Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Graphics & Text | 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 212313

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
613 PM CDT SUN AUG 21 2016

.UPDATE...for 00Z Aviation discussion below


.SHORT TERM...(This evening through Monday)
Issued at 334 PM CDT Sun Aug 21 2016

A highly amplified upper level trough over the Great Lakes region
will continue to shift east today, and upper level subsidence will
lead to surface high pressure across the Upper Midwest. This will
keep the region dry through Monday.

As of early this afternoon, the surface ridge was centered across
western MN. The cool air to the east of this ridge led to some
afternoon clouds across eastern MN and western WI. These clouds will
dissipate overnight. Meanwhile a surface low will form over the
western Dakotas overnight which will allow the surface pressure
gradient to tighten across the region leading to southerly winds.
These winds will gust 20 to 30 mph by Monday afternoon and high
temperatures will approach 90 along the upper Minnesota River

.LONG TERM...(Monday night through Sunday)
Issued at 334 PM CDT Sun Aug 21 2016

Strong warm air advection will continue Monday night and Tuesday.
Gusty south winds ahead of the approaching trough and mixing to
875 mb will allow us to reach the mid 80s to lower 90s Tuesday.

Low pressure associated with the trough will track eastward across
the Dakotas and across the northwestern corner of Minnesota
Tuesday night. A trailing cold front should spark off some
thunderstorm activity across western MN by late Tuesday afternoon
or early evening, particularly as deeper moisture arrives in
earnest between 21-00Z. However, a developing low along the
southern end of the front over Kansas, with a surface warm front
extending to the east along the IA/MO border, may produce clusters
of storms or an organized MCS along I-80 which could prematurely
steer the healthy 45-55 kt low level jet to the east. If that were
to happen, it would be tough to get widespread storms across MN
and WI, particularly being in the entrance region of a secondary
LLJ centered over northern MN. Models have backed off on this
somewhat from yesterday`s solutions, aside from the Canadian, so
kept pops in the 50-70 percent range which is similar to the
overnight shift.

If Iowa doesn`t steal the show, Tuesday night`s convection may be
yet another event that has potential for heavy rainfall totals.
NAM/GFS/ECMWF 850 mb dew points rise to a very respectable +16 to
+19C range, 850-300mb bulk wind shear is expected to be 25 kts or
less, pwats increase toward 2 inches, and long skinny CAPE given
moist lapse rates all point toward heavy rainfall.

Cooler and drier weather follows for Wednesday night through
Friday before the next system approaches Saturday.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 614 PM CDT Sun Aug 21 2016

High confidence in VFR conditions through the period. Skies will
become mostly clear for the overnight hours, with merely few-sct
mid/high clouds on Monday. Light southerly winds overnight will
become gusty by late Monday morning...reaching sustained speeds of
15-20kts with gusts from 25-30kts.

VFR conditions will prevail. West/southwest winds become
southerly tonight then gusty on Monday. Sustained speeds will
reach around 17 kts by 18z Monday with gusts to around 25 kts.

Tue...VFR. -TSRA possible late. Wind SSW 15-20G25 kts.
Wed...VFR with -TSRA/MVFR possible. Wind SW 5-10 kts becoming W.
Thu...VFR. Wind NW 5-10 kts.


.MPX Watches/Warnings/Advisories...


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