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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
659 am CDT Tuesday Jun 30 2015

Update...
issued at 646 am CDT Tuesday Jun 30 2015

Updated to include 12z aviation discussion below.

&&

Short term...(today and tonight)
issued at 400 am CDT Tuesday Jun 30 2015

Today and tonight...surface analysis shows a cold front draped from near
kgrb to the Iowa/Minnesota border then snaking back nwwd into the
central-western Dakotas. The upper level low responsible for nudging the
surface front southward is shifting eastward through the northern Great Lakes and away from
the area. Any lingering precipitation activity has long since diminished
early this morning...and with surface high pressure combined with slight 500 mb
and 700 mb height rises...indicating minor upper level ridging...plus
drier air moving into the region behind the front...Tuesday will be
devoid of precipitation.

The only real concern is for fog development in western WI into eastern Minnesota
where winds are nearly calm and decoupling from 15-20kt winds
within the blyr has been better established. Metars have generally
reported 2-4sm visibility with the occasional 1/2sm-1/2sm report. Since dense
fog only has spotty coverage this morning...have opted to hold off
issuing a dense fog advisory. Will monitor trends through this morning...but
am thinking only area fog mention should suffice.

Otherwise...a mix of clouds sun and clouds will prevail through the
day today...with partly cloudy skies continuing into tonight as modest
upper level ridging plus weak surface high pressure will keep precipitation streams
off to the west and S of the weather forecast office mpx County warning forecast area.

Slightly cooler and less humid conds can be expected today behind
the front with highs ranging 70-80 degrees and dewpoints
dropping into the 50s. As such...this will lead to cooler temperatures
Tuesday night with lows from the upper 40s in western WI to the upper 50s in
western Minnesota.

Long term...(wednesday through monday)
issued at 400 am CDT Tuesday Jun 30 2015

The main changes to the forecast in the long term was to trim much
of the low end probability of precipitation across western WI and eastern Minnesota further
west...so the forecast reads quite a bit drier in these areas
through Saturday.

High pressure over Ontario this morning will drift south into the
western Great Lakes. The low level dry air intrusion will spread
further east by tomorrow. The newest runs of the GFS/ec/NAM/sref
all push the quantitative precipitation forecast further west...and the reflectivity forecast off
the arw and nmm indicate all activity to remain across western Minnesota
an the eastern Dakotas...which makes sense given the shortwave
will mainly pass over the eastern Dakotas with the pv advection
and q- vector convergence focused there. This wave will depart
Wednesday night...as probability of precipitation again are pulled back to the west ahead
of the next wave.

The wave on Thursday looks a bit stronger...but will follow a
similar path through the eastern Dakotas. Stronger and deeper
forcing looks likely...with strong differential divergence moving
from near Aberdeen...through Sioux Falls and continuing southeast
of there...so a glancing blow for our forecast area. The European model (ecmwf)
had been an outlier in continuing to show precipitation potential
Thursday night across eastern Minnesota and western WI...but the 00z run
came in more in line with a dry forecast for this area and looks
to be in good agreement with the NAM/GFS/sref which all indicate a
fry forecast for eastern Minnesota and western WI Thursday and Thursday
night.

Daily temperatures through Friday will be very consistent as the
thermal field stays mainly stagnant as we remain between the
western ridge...and the upper trough to our east.

For this weekend...the surface high over the Great Lakes will be
pulling away...moving east. Southerly low level flow will
increase...and the temperatures will begin increasing over the
previous few days. The focus for this period will be a stronger
system developing in Canada and pushing a cold front across our
area...which looks to be late in the weekend. Continued a dry
forecast for Independence day...but in the southerly flow we may
see some instability develop by the afternoon. At this point
however...the GFS and European model (ecmwf) indicate that any convective
development will be north of our area during that time...so I felt
OK leaving a dry forecast in place but again later forecasts will
need to evaluate this period and possibly add low probability of precipitation depending
on the timing of the approaching system.

The GFS/ec agree on the cold front sweeping through the upper
Midwest...but disagree on timing. The ec is about 12 hours faster
and brings the front....and thunderstorms along it...through the
area Sunday...where the GFS does so Sunday night into Monday. So
we'll likely be dealing with thunderstorms at the end of the
weekend...but the exact timing will need to be sorted out.
Temperatures could warm well into the 80s ahead of the cold front
on Sunday.

On the heels of this system...northwest flow will drive cooler
temperatures and a Canadian surface high down into the upper
Midwest by Tuesday...so expect a cooling trend toward the middle
of next week.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 646 am CDT Tuesday Jun 30 2015

After some morning MVFR-IFR ground fog Burns off at a few
locations...tafs will be VFR through Wednesday morning. High pressure will
prevail over the next 24-30 hours...allowing for scattered-broken middle- and
upper-level layers during the period with no precipitation. Winds will
gradually shift from north to east through tmrw morning with speeds at or below 10 knots.

Kmsp...VFR throughout this taf set with no significant weather impacts
expected.

/Outlook for kmsp/
Wednesday...VFR. Winds east-northeast at 5-10 kts.
Thursday...VFR with slight chance MVFR -tsra. Winds southeast at 5-10 kts.
Friday...VFR with slight chance MVFR -tsra. Winds west-southwest 5-10 kts.

&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Update...jpc
short term...jpc
long term...speed
aviation...jpc

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