Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 202345
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
645 PM CDT Fri Apr 20 2018

.SHORT TERM...(Tonight through Monday)
Issued at 310 PM CDT Fri Apr 20 2018

The chance for rain tonight through Saturday night is the primary
forecast concern through Monday.

Upper low moving across the Four Corners region this afternoon will
be our main weather-maker this weekend as it moves mainly east
across the Southern Plains. In diffluent mid level flow ahead of it,
moisture return was well underway, leading to scattered showers and
thunderstorms across the High Plains aided by vort lobe rotating
toward the Nebraska Panhandle. Several of these impulses will likely
eject into the Plains through Saturday night, with each bringing
a chance for showers to parts of Nebraska and western Iowa before
low settles toward eastern Oklahoma later Saturday night.

Instability progs suggest little if any chance for thunderstorms
across our area, with the focus most in line with steeper lapse
rates nearer cold core aloft and where lower level theta-e is
maximized with daytime heating, mainly south and west of our CWA.

Thus will maintain our current forecast trend of increasing rain
chances tonight into Saturday with approach of system into the
Plains, then decreasing chances as low drifts farther away from our
area Saturday night.

The rest of the period through Monday appears to remain dry with
warming temperatures. Highs Saturday will most likely remain in the
50s as rain and clouds hinder insolation. We should gain a category
or two both Sunday and Monday as more sunshine is realized each
day.

.LONG TERM...(Monday night through Friday)
Issued at 310 PM CDT Fri Apr 20 2018

Upper flow pattern turns cooler for us next week as a couple of
significant mid level troughs drop through the Plains with cooler
air to follow each. However temperatures are not expected to be
drastically colder than normal late April values.

Models are in fairly good agreement in showing this weekend`s upper
low drifting east into the southeastern U.S. Monday night. Behind
it, a strong shortwave will drop southeast into our region Tuesday
afternoon, with another to follow on Thursday. Best chances for
precipitation will come with Tuesday system as sufficient moisture
will linger in the Plains behind southeastern upper low. However
Thursday system will likely produce at least scattered precipitation
as well. Both days there appears to be limited instability, so
widespread thunder is not anticipated. Also, colder airmasses will
follow each system dropping 850 temps by 5C or so each time. But
both GFS and ECMWF indicated sub-0C 850 temps by Friday morning,
suggesting the potential for lows getting close to freezing.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 645 PM CDT Fri Apr 20 2018

Upper level low near Four Corners area continues to move east
slowly. Large scale, diffluent lift in advance of system spreading
mid- to high-level cloud shield across the area. Due to slow
movement of upper system, expect VFR conditions and unrestsricted
visibilities to continue at all three TAF sites during the first
six hours of the TAF period. Ceilings will begin to lower into
60-100K AGL range as atmosphere continues to moisten. Forecast
models continue to indicate several upper level disturbances
moving across the region in advance of the main upper system,
which will generate scattered showers across the region,
particularly at the KLNK TAF site, where Prob30 group continued
from previous forecast, begining 07UTC.

&&

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

$$

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



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