Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 071638
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1038 AM CST Sat Dec 7 2019

.SHORT TERM...(This afternoon through Sunday afternoon)
Issued at 954 AM CST Sat Dec 7 2019

Surface analysis shows extensive high pressure from the
northeastern CONUS through the Deep South. A warm front is nudging
its way eastward across the Dakotas into far western MN with an
associated cold front over south-central Canada into Montana.

Plenty of cloud cover is evident over much of the Dakotas through
MN/WI on satellite imagery in advance of the frontal boundaries
and the extensive cloud cover is expected to remain in place
through Sunday afternoon. While warm air advection will commence
today after the cold day experienced yesterday, it will be
tempered by the cloud cover and also create a small diurnal range
from today to tonight to Sunday. After lows this morning in the
teens to lower 20s area-wide, highs today climbed into the 30s,
particularly mid-to-high range. Lows tonight will only drop to the
mid 20s to lower 30s, followed by highs on Sunday from the upper
20s to mid 30s.

As the surface front approaches and cloud layers lower, the low-
to-mid levels will still have some degree of dry air available
which will help mitigate the development of precipitation during
the daylight hours on Sunday. Models have continued to show the
recent slow northward shift in the main precipitation initiation
band so have reflected this by keeping the Sunday daytime hours
dry. That said, a few patches of light freezing drizzle and/or
flurries cannot be ruled out for portions of central Minnesota
(mainly from Douglas county eastward thru Kanabec county). May
need to see how this is handled right around that 00z timeframe to
determine if a mention may be warranted for late Sunday afternoon.

.LONG TERM...(Sunday night through Friday)
Issued at 325 AM CST Sat Dec 7 2019

700-600mb frontogenesis enters west central MN between 21Z Sunday
and 00Z Monday, and spreads eastward overnight into Monday
morning. The primary change in models (with the exception of the
NAM) was a slight northward shift in the axis of heavier snowfall
amounts, which now hugs the I-94 corridor and a few rows of
counties to its north. Still looks like a solid 3-5 inch event for
central MN/WI, with amounts tapering down to around 1 inch along
the I-90 corridor.

Deep upper troughing will be in place across eastern North
America for the majority of the latter forecast period, with cold
and dry northwest flow across the upper Midwest. The western ridge
looks to flatten later in the week, and the pattern will de-
amplify downstream, with the flow becoming more zonal by week`s
end. There are no significant forecast concerns from Tuesday
through Saturday, with a few chances for light precipitation from
Thursday into Saturday. The guidance envelope does include a few
solutions that lift a surface low up into the Great Lakes region
from Friday into Saturday, but at this point the overwhelming
consensus with that feature (for the solutions that support it) is
to keep it well to our east. Our main precipitation chances from
Thursday though Saturday will be tied to weak quick moving
shortwave troughs embedded in the developing westerly flow, and
with significant differences in timing and location (as to be
expected), there is an extended period of fairly low PoPs in the
forecast to account for the potential.

High pressure and an Arctic airmass will build into the region
Tuesday into Wednesday, and remain entrenched through early
Thursday. Details such as cloud cover and winds will dictate exactly
how cold we get, making it tough to stray too far from consensus
guidance at this point. However, with the expectation of some new
snowfall Sunday into Monday, it seems we should be on the colder
side of the guidance given the anticipated airmass. With that in
mind, trended temperatures Tuesday through Wednesday night closer to
the 25th percentile of available guidance. Return flow and
moderation of temperatures will setup later on Thursday, and we`ll
see some chances for precipitation from then into the weekend as a
few shortwave troughs and surface frontal boundaries traverse the
region. At this point, any precipitation during that period looks to
be in the form of snow with temperatures (surface and aloft)
expected to remain below freezing.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 954 AM CST Sat Dec 7 2019

VFR conditions at all TAF sites to start but with gradually
lowering ceilings from the pre-dawn hours through the day Sunday,
down to IFR levels by Sunday afternoon. No precipitation expected
through 18z Sunday but there is a small, non-zero chance of either
FZDZ or SHSN in portions of western MN prior to 00z Monday. Thus,
later TAFs will evaluate the need to include precip at TAFs such
as KAXN-KSTC prior to 00z. The other main concern will be winds in
the lower levels late this afternoon through the evening hours. A
strong low level jet with the warm front will push SW winds to
around 45-50kt at 2kft with surface winds still southerly. Even
with surface winds reaching 15G25kt, the vector difference leads
to keeping LLWS mention in the TAFs.

KMSP...Ceilings will come close to dropping to IFR levels around
midday Sunday and lasting through the rest of the day. This seems
a bit bullish at this point so have kept ceilings within MVFR
range, but still a good shot at ceilings below 1700ft. Have also
kept mention of LLWS going at KMSP since the swath of strong low
winds will be rather broad over much of southern MN through
southern WI.

/OUTLOOK FOR KMSP/
Mon...IFR/SN likely, mainly in the morning. Several inches
possible. Wind NNE bcmg NNW 10-15G25 kts.
Tue...VFR but bitterly cold with wind chills in negative teens.
Wind NW 5-15 kts.
Wed...VFR but bitterly cold with wind chills in negative teens.
Wind W 5 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...JPC
LONG TERM...
AVIATION...JPC


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