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Area forecast discussion
National Weather Service Omaha/valley NE
656 PM CDT sun Jul 23 2017

Short term...(tonight through Monday night)
issued at 321 PM CDT sun Jul 23 2017

As advertised, a somewhat cooler and drier airmass continues to
build south across the region today with temperatures ranging from
the middle 80s in northeast Nebraska to the lower 90s in far
southern reaches of the forecast area. Dewpoints have also dropped
considerably, with comfortable 55-63 degree dewpoints expected to
be common across the entire area by mid evening. Surface high
pressure will build southeast overnight with the surface ridge
axis extending down the Missouri Valley by sunrise on Monday. This
should promote light or calm winds and effective radiational
cooling in the presence of remnant near-surface moisture. These
ingredients suggest at least the potential for patchy fog
especially in low areas along the Missouri Valley and eastward
into western Iowa. At this time, confidence in fog development is
low but if/where it does develop, some patchy dense fog is
possible.

On Monday, surface winds turn back out of the southeast with some
warm advection gradually nosing into the area. All-in-all it will
be a pleasant day especially when compared to the past week, with
near-normal temperatures expected. There is a vorticity maximum
currently very evident in WV imagery over SW Montana which will
slowly but surely track across southern South Dakota. This may
provide adequate lift to initiate convection late Monday into
Monday night mainly near the NE/South Dakota border. Low levels will be very
dry but model soundings (and WV imagery) suggest mid-level
moisture associated with the system may support uncapped
convective parcels over far northern NE and perhaps into west
central Iowa. Severe potential is low as the elevated instability
and effective shear are not particularly impressive.

Warmer weather is expected Tuesday into Wednesday as south winds
increase and a strong short wave trough tracks across southern
Canada. This trough will push a cold front toward northern parts
of the forecast area by early Wednesday morning while reinforcing
short wave energy gradually pushes the front through the whole County Warning Area
by Thursday. Should see quite a bit of convergence along this slow
moving frontal boundary while the interaction with the modified
monsoonal moisture plume and weak periods of mid/upper level
energy to produce a few rounds of thunderstorms. Have thus gone
with relatively high precip chances for the general Wednesday time
frame with the exception that the activity will be scattered in
nature and a few locations may still very well go untouched by
precipitation. In the end though, the slow movement of the system
and availability of multiple forcing mechanisms suggest that
higher end pops are reasonable.

Temperatures behind this system may actually fall below normal for
multiple days as a northwest to nearly meridional flow pattern is
set to dominate the local forecast area.

Long term...(tuesday through sunday)
issued at 321 PM CDT sun Jul 23 2017

Warmer weather is expected Tuesday into Wednesday as south winds
increase and a strong short wave trough tracks across southern
Canada. This trough will push a cold front toward northern parts
of the forecast area by early Wednesday morning while reinforcing
short wave energy gradually pushes the front through the whole County Warning Area
by Thursday. Should see quite a bit of convergence along this slow
moving frontal boundary while the interaction with the modified
monsoonal moisture plume and weak periods of mid/upper level
energy to produce a few rounds of thunderstorms. Have thus gone
with relatively high precip chances for the general Wednesday time
frame with the exception that the activity will be scattered in
nature and a few locations may still very well go untouched by
precipitation. In the end though, the slow movement of the system
and availability of multiple forcing mechanisms suggest that
higher end pops are reasonable.

Temperatures behind this system may actually fall below normal for
multiple days as a northwest to nearly meridional flow pattern is
set to dominate the local forecast area.

&&

Aviation...(for the 00z tafs through 00z Monday evening)
issued at 654 PM CDT sun Jul 23 2017

VFR conditions through the period. There may be some patchy MVFR fog
in the area 10-13z at koma.

&&

Oax watches/warnings/advisories...
NE...none.
Iowa...none.
&&

$$

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