Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200922
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
422 AM CDT Mon Aug 20 2018

.SHORT TERM...(Today and tonight)
Issued at 420 AM CDT Mon Aug 20 2018

Scattered showers and thunderstorms will move across the region
today. The main threat is localized heavy rain. For example, radar
estimates up near Mille Lacs showed 5 to 6 inches on both the Dual-
Pol and MRMS precip maps, but this was only over a few square miles.
At this point, it appears the heaviest rain should fall along and
south of I-90. There is nearly zero chance of severe storms. The
clouds and rain will keep temperatures on the cooler side for today.

Early morning water vapor and radar imagery showed a compact
upper level low across southwest Iowa, with widespread rain
covering much of the state. Over the next 24 hours, the forcing
associated with this wave will lift northeast and bring rain
across southeast Minnesota and western Wisconsin. Meanwhile,
another area of showers and thunderstorms from southwest MN to
northeast MN should gradually weaken this morning as the forcing
subsides. HiRes models are in good agreement with this solution,
but still develop convection along the boundary throughout the
day, so did not go dry but did try to emphasize the better
rainfall potential across the south.

As mentioned earlier, the main threat with todays storms is
localized heavy rain. Storms will be very slow-moving, so a quick 2
to 3 inches is certainly possible under a few of the stronger cells.
There is not enough CAPE or Shear to support a realistic threat for
severe weather today which is why SPC only had general thunder
chances across the Upper Midwest.

.LONG TERM...(Tuesday through Sunday)
Issued at 420 AM CDT Mon Aug 20 2018

High pressure builds into the upper Midwest Tuesday, with northerly
winds keeping highs in the mid-70s under clearing skies. Dry
weather continues into Thursday as high pressure remains over the
region with Northwest flow aloft keeping temperatures a few
degrees below normal. Northwest flow aloft may usher in the return
of smoke and hazy skies from western Canadian wildfires, but the
impact of this smoke on air quality on the ground is still
unknown. Models remain in good agreement with brining a shortwave
into the upper Midwest Thursday night into Friday. Current timing
would bring the best forcing into our area overnight into Thursday
into Friday morning when instability is at its lowest so not
expecting strong/severe weather with this system. With the broad-
scale forcing aloft from the shortwave and PW values up around 1.5
inches models are depicting the potential for a widespread
soaking rain of 0.5-1 inches across Minnesota and Wisconsin, which
would help areas continue catch up on the rainfall deficit in
August so far.

Heading into the weekend, 500 mb ridging begins to build over the
lower Mississippi valley allowing heat and humidity to build. A
stationary front sets up somewhere over Minnesota/Wisconsin
Saturday afternoon through Monday providing a focus for the next
chance of showers and thunderstorms. Confidence is low in the
location of this front so have kept low precipitation chances for
now. South of this boundary temperatures will warm well-above
normal as the ridging aloft builds, with highs likely reaching the
upper 80s and even a few 90s into early next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1104 PM CDT Sun Aug 19 2018

Not expecting too much eastward progress in the showers and
thunderstorms tonight from western MN. This activity will weaken
to showers as it finally advances eastward across eastern MN and
western WI Monday. Cigs will be VFR tonight, but will likely
become MVFR at times Monday.

KMSP...A few stray showers are possible tonight, but the best
chance for any rain will wait until Monday morning. Cigs will
deteriorate during that time as well.

/OUTLOOK FOR KMSP/
Tue...MVFR possible early, then VFR. Wind NNW at 10G15 kts.
Wed...VFR. Wind W at 5 kts.
Thu...VFR. Wind SW 10-15 kts.


&&

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

$$

SHORT TERM...JRB
LONG TERM...ETA
AVIATION...BORGHOFF


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