Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 211155

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
655 AM CDT Sat Oct 21 2017

.Updated for 12Z Aviation Discussion...
Issued at 634 AM CDT Sat Oct 21 2017


.SHORT TERM...(Today and tonight)
Issued at 317 AM CDT Sat Oct 21 2017

The multiple rounds of precip discussed in the earlier discussion
appears more likely, so continued with that concept in the
weather grids. Early morning IR imagery with radar showed cooling
cloud tops associated with an area of convection in eastern Iowa.
HiRes models have a pretty good handle on this precip, but they
are just about an hour or two slow in the timing. They show the
precip lifting up across central/eastern Minnesota and far western
Wisconsin this morning with a break in the action around mid day.

A second area of precip tied to the parent wave and cold front
will develop later this afternoon and early this evening across
western MN and advance eastward into the overnight hours. SPC
still has a slight risk of severe weather across southeast MN, but
most of our CWA is in a marginal risk for severe weather which
makes sense given this set up. Not anticipating any severe storms,
but at the same time can`t rule out the possibility.

Looking ahead, westerly winds will increase tonight behind the
passing cold front, but temperatures will remain fairly mild by
climatology standards with H850 temps remaining above zero and
Sunday morning lows only falling into the 40s at most locations.

.LONG TERM...(Sunday through Friday)
Issued at 317 AM CDT Sat Oct 21 2017

The extended period remains active with a seasonably strong upper
level jet remaining across northern hemisphere with several mid-
latitude cyclones developing over the continent. This strong jet
is tied to a strong low level temperature gradient, so it is easy
to see the environment is ripe for these cyclones to form and wrap
cold air behind them. At this point it appears the storm track
will stay north of the region so MN/WI will notice mainly
temperature changes and slight chances for light precip.

Early next week an upper level trough will interact with a cutoff
low over the southern plains. Cold air will surge across the
region on Tuesday, but be quickly replaced by the warm air ahead
of the next approaching shortwave on Wednesday.

The track and evolution of this system remains uncertain with the
GEM being more progressive and driving a cold front through the
region and building in surface high pressure, while the ECMWF
wraps up a powerful cyclone and brings widespread precip late next
week and into the weekend. The GFS is somewhere in the middle, but
the case and point is that despite the fact the weather pattern
looks unsettled, there is high uncertainty in the weather
forecast beyond the middle of next week.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 634 AM CDT Sat Oct 21 2017

Showers and thunderstorms will lift northward across the region
this morning, but then there should be a break from the precip
before another line develops later this evening. As of now it
appears that the best chance for rain later today will be across
southern MN. Could see some MVFR clouds today as well, but these
should improve once a cold front moves through later this evening
and brings drier air across the region.

Could see some gusts near 30 kts with the thunderstorms this
morning, but these storms will exit the region and should be dry
most of the afternoon. The chance for thunder later this evening
has decreased, so removed thunder mention from the TAFs later
today. Southerly winds should shift around 03-04Z this evening.

Mon...VFR. Winds W 20G30 kts.
Tue...Chc MVFR. Wind NW at 15G25 kts.
Wed...Chc MVFR. Wind NW at 15G25 kts.




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