Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 202340
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
640 PM CDT Mon Mar 20 2017

.SHORT TERM...(tonight through Thursday)
Issued at 308 PM CDT Mon Mar 20 2017

Early afternoon water vapor imagery indicated a progressive
shortwave trough crossing southern Canada associated with a
seasonably strong 110 kt H3 jet. This system will shift into the
Great Lakes tonight allowing for the central and northern Plains
to become located in the right rear entrance region of the jet.
This should provide a favorable synoptic pattern for low-level WAA
starting after midnight into Tuesday. This will likely lead to a
tightening of the existing mid-level thermal gradient/frontogenesis
in the 850-700 mb layer. Short term models are in fair agreement
in this process producing a stripe of light precipitation after
midnight in the far northwest CWA, across the northern CWA Tuesday
morning, and east of the area by Tuesday afternoon. Initially
precipitation should be all rain, but point forecast soundings in
this stripe indicate considerable dry air below 800 mb and we
should see a wet-bulb process allow for snow to mix in late
tonight and into Tuesday morning. We will currently paint a stripe
of 1 inch snows over Knox/Cedar counties, but placement of such a
narrow band is difficult even at this range. In addition, if the
rain changes to snow quicker than currently progged we would not
be surprised to see an isolated 2 inch amount within this band
give the weak static stability above the frontal slope.

A short break in precipitation is expected for Tuesday afternoon
into most of Tuesday night before low to mid-level WAA increases
ahead of a strong trough progged to move into the Great Basin
later this week. This should again lead to isentropic lift and
associated light precipitation, mainly in the western/northern CWA
into the first half of Wednesday. Point forecast soundings would
indicate mainly snow to start, but some potential for any
precipitation to end as some light rain. Amounts from this period
appear to be under one inch though.

The previously mentioned Great Basin trough will start to shift
east into the Rockies on Wednesday night into Thursday and this
should again lead to a nocturnal Plains low-level jet and
associated thermal advection/isentropic upglide with another
period of showers or some drizzle possible into the day on
Thursday.

.LONG TERM...(Thursday night through Monday)
Issued at 308 PM CDT Mon Mar 20 2017

The active weather will continue into the extended range of the
forecast. Global models are in good agreement that the Rockies
trough will swing slowly through the central and southern Plains
from Friday through the weekend. This should bring seasonably cool
and wet weather to the region. With surface to 850 mb moisture
increasing on Thursday night into Friday we may also see a few
thunderstorms across the area with the steeper lapse rates. This
will likely transition to more general showers for Saturday into
Sunday.

As this system clears during the day on Sunday another system will
be in the western US that will emerge to start the new work week
with a renewed chance for some showers. With the continued active
pattern overall temperatures should be at or below normal to end
the period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 606 PM CDT Mon Mar 20 2017

Main concern is possible pcpn at KOFK early Tuesday morning. An
upper disturbance moving across the Dakotas will aid with
development of narrow swath of pcpn extending from s-cntrl SD into
nern Neb. Activity/MVFR cigs should reach KOFK sometime around
11z and continuing on thru Tuesday morning...and MVFR cigs thru
the aftn. Otherwise VFR conditions will prevail at both KOMA/KLNK

&&

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

$$

SHORT TERM...Boustead
LONG TERM...Boustead
AVIATION...DEE



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