Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200349

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1049 PM CDT Fri May 19 2017

Issued at 902 PM CDT Fri May 19 2017

Just some minor changes made to both PoPs and QPF for impending
rain tonight/Saturday.

First, HRRR/HopWRF/NAM/RAP all show a slowing trend with northward
push of precip tonight, which makes sense given our persistent dry
east flow. The slowing wasn`t much and amounts to about a 2 hour
delay in precip arrival at any one location.

For QPF, trended it tonight/tomorrow closer to what we are seeing
from the RAP and other short term hi-res models. They show a
heavier area of QPF coming into SW up into central MN tomorrow.
This is associated with the precip currently down around Omaha.
This region of precip will find itself at the nose of the LLJ in a
zone of good isentropic upglide, moisture convergence, and fgen as
it lifts north through the day Saturday. Current run total QPF
looks very similar what the 21z SREF has with storm total rainfall
amounts a little over an inch out toward Willmar and Redwood


.SHORT TERM...(This evening through Saturday)
Issued at 259 PM CDT Fri May 19 2017

Showers continue to fall apart across far southern Minnesota this
afternoon as they encounter dry air. The next round is beginning
to take shape across northern Kansas into western Missouri. Models
have slowed down its northward progress a bit, reaching southern
Minnesota after 3-4 am and expanding into central MN/western WI
between 7-9 am. Rain will persist all day Saturday into Saturday
night, although the most intense rain should last for maybe 3-4
hours beginning shortly after its onset. Widespread rainfall
amounts of a half to one inch appear likely.

Temperatures will be about 5 degrees cooler than normal tonight,
but 20 degrees colder than normal Saturday with highs only in the
mid 40s to lower 50s.

.LONG TERM...(Saturday night through Friday)
Issued at 259 PM CDT Fri May 19 2017

The extended looks cool, cloudy, and wet through the first half of
next week. Things will dry out by the middle of the week, but at
this point not putting much faith in the drier solutions.
Temperatures will be near or below the seasonal average for late
May, which should help make the case that this month could be below
normal in the Twin Cities for the first time since August of 2015.

Increased chances for pops on Saturday night and Sunday as the upper
level system brings cool air, low clouds, and a few rain showers.
Forecast models show a brief reprieve on Monday, but forecast
soundings show quite a bit of moisture in the H900-700mb layer so
increased the cloud cover and lowered the temperatures for Monday.

On Tuesday another area of vorticity will sweep across the region
which will lead to forcing for ascent, clouds, and another round or
seasonably cool rain showers. Decreased Tuesdays temperatures as
well with a cool, cloudy forecast in mind.

Looking ahead, models are generally in good agreement that northwest
flow and subsidence should bring drier conditions across the region
for the middle of the week, but another shortwave will follow for
the end of the week. There are still timing differences between the
models, but overall not optimistic that a prolonged period of warm
and dry weather will set up across the Midwest between now and the
end of the month.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1049 PM CDT Fri May 19 2017

Edge of rain lifting into the Sioux City area at 11pm. Delays made
to 00z TAFs still look good, so made no changes to rain and
mvfr/ifr cig timing with the 06z TAFs. We`ll have a dry slot
working into ern MN/wrn WI after 00z, with steady rain expected to
end pretty quick once it moves in and is also why we have
transitioned TAFs from STC on east over to DZ to end the TAF. The
end of the TAF will also feature a sfc low centered somewhere
between MSP and EAU at 6z Sun. Given discrepancies in the
placement of the low, confidence is low in wind direction at the
end of the TAF and they`ll be dependent on where the low tracks.
Finally, NAM soundings continue to show AXN cooling enough to
where they are awfully close to supporting snow at AXN Saturday
night. Have not introduced snow at this point, but it will have to
be watched for AXN.

KMSP...High confidence in the forecast until the dry slot arrives.
Expect us to be stuck with IFR cigs when the dry slot gets here,
but precip may cut off completely, with vis not being as bad as we
currently have. Our wind forecast for Saturday night sticks close
to what our gridded forecast has, which is a blend of the models,
but with the low passing close to MSP Saturday night, changes in
the wind direction forecast for Saturday night as we work
through the day Saturday and get more confidence for where the low
is heading.

Sun...MVFR. Chc -shra. Wind WNW at 15G25kt.
Mon...VFR. Chc MVFR/-shra. Wind NW at 5-10kt.
Tue...VFR. Chc MVFR/-shra. Wind N 5-10 kts.




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