Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 172017

Area Forecast Discussion
National Weather Service Omaha/Valley NE
317 PM CDT WED AUG 17 2016

.SHORT TERM...(tonight through Saturday)
Issued at 315 PM CDT Wed Aug 17 2016

The main forecast concerns are in regards to thunderstorm chances
from late Thursday night into Saturday morning. There is some
threat of severe storms and heavy rain mainly from 1 pm Friday to
about 4 am Saturday.

The primary main features were noted from the 12z upper air charts.
At 300 mb...main jet stream winds extended from southern California
into Texas then into New England. Strongest winds at that level
were around 75 knots from northern New York into Maine. Pattern at
500 mb showed a weak trough over the far western United States
with weak 12 hour height falls. There was a weak ridge over the
Rockies and western high Plains and then a weak trough from the
western Great Lakes southwest into Missouri. Thermal ridge at both
700 mb and 850 mb was well to our west with 850 mb temperatures
mainly 21-24 degrees C over Nebraska and Kansas. Surface analysis
at mid afternoon showed high pressure to our east and low pressure
developing from eastern Montana into eastern Colorado.

Tonight...we expect warmer air to start moving northeast across
the region. Can not completely rule out an isolated storm or two hinted at by some of the 12z model guidance but
chances seemed too low to mention at this time. Lows should range
mostly from the mid 60s to around 70. Some patchy fog is possible
again late tonight...but confidence not high enough to include.

Thursday...good low level mixing with south/southwest winds is
expected to push highs into the lower and mid 90s for eastern
Nebraska and around 90 or lower 90s in southwest Iowa.

Will not include any mention of precipitation before midnight
Thursday night. A cold front will be moving into northeast
Nebraska and some isolated thunderstorms there. Chances look
a little better after midnight in the northwest 1/3 of the
forecast area. The combination of cloud cover and north winds on
Friday should keep highs in the 75 to 80 degree range in our far
northwest counties and 80s elsewhere. Heavy rain and severe
weather potential is definitely there Friday (as depicted in the
SPC Day 3 Outlook)...but will need fine tuning for our local area
as we get closer. This lingers into Friday night. Precipitable
water (PW) values should be around or above two inches by 00z

The 12z NAM was the odd model out compared to the GFS...ECMWF
and Canadian models which were all dry for Saturday. We have a dry
forecast for Saturday for now...with highs only in the 70s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 315 PM CDT Wed Aug 17 2016

A trough at 500 mb should extend from a closed low over Hudson Bay
down into the midlands at the start of this period...with our area
in west or northwest flow. Mid level heights become more zonal
early next week as a trough digs over the Rockies. With time...a
broad trough develops east into the central and northern Plains.

Cool temperatures will continue Sunday...with highs in the 70s...
then moderate to the lower/mid 80s for Monday through Wednesday.
Sunday morning is probably going to be the coolest morning...with
lows near 50 or in the lower/mid 50s depending on location.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1219 PM CDT Wed Aug 17 2016

VFR conditions are indicated through the TAF cycle at all sites.
May see some afternoon mid-level to low-level cu at all sites, but
have only broken a separate group at KOMA, where cu is lower.
Winds will become light and southeasterly this afternoon, then
light and southwesterly on Thursday morning.


.OAX Watches/Warnings/Advisories...


LONG TERM...Miller
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