any further precipitation through the rest of this forecast cycle.
With the upper level low dropping into the region overnight into
tomorrow morning, some MVFR ceilings are possible for several
hours either side of daybreak tomorrow morning. Otherwise, mainly
VFR skies will prevail with winds gradually shifting around from
WNW to N with speeds in the 5-10 kt range.

KMSP...VFR into the early morning hours then MVFR ceilings likely
throughout the Thursday morning push. Then VFR conditions expected
for the rest of the day tomorrow.

/OUTLOOK FOR KMSP/
Fri...VFR. Chance MVFR with likely TSRA. Winds variable 5 kts.
Sat...VFR. Winds WNW 5-10 kts.
Sun...VFR. Chance of TSRA/SHRA. Winds light and variable.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

UPDATE...JPC
SHORT TERM...MPG
LONG TERM...JRB
AVIATION...JPC



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