Area Forecast Discussion
Issued by NWS Twin Cities, MN
FXUS63 KMPX 170416 AAB
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1116 PM CDT TUE AUG 16 2016
.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM CDT Tue Aug 16 2016
Cyclonically curved flow and 400-250mb PV is tracking across
Minnesota this afternoon. This forcing combined with the heating
this afternoon (that has generated 1500-2500 J/Kg of MLCAPE across
the forecast area) is producing 2-3 areas of convection. The most
established convection early on has been the cluster of
thunderstorms in west central MN, however, convective towers are
also being observed in west central WI and also now across south
central MN with a few taller convective towers based on the latest
visible satellite trends.
The storms should continue to build through the late afternoon and
gradually increase in coverage. Given the expected storm coverage,
it`s tough to go much beyond 50%-60% for the probability of
rainfall. Organized convection and the potential for severe weather
will be limited by the lack of deep shear. The instability is
respectable, so a few pulse-up storms or multi-cell clusters could
gain enough height to produce marginally severe hail or wind. Given
the environment, convective updrafts aren`t expected to be long
lived and thus large hail will be difficult to grow. The slow storm
motion this afternoon suggests that localized heavy rain might just
be the biggest hazard if we get a couple cells to hang over the same
spot for a couple hours. That`s not to say we end up with a couple
reports of quarter-size and wind gusts to around 50 mph, though this
will be the exception rather than the rule over the next 6-7 hours.
The trough will move east this evening and gradually diminish the
thunder threat before midnight in eastern MN and western WI - most
locations will be done with thunder well before midnight.
While we expect a quieter weather day tomorrow with the upper
support well to the east of the area, the moisture will remain about
the same as today, so there isn`t much of an air mass change in
eastern MN and western WI - and especially in southeast MN. It`s
tough to be completely comfortable with a dry forecast tomorrow in
the eastern forecast area as we can`t completely rule out a shower
or two. Temperatures will also be about the same tomorrow as they
.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 PM CDT Tue Aug 16 2016
The longer term concern remains development/movement of upper
trough and attendant surface front through Friday and the cooling
trend for the weekend.
We should start the long term period on the dry side with weak
high pressure retreating to the east of the region. There may be
some mid/high level clouds lifting over the southwest during the
night. The models have trended slower with the front with some jet
energy riding north across southern Canada during the
Thursday/Thursday night period. Thermal ridge builds ahead of the
front and should warm temperatures to around 90 into southern
Minnesota Thursday afternoon. Dewpoints will rise to around 70 as
well with humid conditions returning. Will develop likely pops
north of the boundary Thursday night...as forcing with the
entrance region of the jet stream moves through the area.
Instability increases with steep mid level lapse rates building
into the southwest. Locally heavy rain will also be a possibility
if training of any convective activity occurs.
The front sags slowly to the southeast Friday and Friday night
with a continued threat of heavy rain. The upper trough is slow to
advance east into Saturday so we may have some lingering showers
as the cooler air arrives to the region. Clouds may hold tough to
the east as well. With H85 temperatures dropping to 8C to
10C...afternoon temepratures will struggle to warm through the
lower 70s. Sunday looks to be the coolest day for the region with
rather pleasant dewpoints. The dry and cool regime continue with a
slow warming trend expected by midweek as heights begin to rise
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1116 PM CDT TUE AUG 16 2016
Thunderstorms have pushed south and east of all the TAF sites.
Areas of fog are expected to develop during the next few hours as
skies clear. It could be dense in places, particularly where
heavy rain fell this evening. VFR conditions expected thereafter.
KMSP...There may be some fog late tonight, but the most widespread
and dense fog should remain away from the terminal.
/OUTLOOK FOR KMSP/
Thu...VFR. Chc MVFR/TSRA late. Wind S 5-10 kts.
Fri...VFR. Chc MVFR/TSRA. Winds S 10-15 kts.
Sat..VFR. Winds N-NW 10-20 kts.