Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 180912

Area Forecast Discussion
National Weather Service Sioux Falls SD
412 AM CDT THU AUG 18 2016

.SHORT TERM...(Today and Tonight)
Issued at 411 AM CDT Thu Aug 18 2016

Unsettled weather expected today and tonight across the region.
Isolated to scattered high based thunderstorms will continue through
around daybreak as elevated boundary shifts through the area. Storms
will mainly be found north of I90 with only isolated chance to the
south. These storms will be relatively weak, remaining below severe
limits. Warming aloft will help shut off the convection by mid to
late morning.

This afternoon, an advancing upper level trough digs across the
northern Plains, while a cold front drops across southeast South
Dakota. Strong surface heating along with moderate instability ahead
of the front will allow thunderstorms to become likely late
afternoon through the evening hours, mainly across south central SD
into west central Minnesota. Thunderstorm chances taper off rapidly
to the southeast of this region, with only isolated chances in
northeast NE, northwest IA, and far southeast SD. While MLCAPE
values increase to around 2000 j/kg and lapse rates increase in the
area of greatest thunderstorm chances, shear is quite a bit more
marginal for severe storm support. Cannot rule out a few severe
storms in the late afternoon and evening with hail to the size of
ping pong balls and gusts to 65 mph. Main severe threat will be in
the highway 14 corridor, and extending into south central SD.
Frontal boundary hangs up over the area overnight. Scattered showers
and thunderstorms will persist in the same general area, but the
severe threat will likely wane after the early morning hours.

Highs today will reach the upper 80s to mid 90s, with lows in the
lower to mid 60s.

.LONG TERM...(Friday through Wednesday)
Issued at 411 AM CDT Thu Aug 18 2016

Strong front will continue to work through the area on Friday
morning.  As the front moves through the area, 850 hpa temps will
fall from around 20C into the mid teens.  With the cooler air mass
moving in, extensive cloud cover, and scattered showers on Friday,
will be a hard time for temperatures to recover.  In fact, could see
temperatures fairly steady throughout the daytime hours. Based on
the thermal structure, it appears that limited heating into the
upper 60s will result in showers/isolated thunderstorms developing.
Once the upper trough shifts through the area on Friday night, the
precipitation chances appear to decrease.  Discounted the NAM
solution as it continues to be slower than other solutions.

Could see some scattered showers develop Saturday afternoon mainly
across southwest Minnesota into northwest Iowa due to a cold pocket
from 850-700 mb. With 850 hpa temperatures around 10C, it will be a
struggle to get temperatures to 70.

Really wasn`t all that confident in cloud cover Saturday night.
Models suggest some lingering moisture, but if skies clear, would be
a great radiational night. Nam suggests the potential for fog,
especially in the east while the gfs is much drier.  For now, left
the mention out of forecast.

Expect a nice warming trend into the middle of next week.  Still
appears as though a 30-35 knot low level jet develops east of the
James River Valley Tuesday night and have focused highest pops east.
Cold front moves through the area on Wednesday with a chance of
mainly afternoon and evening thunderstorms.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1030 PM CDT Wed Aug 17 2016

There is a possibility of isolated to scattered thunderstorms in
the vicinity of KHON from around 08z to 12z. Otherwise, VFR
conditions are expected through at least late afternoon on
Thursday. By late Thursday afternoon or evening, thunderstorms are
expected to develop from south central SD into east central SD.
These storms could affect the KHON area after 00z Thursday


.FSD Watches/Warnings/Advisories...


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