Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 212004

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
304 PM CDT Mon May 21 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 246 PM CDT Mon May 21 2018

The secondary trough will continue moving through the area this
afternoon and tonight, with plentiful low level moisture and
modest lift persisting but lifting north of the area later this
evening. Scattered showers will continue slowly lifting north, and
QPF values will be very insignificant, generally less than a tenth
of an inch.

With the increased low level moisture and winds becoming quite
light tonight, expect fog to develop overnight. Western MN will be
the most susceptible to potentially dense fog, especially in the
wake of the showery activity that moved through today.

The trough will slowly depart to our east tomorrow as gradual
clearing is anticipated to ensue late in the day. Highs tomorrow
should rebound into the mid to upper 70s.

.LONG TERM...(Tuesday night through Monday)
Issued at 246 PM CDT Mon May 21 2018

The main concerns in the long term period are the rain amounts for
Wednesday through Thursday night and the chance for severe weather
Thursday/Thursday night. Split upper level flow does present a
problem for shear parameters, but instability and moisture will be
ample Thursday/Thursday night.

By tomorrow night, the next shortwave will be quickly approaching
from the southwest with showers and thunderstorms expected to
spread into southwestern MN overnight into Wednesday morning. An
increasing LLJ will provide ample low level moisture convergence
and lead to enhanced lift, tapping into some modest instability.
Precipitable water values will increase to about 1.5", maybe
slightly higher.

The latest guidance for Thursday holds off convective initiation
across western MN to Thursday night as the shortwave arrives from
the west, steepening the lapse rates quickly as mid/upper levels
cool. MUCAPE values around 3000 J/kg will be ample to produce
strong to severe thunderstorms, but shear parameters are weak,
particularly in a deep column, which limit supercell potential.
More than likely, multicell clusters are possible and cold pool
development could lead to forward propagating clusters. Some
severe hail could be possible with that amount of CAPE, but with
the lack of shear, don`t expect widespread severe weather at this
time. Continue to monitor for the latest updates.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1249 PM CDT Mon May 21 2018

Scattered shower activity will continue across Central MN this
afternoon before drying out this evening. Widespread MVFR ceilings
are also expected to continue today for West Central MN, Southern
MN, and West Central WI. A slightly drier pocket of air from MSP
to RNH has allowed for VFR conditions for those sites. Otherwise,
Southeasterly winds are expected to continue this afternoon and
become lighter overnight. The very light winds in combination with
low-level moisture will allow for fog development overnight.
Widespread MVFR conditions due to fog and low ceilings are
expected during early to mid morning hours on Tuesday and IFR
conditions are possible.

KMSP... The rain threat has decreased and VFR conditions look to
persist through the remainder of today. Beginning Tuesday
morning, MVFR conditions look to return as ceilings will decrease
and fog is likely. Conditions will approve during the late morning
with dry/VFR conditions for the remainder of Tuesday.

TUE Night... VFR. Wind SE 5 kts.
WED... VFR with chc SHRA/TSRA. Wind SE 5-10 kts.
THU... VFR. Chc -TSRA. Wind S 5-10 kts.




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