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Forecast Discussion
NWS Omaha/Valley, NE


000
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

NWS OAX Office Area Forecast Discussion



Forecast Discussion
NWS Hastings, NE


000
FXUS63 KGID 221811
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
111 PM CDT Fri Sep 22 2017

.SHORT TERM...(Today and Saturday)
Issued at 300 AM CDT Fri Sep 22 2017

An area of surface low pressure currently over western Nebraska
is forecast to move to the northeast into South Dakota. Behind
this, we will be left with a weak dryline and subtle wind shift
stretching across west-central Nebraska. This means another very
warm day for the region with high temperatures in the 90s. Winds
should gust to around 30 to 35 MPH during the afternoon for most
of the area. The good news is that increased moisture should keep
us from reaching critical fire weather conditions in our CWA, but
still may be near-critical along and west of a line from
Lexington to Stockton (RH in the 20 to 25% range and wind gusts 30
to 35 MPH).

By late afternoon, the HRRR and NAMnest are developing scattered
diurnally-driven thunderstorms along the aforementioned boundary.
This should be west of a line from Cambridge to Greeley. With 30
to 40 kts of bulk shear, there is a marginal risk for severe
weather, but low-level moisture will be a limiting factor. Without
much upper-level support, I expect that any thunderstorms will
start to wane by late evening and re-focus across northern
Nebraska and South Dakota along the edge of an increasing 850mb
low-level jet.

Heading into Saturday, a strong upper-level cutoff low will start
to push eastward across the Rockies. This will start to impart
some upper-level forcing into our area as well as gradually nudge
a surface cold front closer to the area. This will make rain and
thunderstorms likely across western and northern parts of the CWA,
but will take until at least Sunday before most of the CWA sees
appreciable precipitation.

.LONG TERM...(Saturday night through Thursday)
Issued at 300 AM CDT Fri Sep 22 2017

The long term forecast is dominated by widespread rainfall
expected Saturday night through Monday evening, followed by cooler
and mainly dry weather Tuesday through Thursday.

Well advertised, multi-day rain event still appears on track
although its progression eastward across the forecast area is
methodical. Its all about high rain chances from Saturday night
through Monday, just gradually spreading east. Best shot for rain
from Highway 281 west is Saturday night through Sunday night. Most
likely rain chance from Highway 281 east is Sunday night and
Monday. Several models show multi-inch rainfall totals and we area
currently forecasting rain amounts ranging from 1.50" in Mitchell
and Jewell counties, to nearly 3" in Valley county. The western
half of the area still appears to be the most likely area for
heavier rain amounts although developing a secondary southwest to
northeast rain axis further east not uncommon and certainly
possible. Localized 4"+ rainfall is possible with feed of moisture
into the region (2+ standard deviations above normal precipitable
water), but even with the heavy amounts, recent dry weather and
the slower nature of the rainfall should keep flooding concerns
minimal (if any) at most.

The slow moving surface front doesn`t really make great progress
until later in the day Sunday, which keeps the best rain chance
along or behind the front. Some MUCAPE along and ahead of the
front warrants T-storm chance, but sketchy mid-level lapse rates
averaging about 6 deg. C/KM should keep strong storm risk at bay
and coverage more isolated. Obviously the extreme warmth leading
up to this event will be squelched with the copious cloud cover
and expected rainfall with highs in the 60s for some areas Sunday
and Monday.

Have gone with a dry forecast for Tuesday through Thursday in the
wake of the main upper trough. ECMWF is settling more of cut off
system in the intermountain west and all the models are consistent
to some degree with surface pressure moving across the Central
Plains. Believe this trend will result in mainly dry conditions
with low dewpoints, cool mornings and afternoon temperatures
roughly 5-7 degrees below normal, but still some pleasant early
fall weather.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Saturday)
Issued at 105 PM CDT Fri Sep 22 2017

The gusty south winds will continue this afternoon and although
they will die off some overnight, they should remain breezy.
Mostly clear skies should continue through the evening hours with
a gradual increase in high level clouds late tonight into
Saturday. South winds will again become gusty by later Saturday
morning.

&&

.CLIMATE...
Issued at 456 AM CDT Fri Sep 22 2017

Record warm minimum temperatures will likely be broken today,
September 22nd. Low temperatures will only fall into the low to
mid 70s this morning and should only drop to around 70 degrees by
midnight tonight. Current records are:

Grand Island: 67 degrees (1936)
Hastings: 65 degrees (2008,1969, 1945)

We may also approach new record warm minimum temperatures for
tomorrow, September 23rd. The current record is 70 degrees at both
Grand Island and Hastings, set in 1930 and 1945, respectively.
Currently, a low temperature of 70 degrees is expected for both
Grand Island and Hastings.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

SHORT TERM...Mangels
LONG TERM...Moritz
AVIATION...Wesely
CLIMATE...Mangels

NWS GID Office Area Forecast Discussion