Scientific Forecaster Discussion
fxus63 kmpx 221025
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
525 am CDT Mon may 22 2017
Updated for 12z aviation discussion below...
Short term...(today and tonight)
issued at 329 am CDT Mon may 22 2017
The short term concerns development of showers/thunder into the
afternoon and evening. Also threat of strong thunder over the far
Water vapor imagery showing the initial short wave exiting to the
east of the area at this time. This should exit the east by 12z.
The next short wave is moving into northwest South Dakota. This
is progged to move into the southwest portion of the cwa this
afternoon. Ncar ensemble showing mean Li and MUCAPE fairly meager
this afternoon and mainly along i90 region. GFS and NAM also show
some potential of MUCAPE to 500 j/kg this afternoon. Will continue
to trend pops toward likely over far south central Minnesota later this
afternoon. Severe potential appears fairly limited but at least
some small hail will be possible with steep mid level lapse rates.
If enough heating does occur to the north...we may see an
isolated thunderstorm develop in the late afternoon/early evening
before diurnal trend kicks in. We should see temperatures warm
some today...in the lower and mid 60s most areas.
Tonight the short wave exits to the southeast and the upper trough
drops south over the area. We should see increasing clouds/pops
especially to the west overnight as forcing moves into the central
part of area by 12z Tue.
Long term...(tuesday through sunday)
issued at 329 am CDT Mon may 22 2017
Tuesday...the day will start with the previous day's low pressure
center located near kmke while a large upper level low shifts into
central Minnesota. Due to the surface low and associated cold
front having passed through the area, instability will be
diminished but deep moisture will remain underneath the large cold
core low. Thus, the expectations are to have scattered to numerous
showers rotate through the area about the large upper low with the
potential that stronger showers could produce small hail (a.K.A.
Graupel). The potential for precipitation will diminish going into
the evening hours Tuesday and early morning hours Wednesday as the
upper level low moves southeast of the area and deep ridging from
the western Continental U.S. Shifts east.
Wednesday and Thursday...both days will be under the influence of
a drier airmass along with a large ridge axis moving into the
region. Surface high pressure will attempt to reassert itself but
the main influence during these two midweek days will be the upper
level low. This will spell clearing skies along with a noticeable
uptick in temperatures. Whereas highs hold in the 50s area-wide on
Tuesday, highs increase to the 60s on Wednesday then to around 70
Friday through Sunday...a bit more unsettled pattern is expected
for the end of the week into the weekend, mainly due to Canadian-
centered low pressure areas both at the surface and aloft. There
is better agreement on the timing of the systems, as a cold front
looks to push through the area late Friday followed by a brief
respite from precipitation during the day Saturday followed by
another large upper level low which may again bring scattered
showers going into Sunday. There also looks to be little in the
way of airmass change with these systems as highs look to remain
in the lower 70s throughout this period.
Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 520 am CDT Mon may 22 2017
First area of light rain exiting the far eastern area...not
affecting taf sites. We will see VFR conditions through the day
with a chance of thunder working into the southwest later this
afternoon. Expect this to remain south of krwf-kmsp. This will
spread east south of the taf sites this evening. A few showers may
develop later in the afternoon across central Minnesota as the upper
trough/cold air aloft develop some instability cu/-shra. Expect
this to be widely scattered with limited moisture. Then as the
upper trough drops south overnight...we may see MVFR cigs develop
over the western area by 12z Tue. Mentioned this possibility as
kaxn and kstc for now.
Kmsp...high confidence of VFR conditions this period. Some threat
of -shra late afternoon/early evening but with limited
moisture/instability too isolated to mention at this time.
/Outlook for kmsp/
Tue night...MVFR. Chc IFR -ra. Wind north 5-10 kts.
Wed...VFR. Wind NE 5-10 kts.
Thu...VFR. Wind southeast 5-10 kts.