Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 181646

Area Forecast Discussion
National Weather Service Sioux Falls SD
1146 AM CDT WED MAY 18 2016

.SHORT TERM...(Today and Tonight)
Issued at 338 AM CDT Wed May 18 2016

The weather still looks quiet today and tonight. A very large area
of high pressure at the surface drifts ever so slowly eastward,
extending across the MS valley, OH valley and Great Lakes region.
Therefore a south to southeast flow of air will begin, but will not
be breezy yet today and tonight. Looks like another very pleasant
day today, with dry air in place, and a well mixed atmosphere should
produce highs in the upper 60s and lower 70s. Still looks like a
decent amount of fair weather cumulus should form, mainly east of
the James River valley. Like Tuesday, the moisture depth is shallow,
so not expecting any light rain although a couple of the hires
models including the NMM and ARW have some light QPF output late this
morning in the Storm Lake and Cherokee areas. At this time, that
scenario was not included.

Should be a mainly clear night tonight, with a possible increase in
mid level cloudiness late across our far southern zones. With a bit
of a south or southeast breeze, lows should not radiate as much with
the possible exception in our far eastern zones from Windom MN to
Storm Lake IA where winds will be light.

.LONG TERM...(Thursday through Tuesday)
Issued at 338 AM CDT Wed May 18 2016

GFS continues to show some light precip developing through the
central portions of the forecast area on Thursday, as a subtle wave
swings into the Dakotas. GFS is by far the most aggressive on this
precip chance; however, some of the higher-resolution models also
produce some skittish light qpf during the afternoon. While most
areas will more likely see non-measurable sprinkles, decided to add
a slight chance of light showers from Sioux Falls northward for the
afternoon. Temperatures expected to be similar to today, with highs
in the upper 60s to lower 70s.

Thursday night through Saturday we see gradually building heights
aloft as mid-upper level ridge builds northward through the Plains.
This will be accompanied by slowly warming temperatures and breezy
southerly flow. Models producing spotty light precip through this
period, with the GFS again the most widespread/persistent. However,
with building heights acting to suppress any weak lift from lower
level warm advection, and low level moisture return largely blocked
by ridge axis extending from north Texas into the Great Lakes, think
precip threat through this time frame looks overdone and will stick
with our dry forecast. High temperatures nudge a little warmer on
Friday, with most areas in the lower to mid 70s, then warm further
on Saturday with readings from the mid 70s to around 80. Overnight
temperatures through this period will likewise see a warming trend,
with lows generally in the 50s.

Upper ridge axis begins to shift east Saturday night/Sunday, and
models have reverted to allowing for some spotty convection near and
west of the James River Valley on Sunday. Greater rainfall chances
still look to work into the area Sunday night/Monday as the upper
level trough swings across the Dakotas. See increase in instability
during this time frame ahead of approaching surface front, with deep
layer shear still quite weak ahead of the boundary but increasing
along/behind the front on Monday. At this point the severe threat
looks low in our area, but will be the period to watch. This wave
lifts northeast of the area Monday night, but will remain on the
unsettled side into Tuesday as additional waves slide through the
southwest flow. Temperatures remain on the warmer side through the
early part of next week. Highs Sunday should easily be in the upper
70s to lower 80s ahead of the front, with only slight cooling back
into the 70s for Monday and Tuesday.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1144 AM CDT Wed May 18 2016

VFR conditions through the period.


.FSD Watches/Warnings/Advisories...


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