Area Forecast Discussion
Issued by NWS Twin Cities, MN

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188
FXUS63 KMPX 240301
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1001 PM CDT Sun Apr 23 2017

.UPDATE...
Issued at 1001 CDT Sun Apr 23 2017

Updated to include 06Z Aviation Discussion below.

&&

.SHORT TERM...(This evening through Monday)
Issued at 405 PM CDT Sun Apr 23 2017

A few showers and thunderstorms are possible on Monday as we
transition to a more active weather pattern across the Upper
Midwest. The instability is very low, only a couple hundred J/kg
at best, so no severe weather is expected. This matches up well
with SPC outlook of only general thunder. Areas to the northwest
will be cooler than areas to the southeast.

Early afternoon satellite imagery together with surface obs and
radar showed a stationary front across the region with rain and
snow falling on the cool side of the boundary. Over the next 24
hours this front will gradually lift northward as a warm front,
but mid level clouds will develop which should keep Monday`s
temperatures from getting out of control despite the strong
dynamic mixing of the boundary layer. This mixing will create
breezy conditions, with gusts near 30 mph expected by late
morning.

HiRes models continue to show a few showers and possibly some
thunderstorms for Monday afternoon as an upper level shortwave
trough moves across the region. The heaviest precip will tied to
the warm front across northern MN, so only have around 20 to 30
percent chance for seeing precip in our area.

.LONG TERM...(Monday night through Sunday)
Issued at 405 PM CDT Sun Apr 23 2017

There appears to be two systems that impact much of the area
throughout the long term, one Tuesday/Tuesday night and the other
next weekend although there is an option for a third Wednesday
depending how things shake out. Regardless, we will be on the
cold side of each of these systems and will be regressing back to
early spring in the temperature department.

Any showers with the Monday system should slide off to the east
during the evening with a brief break until the next system
arrives Tuesday. NAM/ECMWF remain on the northwest side of the
guidance envelope with the rain shield whereas the GFS/GEM
focus more across Iowa into northern WI. Regardless of where the
heaviest rain falls, it does appear much of srn/ern MN and wrn WI
will see at least something out of this, so continued the upward
trend in PoPs.

That piece of energy will lift northeast Tuesday night with
another embedded in the southwest flow aloft arriving to the mid
or upper Mississippi valley Wednesday. How this feature kinks the
baroclinic zone to the southeast will determine where the low
tracks and where the heaviest rain will fall. Best chances with
this one look to remain near the baroclinic zone itself, but the
Canadian (and to a lesser degree the ECMWF and to an even lesser
degree GFS) show some negative tilt to the system and thus
a potentially healthy slug of cold sector precip, similar to
Tuesday`s set up. The risk of this occurring is relatively low,
so continued the 30-50 PoPs.

High pressure will build in Thursday night into Friday before the
next system for the weekend heads into the southern Rockies/
southern Plains. All operational guidance shows a healthy system
eventually heading northeast across the Midwest, but timing has
been problematic for several runs.

There may be enough cold air from midweek onward for at least some
snow with any of these systems, but inconsistent temporal and
spatial precip/temperature patterns make it impossible at this
point to assess the true risk. Most snowfall from mid April onward
is quite difficult to forecast more than a day out.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 1001 CDT Sun Apr 23 2017

Made few changes to previous forecast, with things still looking
mostly on track. VFR conditions will predominate, with some MVFR
possible toward the end of the period as a cold front works
through the area. Some rain is also possible, but looks most
likely at the eastern sites (more widespread rain during the day
looks to stay to the north).

KMSP...Only real uncertainty at this point looks to be at the end
of the period when some lower ceilings will arrive along with
perhaps a few showers. For now, it still looks like things should
remain VFR through the period.

/OUTLOOK FOR KMSP/
Tuesday...MVFR expected, IFR possible. Rain likely in the
afternoon. Northwest wind 5 to 15 kt becoming northeast 15 to 25
kt.
Tuesday night...MVFR expected, IFR possible. Rain likely.
Northeast wind 10 to 20 kt.
Wednesday...MVFR expected in the morning. Rain likely in the
morning. Northeast wind 10 to 20 kt.
Wednesday night...MVFR possible. Chance of rain and snow showers.
North wind 5 to 15 kt.
Thursday...MVFR possible early. Chance of rain and snow showers
early. North wind 5 to 15 kt becoming variable less than 10 kt.

&&

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

$$

UPDATE...
SHORT TERM...JRB
LONG TERM...BORGHOFF
AVIATION...



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