Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 231731
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1231 PM CDT SAT JUL 23 2016

.UPDATE...
Issued at 1218 PM CDT Sat Jul 23 2016

Morning clouds and showers have hindered temperature rises across
the area, and dewpoints also are lower today than the last few
days at least in parts of eastern Nebraska. The result is that
most areas will see lower heat index readings today than the last
several days. A few areas may still top 100 degrees for heat
index, but widespread 105+ degrees is now unlikely in most areas.
Highest heat index readings are expected from northeastern
Nebraska (where there is more clearing and still a pool of higher
dewpoints) through Omaha and into western Iowa (where higher
dewpoints remain). Heat will not be dangerous in many areas, and
may begin to cancel the extended excessive heat warning early.

&&

.SHORT TERM...(today through Monday)
Issued at 343 AM CDT Sat Jul 23 2016

The large-scale pattern will start to undergo changes in the
short term of the forecast. The 00Z upper air analysis indicated
the center of the mid-level ridge had started to retrograde
slightly with heights about 20 m lower than 24 hours ago over the
central and southern Plains. A well-defined shortwave trough was
evident over western SD/NEb at 00Z with a stronger system over the
northern Rockies. The western SD/NEb shortwave was responsible for
thunderstorms over the high Plains on Friday afternoon. Early
morning regional radar mosaic indicated these were now moving
through central Nebraska associated with a obvious MCV. Short-term
guidance indicated that WAA ahead of this wave would increase
early this morning, and this appears reasonable given the
increase in the low-level flow on the VWPs from KOAX and KTWX.
This increased WAA is likely responsible for expanding area of
SHRA/TSRA over SE NEb/SW IA this morning. All of this activity
will be slowly moving east across the CWA this morning. We have
increased pops into the likely category through about mid morning.
There will be some tendency for some mid-level clouds and maybe an
isolated light shower to continue into the early afternoon
associated with the MCV. This creates some uncertainty for high
temperatures today across the area. Given the current trends we
have lowered highs for today, but if clouds move out earlier there
is the potential to get warmer than the current forecast would
indicate. Even with the cooler highs, the low-level moisture will
remain in place and allow for heat index values around 100 to as
high as 105 this afternoon so no change in the warning for today.

The northern Rockies system will cross the northern Plains today
associated with some 30-50 m H5 height falls. This will allow for
a cold front to sweep through the Dakotas and into Nebraska by
late afternoon. Current thinking is that any thunderstorms
associated with the cold front will stay to our northwest through
the afternoon, but there is some chance as we get into the
evening that some of these may brush northeast Nebraska, and
possibly west central Iowa. Given the very warm mid-level
temperatures /700 mb temperatures of 14-16C/ any activity will be
isolated at best though. The surface cold front will drop
southeast through the CWA overnight. We will hold onto some pops
along and behind the front given the steep mid-level lapse rates
and associated moisture, but the better coverage of storms should
be well east and north of our FA. Cooler temperatures and
increased clouds are expected on Sunday for a good part of the
area. The CWA will reside in the entrance region of the 50-60 kt
H3 jet over the northern Plains. This along with confluent mid-
level flow may allow for isolated showers to continue into a good
part of the day on Sunday, but coverage and intensity will be
light/isolated. A bit better of a focus for SHRA/TSRA may evolve
Sunday evening/night as a low-level jet increases over KS with an
area of mass convergence expected over southeast NEb/SW IA area
and points south. Some of this activity may linger into Monday
morning in the south, but otherwise a dry day is expected over the
area with continued near or slightly below normal temperatures.

.LONG TERM...(Monday night through Friday)
Issued at 343 AM CDT Sat Jul 23 2016

This period of the forecast continues to look active for precip
chances with over-all cooler weather. The stalled frontal
boundary in the short term will either wash out or retreat on
Monday night/Tuesday. This may allow for storms to increase late
Monday night and into the day on Tuesday across the area. Longer
range models are in fairly good agreement that a shortwave trough
will track across the area on the Tuesday/Wednesday time frame and
pops have been increased to likely for Tuesday night as the front
moves through. Some chance for additional showers/storms continues
through the rest of the week, but predictability decreases
signficantly with time in the northwest flow regime.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1218 PM CDT Sat Jul 23 2016

VFR conditions are expected through the TAF cycle, with scattered
to broken ceilings largely at or above 15kft. Winds will change
from south to southwest today to northwest tonight and Sunday,
with speeds remaining below 10kt. Isolated showers and even more
isolated thunderstorms are moving away and should stay out of the
TAF sites this afternoon, with potential too low yet to mention
tonight.

&&

.OAX Watches/Warnings/Advisories...
NE...Excessive Heat Warning until 7 PM CDT this evening for NEZ011-
     012-015>018-030>034-042>045-050>053-065>068-078-088>093.

IA...Excessive Heat Warning until 7 PM CDT this evening for IAZ043-
     055-056-069-079-080-090-091.

&&

$$

UPDATE...Mayes
SHORT TERM...Boustead
LONG TERM...Boustead
AVIATION...Mayes



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