Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 261716
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1216 PM CDT Sat May 26 2018

.UPDATE...
Issued at 1209 PM CDT Sat May 26 2018

Updated to include 18z aviation discussion below.

&&

.SHORT TERM...(Today and tonight)
Issued at 405 AM CDT Sat May 26 2018

Upper level ridging begins building into the region today, but a
shortwave trough will continue traveling eastward through Southern
Saskatchewan with weak vorticity over Northern WI. As a result,
the NAM, HRRR, and other hi-res models develop convection this
afternoon in the Eastern WI counties of the CWA. MUCAPE values are
forecast to reach near 1500 J/kg and effective bulk wind shear
should reach near 30 kts. So, there is a possibility for some
isolated strong updrafts and a few strong wind gusts and hail.
Otherwise, the bulk of the thunderstorm activity should occur to
the east and north of the CWA.

Another concern for the Memorial Day Weekend is the unseasonably
warm temperatures. Mostly clear skies and diurnal heating will
allow mixing through about 700 mb by late Saturday afternoon. This
will allow temperatures to reach the lower to mid 90s with the
warmest temperatures expected on the Buffalo Ridge. A few record
high temperatures for May 26th may be broken. The record highs
are: 96 at MSP (1978), 93 at STC (1914), and 93 at EAU (1914).
Relative humidity will be lower than Friday as values are expected
to drop into the upper 20s to lower 30s with dewpoints in the
50s. Thus, heat index values are not expected to differ very much
from the temperatures. Westerly winds will be near 5-10 kts during
peak heating. Then, temperatures overnight into Sunday are
anticipated to fall into the 60s with the TC metro being closer to
70 degrees.

.LONG TERM...(Sunday through Friday)
Issued at 405 AM CDT Sat May 26 2018

The heat builds on Sunday, with relief not expected until the last
half of the upcoming week when shower and thunderstorm chances
also return.

The omega block will be fully in place on Sunday, with mid/upper
ridging reaching its peak. At daybreak, there looks to be the
potential for nocturnally-driven convection over the Dakotas to be
knocking on the doorstep of western MN, per NSSL-WRF and NAMnest
solutions. Have included a small area of 20-30 POPS over west
central MN, but may need to expand this area spatially if the
signal proves to be consistent. H85 temps look to moderate to
around +22C on Sunday afternoon. Other than a few cumulus clouds,
ample sunshine will combine with southerly winds and mixing to
700-750mb. Model guidance has come in a bit warmer than previous
runs, thus giving more credence to the potential for highs from
90-100 degrees. Dewpoints will also be up around 60 degrees, which
will push heat indices close to advisory criteria. Will continue
to monitor trends, but a heat advisory is a strong possibility for
Sunday.

Still have reservations about an entirely dry forecast for Sunday,
given progged 700mb temperatures are only around +10C, which is
borderline as far as a CAP is concerned. There won`t be much in
the way of a triggering mechanism provided any ripples of energy
topping the ridge stay north, but wouldn`t be surprised if
instability proves sufficient to yield pop-up, isolated activity.

Sunday night into Monday the low over the Great Basin begins to
progress eastward. Warm/moist air advection ahead of this feature
noses into central MN/WI on Sunday night. Have included 20-30 POPS
primarily along/north of Interstate 94, with any activity expected
to wane Monday morning.

More widespread shower and thunderstorm activity is expected late
Monday night through Wednesday as the aforementioned low ejects
across the area while weakening. After that, we look to be dry
overall to finish the week, with more tolerable highs in the mid
70s to mid 80s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1209 PM CDT Sat May 26 2018

VFR conditions are forecast for this period. Aside from a few
passing high clouds this afternoon, SKC conditions are expected.
Westerly winds will increase to near 10 kts this afternoon then
become light overnight into Sunday then pick up from the
southeast to south near 10 kts.

KMSP... No concerns.

/OUTLOOK FOR KMSP/
MON...VFR. Wind S 5 kts.
TUE-WED...Mainly VFR. Chc -SHRA/-TSRA. Wind SE 5-10 kts.
THU...VFR. Wind NW 5-10 kts.

&&

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

$$

UPDATE...JPC
SHORT TERM...AMK
LONG TERM...LS
AVIATION...JPC


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