Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 302337
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
637 PM CDT SAT JUL 30 2016

.SHORT TERM...(Tonight through Tuesday)
Issued at 305 PM CDT Sat Jul 30 2016

The primary forecast issues in the short term are precipitation
chances for tonight...temperatures Sunday and then the chance for
thunderstorms through Monday night.

Upper air maps from 12Z showed that northwest mid tropospheric
flow was still in place from Montana and Wyoming into the central
plains. 12 hour height falls at 500 mb were strongest over the
Pacific Northwest and southwest Canada...up to 90 meters...where
a trough was digging. A disturbance in the flow produced a
mesoscale convective system that moved through parts of central
and southeast Nebraska earlier today. As of 300 pm...the bulk of
that had moved out of our area. Ridging was in place over the
Rockies...which extended northward from a mid/upper level
anticyclone centered over the Four Corners region. Latest water
vapor satellite imagery showed that a weak disturbance appeared to
be moving into western Wyoming as of mid afternoon. Surface
analysis at 20Z showed weak high pressure from Minnesota into
Missouri...with south or southeast winds locally in eastern
Nebraska and southwest Iowa.

Tonight...models in general (especially the 12Z NAM and GFS) seem
to want to produce scattered showers and thunderstorms for our
area. However...recent RAP and various runs of the HRRR are not
totally onboard with that thinking. We expect a 35 to 40 knot
low level jet to develop in central Nebraska by around midnight...
but shift eastward then focus the strongest lift more into the
eastern part of the state later tonight. Models increase
precipitable water (PW) values to around 2 inches by 12Z
Sunday...and that seemed plausible...even though the KOAX sounding
from 12Z only had 1.03 inches. So because of the high moisture
content in the atmosphere...there could be areas of locally heavy
rain late tonight into Sunday morning.

Clouds should diminish Sunday afternoon...but could hold back
highs at least somewhat. Currently still expect highs in the
80s...coolest in southwest Iowa where clouds and rain may linger
longer.

The overall pattern for heavy rain potential seems to shift a bit
farther east Sunday night...but could still affect our Iowa
counties. Will maintain the highest POPs the eastern 1/3 of the
forecast area. It generally looks like Monday will be dry with
not much of a focus for thunderstorms locally. It will be warmer
though...with highs around 90 to the mid 90s. Highs Tuesday
should be similar.

.LONG TERM...(Tuesday night through Saturday)
Issued at 305 PM CDT Sat Jul 30 2016

Fairly high heights should be in place by Tuesday night for much
of the area from the Desert Southwest toward the Gulf Coast
region. That pattern generally favors the highest rain chances
from 03z to 15z. A closed low initially over eastern Washington
state will track east into southern Manitoba by Thursday. That
should help a low pressure system bring a cold front into the area
from the northwest...with cooler temperatures for later in the
week. That boundary may become nearly stationary across our area
Thursday night into Friday...with modest potential for nocturnal
thunderstorm episodes.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 633 PM CDT Sat Jul 30 2016

A thunderstorm complex is forecast to roll southeast from western
South Dakota, and affect eastern Nebraska TAF sites between 09Z
and 16Z. Attendant MVFR vsbys and cigs are likely within storms,
with brief IFR conditions as well. Otherwise expect VFR conditions
with southeast winds increasing into the 14 to 21kt range by 18Z.

&&

.OAX Watches/Warnings/Advisories...
NE...None.
IA...None.
&&

$$

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



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