Scientific Forecaster Discussion
fxus63 kmpx 232058
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
358 PM CDT Wed Aug 23 2017
Short term...(this evening through thursday)
issued at 354 PM CDT Wed Aug 23 2017
A pleasant late-Summer day this afternoon across the upper Midwest
today with highs topping out in the mid-70s & dewpoints in the upper
40s to low 50s. This drier air at the surface will be a limiting
factor in our precipitation tonight, associated with a shortwave
trough diving south from Manitoba. Precipitable water values remain fairly low
with the lack of moisture so despite fairly organized isentropic
ascent & divergence aloft, really not expecting anything more
than 0.25" of precipitation tonight across central Minnesota & west-
central WI. Additionally, we're looking at little to no cape with
this system so expecting tonight's precipitation to be light &
showery with no thunder forecasted.
This area of showers will clear out of the area around sunrise
tomorrow with broken cloud cover holding on into the afternoon. Held
off on any fog mention across the northern County Warning Area tomorrow morning
despite the damp ground & calming winds, as cloud coverage should be
enough Thursday am to put a damper on peak radiational cooling.
Winds become southerly tomorrow as an area of high pressure at the
surface slides off to the southeast. This warm advection aloft &
moisture return at the surface looks to be enough to generate some
scattered showers towards Thursday evening, as another shortwave
trough approaches from the west. Cloud cover Thursday will keep
temperatures close to 10 degrees below normal, with highs remaining
in the low 70s.
Long term...(thursday night through wednesday)
issued at 354 PM CDT Wed Aug 23 2017
The long term period remains rather unsettled looking, really not a
lot has changed from the previous forecast. All in all, cooler than
normal temperatures are expected, along with showers and periodic
Thursday night through Friday...by Thursday night, the longwave
trough will be centered over the Great Lakes as the wave that is
expected to move through our region tonight will end up near Detroit
by Thursday evening. Our cool northwesterly flow aloft will
continue, whereas at the surface we expect southeasterly winds by
Friday. Low pressure will be developing to our west by Friday with
a warm frontal boundary extending eastward. We could see some light
precip during the day Friday to the north of the front, and with
mostly cloudy skies as well expect temperatures to be held in the
60s for much of the area.
Friday night through Sunday...the next system to watch will be a
developing shortwave across the Dakotas on Friday, which will move
east through our are this weekend. Precip will begin spreading into
western Minnesota ahead of this wave overnight Friday night most likely.
Instability is not impressive, but there could be some embedded
thunderstorms in this activity. Increased pops to 60% for much of
west central Minnesota through the Metro during this period. The trough
will continue to move through Saturday with the surface front across
portions of southern Minnesota, a good bet for continued showers and storms
to move through. At this point, the threat for severe weather is
low. As we get to Sunday, we'll see the winds turn northwesterly as
the system passes to the east, and the main slug of moisture GOES
with it. But, showers are still possible during the day with the
cold air aloft in place on the back side of the upper trough,
leading to sufficient lapse rates for showers to develop. Meanwhile,
Harvey will be slowing moving through the Gulf Coast of Texas, which
could limit the southern extent of our northern stream trough and
ultimately dictate the large scale weather pattern to some degree.
Monday through Tuesday...after the weekend system finally departs
the area, conditions should dry out and improve. Again, will have
to watch how the long range pattern may be altered by the acitivity
of harvey; hence a lower than normal confidence forecast at this
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 113 PM CDT Wed Aug 23 2017
VFR conditions prevail today with a scattered mid-level cu field
developing over east Minnesota/west WI. An area of showers will move in from
northwest Minnesota late this evening & continue through the early
morning. Ceilings & visibilities are expected to remain VFR.
Light northwest winds today, becoming light & variable overnight, &
veering to the southeast tomorrow.
VFR expected through the period. Showers expected to move into the
airfield shortly after midnight tonight. May see a few breaks in
the rain but showers should persist through 12z. Not expecting
ceilings or visibility to drop below VFR during the rain.
/Outlook for kmsp/
Thu...VFR with MVFR possible. Wind southeast at 10 kts.
Fri...VFR with MVFR/-shra possible. Wind southeast at 10 kts.