Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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872
FXUS63 KOAX 251725
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1225 PM CDT Sun Jun 25 2017

.SHORT TERM...(Today through Tuesday)
Issued at 322 AM CDT Sun Jun 25 2017

Another day or two of pretty mild weather before temperatures
rebound back into the 80s on Tuesday. Precipitation chances should
be confined to late tonight into Monday, but most likely only a small
chance for thunder during that time.

Northwest mid level flow continues this morning from western Canada
into the central CONUS. Shortwave within this flow was noted in
Manitoba and southern Saskatchewan, which is forecast to dive
southeast into the Plains today and tonight, ushered southeast by
100kt upper level jet streak. While moisture availability will be
fairly low, a good majority of model output continues to paint areas
of QPF in eastern Nebraska and western Iowa beginning later tonight
into Monday. Our current forecast has mention of showers tonight and
Monday morning, so see no reason to remove those given consensus
of model output. However rain amounts should remain spotty and
light through 18Z. Attendant surface cool front should be settling
into southeast Nebraska and southwest Iowa Monday afternoon when
and where moisture profiles are a little better and yield minimal
instability.

Forcing for precipitation will end late Monday afternoon as upper
jet streak tracks east and southeast of our area. Then shallow
mid level ridging builds into the region ahead of potent shortwave
approaching from the west for Tuesday night. Warm advection
regime under building ridge may spark convection to our west and
north during the day Tuesday where moisture return, instability
and surface convergence are maximized. Inhibition should be too
much to overcome in our area during the day Tuesday. However with
southerly low level flow well under way, noticeable humidity
increase will be felt as dew points surge back into the 60s.

.LONG TERM...(Tuesday night through Saturday)
Issued at 322 AM CDT Sun Jun 25 2017

A more active weather pattern is taking shape for mid and late week.
Zonal mid level flow through Wednesday night will buckle as strong
shortwave drops into the High Plains on Thursday, placing our area
under diffluent flow aloft.

Convection chances begin Tuesday night when mid level shortwave
rolls out of the Rockies, triggering storms in instability axis
under steepening lapse rates over western Nebraska Tuesday
afternoon, with that activity moving/spreading east overnight. Low
level jet increases to near 50kt as per ECMWF and GFS with ample
lower atmospheric moisture in place, suggesting continued
progression of MCS across our area overnight. System will likely
still be affecting at least the eastern half of the CWA Wednesday
morning. Trailing cold front settling into southeast Nebraska and
southwest Iowa will offer a focus for afternoon development as well,
when pooled moisture near boundary yields MLCAPE potentially over
3000 J/kg in area of 50kt bulk shear. Approaching mid level trough
Wednesday night and Thursday may initially trigger convection in
northeast Nebraska overnight, but will also draw Wednesday frontal
boundary north. Cooling aloft will only help to increase afternoon
instability as low level moisture remains in place and bulk shear
remains impressive. Severe storms are likely if the above scenario
plays out even close to model output, especially Wednesday and
Thursday.

Lingering storms may affect part of the area on Friday, but by
Saturday we should be on back side of mid level trough with rising
heights and warmer mid level temperatures keeping a lid on
convection.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1223 PM CDT Sun Jun 25 2017

VFR conditions through the period. Northwest winds at 12 to 18
knots at KOMA will diminish by 21z. Otherwise, there will be 30
percent chance of showers at KOMA/KLNK in the 14-18z period.

&&

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

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...DeWald



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