National Weather Service Raw Text Product

892 
FXUS63 KFSD 210347
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1047 PM CDT Sat May 20 2017

.SHORT TERM...(This evening through Sunday)
Issued at 413 PM CDT Sat May 20 2017

Low pressure center is presently located over west central IA this 
afternoon, with a dry slot pushing into our northwestern IA zones at 
this time. Back to the north and west, scattered showers continue 
across the area. The low pressure will slide to the northeast 
overnight, becoming situated over western Wisconsin by Sunday 
morning. For this evening, the shower threat will continue across 
the area, focused mainly through the James River Valley and Highway 
14 corridor in association with a trowal wrapping around to the 
north and west of the low. While there have not been any lightning 
strikes for several hours in our area, did leave in isolated thunder 
in portions of northwestern IA and southwestern MN through the 
evening with weak instability (CAPE values of 100 to 200 j/kg) over 
that area.

Later tonight, will see diminishing shower chances from west to east 
as the low pulls away, though clouds will hold over most of the 
area. Thermal profiles support a little snow possibly mixing in with 
any lingering rain over the central Highway 14 corridor after 06Z 
tonight, though surface temperatures will remain in the upper 30s 
over that area so not looking at any accumulation. Northwesterly 
winds will stay in the 10 to 15 kt range tonight, and lows will run 
in the upper 30s to lower 40s.

Clouds will be slow to clear on Sunday, especially in the east, and 
cannot rule out isolated shower chances remaining in our far 
southwestern MN zones as the upper level low spins over the Upper 
Mississippi Valley. Gusty northwest winds will remain through the 
day, and while we will have warming temperatures, readings will be 
below normal with highs only lower 50s over southwestern MN where 
clouds will persist, to as warm as the mid 60s through the James 
River Valley where some sun is expected in the afternoon.

.LONG TERM...(Sunday night through Saturday)
Issued at 413 PM CDT Sat May 20 2017

Deep trough circulating across Minnesota as it wraps up Sunday 
night.  While is does dry out at lower levels as flow turns 
southwest and westerly, indications are that there could be more mid-
level clouds than expected as weak lobe rotates through southwest MN 
during the evening, and maybe even enough for passing couple of 
sprinkles or light showers. 

Main precipitation chance in intermediate range begins Monday, as 
more coherent lobe swings around the deep Minnesota trough across 
the Dakotas and Nebraska.  Most solutions are showing at least a 
small degree of splitting to dynamics, but with weak stability 
there should be a good response to the most minimal forcing, and 
supportive of likely PoPs over much of the area during the afternoon.
Still potential for 500-800 J/kg MLCAPE, with weaker shear largely 
in a linear mode. Not out of the question that parameters could be 
briefly stronger near convergence boundary as it pushes across 
northwest Iowa and extreme northeast Nebraska during the afternoon, 
but probably not enough for more than the most minimal threat for a 
stronger storm. 

Wave takes with it the precipitation chance during the evening, and 
should remain fairly quiet other than increasing northerly winds 
Monday night.  Final strong lobe will wrap southward on Tuesday, 
with impacts to be largely felt east of the James River, as 
precipitation coverage is enhanced along with the diurnal cycle. 
Instability does not look strong, but could see an isolated rumble 
around northwest Iowa and adjacent areas from midday through the 
afternoon.

Moisture wrapping around the upper low should again bring a diurnal 
cloud increase to areas around northwest Iowa on Wednesday, but 
enough subsidence with folding upper ridge to keep a lid on shower 
development this far north/west.  As upper ridge axis shifts across 
the area toward mid to late week, Thursday should be the most 
pleasant day of the week with temperatures moderating back to 
near/above normal, perhaps diminished in quality a bit by breezy 
southerly winds.

Upper ridge begins to be knocked down by wave toward the end of the 
week, with EC quicker than Canadian/GFS. Regardless, should see a 
push of steeper mid-level lapse rates along with wave sliding up the 
ridge, for a threat for elevated showers/thunderstorms pushing 
northeast across the area, followed by additional precipitation 
changes around a frontal passage around Saturday. Temperatures 
Friday into Saturday should remain near/above normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1044 PM CDT Sat May 20 2017

Light rain, scattered showers, and drizzle will continue to 
slowly rotate across the region through the overnight hours.
Predominate conditions will be MVFR and IFR with ceilings dropping  
as low as 800 ft agl with visibility as low as 2 miles at times. 
Conditions will begin improving late tonight through Sunday 
morning, with ceilings lifting or becoming scattered at all three 
TAF sites through mid afternoon Sunday.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...JM
LONG TERM...Chapman
AVIATION...