Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 201804

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1204 PM CST Fri Jan 20 2017

Issued at 1152 AM CST Fri Jan 20 2017

Updated to include 18z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 500 AM CST Fri Jan 20 2017

Early morning water vapor imagery showed an upper level low across
the region. Low clouds and fog were widespread across much of MN,
with some light drizzle as well.

Low clouds or fog will remain in place for the foreseeable future as
an upper level low slowly rotates overhead. Light drizzle is likely
across the region given the low level saturation. A better chance
for a more steady rain will be later tonight as an upper level PV
anomaly rotates up from the south. This will provide a more focused
area for ascent, deeper saturation, and heavier precip. Temperature
will remain above the seasonal average for late January with little
diurnal fluctuation.

.LONG TERM...(Saturday through Thursday)
Issued at 500 AM CST Fri Jan 20 2017

Rain is expected Saturday...rain clears Sunday...snow looking
more likely TUE-WED.

A surface low will track directly over Minnesota on Saturday
bringing light rain to MN/WI throughout the day. It looks like
most locations will pick up 0.10"-0.20" by the time the wave lifts
northeast over Lake Superior by sunrise Sunday morning. A couple
days of dry weather are expected Sunday-Monday with building
heights by Monday. The longwave ridging early next week will
quickly be replaced with a trough on Wednesday. Ahead of the
upper trough, a deep surface cyclone will track from Michigan from TUE-WED. This is a good
snowfall track for the local area, and over the past few runs
there has been good decent agreement on the track between
ECMWF/GFS. We have increased the probability of snow during this
time to reflect the increasing confidence. There`s still a long
way to go with this one, but the track looks reasonably steady and
past historical matches suggest winter storm warning criteria
potential (>6" snow). From CIPS...the top historical match off the
120hr GFS is a significant snowfall that happened on December 9,
2012. It was a whopper with a large swath of 12+". Good looking
jet and PV punch with this system. The surface temperature is
warmish and the low is fairly progressive, but the forcing is very


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1152 AM CST Fri Jan 20 2017

IFR-or-worse conditions expected to prevail over the next 24-30
hours with a deeply moist and mild atmosphere atop slowly melting
snowpack and continued light SE winds. Occasional rounds of -DZ
are possible through this afternoon, mainly over the WI TAF sites.
Conditions may slightly improve tomorrow with more sustained -RA
possible which may allow for a scouring out of the near-surface
BR/FG. However, even if visibilities improve to MVFR, ceilings are
expected to remain in IFR range.

KMSP...Visibility has improved to VFR while ceilings remain within
IFR at initialization but both are expected to deteriorate by this
evening to LIFR or lower. Timing may be a little tricky but
confidence remains high in having IFR-or-worse conditions prevail
throughout this TAF period. Growing confidence in having more
sustained -RA showers by daybreak and lasting through the day so
this may actually improve conditions back "up" to IFR for much of
the day tomorrow.

SUN...MVFR likely. Slight chance -RA/-SN. Winds NW 5 kts.
MON...MVFR likely. Winds NW 5 kts.
TUE...MVFR likely. IFR possible late with chance -RA/-SN. Winds NE
5 kts.




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