Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 241727

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1227 PM CDT TUE MAY 24 2016

.UPDATE...For 18Z aviation discussion below


.SHORT TERM...(Today and tonight)
Issued at 450 AM CDT Tue May 24 2016

Today will be mostly dry with warm temperatures and more humidity.
Although not in forecast just yet, there is a slight chance for
showers or weak thunderstorms this afternoon in central
Minnesota. Isolated showers will continue in southeast Minnesota
and portions of western Wisconsin today as well.

Aside from fog in central and western MN behind the cloud cover
and a few showers in eastern MN/western is fairly quiet
weather-wise out there this morning. There is, however, a lot of
ongoing shower and thunderstorm activity throughout the region
this morning due to a couple different features. A surface trough
extends from Lake Superior down through the Southern Plains with a
couple shortwave propagating across the Upper Mississippi River
Valley this morning. The complex of thunderstorms in KS is an area
of pronounced 1000-500mb thickness diffluence. This complex of
storms is sending an anvil cirrus shield toward MN/WI. There isn`t
a pronounced convective trigger after this morning locally and
the flow below 10kft is weak, so we think the radar scope will be
mostly clear across the local forecast area. We should, however,
heat up nicely today and generate instability, so there could be a
few diurnally drive showers that pop up this afternoon in the
presence of 500-1000 j/kg of MLCAPE. Temperatures will likely make
it into the 80s this afternoon. A shortwave and warm front begin
to head this way late tonight and will bring numerous showers and
storms to the area (especially across southern Minnesota) by
Wednesday morning.

.LONG TERM...(Wednesday through Monday)
Issued at 450 AM CDT Tue May 24 2016

We continue to have high confidence in the fact that an active
pattern will dominate the upper MS Valley through the upcoming
holiday weekend as we see persistent large scale SW flow.
However, confidence in timing/coverage of precip through the period
remains low, resulting in a forecast that continues to be littered
with chances for thunderstorms.  The two periods though that look to
offer our best shot at seeing more widespread thunderstorm
activity, including the threat for severe weather, are Wednesday and
Friday through Saturday. Given the variety of solutions for precip
that exist, did not stray far from the blended guidance for PoP/QPF,
so would expect both of those to change in the coming days as we get
better confidence in timing/placement of precip, much of which
will be driven by how convection from the previous day has
impacted the placement of upper waves and surface boundaries for
the next day.

From the large scale, Wednesday looks pretty good for seeing precip,
with a shortwave coming out of the central Plains Tuesday night
working across southern MN Wednesday, this is occurring within the
right entrance regions of a jet streak up along the international
border. Still anticipating a complex of showers and storms to come
at us from Nebraska/Iowa Tuesday night as main shortwave and leading
edge of increased 925-700 moisture transport move through the area.
Our severe threat Wednesday will be largely driven by how convection
we see Tuesday night unfolds.  We will certainly have a moist and
unstable environment in place, but bulk shear again looks marginal
in the 30-40 kts range.  The difference though with Wednesday
compared to what we saw Monday, is there looks to be a bonafide warm
front coming into MN during the afternoon, with increased and backed
surface winds expected out ahead of it. Certainly would not be
surprised if the current Day 2 slight risk needs to be pulled
farther north quite a bit in future updates, as the
ECMWF/NAM/NMM/ARW all show the warm front lift to or even north
of I-94 by Wednesday afternoon.  The GFS brings the front up to
about the upper MN River Valley.  In addition, the NMM/ARW updraft
helicity forecasts show they are generating supercells along the
warm front Wednesday afternoon in central MN, so Wednesday certainly
bears some watching.

For Thursday we will see building heights in the wake of Wednesdays
wave, with our region getting more on the poleward side of a jet
streak coming out of the southern High Plains.  So there will be
large scale subsidence to contend with. However, we will see
thunderstorms re-fire again in the moist and unstable boundary
layer east of the cold front. What happens with convection
Wednesday/Wednesday night will help drive the location of the
front for Thursday and chance pops angling from SW MN toward NW
WI reflect the current thinking for the most likely location of
the front Thursday.

Friday and Saturday look like another good period for seeing showers
and thunderstorms as an upper low slowly tracks out of the TX
panhandle and up into the Red River Vally of the north.  The
GFS/ECMWF are depicting a warm front coming up into MN again on
Friday, while the arrival of the upper low sends a surface low
across western MN on Saturday.  This could be a fairly damp period
considering PWATS again increase to near and above 1.5".  The
presence of the warm front Friday followed by the surface low
Saturday could certainly continue our threat for severe weather too.

Precip chances look to diminish again for Sunday and Monday as we
get into some drying and subsidence behind Saturday`s shortwave, but
we will be maintaining our wavy SW flow aloft, with no frontal
boundary looking to clean the low level moisture out of the region,
so the chance pops continue for Sunday and Monday as we will likely
see storms redevelop along any remnant boundaries we have hanging


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1226 PM CDT Tue May 24 2016

The primary concern this TAF period is on the potential for
thunderstorms and MVFR conditions...primarily on Wednesday.

The pesky stratus deck that developed and lingered across central
MN this morning will continue lifting/eroding...with mainly sct-
bkn cumulus and cirrus clouds prevailing this afternoon. Could see
a few widely scattered showers and thunderstorms develop over
central MN this afternoon and early eve...but expect the bulk of
the activity to hold off until after 09Z widespread activity
moves in from the southwest. Expect most sites to be affected with
showers and thunderstorms between 12z and 18z Wednesday. There
could be instances of mvfr cigs/vsbys in conjunction with the
heavier activity. Winds are variable as of now...but will
eventually take on a southwest directional component...then become
east/southeast tonight and Wednesday with gusts developing.

Northwest winds to start the period, but expect a shift to
southwest early afternoon. An isolated shower/ts is not entirely
out of the question by early eve...but probability is very low.
Higher chances arrive around daybreak Wednesday, with periods of
SHRA/TS expected through the morning.

Thu...Mainly VFR. Chc TSRA/MVFR. Wind S to SW 5 kts.
Fri...Mainly VFR. Chc TSRA/MVFR. Wind SE 5 kts.
Sat...MVFR. TSRA/MVFR Likely. Wind SSE 5 kts.


.MPX Watches/Warnings/Advisories...


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