Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 260805

Area Forecast Discussion
National Weather Service Sioux Falls SD
305 AM CDT MON SEP 26 2016

.SHORT TERM...(Today and Tonight)
Issued at 305 AM CDT Mon Sep 26 2016

A pleasant, albeit breezy, early fall day in store across the area.
An axis of surface high pressure will extend from the Northern
Rockies into the Central Plains, while surface low pressure over
southern Canada will drift into the western Great Lakes region by
afternoon. This will result in a decent gradient over our area, most
pronounced from east central SD/southwestern MN into northwestern
IA, where mixed layer winds will average around 30 kts in the
afternoon. Skies will be mostly clear during the day, though cannot
rule out some cumulus development through the Missouri River
corridor as low/mid level moisture slides through that area. Thermal
profiles warm just a tad over yesterday, and looking at highs in the
mid 60s through east central SD and southwestern MN to lower 70s
through the James River Valley/Missouri River corridor.

Tonight, northwesterly winds will drop off in the early evening,
becoming light overnight. This in combination with mostly clear skies
will result in optimal cooling, and lows will drop to around 40 over
much of the CWA, with some mid 40s through south central SD.

.LONG TERM...(Tuesday through Sunday)
Issued at 305 AM CDT Mon Sep 26 2016

Much of the medium and extended range looks to be settling in on
quiet times, in proximity to upper-level ridge between closed low
across the Great Lakes area and trough through the western U.S.. One
subtle change from yesterday deals with the trough to the east,
which now wraps up a bit more westward as lobe wraps southward
across Wisconsin early Wednesday, and is more sluggish in gradual
eastward drift.  With a greater influence of this feature on
Wednesday, there appears to be a stronger westward push to stratus
field behind upper low which should have a fairly easy path westward
toward sub-850 hPa ridge axis as gradually works to dissipate on
western flank with mixing/subsidence on Wednesday. Am quite leery of
this pattern, especially given model trends over last 24 hours, as
one which will end up with a lot more persistence to clouds in the
Wed./early Thu. time frame.

As a result, warmer day could easily end up being Tuesday in the
intermediate term, as even cooler air undercuts on north/northeast
low-level flow for Wednesday and warming finds difficult path on
Thursday with low-level ridge trapped in place across the
mid/eastern CWA.  As far as numbers go, mainly upper 60s to mid 70s
on Tuesday with 4-7 degrees cooling, greatest east, on Wednesday. A
couple degrees of moderation on Thursday, and a shade more on Friday
would appear all fairly stagnant pattern can attain, even as try to
get strengthening south/southeast flow by Friday across SD CWA.
Lows will mainly be in the 40s, although some spotty upper 30s near
the mid James to Big Sioux valley areas will be possible Tue night.
As air mass moistens a slight bit and get start of the southerly
return flow, should see some lower 50s return.

The start of the weekend will be dry as features struggle to
displace the sharp but narrowing upper ridge. A tighter surface
gradient will become more prevalent as pressure fall in the western
plains, with stronger southerly flow bringing seasonally mild
temperatures with highs in the 70s and lows in the upper 40s to mid
50s.  In all likelihood, will take until sometime Sunday at the
earliest to get enough lift forcing to support a chance of showers
and thunderstorms as trough pushes across the central and northern
Rockies.  Better chance for rainfall will likely spread across the
area Sunday night and Monday with passage of cold front.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1055 PM CDT Sun Sep 25 2016

Gusty northwest winds are expected to develop again after 15Z
Monday, with winds again diminishing toward sunset Monday evening.
VFR conditions will prevail through the period.


.FSD Watches/Warnings/Advisories...


LONG TERM...Chapman
AVIATION...JH is the U.S. government's official web portal to all federal, state and local government web resources and services.