Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 191805
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1205 PM CST Tue Feb 19 2019

.SHORT TERM...(Today through Thursday)
Issued at 308 AM CST Tue Feb 19 2019

...Winter Storm on-track to impact all of our area later
today/tonight...

Impressive mid-level trough axis moving across the western US will
continue to strengthen as it rapidly moves northeast into the
central CONUS and becomes slightly negatively tilted. Ahead of
it, we can already see a few returns showing up on radar mosaics
to our southwest and as isentropic upglide increases throughout
the day, expect the snow to expand northeast into our area by
later this afternoon. This evening and especially overnight we
will see the heaviest snowfall rates as forcing for ascent greatly
increases in advance of the approaching upper wave. In addition,
forecast mid-level lapse rates increase, especially over our
northeastern counties where we could see some near 1 inch/hr or
greater amounts overnight. QPF values range anywhere from
0.30-0.55" with snow-liquid ratios varying throughout the event
but on average around 15:1 give or take. All this put together
produces a storm total anywhere from 4-9" across our CWA (see maps
on our web for totals). Would not doubt if we get some higher
totals across portions of western Iowa where some intense snowfall
rates are possible overnight with increasing lapse rates. Snow
will quickly taper off from southwest to northeast as the system
moves rapidly northeast. If the surface low begins to deepen more
quickly than forecast, our wind forecast will need to be adjusted
accordingly. But for now do have some of our stronger gusts across
southwest Iowa overnight which the RAP is indicating some near
0.25 mile visibilities for a time in heavy falling snow/blowing
snow. Otherwise, strong winds don`t look to be too much of an
issue with the surface low passing overhead keeping them on the
lighter side.

Impacts are expected to be significant with this storm given the
near 8-10" snowpack we already have on the ground, in addition to
the high snowfall rates. Transportation will likely see the most
significant impacts as snow accumulates rapidly. In urban areas, the
lack of space to put new snowfall may hinder snow removal operations
to some degree. Even though the system will be moving out of the
region by Wednesday afternoon, the effects of the storm may linger
well into Wednesday night. Roads conditions are expected to
quickly deteriorate tonight.

.LONG TERM...(Thursday night through Monday)
Issued at 308 AM CST Tue Feb 19 2019

Another aggressive trough will take a similar path later this week
into the weekend. The main difference will be warmer temperatures
initially with the the weekend system. This system is forecast to
produce areas of rain/snow/and a mix of precipitation types in
between. In addition, the weekend system is much more wound up
and therefore places a very strong pressure gradient across the
CWA behind the system, in addition to a fairly strong deformation
zone. This will be one to keep an eye on for anyone with weekend
travel plans as significant snow totals are likely again with this
system.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1201 PM CST Tue Feb 19 2019

Deteriorating aviation conditions will begin late this afternoon
as snow begins in southeast Nebraska, then spreads north across
all TAF sites between 00Z and 06Z. Snow should intensify quickly
once it begins, driving cigs and vsbys downward into the LIFR or
VLIFR categories between 03Z and 06Z. These conditions should hold
through at least 12Z with only gradual improvement through 18Z.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Warning from 6 PM this evening to 9 AM CST
     Wednesday for NEZ011-012-015>018-030>034-042>045-050>053.

     Winter Storm Warning until 9 AM CST Wednesday for NEZ065>068-078-
     088>093.

IA...Winter Storm Warning from 6 PM this evening to 9 AM CST
     Wednesday for IAZ043-055-056-069-079-080-090-091.

&&

$$

SHORT TERM...Kern
LONG TERM...Kern
AVIATION...Dergan


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