Area Forecast Discussion
Issued by NWS Twin Cities, MN

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589
FXUS63 KMPX 212002
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
202 PM CST Sat Jan 21 2017

.UPDATE...
Issued at 200 PM CST Sat Jan 21 2017

Updated to include 18z aviation discussion below.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 200 PM CST Sat Jan 21 2017

Tonight and Sunday...Very damp and mild pattern will persist
through tomorrow as a stacked but unimpressive low pressure system
slowly shifts northeast across the area overnight through Sunday
morning. The deep low will move from southern MN later this
evening into western Lake Superior by daybreak Sunday morning.
This will result in the moist atmosphere remaining in place and
winds going nearly calm later this evening through overnight
before picking up from the NW tomorrow on the backside of this
system. As a result, the northeast winds today to calm winds
tonight along with mild temperatures atop a melting snowpack
within the continued moist atmosphere will maintain widespread fog
with areas of dense fog across the entire coverage area at least
through tonight. With much of the western and southern portions
still dealing with dense fog, to be followed up in eastern
portions later on this evening once the current precipitation ends
with the departing low, have included all of the WFO MPX coverage
area in a dense fog advisory. Southwestern portions will see a
shift in winds to northwesterly tomorrow morning so there is a
chance that these northwest winds will bring in slightly drier low
level air to scour out the moisture and eliminate much of the
dense fog concern earlier than midday tomorrow.

Beyond the fog concerns, light rain has generally diminished
across all of the coverage area, leading to mainly areas of
drizzle through tomorrow morning. In northwest portions, where
overnight temperatures will drop to around freezing, some of the
precipitation may come as freezing drizzle and could present icing
problems around daybreak tomorrow morning.

As for temperatures, much of the coverage area will remain steady
in the middle 30s. However, northwest portions may be subject to
weak cold air advection, just enough to bring temperatures briefly
down to 31-32 degrees before warming back into the mid 30s
tomorrow.


.LONG TERM...(Sunday through Friday)
Issued at 350 AM CST Sat Jan 21 2017

Sunday and Monday, will still in all likelihood be cloudy with
some light fog/mist. These days, however, should be free from
precipitation with the shortwave having moved well north of the
area and a surface high building in from the west. After Looking
at the forecast soundings and the amount of saturation, Monday
afternoon is our best hope for seeing a little sunshine. That
window quickly shuts on Tuesday with the advance of a deep trough
from the west and a surface low that will track across Iowa,
perhaps northern Missouri. The 00/06z model runs this evening are
a little farther south than yesterday`s runs. The FGEN between
850-600mb is present and solid across the southern half of MN and
in western WI - there also remains good upper support from a
strong Polar Jet. The axis of heaviest QPF is across northern IA
(at this point), but light snow would stretch all the way to
central MN given the amount of large-scale ascent with this
system. If the track remains roughly the same, most of the
forecast area (southern half of MN and west central WI) would be
in the 2-6" snowfall range - with the heaviest down near the MN/IA
border. A northern shift would ensure a bit more snow for the
local area and ensure that nearly all of the forecast area would
get at least some snow, but a southward shift would really reduce
the amount of snow in MN and central WI. Cooler temperatures will
follow the TUE-WED system.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 200 PM CST Sat Jan 21 2017

IFR-or-lower conditions to prevail over the next 24 hours as a
weak but deep low slowly moves across the area overnight through
tomorrow. With rain having ended, any visibilities that increased
to VFR-MVFR will lower back to IFR-or-lower. However, the
prevailing ceilings of no higher than IFR will be the dominant
factor until the visibilities also drop. Dense fog again likely
tonight but improvement is expected mid-to-late tomorrow.

KMSP...Visibilities have improved to VFR this afternoon but that
is not expected to last into the evening hours. Ceilings are
already at IFR and will drop into LIFR, to be followed with
visibility doing the same through the overnight hours. Improvement
will be slow to come by after daybreak as northwest winds kick in
but even if visibilities increase to VFR, ceilings will still
remain in IFR levels.

/OUTLOOK FOR KMSP/
MON...MVFR likely. Winds WNW 5 kts.
TUE...MVFR likely. IFR with SN aftn/night. Winds NE 5 kts.
WED...IFR likely with SN early. NW 5-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Dense Fog Advisory from 6 PM this evening to noon CST Sunday for
     WIZ014>016-023>028.

MN...Dense Fog Advisory until noon CST Sunday for MNZ041>044-047>051-
     054>059-064>070-073>078-082>085-091>093.

     Dense Fog Advisory from 6 PM this evening to noon CST Sunday for
     MNZ045-052-053-060>063.

&&

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...CLF
AVIATION...JPC



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