Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 131947

Area Forecast Discussion
National Weather Service Omaha/Valley NE
247 PM CDT Tue Mar 13 2018

.SHORT TERM...(Tonight through Friday)
Issued at 245 PM CDT Tue Mar 13 2018

Fire weather concerns develop on Wednesday, and slightly less on
Thursday, then focus shifts to a wide mix of rain and wintry
precip Thursday night into Friday with the potential for minor
icing and snow accumulations in some areas.

High pressure and clear skies today, with high pressure shifting
east overnight. Winds will diminish and may even become light in
some areas overnight, before becoming southwest by daybreak
Wednesday, with temps dropping into the lower 20s.

Breezy southwest winds increase to 10 to 20 mph through the day
Wednesday, which should help tap into warmer temperatures aloft,
helping to push surface temps into the 60s for many areas, possibly
making a run for 70 in parts of eastern NE. This does lead to
increased fire danger which will be detailed later in this

Lee cyclogenesis develops Wednesday night as a weak front settles
southward through the area, in response to the closed low pushing
into the Rockies. This sets up a tighter temperature gradient
across the forecast area for Thursday, with highs in the upper 40s
to lower 50s north of the front, but still in the mid 60s near the
KS border. Increased surface dewpoints help keep minimum
humidities in the 35 to 45 percent range, which should help
somewhat mitigate fire weather concerns.

Challenging weather develops Thursday night into Friday as the
weather system begins to move out of the Rockies. We are
fortunately seeing much better model agreement today than the
previous several days. Unfortunately, due to substantial warm air
advection aloft around a very strong low pressure system, this
leads to precipitation type issues in our forecast area, ranging
from just rain along our southern areas, to a wintry mix of
freezing rain, sleet and snow as you transition north toward the
SD border. Have increased Pops into the 80-90% range through
Friday, which is a substantial increase from previous forecasts.
The wintry mix will occur along/north of a line from about David
City, NE to Clarinda, IA. Snow amounts of 1-3" could occur in
northeast NE. Minor icing of 0.02 to 0.15 could also accompany the
wintry mix Friday morning. Some of this will be mitigated by
warming temperatures through Friday afternoon, which should help
switch over precip to mostly rain, and should also help with any
slick roads that develop earlier in the day.

.LONG TERM...(Friday night through Tuesday)
Issued at 245 PM CDT Tue Mar 13 2018

The weather system begins to transition out of the area Friday
night into early Saturday morning, but again, should end as a
messy transition of rain, changing back to snow, or possible
freezing rain or drizzle as we lose the deep moisture toward the
end of the event.

Saturday afternoon and night should be dry, but another strong
weather system moves out of the Rockies Sunday through Monday
which brings us another chance of rain and possibly accumulating
snow mostly along/north of I80. Winter isn`t over yet.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1228 PM CDT Tue Mar 13 2018

VFR conditions will continue across the area through the forecast
period. High pressure from the eastern Dakotas into eastern
Nebraska at 17Z will drift southeast towards the lower Mississippi
Valley through tonight. After 12Z southwest to west winds will
increase as surface gradient tightens.


Issued at 245 PM CDT Tue Mar 13 2018

Afternoon temps rise into the 60s on Wednesday, and while
dewpoints will be slowly increasing, minimum afternoon humidities
are forecast to drop into the lower 20 percent range across
southeast NE and southwest IA, and down to 30 to 40 percent
elsewhere. Wind gusts could approach 20 to 25 mph at times. This
will push rangeland fire danger (RFD) indicies into the very high
category for most areas, but grassland fire danger indices (GFDI)
only get to about 15 to 21, well below a critical threshold for
red flag conditions. Thus, will continue to highlight very high
grass fire danger in our hazardous weather outlook, but believe
we will remain critical thresholds for red flag warning (RFW)




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