Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 291746

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1246 PM CDT Sat Apr 29 2017

.UPDATE...For 18z Aviation discussion below


.SHORT TERM...(Today and tonight)
Issued at 420 AM CDT Sat Apr 29 2017

High pressure will dominate the weather today with another day
similar to yesterday with temperatures a couple of degrees warmer,
still about 15 degrees below normal. High pressure slides north of
Lake Superior tonight as low pressure in Texas moves toward
northeast Oklahoma. High clouds will move into southern Minnesota
this morning with cloudy skies expected by late afternoon. Showers
will remain just south of the forecast area through midnight with a
chance of showers far south after midnight. Precipitation chances
increase dramatically by sunrise Sunday morning across all of
southern Minnesota.

.LONG TERM...(Sunday through Friday)
Issued at 420 AM CDT Sat Apr 29 2017

The main concern in the long term remains how much rain and snow
will fall over the FA from a massive storm system moving across
the region from Sunday through Monday. Deterministic and ensemble
solutions are pretty much in step with this system moving from
Kansas on Sunday to Wisconsin on Monday. Rainfall amounts from the
ECMWF and GFS remain in the 1.5 to 2 inch range with the high end
amounts from south central MN through east central MN (Twin
Cities) and west central WI. Will continue to highlight the hydro
concern in the HWO.

The real problem remains the snowfall forecast for Sunday night
and Monday morning. Profile data points to west central into
central MN as having the best chance for accumulating snow. The
ECMWF remains just a little too warm between the surface and 925
MB for it to produce much if any snow. However, that`s not the
case with the GFS and NAM which produce some 6 to 12 inches of
snow in the Morris and Alexandria areas. Amounts drop quickly
heading east with 2 to 4 inches from Redwood Falls to St. Cloud.
The GEFS plumes remain bullish as well with around 5 inches
indicated for Alexandria MN and Watertown SD. Amounts are more
near 2 inches for Redwood Falls and St. Cloud. Collaborated with
our three surrounding offices in this area for a potential Winter
Storm Watch (seems prudent with the plume data), but they wanted
to wait another cycle, which would still allow plenty of lead
time. As it stands now, we have a solid 3 to 5 inches of
accumulation in the grids for west central into central MN for the
aforementioned times with amounts dwindling down to a few tenths
to the west and north of the metro. Modified highs on Monday to
keep upper 30s across central MN.

After this system clears the region on Tuesday, upper heights will
be on the rise as ridging begins to move into the center of the
country. There remains a few short waves that will drop southeast
ahead of the ridge for Wednesday and Thursday with some small
chances for showers. Highs will rebound into the lower and middle
60s from Thursday onward.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1246 PM CDT Sat Apr 29 2017

VFR conditions are expected through the majority of the period,
with quickly deteriorating conditions Sunday afternoon as the next
system arrives. High clouds will be on the increase, with gusty
northeast winds. Will see some decline in wind speeds this
evening, but an early return of the gusts on Sunday morning as the
pressure gradient tightens with the approaching trough. The main
change this TAF issuance was to slow down the onset timing of
precip by 3-6 hours, along with slowing the degradation to MVFR
cigs on Sunday morning. For central MN/WI sites, onset now looks
to be delayed to between 15z and 18z.

VFR is expected through at least daybreak Sunday. Delayed precip
onset and attendant MVFR cig/vsby reductions to 18z, but could
start seeing showers near the field with MVFR conditions as early
as 15z. Northeast winds lose gustiness this eve, but return by
daybreak Sunday.

Mon...IFR/RA mixing with SN AFTN/EVE. Winds N 15-20G30kts.
Tue...MVFR ceilings possible. NW 10-15 kts.
Wed...VFR ceilings. S 10 kts.




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