Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 170517

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1217 AM CDT Tue Apr 17 2018

.SHORT TERM...(Tonight through Thursday)
Issued at 242 PM CDT Mon Apr 16 2018

WV imagery this afternoon showing a closed circulation has
finally pushed ashore over the Pacific NW with 130kt jet streak
rounding the base...per UAA. Meanwhile...downstream ridge axis
extending northward from the central High Plains in to central
Canada was slowly progressing east. At the surface, an elongated
narrow wedge of high pressure oriented north-south was extending
from the Dakotas to the southern Plains.

Active weather returns to the region Tuesday night/Wednesday with a
mix of snow/rain/thunderstorms to contend with. Strong vort energy
is progged to cross the central Rockies Tuesday afternoon with
associated DPVA inducing leeside cyclogenesis in eastern CO. Strong
boundary layer moisture advection into the central Plains ensues.

Precip development over the western Dakotas Tuesday afternoon
corresponds well with increasing isentropic upglide. Precip is
progged to quickly spread into the CWA Tuesday evening along axis of
850-700mb frontogenetic forcing/CAA sweeping southward.

Both GFS/NAM show instability parameters ramping up in the
vicinity of the southern CWA by late Tuesday afternoon with MUCAPE
pushing 1500J/KG...steep mid layer lapse rates with thunderstorm
initiation along strengthening boundary layer moisture
convergence/lifting warm front. And with such steep lapse rates
atop pooling boundary layer moisture/sfc-6km`s probably
a safe assumption a few elevated storms could produce near-
severe/severe hail. Expect thunderstorm activity to clear the CWA
by late Tuesday evening when best instability shifts east.

As for precip over the northern CWA, models in agreement initial
precip type will be rain Tuesday evening followed by a rain/snow mix
after midnight. Given that best omega pulls away into srn MN/nrn IA
shortly after MaxT aloft goes below freezing, expect that any snow
accumulations that may occur will most likely be on the light side
with amounts generally up to an inch or so.

.LONG TERM...(Thursday night through Monday)
Issued at 242 PM CDT Mon Apr 16 2018

Another strong upper circulation crossing the central Plains this
weekend will be the focus for the next round of precipitation.
Precip chances begin Friday night and continue into late Saturday
night. Thermal profiles do suggest the potential for a brief
period of a rain/snow mix Saturday morning over the northern CWA,
but the dominate type will be rain. Little in the way of
instability advertises, so chance for any convection as of now
looks NIL.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1154 PM CDT Mon Apr 16 2018

VFR conditions overnight. There may be some patchy ground fog that
develops in northeast Nebraska, however confidence too low to
include. Surface high pressure pushes east with northeast winds
becoming east southeast under 10kts. Clouds thicken during the day
with mvfr conditions developing after 00Z with showers and
scattered thunderstorms. East winds increase to 10 to 20kts after




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