Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 261727
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1227 PM CDT Thu Apr 26 2018

.SHORT TERM...(Today through Saturday)
Issued at 310 AM CDT Thu Apr 26 2018

A short-wave trough from southern Manitoba to the northern High
Plains early this morning will translate through the mid Missouri
Valley today in tandem with a surface cold front. Current
satellite-derived PW data and 00z regional soundings indicate the
presence of a very dry air mass ahead of this weather system with
the prospect for measurable precipitation seemingly quite small.
Short-term model guidance does hint at a narrow band of light
precipitation developing across portions northeast NE later this
morning. However, forecast soundings indicate a dry low-level air
mass with most if not all of any falling hydrometeors evaporating
before reaching the ground. Nonetheless, we will maintain slight-
chance PoPs across portions of northeast NE.

With the passage of the front, steepening low-level lapse rates
and a unidirectional wind profile will yield gusty northwest
winds of 25 to 40 mph, namely during the afternoon hours. The
winds coupled with the dry air mass and temperatures in the 60s
will result in very high fire danger generally north of U.S. 30.

Another weak front will move through the area on Friday with gusty
northwest winds developing over far eastern NE into western IA.
Afternoon temperatures are expected to be warmer than today (i.e.
upper 60s to lower 70s), and when combined with the wind and low
relative humidity, another day of very high fire danger is
expected.

On Saturday, a mid-level ridge will shift east from the Rockies
into the High Plains ahead of a strong storm system moving into
the northwestern CONUS. This will induce the development of a lee
trough over the High Plains with our winds gradually becoming
southeast. Low-level trajectories originating from Canadian high
pressure to our east will temper daytime highs with readings in
the lower to mid 60s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 310 AM CDT Thu Apr 26 2018

On Saturday night into Sunday, a strong low-level jet (LLJ) will
develop across the Great Plains in response to the slow eastward
progression of the aforementioned upper-air system across the
northwestern CONUS. Increasing heat and moisture fluxes along the
LLJ axis will yield decreasing static stability and the potential
for isolated showers Sunday morning. Downward momentum transfer
along the LLJ will also create breezy to windy conditions Sunday
afternoon. By Sunday night, there is some evidence in model
guidance that a weak short-wave trough will eject from the High
Plains into the mid MO Valley, supporting an increasing chance of
showers and thunderstorms.

From Monday into Wednesday, medium-range guidance is now in better
agreement in the evolution of the large-scale pattern. On Monday,
it appears that another short-wave trough will emerge from the
Rockies into the central Plains, contributing to the development
of thunderstorms along a cold front and attendant dryline to our
west. The continued northeastward progression of the mid-level
impulse and nocturnal strengthening of the LLJ will likely
maintain clusters of thunderstorms that would affect portions of
our area Monday night. Some severe weather is possible.

On Tuesday, it appears that the above-mentioned cold front will
settle into southeast NE and southwest IA by afternoon where it
will serve as a focus for another round of thunderstorms, some of
which could be severe.

By Wednesday, a stronger short-wave trough translate from the
southern Rockies into the central and southern High Plains,
driving the deepening of a surface low over western KS. This setup
appears supportive of a more widespread severe weather episode to
from the southern Plains through KS potentially into the southern
part of our forecast area. The northern extent of the severe
weather threat will be contingent on the movement of the
associated warm front. Excessive rainfall could also become a
concern by Wednesday night.

Of course, the above scenario is based on current model guidance
which is likely to change between now and early next week.
Nonetheless, it does appear that the weather will become more
active and springlike.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1224 PM CDT Thu Apr 26 2018

Surface cold front continues to move southeast through the region.
Gusty northwest winds to 30kts is possible behind the boundary but
winds will subside this evening. VFR conditions are expected
through the TAF cycle.

&&

.CLIMATE...
Issued at 630 AM CDT Thu Apr 26 2018

With the rain yesterday, Omaha has dropped to third driest April
on record. With five days left, rain is now possible both Sunday
and Monday before the end of the month.

April Precipitation Records

Location   April to Date   Record  Year
Lincoln    0.67"           0.02"   1910 to remain in top 10 0.67"
Omaha      0.27"           0.23"   1936 to remain in top 5  0.38"
Norfolk    1.32"           0.11"   1928 to remain in top 35 1.46"

&&

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

$$

SHORT TERM...Mead
LONG TERM...Mead
AVIATION...Kern
CLIMATE...Zapotocny


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