Scientific Forecaster Discussion
fxus63 kmpx 202358
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
658 PM CDT Wed Sep 20 2017
Short term...(this evening through thursday)
issued at 225 PM CDT Wed Sep 20 2017
The main forecast concern in the near term is temperature trend.
The cold front has exited the far eastern area of the cwa late this
afternoon. High pressure will builds southeast over the area during
the night. With light wind and a clear sky, some threat of patchy
fog developing under the ridge considering last nights rain. We
expect temperatures to cool through the lower 50s in the south with
some upper 40s in the northeast cwa closer to the surface ridge.
The front will drop into Iowa overnight and as the ridge exits to
the east, we will see the front lift back north into southern
Minnesota as a warm front by late Thursday afternoon. We should
remain dry through the day, but instability increases in the
vicinity of the front as dewpoints rise into the 60s once again. We
also expect some cumulus to form as the moisture begins to return to
the area. Temperatures should warm through the lower 80s along and
south of the front with 70s to the north.
Long term...(thursday night through wednesday)
issued at 225 PM CDT Wed Sep 20 2017
The numerical guidance is in fairly good agreement on the
evolution of the large scale pattern during the Friday through
Wednesday period. The western trough looks to remain in place
through the weekend, with southwest flow and warm temperatures
over our area. However, the trough looks to move east Monday
through Wednesday, albeit slowly, bringing cooler temperatures
(and eventually, drier weather) into the area. We still look to
have a prolonged period of precipitation chances from Friday into
early next week as the aforementioned trough and associated
surface frontal boundary slowly push eastward.
We could see some elevated convection over the area Thursday night
with warm advection and an increasing low level jet, but the best
chance of activity looks to be north of I-94. Things look to be
capped across our area on Friday, with sunshine likely making it
our warmest day during a stretch of above normal days. Continued
to go a bit above guidance given recent overachievement on warmer
days and an overall favorable pattern for near record highs.
Frontal boundary to our west on Friday will ever so slowly push
east, and find its into the west Friday night. Storm Prediction Center has outlooked
the western portion of the area for day 3, mainly due to
convective potential Friday night ahead of the frontal boundary.
We will then likely see rounds of showers and thunderstorms
Saturday into Monday, with the boundary not making much in the way
of eastward progress until the Sunday night/Monday time frame. So,
it still appears that we'll have a prolonged period of rainfall
potential (oriented southwest to northeast) from Friday night
through Sunday night in roughly the same area, which could lead to
some significant rainfall totals and potential flooding. The main
area of concern still looks to be near and north/west of a line
from Redwood Falls to Mora, but we could certainly see that shift
some depending on what convective outflows do to the baroclinic
zone, and the eventual position/timing of shortwave troughs
embedded in the southwest flow. We will begin cooling down from
northwest to southeast on Sunday, but much more so Monday and
Tuesday, with things eventually drying out from west to east
Tuesday and Tuesday night.
Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 637 PM CDT Wed Sep 20 2017
VFR conditions are anticipated through the next 24 hours.
Northwest winds will calm tonight and veer southeast by Thursday
morning. A cumulus field will likely develop across southern Minnesota
and west central Minnesota during the afternoon. A warm front will lift
through Minnesota and WI during the late afternoon, but precipitation is
not expected until after 00z Thursday.
Kmsp... sky clear will continue tonight as winds calm and shift to the
southeast. Cumulus clouds are expected to develop ahead of a warm
front Thursday afternoon, and chances for showers and storms
begins late Thursday evening.
/Outlook for kmsp/
Fri...VFR. Chance MVFR/thunderstorms and rain early. Winds S 10-15 kts.
Sat...mainly VFR. Chance MVFR/tsra. Winds SW 5-10 kts.
Sun...mainly VFR. Chance MVFR/tsra. Winds SW 5-10 kts.