Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 171745

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1245 PM CDT MON OCT 17 2016

Issued at 1235 PM CDT Mon Oct 17 2016

Updated to include 18z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 345 AM CDT Mon Oct 17 2016

Temperatures this morning are rather summer-like with 50s to
lower 70s, and even a 73 at Red Wing at 3 am. These readings are a
good 20 to 35 degrees above normal, quite impressive. Equally
impressive is how models are overdoing the amount of moisture in
the boundary layer. While there are patches of dense fog and
stratus, it hasn`t been persistent and certainly not as widespread
as model fields and forecast soundings would indicate.

The diffuse front in place will become better defined this
afternoon across northern Iowa into southeastern Minnesota and
northern Wisconsin as low pressure over the central Plains tracks
northeast to the Upper Mississippi Valley. Showers and
thunderstorms will form along the boundary late this afternoon
before quickly lifting north and becoming elevated. There is a
narrow window for a few surface- based storms across south central
MN to west central WI if the boundary layer warms enough to
overcome the capping aloft. While instability is expected to be
marginal on a widespread scale, impressive hodographs could lead
to short lived supercells if local enhanced heating can
materialize. Large hail, damaging winds, and a tornado would be
possible with any surface based cell.

By early evening, showers and thunderstorms should be widespread
just north of the boundary and in advance of the low center along
the MN River from Mankato to the Twin Cities and into northern WI.
This activity will exit to the northeast by late evening with the
low passage. Additional showers may form further west with the
upper low across the Dakotas and western MN before weakening as
they rotate eastward across the remainder of the area overnight.

.LONG TERM...(Tuesday through Sunday)
Issued at 345 AM CDT Mon Oct 17 2016

The longer term looks to be a mainly dry period with temperatures
starting out above normal...trending toward slightly below
normal through midweek...and then warming a bit toward the end of
the period. The upper level flow begins to amplify by midweek as
the eastern CONUS trough develops and tries to merge a tropical
system moving through the Bahamas. This may affect timing a bit
into the later half of the period...but ridging develops to the
west and gradually shift east as more troughing energy digs into
the northwest.

Models are trending dry Tuesday with decreasing clouds during the
day. It looks dry then through the remainder of the work
week...although the ECMWF does bring in some light QPF with the
weak short wave around the Wednesday night/Thursday period. The
GFS is not as amplified with this trough and does go through dry.
There remains some model variability to timing of the next short
wave...with the GFS again weaker and dry in the Friday night to
Saturday night period. We will continue that trend for the most
part. Temperatures will rebound into early next week as the ridge
breaks down west and moves into the central CONUS.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1235 PM CDT Mon Oct 17 2016

VFR conditions expected for all TAF sites early this afternoon
(including EAU which is initialized at MVFR but the lower ceilings
there will lift, as they did for the remaining TAF sites).
However, a stalled cold front wobbling over NW WI through SE MN
will become the focusing mechanism for convective development late
this afternoon through this evening. Scattered to numerous
-SHRA/TSRA can be expected, mainly after 22z, lasting through
02z-04z this evening. For now, have capped flight condition
degradation into MVFR range but IFR visibilities surely cannot be
ruled out should a heavy shower move atop any terminal. That said,
the terminals most likely affected by convection look to be KRWF-
KMSP-KRNH-KEAU while KAXN-KSTC look to be too far displaced to the
NW from the stalled front to have much of an influence. Once the
precipitation ends, which will be during the pre-dawn hours, drier
air moving in from the NW will help scour out low level moisture,
leaving mid-to-high clouds for the first half of tomorrow,
followed by clearing skies late tomorrow.

KMSP...Am generally expecting MVFR conditions with the
thunderstorms but a few periods of IFR cannot be ruled out. In
addition, the earliest TSTMs look to impact KMSP is 22z while the
latest timing is about 02z, so there is a good possibility the
duration may well be less than the 4-hours currently advertised.
Some gusty winds may accompany the TSTMs while additional gusts
from the NW may develop in the wake of the front during the pre-
dawn hours.

Wed...VFR. Wind NW 5-10 kts.
Thu...VFR. Wind NW 5-10 kts.
Fri...VFR. Wind SE 5 kts.


.MPX Watches/Warnings/Advisories...


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