Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 242044
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
344 PM CDT WED AUG 24 2016

.SHORT TERM...(tonight through Saturday)
Issued at 338 PM CDT WED AUG 24 2016

Chance for precipitation into the weekend is the primary forecast
concern.

Surface cold front had slipped into far southeast Nebraska and
southwest Iowa this afternoon where calm winds and dew points were
near 70. Upper level jet segment of 75kt at 300mb was knifing
northeast through northeast Nebraska, placing tendency for upward
motion over frontal zone in southeast Nebraska and southwest Iowa.
As such, thunderstorms have developed in the 18Z to 1930Z time frame
in our area, more along 850mb wind shift line. As upper/mid level
jet segments lift northeast, so to will area of convection along 850
front. Shorter range hi-res model output has become relatively
consistent this afternoon from run to run and between various models
in suggesting this scenario. Those models also agree with ending
largest threat of rainfall during the evening as forcing shifts
east.

So, a few things. One, will continue with fairly high precipitation
chance in southeast Nebraska and southwest Iowa. Two, northern
fringe of precipitation should hold to or just north of Interstate
80, but again stronger storms should remain farther south. Three,
with forcing shifting east this evening, do not have high confidence
in Flash Flood Watch currently in effect for five of our far
southeast counties. Elevated instability now and into this evening is
not expected to be high enough to support continued redevelopment of
cells along convergence lines, especially with aforementioned
forcing moving away. Precipitable water values remain very high,
however, and any storms could dump a fair amount of water in a short
time. Thus will continue the Flash Flood Watch thinking biggest
threat is during the evening.

Severe threat is also limited by only modest instability and shear
parameters in Nebraska and Iowa. But again, areas just south of here
have better numbers, and a slight northward shift is likely.
Freezing levels remain relatively high, near 14kft, so large hail
looks unlikely given modest instability. But there is still a
small threat in our south nearer higher moisture/instability.

Beyond this evening, eastern Nebraska and southwest Iowa remain in a
relatively unsettled pattern into at least Saturday, with rain
chances just about every day/night. Cold front just to our south
should be pushed a little farther into Kansas with passing
convection this evening. However given southwest flow aloft, front
will not move very far south, and will tend to drift back north
later tonight and Thursday. Overrunning precipitation will be
possible north of this front late tonight and Thursday over the
southern parts of Nebraska and Iowa. Better chances come Thursday
night into Friday when shortwave ejects from the Rockies and drags
front and higher dew points back into our area. Strongest storms
with this system come Friday night when surface reflection rolls
through eastern Nebraska providing focused convergence.

Though we will continue with a small chance for precipitation on
Saturday, chances are lowest of the 3-day period as subsidence
suppresses most convection through much of the day.

Temperatures through Saturday should hold in the 70s Thursday and
Friday before return flow helps boost high back into the 80s on
Saturday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 338 PM CDT WED AUG 24 2016

Our unsettled weather pattern appears to hang around into the middle
of next week. The strongest mid level westerlies will lift into the
Northern Plains, however both GFS and ECMWF suggest a slow-moving
shortwave will drift east through the Plains Monday through
Wednesday. Persistent southerly low level flow will maintain
moisture profile in lower layers of the atmosphere under slightly
divergent mid level flow associated with shortwave. Will maintain at
least small precipitation chances each day Sunday through Wednesday.
Chances will likely diminish Wednesday afternoon as shortwave shifts
east.

Persistent high temperatures are expected with highs in the low
to mid 80s, but lows should gain a few degrees given dew points in
the 60s to near 70.

&&

.AVIATION...(18Z TAFS for KOFK...KLNK and KOMA.)
Issued at 1211 PM CDT WED AUG 24 2016

Generally VFR conditions are forecast through Thursday morning. An
area of showers and thunderstorms will move and develop northeast
from north central Kansas into southeast Nebraska. Some of this
activity could reach as far north as the Interstate 80 corridor,
affecting KLNK and KOMA for a few hours between 22Z and 02Z.
Attendant MVFR/IFR vsbys/cigs in storms will be possible.
Otherwise expect north or northeast winds and broken mid level
clouds through the TAF period.


&&

.OAX Watches/Warnings/Advisories...
NE...Flash Flood Watch through Thursday morning for NEZ091>093.

IA...Flash Flood Watch through Thursday morning for IAZ090-091.

&&

$$

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


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