Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 250359

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1059 PM CDT SAT SEP 24 2016

.UPDATE...For 06z Aviation discussion below


.SHORT TERM...(This evening through Sunday)
Issued at 317 PM CDT Sat Sep 24 2016

Showers and thunderstorms are developing quickly across eastern
South Dakota and southwest Minnesota on southward. CAMs have
significantly downplayed the convective coverage and intensity all
day, possibly because the extensive cloud cover has eroded and
temperatures there have warmed into the 80s across southern MN.
This has produced MLCAPE values of 1500 J/kg within the corridor
of deep moisture characterized  by pwats of 1.7 to 2 inches along
the front. The synoptic scale models seem to be handling this
better with widespread showers and thunderstorms pushing through
the region tonight.

The main threat from this activity is heavy rain. Already, there
are lines of training thunderstorms across southwest Minnesota.
As this activity builds eastward with time, instability should be
trending downward but rich moist air will remain intact along the
front. Soil moisture is in excess of 60% and even higher in some
spots from south central MN to west central WI. Any additional
heavy rain would bring the potential for flash flooding and
possibly exacerbate ongoing long term flooding. In collaboration
with WFO ARX/DMX, issued a flash flood watch for the areas at
greatest risk. However if the training activity over WFO FSD`s
area continues, may need to expand the watch further west.

Most of the activity should be to the east Sunday morning. A few
showers may persist toward EAU but the heavy rain threat should be
over after mid morning. A dry slot should bring a period of
clearing before the wrap around stratus arrives by afternoon.

.LONG TERM...(Sunday night through Saturday)
Issued at 317 PM CDT Sat Sep 24 2016

Things look to turn quiet and dry, thankfully, for the extended
period. In the big picture, the upper trough will move through
Sunday night and Monday, then work its way into the Great Lakes by
Tuesday. There are some differences in the guidance as to what
happens with it after that, but all of the guidance takes it
sufficiently east to bring ridging into our area on Wednesday, with
fairly stout upper level ridging for Thursday and Friday before we
start to get back into some southwest upper flow by Saturday. With
the upper trough and low-level cyclonic flow around, we could see
some showers Sunday night into Monday, particularly across the north
and east. After that things look to be dry through the remainder of
the period. Temperatures will slowly moderate by midweek, then look
to warm more significantly the latter half of the week as warm
advection increases across the region. There is a chance we could
see some SHRA/TSRA in the Friday/Saturday time frame, particularly
across the west, but the 12Z solutions are less bullish in
comparison to earlier runs, and forcing is still quite weak over our
area at that point, with the upper level ridge still in control of


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1059 PM CDT Sat Sep 24 2016

A broken line of showers and thunderstorms extending all the way
from Texas up through Iowa will continue feeding north and
slightly east into the TAF area overnight. While the activity has
become a bit straggly this evening, expect it to become more
organized again over central MN into west central WI as a low
level jet of 40+ knots develops overnight. Have therefore retained
a mention SHRA/TS in the TAFs. MVFR and IFR conditions are
expected attendant with the shra/ts. Outside of the convective
activity, clouds will scatter out to yield VFR conditions
overnight at MN sites, but WI sites are expected to stay MVFR/IFR.
Low cigs are expected to redevelop by late Sunday morning under
the cold air advection regime with scattered showers possible.
South winds veer to west then northwest with the frontal passage.
Sustained 15-20 kt speeds with gusts between 25 and 30kts develop
by 18z Sun.

Despite the absence of much activity on radar, do expect more
development as the low level jet strengthens overnight. Attendant
conditions with the SHRA/TS should be primarily MVFR but
temporary IFR conditions are possible. Clouds should scatter to
VFR in the wake of the convection, but MVFR cigs and possibly a
few scattered light rain showers redevelop by 18z Sun, along with
sustained west winds circa 18kts gusting to 25 kts.

Mon...Chc MVFR/-SHRA. Wind WNW 15g25kts.
Tue...Chc MVFR early then VFR. Wind NW 5-10kts.
Wed...VFR. Wind N 5 kts.


.MPX Watches/Warnings/Advisories...
WI...Flash Flood Watch until 10 AM CDT Sunday for WIZ023>028.

MN...Flash Flood Watch until 10 AM CDT Sunday for MNZ063-070-078.

     Flash Flood Watch until 7 AM CDT Sunday for MNZ076-077-083>085-



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