Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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231
FXUS63 KOAX 240859
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
359 AM CDT Thu May 24 2018

.SHORT TERM...(Today through Saturday)
Issued at 335 AM CDT Thu May 24 2018

Forecast concerns in the short term will be where thunderstorms
will focus today and tonight with increasingly moist and unstable
airmass in place and what is the risk for severe storms.

A look at the WSR-88D storm total rainfall for today shows some of
the better storms were in northeast Nebraska, however a few
showers did pop up in the OMA/LNK/CBF metro areas too, but they
were hit and miss. The better storms were tied to the better
moisture and vertical motion.

The latest WSR-88D mosaic shows a cluster of storms in north
central Nebraska into South Dakota. The latest RAP/HRRR have these
thunderstorms lifting into southeast SD and continuing in
northeast Nebraska with additional development in other parts of
eastern Nebraska, central Nebraska and Kansas by 12Z. There is not
good agreement in the exact placement of the storms this morning
as the RAP/HRRR/GFS/ are farther south near I80 while the
NAM/EC/Canadian are over northeast Nebraska. The sounding from
00Z showed that we reached our convective temperature with SBCAPE
around 1600j/kg and 1.13 pwat. H7 moisture is increasing along
with the instability axis moving more into eastern Nebraska and
western Iowa. SBCAPE of 2500 j/kg Precipitable water values
around 1.5 inches are forecast for today. There is an outflow
boundary for storms to focus in north central and northeast
Nebraska this morning for now will mention scattered
thunderstorms. Where there is lift this morning storms will be
possible and this afternoon heating to our convective temperatures
will also contribute to storm development. The low level jet is
more over the local forecast area tonight, so this should increase
the coverage and chances for thunderstorms.

We are in the marginal and slight risk for severe storms and this
seems reasonable given the expected instability around 2500j/kg.
0-3km and 0-6km bulk shear are less than 30kts, so this may limit
severity. There are stronger shear values to the west, so this
could affect storms in southeast Neb. with more wind. Storm
motions are less than 20kts, so locally heavy rain will be
mentioned.

Once the storms move out Friday, look for temperatures to recover
in the upper 80s to lower 90s as drier air works in from the west.
Saturday is forecast to be dry with the mid level ridge building
in.

Although temperatures will be above normal, we do not have any
record highs forecast.  See climate section below for details.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 AM CDT Thu May 24 2018

A mid tropospheric ridge will dominate the weather pattern
Saturday night through Memorial Day with above normal
temperatures continuing. The closed h5 low over Nevada/Utah
remains in about the same location. Possibly Sunday night into
Monday night some energy does move into the western Plains and
thunderstorms that develop in the western Plains could push into
the forecast area. Current forecasts of moisture, instability, and
shear are on the high end, so these storms could be severe along
with locally heavy rain. The unsettled weather continues through
the extended with storm chances Tuesday with thunderstorm coverage
increasing with the breakdown of the ridge and shortwave
trough/cold front Tuesday night.

Temperatures Sunday and Monday are forecast to be in the 90s then
upper 80s and 90s Memorial Day with 80s for Tuesday and Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1135 PM CDT Wed May 23 2018

Convection had ended to the west and north of KOFK at 05Z but some
storms continue further west in north central Nebraska. Latest
models show this area to drift slowly east through 18Z in tandem
with instability axis. VFR conditions will prevail outside of
convection through the period.


&&

.CLIMATE...
Issued at 330 AM CDT Thu May 24 2018

Temperatures today warmed into the 90s for most locations and with a
weak record at OMA (93 degrees), we came within one degree of that
record with a high of 92.  The old record was set back in 2012 and
1939.  Over the next few days, the records are a bit stronger.

Location   May     Record  Year
Omaha      24th      99    1939
           25th      97    1967
           26th      96    1912
           27th      94    2012
           28th      97    1895
           29th     102    1934

Lincoln    24th     100    1967
           25th      98    1967
           26th      98    1912
           27th      95    1966
           28th      98    1895
           29th     102    1934

Norfolk    24th     102    1967
           25th     103    1967
           26th      95    1914, 1912
           27th      93    2006
           28th     100    1934
           29th     106    1934

&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Fobert
CLIMATE...Zapotocny



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