Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

FXUS63 KMPX 180331

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1031 PM CDT WED AUG 17 2016

.SHORT TERM...(This evening through Thursday)
Issued at 230 PM CDT Wed Aug 17 2016

The short term concern is the chance of fog developing east
tonight and the timing of incoming front/convection into Thursday.

Initially...we have some isolated -shra/-tsra over northwest
Wisconsin...which may affect the far northeast portion of the cwa
through 00z. This lake breeze induced acitivity should wane as it
sags south into more stable air.

With light winds...moist boundary layer and mainly clear
conditions...we should see areas of fog redevelop...mainly to the
east later tonight. The far west will see some high clouds and
some increase in gradient winds develop so this should limit any
significant fog issue. The threat of at least isolated convection
working into far western cwa late as waa and some mid level
moisture tries to work east into the area. The HRRR and HRRR
experimental is showing some type of complex/area working across
the dakotas and into the far west after 09z Wed.

Instability increases into Thursday as thermal ridge moves into
southwest MN. The front sags into the northwest cwa by late in the
afternoon and this should regenerate thunderstorms over the
northwest area during the day. The severe weather threat will
increase by late afternoon as well as steeper lapse rates and
35 kts deep layer shear moves into the region. PW`s increase to
around 2 inches once gain by late afternoon along the boundary.
This will yield the possibility of heavy rain by evening.
Hail...strong winds and torrential rain will be the main severe
weather threats once again.

.LONG TERM...(Thursday night through Wednesday)
Issued at 230 PM CDT Wed Aug 17 2016

The main focus of the long term period is the frontal boundary
expected to move into the area and essentially stall out tomorrow
night through much of the day Friday.  This will be followed by a
cool down to below normal temperatures as a deep longwave trough
overspreads the north central CONUS.  Temperatures will rebound
early next week as low level southwesterly flow increases, which
will again lead to chances for thunderstorms.

By tomorrow evening, the cold front will still be off to our west,
with a pool of very unstable air across the forecast area.  Storms
should not have any problems initiating along the front given the
low level convergence and available buoyant energy. In terms of
severe potential in our area, the effective deep shear is rather
unimpressive. 2,000 to 3,000 ML CAPE values combined with 25-40
knots of effective shear will lead to primarily multicellular
storms which will likely conglomerate into an MCS tomorrow night.
This area should track east across southern/central MN through
west central WI overnight. With the lack of deep layer shear,
PWATS increasing to ~1.75" and the front not moving much, there is
potential for a couple inches of rain to fall in south central MN
through west central WI. The pops were pretty consistent with the
previous forecast, but we did nudge them south a little. This
front will essentially stall out from southwest MN through
northwest WI through much of the day Friday and into Saturday,
with continued rounds of showers and thunderstorms possible as the
main upper level trough swings through from the west.

With a deeper trough expected, the system looks to slow down
some, which means the cool down is still on for Saturday and
Sunday, but we will likely be dealing with the low level moisture
in cyclonic flow for a longer period of time. Cool temps and
cloudy skies with showers possible will result on Saturday
directly underneath the trough axis. We should see conditions
drying out a bit more on Sunday as low level flow becomes more

For next week, we`ll see return flow and warm air advection increase
on Monday but with not much in terms of moisture to warrant pops. By
mid to late week, shortwave energy will move through the area
with another slow moving frontal boundary being the source of


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1029 PM CDT Wed Aug 17 2016

Mainly VFR tonight with the exception of patchy fog that could
show up at KSTC/KRNH/KEAU. Otherwise the TAF sites will remain dry
until at least tomorrow afternoon. Storms move into Minnesota
during the late afternoon and continue Thursday night.


Some patchy fog is possible late tonight and early in the morning
around the airport grounds. The airport itself will likely remain
clear. Otherwise, look for storms late in the day tomorrow.

Fri...Becoming MVFR with SHRA/TSRA. Winds becoming N 10 kts.
Sat...Periods of MVFR Cigs & SHRA/TSRA. Winds N 10-15 kts.
Sun...VFR. Morning MVFR Cigs Possible. Winds NW 10 kts.


.MPX Watches/Warnings/Advisories...


AVIATION...CLF is the U.S. government's official web portal to all federal, state and local government web resources and services.