Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 191756

Area Forecast Discussion
National Weather Service Sioux Falls SD
1156 AM CST Thu Jan 19 2017

.SHORT TERM...(Today and Tonight)
Issued at 348 AM CST Thu Jan 19 2017

Stratus remains at bay very early this morning, with current IR
satellite showing the low clouds over southeastern Nebraska/southern
IA and moving northward. All model low level rh time sections
indicate these clouds slowly overspreading the CWA from south to
north toward 12z. Hi res model visibility guidance would also suggest
some fog development in the morning hours, and with the low level
moisture it may persist in at least a patchy nature into the
afternoon. Due to the shallowness of the moisture and little lift
above, refrained from any drizzle mention through the day. The low
clouds will impact temperatures today in spite of the continuing
warm air advection regime, though still mild with highs upper 30s to
lower 40s.

Tonight the low level moisture increases in depth, and with enhanced
lift there are indications of drizzle development overnight. The
depth of moisture is still relatively shallow however, and am
doubting that any measurable precipitation will occur, so kept pops
less than 15 percent. It will be a very mild night with lows warmer
than typical high temperatures for this time of year, as minimums
only drop into the mid and upper 30s.

.LONG TERM...(Friday through Wednesday)
Issued at 348 AM CST Thu Jan 19 2017

Forecast soundings continue to show the low level moisture
deepening through the morning on Friday, with a lack of moisture
above the stratus. This should lead to a continued potential for
drizzle throughout the day, perhaps increasing in coverage as the
low level moisture deepens and lift increases ahead of broad
trough approaching the region. Cannot rule out some very spotty
icing if drizzle occurs in areas where temperatures remain cool
enough, but overall expect surface temps above freezing across the
area throughout the day.

Friday night/Saturday will bring an increase in mid level moisture
as the upper trough swings through the region. This should allow for
more of a bonafide light rain potential, or possibly some light snow
as the near-surface warm layer becomes more shallow late Friday
night into Saturday morning. Precipitation amounts generally looking
to be right around a tenth of an inch or less east of a Yankton to
De Smet line, with very light snow accumulations possible Saturday
morning. Temperatures Friday through Saturday will not move too much
given the thick cloud cover expected across the region, with highs
largely in the mid 30s-lower 40s and lows in the upper 20s-mid 30s.

The streak of mild weather will continue into early next week. The
low clouds will likely persist in many areas through Sunday, and
while they should shift northeast on Monday, will see an increase in
mid-high level clouds in advance of the next system, so sunshine on
Monday could still be somewhat limited.

A stronger trough swings across the Plains Tuesday/Tuesday night.
Still seeing fair amount of discrepancies regarding track/timing, so
have not altered blended model solution in favor of any specific
solution at this point. Despite these differences, models do agree
on temperatures aloft cooling enough to minimize threat of freezing
precipitation, with snow the more likely type for most of the area
as surface temperatures likewise cool off from the mild readings
expected earlier in the week.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1153 AM CST Thu Jan 19 2017

Visibilities are a bit of a question mark through the TAF period.
However it does appear a low cloud event is setting up for the
forecast period. Hedged the visibilities primarily in the LIFR to
IFR categories. But one thing more certain, is that ceilings
should remain very constant in the LIFR category if upstream
ceilings are any indication. Be aware, especially for tonight,
that VLIFR visibilities of a quarter mile or less could occur.
This is not shown in the TAFs however due to too much uncertainty.




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