Area Forecast Discussion
Issued by NWS Twin Cities, MN

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314
FXUS63 KMPX 182100
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
300 PM CST Wed Jan 18 2017

.SHORT TERM...(This evening through Thursday)
Issued at 300 PM CST Wed Jan 18 2017

A storm system noted on regional satellite imagery across western
Kansas this afternoon will begin to pull ample gulf moisture
northward across the Upper Midwest over the next 24-36 hours.
Temperatures this afternoon has risen into the mid to upper 30s,
with a few lower 40s which is 15 to 20 degrees above normal for the
third week of January. It was also noted that the snow cover across
northeast Iowa and far southwest Minnesota had eroded today which
leads to ample moisture in the boundary layer this afternoon. There
was also still low clouds and fog in far southeast Minnesota where a
strong inversion and the depth of the cloud deck was strong/deep
enough to hold it together. Models have this area of moisture in
southeast Minnesota advecting across western Wisconsin this evening,
which will likely lead to areas of stratus/fog to form.

The amount of low clouds and fog is the main forecast concern
overnight, especially considering the amount of boundary layer
moisture from today`s melting and additional moisture advecting
northward later tonight. The forecast will continue an increase in
cloud cover late tonight, especially north of I-94 where the best
isentropic lift in the 275-285k layer indicated. The other concern
is the depth of the moisture and associated cloud cover Thursday
which may lead to light drizzle by the afternoon. Although the depth
of the moisture remains quite shallow, the strength of the moisture
advection is adequate enough to warrant at least patchy drizzle.
Temperatures overnight will likely only fall to near freezing, with
some upper 20s in west central Minnesota where better terrain
affects area noted.

.LONG TERM...(Thursday night through Wednesday)
Issued at 300 PM CST Wed Jan 18 2017

The long term forecast remained pretty consistent today.  Thursday
night through the weekend and into early next week will feature
temperatures well above normal (about 20 degrees if you average out
the high and low for each day, but mainly thanks to the warm lows).
The normal lows right now are bottoming out and in the single digits
across the local area.  With forecast lows in the 30s in the coming
nights, the departure from normal on the lows will be about 30
degrees above normal.

As an upper low/trough lifts north into our area tomorrow night
dewpoints will rise into the 30s which will be a good setup for fog
and drizzle especially with the melting snow pack.  There will be
some better lift across eastern MN and western WI where primarily
rain will fall, but could see some sleet and freezing rain
overnight. The same holds true through the weekend with likely rain
and drizzle along with fog.  Portions of the forecast area,
primarily central MN, could deal with icing potential overnight this
weekend so did include that in the forecast in those areas.

Over the last several runs of the GFS, a storm for the middle of
next week continues to be advertised.  The 00Z run of the ECMWF
agreed quite well with this scenario, but the 12Z came in with a
much different solution playing out middle of next week.  The big
difference is a much stronger and flatter west to east jet on the
ECMWF which races the parent upper trough straight east from the
four corners region through Tennessee/Kentucky with little impact
here.  The GFS has a more amplified jet pattern which deepens the
trough, with surface cyclogenesis and a northeast trajectory placing
our area in a favorable area for snow.  With such disagreement, kept
pops pretty conservative in the extended forecast.


&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1120 AM CST Wed Jan 18 2017

The first 6 hrs of the taf period should be VFR with a
south/southwesterly flow across Minnesota. The main concern after
00z is whether LIFR ceilings begin to affect KEAU as current
ceilings across southeast Minnesota advect northeast across west
central Wisconsin. Current visible satellite trends continued to
indicate that the lower clouds have not dissipated as anticipated
by models this morning. Therefore, added scattered clouds of 400`
at KEAU by 22z, with LIFR ceilings by 02z. This will likely be
updated as trends infer. Otherwise, kept the remaining taf sites
VFR through 6z with a downward trend between 6-12z. After 12z,
IFR/LIFR ceilings/vsby should be widespread across Minnesota and
western Wisconsin.

KMSP...

Continued the trend of IFR ceilings developing between 6-12z which
will likely be updated as conditions indicate. No aviation
concerns through 3z. A southwest/south wind will become more
south/southeast overnight.

/OUTLOOK FOR KMSP/

Fri...IFR/MVFR. Chc -SHRA. Winds SE 5-10 kts.
Sat...IFR/MVFR. Chc -SHRA. Winds SE 5-10 kts.
Sun...IFR/MVFR Possible. Winds S Becoming W 5 kts.


&&

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

$$

SHORT TERM...JLT
LONG TERM...SPD
AVIATION...JLT



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