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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
513 am CDT Friday Sep 30 2016

Short term...(today and tonight)
issued at 332 am CDT Fri Sep 30 2016

Cut-off 500 mb low that drifted down into Kentucky yesterday is already
starting to lift back to the north-northwest this morning. Biggest implication
for US is that the low stratus looks to return from the east faster
than initially indicated, with sky grids increased considerably this
afternoon in western WI/eastern Minnesota and overnight for western Minnesota. 925-
850 relative humidity off the GFS/NAM/rap shows cloud cover currently over southeast WI
ending up in eastern South Dakota by Saturday morning. Of interest though is
that the NAM in particular shows a wedge of dry air dropping down
from Lake Superior tonight, with skies actually clearing out some in
western WI tonight as the stratus is heading for South Dakota. Given the
expected cloud cover, low 70s are unlikely again today out in
western WI.

Other issue more for this morning is a batch of low stratus coming
down off of Lake Superior. The hrrr shows this cloud cover getting
down to about the Twin Cities/Wilmar in the for of fog/low stratus.
Though this may result for a cloudy morning for much of central Minnesota,
this looks to mix out by mid-late morning with a brief window of
sunny skies in the afternoon before cloud cover arrives from the
east.

Last change made in the short term was to keep the Eau Claire area
dry through 12z Saturday. Cams and deterministic models alike keep
the mpx area dry, with any rainfall Friday night confined to eastern
WI where moisture on the 290-305k isentropic surfaces.

Long term...(saturday through thursday)
issued at 332 am CDT Fri Sep 30 2016

The period begins with a stubborn upper level low lifting slowly
northward across Indiana. Considerable cloudiness will occur
across the forecast area in the morning along with a few showers from the
southeast corner of Minnesota through Keau. The cloudiness should begin
to breakdown from the northeast in the afternoon as drier air
spreads in along with the upper level low beginning to drift east.
This leaves a Horseshoe of higher cloud cover curving from
western Minnesota through Iowa to eastern WI. The cloudiness will breakdown
Saturday night leaving US with a fine early fall day on Sunday.
High temperatures this weekend will be very close to seasonal
values with lows about 5 degrees above normal.

We have had a little bit of a roll reversal for next week between
the ec and GFS with regards to the weather system impacting the
forecast area in the Tuesday through Thursday period. The ec continues to
inch forward a bit on the leading edge of the rain on Tuesday
while the GFS is looking more like earlier runs of the ec on
keeping rain out of the Twin Cities until Wednesday afternoon. The
Canadian would also keep rain out of the local area until
Wednesday afternoon.

One of the differences noted is that the ec has more of a
positively tilted upper wave while the GFS and Canadian are more
negatively tilted. At this point, we allowed small pops into
western Minnesota on Tuesday with the small pops working across eastern
Minnesota and western WI Tuesday night. This will be too fast if the
latter solutions are correct. Another item noted is the strength
of the low level moisture transport Tuesday night and early
Wednesday across western Minnesota. This area will likely see the most
rain from this event with amounts of a half inch to one inch
likely. The long term closes out with a cold front pushing east of
the forecast area with a breezy southwest wind occurring on Thursday.

High temperatures early next week will continue to be close to
seasonal normals. However, highs will trend downward thereafter,
with readings only in the middle 50s to lower 60s expected on
Thursday.

&&

Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 507 am CDT Fri Sep 30 2016

Fog/low stratus has slowly built southwest from Lake
Superior through the night. Only mpx terminal that will
definitely be in it is stc, with axn on the western edge of the
clouds and msp/rnh/eau near its southern edge. Followed the idea
of the hrrr that this fog will slowly mix out through the
morning, finally clearing out of central Minnesota in the mid to late
morning, which is a bit slower than what lamp guidance has. Of
course is this is going on, stratus has been rapidly pushing west
across WI through the night and will be moving from west to east
across the area today. Not expecting fog to be as much of an
issue tonight as forecast soundings show US going the Route of a
2k-5k foot ceiling.

Kmsp...fog/stratus has made it into the North Metro and
northeast winds will continue to try an push it toward msp. At
this point, not very confident of the stratus will reach msp this
morning, so maintained a tempo group. Confidence is high that
status coming in late this afternoon will remain above 018.



/Outlook for kmsp/
Sat...VFR. Wind east-northeast at 5 kts.
Sun...VFR. Wind NE at 5 kts.
Mon...VFR. Wind southeast at 5-10 kts

&&

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

$$

Short term...mpg
long term...rah
aviation...mpg

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