Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 270925

Area Forecast Discussion
National Weather Service Omaha/Valley NE
325 AM CST Mon Feb 27 2017

.SHORT TERM...(today through Wednesday night)
Issued at 316 AM CST Mon Feb 27 2017

Weather will continue to trend milder, along with a somewhat more
active weather pattern in the short term. Subjective 00Z upper-air
analysis indicates largely zonal flow across the CONUS, with an
upper-level trough coming ashore in the Pacific Northwest and a
departing upper-level trough exiting New England. Strongest upper-
level jet extended across the Ohio Valley at up to 150kt, with
weaker upper-level jet in the western half of the CONUS. 850mb
pattern was fairly nondescript, with a north-to-south temperature
gradient that doesn`t seem tight enough to call a true baroclinic
zone and with only weak ridges and troughs in the central US. At
08Z, a lee trough was noted in eastern CO to central WY.

Main forecast concern is potential for fog and drizzle tonight, then
rain and snow in the southern half of the CWA on Tuesday night.
Temperatures today will continue to trend milder under mid-level
warm air advection and low-level southerly winds. By 00Z, a lee
surface low should take shape in northeast CO, sliding across NE on
Monday night.  In the warm sector ahead of the low, should be enough
low-level moisture advecting in for stratus, fog, and drizzle.
The drizzle area should focus mainly in the eastern half of the
CWA and in northeast NE, while the highest risk of fog is more
likely to be in areas with some snow left to melt today and
particularly where snowpack lingers tonight. Temperatures tonight
should remain above freezing in most places, with the exception
being in northeast NE. Thus, a bit of light freezing drizzle is
possible in the far northwestern CWA tonight, but confidence is
low on duration and amounts (i.e. trace to a couple hundredths).

Cold front will move through the CWA on Tuesday, bringing some
reduction in temperatures and probably early-afternoon highs as
temperatures fall off in the late afternoon through evening. The
main upper-level shortwave should slide across SD/NE on Tuesday
evening/night, with a lingering mid-level baroclinic zone extending
from southern IA through northwest MO/southeast NE and into KS.
GFS/NAM/ECMWF have slightly different placement on the baroclinic
zone but do agree that it should be fairly potent, with strong mid-
level frontogenesis on Tuesday evening that slides south of the CWA
through Tuesday night. Should see precipitation develop in that area
of frontogenetic lift on Tuesday evening, with precipitation
changing from rain to snow as colder temperatures advect in behind
the front and as dynamical cooling occurs.  GFS/NAM are quite a bit
farther north than ECMWF, but both of those solutions do pull the
band southward shortly after precipitation likely would change to
all snow. For that reason, have little accumulating snowfall in the
CWA, though did bump up QPF as blended solution looked underdone
where the band does end up developing.

.LONG TERM...(Thursday through Monday)
Issued at 316 AM CST Mon Feb 27 2017

Temperatures on Thursday will take a brief return to near-normal
readings, with a reinforcing cooler air push during the day.  By
Thursday night, return flow should begin the warm air advection
process as mid-level winds become southwesterly and low-level winds
gain a westerly to southerly component. With virtually zonal
upper-level flow and favorable downsloping and mixing winds,
temperatures should rise quickly this weekend. Have added a couple
of degrees to maximum temperatures on both Saturday and Sunday.
An upper-level trough/low moving across the northern Plains to
upper Midwest should drag a cold front through the region on
Sunday night and Monday, bringing temperatures back down to
normal. For now, the trough and frontal passage look to be more
dry than wet, with gusty northwest winds.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1125 PM CST Sun Feb 26 2017

VFR conditions are forecast through Monday evening. There is a
chance for MVFR fog a couple of hours either side of 12Z at all
sites, but it is expected to be patchy and thus not mentioned in
TAF at this point. Otherwise, as a low pressure system approaches
Monday afternoon, southerly winds will increase into the 15 to
20kt range, while mid clouds increase in coverage. Cigs are
forecast to lower to near FL050 between 00Z and 06Z, but could
drop into the MVFR category before the end of the TAF period.




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