Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 141152

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
652 AM CDT Thu Sep 14 2017

Issued at 634 AM CDT Thu Sep 14 2017

Updated to include 12z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 410 AM CDT Thu Sep 14 2017

Despite some fog patches across central MN, the weather is benign
this morning with clear skies, light winds, and warm temperatures
in the mid to upper 60s. A boundary stretching from central SD
northeastward to northern MN will move little today. Storms will
be most numerous near and north of the boundary where the
deeper forcing is expected. The warm sector will remain strongly
capped through tonight due to a combination of the EML and dry
air below 600 mb. In addition, a lack of forcing south of the
boundary should prove very difficult to get any development
across the CWA, even with a 30 kt LLJ overhead. Despite these
negative factors, maintained a slight chance of showers and storms
due to the possibility of ACCAS more than anything.

A good amount of sun is expected today. Thermal profiles aloft
continue to warm, and today should be 1 to 2C warmer than
yesterday. Highs yesterday reached the mid to upper 80s, so still
expecting widespread upper 80s or lower 90s today.

.LONG TERM...(Friday through Wednesday)
Issued at 410 AM CDT Thu Sep 14 2017

By early Friday, the front will have sagged south into central
Nebraska, southeastern South Dakota, into central Minnesota and
far northern Wisconsin. The focus for showers and thunderstorms
will also focus further south and continue to be largely post
frontal. This should continue the warm and humid conditions across
much of the CWA, with the exception of far western MN stretching
up toward Lake Mille Lacs. Storms will become most numerous Friday
night as a mid level wave lifts northeast along the boundary. This
should allow the boundary to make a little more southward progress
for Saturday, but the front will become stationary again after
the wave lifts well north of the region. Clouds and continued
showers or storms Saturday behind the front may keep temperatures
in the low 60s across portions of western and central MN, while
rain-free areas ahead of the front will likely rise back into the
low/mid 80s. Another wave will lift north along the boundary
later Saturday. Showers and storms will grow more numerous again
with this wave, and this time could also occur in the warm sector
due to mid level height falls and the EML shifting east reducing
the cap.

Some severe storms could occur into Saturday evening near this
boundary. Overall the threat is marginal due to most of the
activity being elevated behind the front. The best chance will
occur with any storms nearest the warm sector, and therefore
mostly on Saturday.

A cool down will follow Sunday and Monday, but the trough lifts
out quickly by mid week with southerly flow returning. GFS
continues to advertise widespread WAA showers and thunderstorms
Monday night-Wednesday, and interestingly a well preserved
tropical system originating from the eastern Pacific tracking
northeast across the southern Plains and into the Upper Midwest by
Tuesday night. It has shown this consistently for the last few
days while the rest of the guidance has not. The rest of the
guidance is also considerably drier with respect to the WAA
activity. GFS is likely contaminating the blended guidance
somewhat with its very high PoPs, but the slight chance PoPs the
blended guidance is generating thanks to the GFS is probably not
a bad way to go at this range and given the pattern.

The good news with the deep trough out west is it should
significantly reduce their fire weather concerns and degraded air
quality from frequent bouts of wildfire smoke will greatly
improve locally.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 634 AM CDT Thu Sep 14 2017

Aside from localized fog near KSTC, all sites are VFR this
morning. Satellite imagery shows high clouds drifting in from the
west and these clouds will increase in coverage along with
decrease in height as a frontal boundary slowly approaches from
the west. No precipitation is expected during this TAF cycle (all
expected to remain to the N and W), but clouds will have ceilings
from late this morning onward. KAXN has the best chance at MVFR

KMSP...VFR throughout with no significant weather impacts
expected. High ceilings are expected from late this afternoon
through the overnight hours and tomorrow morning.

Sat...VFR. Chc TSRA/MVFR. Winds S 5-10 kts.
Sun...MVFR cigs possible. Winds WNW 5-10 kts.
Mon...VFR. Slight chc TSRA/MVFR. Winds SE 5-10 kts.




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