Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 242113
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
313 PM CST Tue Jan 24 2017

.SHORT TERM...(tonight through Friday)
Issued at 312 PM CST Tue Jan 24 2017

...Significant Winter Storm Currently Impacting Eastern Nebraska
and Western Iowa...

The 12z subjective upper air analysis indicated a complex system
evolving through the central Plains. The main area of height
falls, 120 m at H5, was located over central NM, and early
afternoon water vapor imagery indicates that this area has shifted
northeast into western KS since. The analysis also indicated a
secondary vorticity maxima and associated height falls center
over CO/WY, and this has shifted toward the NEb border this
afternoon. The interaction of these two systems complicates the
forecast a bit over the next 24 hours.

The initial strong low- to mid-level WAA and associated isentropic
ascent/indirect thermal circulation (most effective around 600 mb)
has lifted northward into SE SD/NW IA. In the wake of this
activity we are seeing additional bands of snowfall associated
with the strong H7 to H4 CDPVA, which has been a bit showery due
to the weak static stability. Over the next 12 hours we expect
this zone of ascent to shift through northeast NEb with continued
occasional moderate to heavy snowfall. Current snow reports range
from generally 2 to as much as 4 inches, and we will see another
3 to 5 inches this evening in this area, especially along highway
20 and north. The southern edge of this precipitation will likely
track from around David City to Omaha this evening with some light
accumulations, generally under an inch.

As this initial surge of height falls lifts north of the area
tonight, additional support for ascent will rotate southeastward
through central NEb into the area on Wednesday morning associated
with the CO/WY height falls. This forcing will not be as intense
and the static stability will increase overnight making the
atmosphere less responsive to the forcing, but we should still see
a general area of light snow slowly move through the area.
Although there may be some light snow in the Omaha metro this
evening, late tonight and Wednesday morning is actually when the
Omaha area will see the best chance for accumulating snowfall,
generally around 1 to as much as 2 inches. As the 993 mb surface
low /currently near KFRI/ moves into southern IA tonight we will
see the winds become north and then northwest. Snow ratios are
currently running near or just slightly better than 10:1, but we
should see these increase tonight and some blowing snow is
possible, especially when snow is falling.

All said we still expect the most significant accumulations over
northeast NEb, generally along and north of highway 20. We have
lowered storm totals a bit to around 8 to 12 inches there. Fairly
sharp gradient in snowfall is expected with amounts from OLU to
TQE of 3-4" and 1-2" form David city through Omaha and into Pott
County, and less than an 1" south of that. No significant changes
to the headlines were made, but we did extend the warning/advisory
into the afternoon Wed over western IA.


.LONG TERM...(Friday night through Tuesday)
Issued at 312 PM CST Tue Jan 24 2017

It still appears that this system will lead to a synoptic pattern
shift with the CWA become aligned with northwest flow aloft,
although there is no arctic air behind this system. Thus we expect
generally near normal temperatures with some variations from day
to day with weak fronts associated with clipper systems, but no
big systems are current expected.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1200 PM CST Tue Jan 24 2017

Snow band associated with H7 frontogenetical forcing lifting
north across northern portions of the CWA, taking with it heavier
IFR/MVFR snow and visibilities. Expect a pause in persistent,
widespread precipitation in the short term, as dry slot associated
with upper/low level system moves across the area. Area sounding
are showing decent mid-level instability, and as large scale
forcing increases with approach of upper level system, may see
increase in convective precipitation, thus introduced a period
of sleet in KOMA TAF, and may do the same for KLNK during
the afternoon hours.

Another round of persistent, widespread snow is expected this
evening and overnight. Maintained previous forecast of IFR/MVFR
visibilities due to SN BR/FG and IFR cigs through 12 utc.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until 4 PM CST Wednesday for NEZ045.

     Winter Storm Warning until 4 PM CST Wednesday for NEZ015-034.

     Winter Weather Advisory until 9 AM CST Wednesday for NEZ042>044-
     050-051.

     Winter Storm Warning until 9 AM CST Wednesday for NEZ011-012-
     016>018-030>033.

IA...Winter Weather Advisory until 4 PM CST Wednesday for IAZ055-056.

     Winter Storm Warning until 4 PM CST Wednesday for IAZ043.

&&

$$

SHORT TERM...Boustead
LONG TERM...Boustead
AVIATION...Fortin


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