Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 280533
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1133 PM CST Mon Feb 27 2017

.SHORT TERM...(tonight through Thursday)
Issued at 310 PM CST Mon Feb 27 2017

The main forecast concerns will be in the first 30hrs of the forecast
related to temperatures...the extent and location of
precipitation and precipitation type tonight into Tuesday
evening.

The 12Z upper air charts and water vapor satellite imagery
highlight a broad trough that extends from Idaho through central
California into the Pacific...with mid level moisture ahead of
this trough. The h85 observations detailed h85 dewpoints across TX
and OK and KOUN showed saturated conditions in the lowest 2500ft.
the moist h85 dewpoints are forecast to spread northward into
southeast Nebraska through 00z. H85 Warm Air advection/Theta-e
advection has been ongoing through the afternoon and visible
satellite imagery shows an increase in clouds.

The forecast is a bit complex as there is a front over South
Dakota with surface low pressure over eastern Colorado. Lead
shortwave trough energy moves into the Plains tonight. During the
evening...The low level jet strengthens to 45 or 50kts. the
deeper moisture shifts quickly eastward into iowa...however does
get pulled northward into northeast Nebraska...with the best
forcing closer to the front across the Dakotas into Minnesota.
There may be a few showers from eastern Nebraska into western
Iowa. There is some elevated instability...cannot rule out some
thunder. Confidence was low...thus did not mention at this time
in our local forecast. Overnight...the surface low tracks from
eastern Colorado into northeast Nebraska. Do have some fog and
light precipitation mentioned in the vicinity of the low and the
precipitation initially is liquid...however could see some mix due
cooling. Low temperatures tonight will vary from 30 near the SD
border to near 50 near the KS/MO border.

Tuesday...the left exit region of the upper level jet combine with
mid level omega/developing frontogenesis. There may be enough lift
for rain or a rain/snow mix to develop in a band behind the front.
The GFS is the most aggressive with this precip (1 to 2
inches)...while the other models show a signal...however the
precip is lighter possibly 0.1" in our area along and south of I80
and into sw Iowa. The NAM tends to accumulate the snow south of
the forecast area. Do mention rain and where it could switch to
snow on the cool side of the precipitation band although kept any
amounts light for now. Highs Tuesday should remain in the 30s to
lower 40s in northeast Neb. and could warm into the lower 60s at
Falls City.

Northwest breezes and highs in the 40s are on tap for Wednesday. A
weak front/clipper helps temperatures rise slightly...but still in
the 40s for Thursday.

.LONG TERM...(Thursday night through Monday)
Issued at 310 PM CST Mon Feb 27 2017

Surface high pressure will be over the Missouri River Valley to
start the extended with h85 temperatures lowering to -4 to -8deg C.
South flow increases for Friday and Saturday as surface low pressure
tracks across Manitoba into Ontario with a trailing front into the
Plains.  H5 flow is fairly zonal Saturday and begins to amplify a
little more Sunday.  Warm air appear to remain in place Sunday with
12-14deg C h85 temps...although there is some difference in the
strength of the flow.  The 12Z GFS has a ridge Sunday...with the 00Z
EC showing a deepening trough with a front approaching the forecast
area. These differences further continue into Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1128 PM CST Mon Feb 27 2017

Area of MVFR cigs will spread north ahead of a low pressure system
and into eastern Nebraska between 06Z and 12Z. A cold front will
quickly follow, with more MVFR cigs just behind the front between
12Z and 18Z. All eastern TAF sites could see MVFR cigs, but KOMA
is most likely to have cigs drop below FL020 through 18Z. Low
level moisture will also increase, leading to areas of MVFR fog,
with some IFR vsbys likely at KOMA between 12Z and 15Z. There is a
chance for rain or a mix of rain and snow to develop near KLNK and
KOMA after 21Z, which could lead to IFR vsbys again. However the
most likely area of development will be southeast of these TAF
sites.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Dergan


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