Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 152109
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
309 PM CST Sun Jan 15 2017

.SHORT TERM...(This evening through Monday)
Issued at 315 PM CST Sun Jan 15 2017

The concern in the short term, as well as the early part of the long
term, is the storm system approaching from the Southern High Plains.
Plenty has happened in the past 24 hours. The deterministic models
have resolved the phasing issue between the northern and southern
streams which has plagued us for many days now. They are now
unanimous with a separation being maintained. This allowed the
precipitation with the incoming system to slide a little more east
and south, along with the vertical profile being a little colder and
more supportive of snow.

Then the 12z solutions started coming in today and the precipitation
shield pushed even more to the south and east. This was really
evident on the CAMS. Investigation into why the significant shift
seems tied to more convection developing to our southeast (MO/IL) on
Monday then previous solutions were thinking. This release in latent
heat makes a big difference in the pressure fields with the system
stronger and more compact to our southeast. This is quite evident
with our local WRF solutions that we run here, one with latent heat
and the other without. The results from 12z today are striking and
show how important convection is in the whole process with this
particular system.

Hence, we have cancelled the Winter Storm Watch and issued a Winter
Weather Advisory for just the southern two rows of our counties in
MN from 12z Monday until 12z Tuesday. This is the area where we have
the best potential for up to a tenth of an inch of ice Monday
morning and afternoon followed by an inch or two of snow Monday
night. Precipitation amounts really dwindle to the north with the
latest 18z NAM only bringing the 0.01 inch line of QPF to northern
Rice and Goodhue counties Monday night. This results in no
precipitation across the Twin Cities, period. This may be too
conservative but is pretty realistic with the 12z GFS and ECMWF
which only had the 0.01 inch line touching the Twin Cities Monday
night for a brief period.

Otherwise, the January thaw got started a little early, with highs
at MSP cracking the 32 degree barrier this afternoon. There will be
plenty more of that coming later in the week. With skies clear for
much of the night, lows will likely drop into the single digits
across central MN and west central WI with guidance lows trimmed a
bit. Highs on Monday will again be around the freezing mark,
especially from I-35 on east with little adjustment made.

.LONG TERM...(Monday night through Sunday)
Issued at 315 PM CST Sun Jan 15 2017

The main issue in the long term is what remains of the weather
system into Tuesday. Then the warming trend through the week with
the timing and development of the next Western CONUS trough as it
moves into the middle of the CONUS be the end of the week.

Model trends continue to indicate the initial upper trough lifting
to the southeast of much of the cwa into early Tuesday. Temperatures
aloft have responded with slightly cooler with the less freezing
rain. It appears the precipitation shield may work as far north as
the southern metro into Monday night and then shift east...
affecting a portion of west central Wisconsin. The 12z NAM_wrf and
ECMWF were farthest north with QPF...with most other deterministic
and HIRES models coming in with a more southeast solution. The cause
of this trend was described in the short term discussion. With this
in mind...we will trim pops some to the northwest and keep the
categorical pops more to the southeast. Forecast QPF generates
maybe an inch or two of snow to the south as the system works east
Monday night. Some marginal ice/less than one tenth inch/ is
forecast mainly along I90 northeast to I94 into west central
Wisconsin. The expansion of any headline into Monday night depends
on further resolution of the models in the longer term in regards to
movement upper trough.

After Tuesday morning...warmer and dry conditions should ensue
across the area as upper ridging develops.  This should bring a nice
thawing period...through at least the lower and mid 40s into the
weekend. This is expected ahead of the next western CONUS trough
which is progged to move ashore around Thursday. Deterministic
models drive an initial short wave toward the region sometime Friday
and could linger through the weekend.  It does appear at least
initially it will remain as liquid...with the possibility of rain
and snow developing later in the period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1119 AM CST Sun Jan 15 2017

Few concerns in the first 12 hours of the cycle with VFR
conditions prevailing with a little HZ/BR around KEAU.
Thereafter, the threat for MVFR/IFR ceilings and visibilities will
be on the increase, primarily for KAXN, KRWF and KEAU as low
level southerly flow increases ahead of a storm system moving into
the central/southern plains. As a result, -FZRA/FZDZ will likely
reach far southern MN, along I-90, by daybreak Monday. However,
the latest WRF simulations do not want to advance the wintry
precipitation very far north during the day, keeping the bulk of
the precipitation south of the TAF sites. The TAF site with the
best chance for FZRA/FZDZ would be KEAU Monday night. Light south
winds this afternoon and tonight.

KMSP...VFR expected until Monday afternoon when MVFR/IFR ceilings
spread in from the south. There is a threat for -FZRA/FZDZ during
the late afternoon and evening, but the trend is slowly shifting
southward. A PROB group inserted for now at 21z with low
confidence.

/OUTLOOK FOR KMSP/
Mon ngt...MVFR/IFR. Chance -SN/FZDZ early. Winds NE 4 to 7 kts.
Tue...MVFR possible early then clearing. Winds NW bcmg W 5-10 kts.
Wed...VFR. Winds SW 5-10 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory from 6 AM Monday to 6 AM CST Tuesday for
     MNZ082>085-091>093.

&&

$$

SHORT TERM...RAH
LONG TERM...DWE
AVIATION...RAH



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