Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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685
FXUS63 KOAX 221725
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1225 PM CDT Fri Sep 22 2017

.SHORT TERM...(Today through Sunday)
Issued at 301 AM CDT Fri Sep 22 2017

A significant mid-level trough from the northern Inter-mountain
region into Great Basin early this morning will slowly edge east
through the Interior West this weekend. Meanwhile, a surface
front will remain quasi-stationary from the upper-MS Valley to
central High Plains for the next couple of days before advancing
southeast into the mid-MO Valley later Sunday into early next
week.

Strong, southerly low-level flow ahead of the mid-level trough
and surface frontal system has allowed an anomalously warm and
moist air mass to overspread the region with highs this afternoon
warming into the lower to mid 90s. For reference, record highs are
96(1940) at Norfolk, and 99(1937) at both Omaha and Lincoln. When
coupled with dewpoints in the upper 60s to lower 70s, afternoon
heat indicies will approach 100 degrees.

There is some indication in both parameterized and convection-
allowing model guidance that the strong boundary-layer heating
and the presence of a subtle pre-frontal confluence zone from
central into northeast NE could foster isolated storm development
late this afternoon into evening. Given the favorable overlap of
moderate instability and a vertically veering wind profile, the
environment will be supportive of strong to severe storms,
conditional on storm initiation and sustenance.

Lows tonight are expected to only fall into the lower 70s, owing
to the high moisture content and sustained south winds. Record
warm minimum temperatures for both September 22 and 23 will be
within reach. Those values are: 67(2016) and 69(1958) at Norfolk,
73(2016) and 72(1892) at Omaha, and 75(1937) and 72(1930) at
Lincoln.

Late this weekend into early next week, ingredients appear to be
coming together for a potentially heavy rainfall event, especially
across portions of northeast NE. The deep-layer wind field will
remain aligned largely parallel to the surface front settling into
area, resulting in the potential for a prolonged period of
training storms. Antecedent rainfall has been well below normal
for the past month generally north of an Albion to Norfolk to
Sioux City line, so runoff should be minimal initially in those
locations. At some point, we could begin to see some flooding
issues on area streams and rivers.

To the south of the frontal precipitation, warm and humid
conditions will prevail with highs in the mid 80s to around 90
degrees.

.LONG TERM...(Sunday night through Thursday)
Issued at 301 AM CDT Fri Sep 22 2017

The aforementioned mid-level trough will begin to spread east
from the Rockies into the Great Plains Sunday night into Tuesday,
supporting a steady southeastward movement of the associated
surface cold front through the forecast area. High precipitation
chances will exist from Sunday night into Monday night before
diminishing on Tuesday with the passage of the front. Storm-total
precipitation amounts may range from two to four inches across
portions of northeast NE to around an inch over far southeast NE
into southwest IA. Locally higher amounts are likely to occur.

Afternoon temperatures will fall back into the 60s to lower 70s
with the passage of the cold front with generally dry conditions
anticipated after Tuesday morning.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1221 PM CDT Fri Sep 22 2017

VFR conditions expected thru the fcst pd.

&&

.CLIMATE...
Issued at 616 AM CDT Fri Sep 22 2017

Temperatures are likely to exceed record warmest minimum
temperatures today and potentially on Saturday. (Keep in mind that
the temperature records must hold from midnight to midnight, so a
daily minimum temperature record includes both the morning AND the
evening of that calendar day.) Record high temperatures will be
close, but think they will remain intact at least at Omaha and
Lincoln.

The records for the next two days are:

          Warm Max   Warm Min   Warm Max   Warm Min
          9/22       9/22       9/23       9/23

Omaha     99 (1937)  73 (2016)  96 (1892)  72 (1892)

Lincoln   99 (1937)  75 (1937)  97 (1921)  72 (1930,
                                               1892)

Norfolk   96 (1940)  67 (2016,  92 (1921)  69 (1958,
                         1937)                 1937)

&&

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

$$

SHORT TERM...Mead
LONG TERM...Mead
AVIATION...DEE
CLIMATE...Mayes



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