Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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903
FXUS63 KOAX 221131
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
531 AM CST Fri Feb 22 2019

.SHORT TERM...(Today through Sunday)
Issued at 400 AM CST Fri Feb 22 2019

Several forecast concerns into the weekend as the forecast area
is affected by several rounds of precipitation and potent storm
Saturday afternoon into Sunday morning and how best to handle
headlines.

You know you have a significant storm system coming your way when
record low maximum temperatures are forecast for southern California
(where snow fell in Malibu/Pasadena Thursday) and record high
temperatures are forecast in Florida!

Water vapor satellite imagery/heights/lightning highlight the large
closed low over southern Nevada/California with lightning at the
base of the trough and another closed low moving into British
Columbia.

The OAX 00Z sounding was moist above 740mb, however very dry below
that layer, while the LBF and TOP soundings were moist top down to
around h85.  Of note on the upper air charts were the strong 130kt
jet diving south across California, the enhanced mid-upper level
moisture ahead of the closed low across Utah into Colorado and
Wyoming, and the mid level trough farther north across the Northern
Plains into Canada.

The first round of snow where the winter weather advisory in effect
across central and northeast Nebraska is a result of mid-level lift
and warm advection where there is sufficient moisture for snow.
Steep lapse rate are in place and the precipitation is on the
showery side with pockets of visibilities around a mile at times at
Albion and Norfolk. This advisory may be ended early depending on
if the lift moves just north of the area or hangs on affecting
parts of Nebraska.

As the mid-tropospheric trough across the northern Rockies and the
closed low moves rotates farther east across Arizona this
afternoon, warm air advection increases and we see a strengthening
low level moist flow. For round 2, temperatures aloft warm above
freezing and some of the surface temperatures also warm across the
southeast portion of the forecast area, while temperatures hover
near freezing along I80. Forecast soundings support a mix of light
snow and freezing drizzle/freezing rain increasing this afternoon
and continuing overnight with some glazing of surfaces and ice
accumulations mostly between a trace and 0.15". Decided to issue a
winter weather advisory mainly along and north of I80 where
surface temperatures were at or below freezing and potential for
icing higher. The day shift will have to metwatch the situation
with the increasing moisture to see if adjustments are needed.

There is still a large spread in the model solutions for round
3...the main event...Saturday/Saturday night related to the
latitudinal location of the heavy snow. For this forecast, used
the EC/NAM/UKMet/Canadian solution for snow placement as the GFS
track has been more of an outlier. Noticed the SREF also is
farther north though. The storm system is a fast-mover which will
limit snow amounts. The greatest lift appear during the afternoon
hours. Snow totals range from 2 to 6+ inches with mostly 4 to 8
inches the watch area. The Garcia method is supportive of 3 to 6
inches.  The current watch is consistent with the
EC/NAM/UKMet/Canadian, so did not adjust the watch.

As the surface low tracks from central Kansas eastern Iowa,
northwest winds increase 20 to 30kts with gusts 35 to 45kts. Will
continue to mention blizzard conditions possible due to the strong
wind gusts. The bulk of the snow ends by midnight, however the
blowing will last until Sunday.

.LONG TERM...(Sunday night through Thursday)
Issued at 400 AM CST Fri Feb 22 2019

The extended Monday into Tuesday, the current forecast of more
zonal or slightly amplified flow has the bulk of the precipitation
north of the forecast area. As the cold air moves in, light snow
is possible Tuesday night

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 530 AM CST Fri Feb 22 2019

Expect deteriorating conditions this afternoon as clouds thicken
and precipitation becomes fairly widespread. MVFR or IFR ceilings
and IFR visibilities are likely late this afternoon and through
the evening. Light freezing drizzle should cause icing.
&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory from 4 PM this afternoon to noon CST
     Saturday for NEZ012-015-018-032>034-042>045-050>053-065.

     Winter Storm Watch from Saturday afternoon through Sunday
     afternoon for NEZ034-044-045-050>053-065>068-078-088>093.

     Winter Weather Advisory until midnight CST tonight for NEZ011-
     016-017-030-031.

IA...Winter Weather Advisory from 4 PM this afternoon to noon CST
     Saturday for IAZ043-055-056-069.

     Winter Storm Watch from Saturday afternoon through Sunday
     afternoon for IAZ043-055-056-069-079-080-090-091.

&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Miller



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