Scientific Forecaster Discussion
fxus63 kmpx 181757
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1257 PM CDT Wed Sep 18 2019
Short term...(this evening through Thursday night)
issued at 1257 PM CDT Wed Sep 18 2019
A cold front is currently heading across western Minnesota where clouds
have cleared and dew points have fallen into the 50s. To the east
of the front, clouds continue to hold temps down a bit, but there
are signs rapid clearing should begin soon with breaks becoming
more numerous. We should still reach the low to mid 80s in the
warm sector yet this afternoon. As the boundary layer recovers,
storms may fire along the cold front late this afternoon across
central Minnesota and then become widespread this evening across portions
of west central WI into far southern Minnesota. These storms could
produce heavy rainfall as the front slows its southeastward
progress. Some areas could exceed an inch or even two if enough
The front will sag a bit further south Thursday, and aside from
areas along and southeast of a line from Eau Claire to Albert Lea,
the County Warning Area should be dry into Thursday evening. Plenty of sun and 925
mb temps in the low 20s c will bring highs back into the upper 70s
or lower 80s.
The front will return north Thursday night with modest moisture
advection shifting into Minnesota overnight. Isolated to scattered
thunderstorm development is expected to occur along the front.
The storms won't be overly organized with the absence of
substantial deep layer shear.
Long term...(thursday night through tuesday)
issued at 224 am CDT Wed Sep 18 2019
The long term period will begin warm and humid, with southwest
flow continuing through Saturday. An amplified upper trough will
work trough the area this weekend, cooling things off by Sunday.
Thunderstorms chances associated with this system look best Friday
night into Saturday. Another digging trough across the western
Continental U.S. Early next week looks more and more likely, which would
bring back deep southwesterly flow and increasing temperatures for
middle of next week.
By Thursday evening, the main feature of interest is the amplified
upper trough which will be centered over Idaho through Nevada at
that time. Through the following 24 hours, the trough will
progress east, but begin lifting northeast especially Friday
afternoon. Theta- E advection locally will increase late Thursday
into Friday as the frontal boundary that was just to our south on
Thursday lifts north through southern Minnesota and western WI by Friday
morning. Guidance continues to suggest convection will be possible
during the day Friday, but this is rather uncertain given lack of
large scale forcing. By Friday evening, pv advection with subtle
ripples in the upper flow ahead of the main trough will reach our
local area, and with about 2,000 j/kg MUCAPE and modest shear,
thunderstorms are expected to develop and advect in from the
eastern Dakotas. There is a risk of large hail and damaging winds
with these storms.
The cold front looks to reach western Minnesota midday Saturday, working
through the remainder of Minnesota and western WI by early Sunday
morning. Dew points will fall into the 50s and temperatures will
be very close to normal as we head into next week.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1257 PM CDT Wed Sep 18 2019
Cold front will continue eastward today with MVFR cigs in advance
of it lifting and scattering out shortly. Storms will redevelop
over eastern Minnesota late this afternoon and become widespread tonight
across portions of west central WI into south central Minnesota. The
front will push the storms south Thursday. Areas of fog are
possible very late tonight behind the rain, if clouds can clear
Kmsp...the clouds are beginning to scatter out and VFR conditions
are expected through the period. A few storms could fire across
eastern Minnesota later this afternoon, but the areal coverage and
confidence is low enough to preclude a mention in the taf for now.
/Outlook for kmsp/
Thu...VFR. Chc MVFR/thunderstorms and rain late. Wind southeast 5 kts.
Fri...VFR. Chc MVFR/tsra. Wind S 10g20 kts.
Sat...VFR. MVFR/thunderstorms and rain likely in mrng. Wind SW bcmg west 15g25 kts.