Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 220828

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
328 AM CDT MON AUG 22 2016

.SHORT TERM...(Today and tonight)
Issued at 328 AM CDT Mon Aug 22 2016

Today and tonight...Surface analysis this morning shows a large area
of high pressure centered over southern IL/IN, expanding well
westward across the middle and upper Mississippi River valley
regions. Aloft, a ridge axis is located over the central-northern
Plains while a compact upper level low develops over the southern
Canadian Rockies. As the day progresses, this ridge axis will shift
eastward, moving atop MN/WI by daybreak Tuesday morning. Meanwhile,
the surface high will also shift eastward to the Mid-Atlantic states
while a surface low strengthens just north of the Montana/Canada
border. While being on the backside of the surface high, it will
maintain its influence over the area. The lingering high combined
with the incoming ridge will result in warmer temperatures as highs
will range from the lower 80s in western WI to the upper 80s in
western MN. There will be some passing clouds from time to time in
response to an increase in mid-level moisture and potentially a
surface trough reaching into MN from the Rockies. However, despite a
few CAMs showing isolated showers this afternoon over the region, am
not expecting precipitation to actually develop that would reach the
ground because of the deep dry air that must be overcome. Since this
trough will then lift north into Canada and the low out in the west
will not arrive to influence sensible weather within the next 24
hours, will maintain a dry forecast with passing clouds. The main
influence of the developing low, especially with respect to
lingering high pressure, will be a tightened pressure gradient over
the area today. This will make for breezy/gusty conditions today
with southerly winds of 15-25 mph and gusts around 30 mph at times
this afternoon. The slight increase in clouds with the strong
southerly flow will make for highs early Tuesday morning about 10
degrees warmer than this morning.

.LONG TERM...(Tuesday through Sunday)
Issued at 328 AM CDT Mon Aug 22 2016

By Tuesday morning, the thermal ridge will be across the eastern
Dakotas and into western MN, with a surface low advancing northeast
through eastern North Dakota with a cold front trailing to its west.
West of there, a closed low will be advancing east across southern
Canada and will begin to merge with the North Dakota low during the
day on Tuesday. For us, this means Tuesday will again be a warm one,
with stout southerly flow and dew points rising into the upper 60s
and temperatures in the upper 80s and heat indices into the 90s.
Skies will start out partly cloudy but late in the day a quick
increase in cloud cover will signal the incoming moisture as a
shortwave advances through eastern Nebraska and into Iowa.

The main focus of the long term is the Tuesday night period.  The
previous discussion issued yesterday afternoon greatly described the
possibilities  at play Tuesday night and the latest model guidance
latched onto the idea of the heavy rain and MCS potential being
across Iowa in association with the strong low level jet.  As a
surface low develops across Kansas, the low level jet evident by the
850mb winds increasing to 50-60 knots across Kansas through eastern
Nebraska and into southern Iowa will drive the storm activity and
likely MCS development across the greatest convergence of warm air
and moisture transport across Iowa.  This area is the most likely
setup for MCS development and with the LLJ staying to our south, the
thunderstorm activity will be limited across Minnesota and west
central Wisconsin.  Continued likely pops along the I-90 corridor for
now as scattered storm development is possible there, but lowered
likely pops to chance across the rest of the forecast area. If this
setup is reinforced by todays newest model guidance, the pops across
Minnesota and Wisconsin could be lowered even more.  The HOPWRF-TS
forecast reflectivity aligns well with this thinking as it indicates
a very plausible scenario in which a strong MCS develops along the
nose of the LLJ in eastern Nebraska and moves through central Iowa,
and in turn makes it very difficult to the north of said MCS for
much of anything to develop.

The previously mentioned cold front with this system will push into
western MN Wednesday morning and work through eastern MN and western
WI during the day.  Winds will turn northwesterly behind it and
those upper 60s dew points will fall into the 50s by Wednesday
night.  Cold air advection will continue and Thursday will be a lot
like yesterday with temperatures in the low 70s and dew points in
the lower 50s.  Southerly flow will develop Friday so we`ll start
warming up some but it should be another pleasant day.  This weekend
still looks unsettled as two shortwaves look to move through the
Upper Midwest and bring chances for thunderstorms across the region.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1050 PM CDT Sun Aug 21 2016

VFR conditions will persist through the period. Skies will be
mostly clear overnight, with only a few-sct mid/high clouds on
Monday. Light southerly winds overnight will become gusty by late
Monday morning...reaching sustained speeds of 15-20kts with gusts
from 25-30kts.

High confidence in VFR through the period. Sustained speeds will
reach around 17 kts by 18z Monday with gusts to around 25 kts.

Tue...VFR. -TSRA possible late. Wind SSW 15-20G25 kts.
Wed...VFR with -TSRA/MVFR possible. Wind SW 5-10 kts becoming W.
Thu...VFR. Wind NW 5-10 kts.


.MPX Watches/Warnings/Advisories...


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