Area Forecast Discussion
Issued by NWS Twin Cities, MN

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046
FXUS63 KMPX 221730
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1230 PM CDT SUN MAY 22 2016

.SHORT TERM...(Today and tonight)
Issued at 400 AM CDT Sun May 22 2016

Today will again feature sunshine and dry conditions with
above normal temperatures. We will, however, add a breezy
southerly wind by the afternoon as the forecast area gets on the
backside of this surface ridge. On this, the 5th anniversary of
the Joplin, MO and north Minneapolis tornadoes, the weather will
be quite contrary to that day five years ago. The air mass in
place is very dry and the moisture doesn`t really start to kick
in across Minnesota until late tonight. Although there could be a
couple isolated and high-based showers this afternoon/evening
near the MN/SD/ND where there is 925-700mb warm advection. The
main bands of showers and storms should hold off until Monday. As
of this morning, we are now within the forecast window of most of
the convective allowing models, and the simulated reflectivity
output suggests scattered to numerous showers and storms moving
into the forecast area late tonight. The band of precipitation
will be orientated parallel to the low level jet and moisture
transport. Any threat for strong to severe storms or heavy rain
in the short term will mainly be confined to the Dakota overnight.
The convective activity will shift into western Minnesota between
12am- 6am tonight. There is just enough shear tonight to lead to a
weakly organized MCS...mainly in the eastern Dakotas.

.LONG TERM...(Monday through Saturday)
Issued at 400 AM CDT Sun May 22 2016

During the long term, the omega block that has helped push our
streak of dry days in the Twin Cities to 9 (when including today)will
finally break down, signaling an end to our dry weather pattern.
Next week is still looking fairly active, with the large scale
pattern looking to feature persistent troughing to our
west/northwest with ridging to our east.  This will put in place a
modest southwest upper flow next week that will send several waves
our direction. The periods that look to have the best chances at
seeing widespread precipitation are Monday/Monday night, Tuesday
night/Wednesday, and Thursday night through Saturday. Though not
expecting any significant severe weather episodes, each of these
periods will at least offer a shot at seeing some strong to severe
storms, along with seeing some much needed rainfall.

As for how the models are handling all of this, they are in pretty
good agreement on the large scale pattern with the broad trough to
our west/northwest and ridging east, but the flow this creates is
not all that strong and there is still quite a bit of spread in
details such as shortwave timing and especially surface frontal
placement through the upcoming work week, which has resulted in a
continuation of an extended period that has no mention of dry
periods, though the highest pops can be found with the periods
mentioned above. This flow pattern will keep mild air flowing into
the Upper MS Valley, but the transition to SW flow aloft will bring
back significantly higher amounts of moisture. This means for
temperatures, we will continue to see highs run slightly above
normal, as we are seeing this weekend, but the added moisture will
keep our diurnal ranges from being as large next week, with
overnight lows next week being well above normal.

Monday, the SPC did upgrade much of the MPX forecast area into a
slight risk, though there is still a high degree of uncertainty with
how much of a severe weather risk we will have. During the morning,
we are anticipating a decaying line of showers and thunderstorms to
move across MN as we get the remnants of convection that will be
moving across the Dakotas overnight. This will generate a good deal
of cloud cover, which may limit the degree of destabilization we see
later in the afternoon along the cold front.  In addition, the
front will be starting to wash out during the day as it outruns
the upper forcing driving it, which should limit the focus for
convection along the boundary.  The CAMs tonight highlight the
issues with the front, as they develop scattered to broken lines
of during the afternoon. 0-6km shear of 30- 40 kts should be just
enough to allow for a risk for some stronger/severe storms in
pockets of better instability that develop, but it certainly does
not look like we would see anything significant or widespread from
the severe weather end of things.

Tuesday is continuing to look dry in the wake of this wave, but we
never really look to push the front out of the area during the week,
with it looking to spend next work week meandering around the area as
a stationary/warm front.  Models show surface waves working along
this boundary Wednesday and again Friday/Saturday which is what
results in the higher precip chances in place then.  Both of these
periods look similar to Monday on a severe threat, with just enough
shear/instability around to create a few problems, but nothing of
significance.

For QPF, at this point, given spread in the models, stuck with a
blended forecast, but by the end of the week, the GFS, ECMWF, and
Canadian are all putting out a good 1-3 inches of total rainfall
across the area.  So at the very least we will see some very timely
precipitation.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1225 PM CDT Sun May 22 2016

An isolated thunderstorm is likely in far western Minnesota for a
few hours this afternoon. However, most areas will remain dry and
not affect MPX taf sites. Quiet weather with VFR conditions is
likely through this evening across the rest of Minnesota and
western Wisconsin. Confidence has increased enough to continue
with VCTS and start it earlier at KAXN around 6z, and near
KSTC/KRWF by 9-10z. Elsewhere, confidence is too low to introduce
VCTS before 12z. CIGS will likely remain in the VFR range for
most of the TAF period, with the exception in western Minnesota
during the morning as MVFR CIGS are possible behind the initial
line of thunderstorms. Confidence is also high enough to warrant
VCTS for the rest of MN tafs, including west central Wisconsin by
the end of the taf period. Winds will continue to be gusty this
afternoon, but remain above 10 kts through the evening, and
overnight hours.

KMSP...

Confidence has increased enough that VCTS is warranted after 12z
with a period of 5-6sm in heavier showers and thunderstorms before
18z. Confidence is high that there will be a period of heavy
rainfall between 15-18z, but timing remains low, so no tempo
period is included. Winds will remain from the south-southeast
through tonight, and veer to the southwest Monday afternoon.

TUE...Mainly VFR. Chc TSRA/MVFR. Wind S 5 kts.
WED...Mainly VFR. Chc TSRA/MVFR. Wind light and variable.
THU...Mainly VFR. Chc TSRA/MVFR. Wind south-southwest 5 kts.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$

SHORT TERM...CLF
LONG TERM...MPG
AVIATION...JLT



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