Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 262008
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
308 PM CDT Sun Mar 26 2017

.SHORT TERM...(Tonight through Wednesday)
Issued at 305 PM CDT Sun Mar 26 2017

Main forecast concerns are in regards to precipitation timing and
location tonight into Monday morning, then precipitation chances
returning Tuesday and continuing into the long term.

Upper air charts from 12Z this morning had the following main
features of interest. A jetstreak of over 100 knots at 300 mb was
moving toward the northern CA coast. At 500 mb, one closed low was
near the IA/MO/IL border and another was over southeast CO. The
second low had 12 hour height falls of up to 100 meters at KABQ.
As of mid afternoon, that feature was moving into southwest KS.
Like yesterday, there was some convection right near the center of
the low with the cold pocket. Convection also noted over OK in
part of the baroclinic leaf that had formed ahead of the low. At
the surface - low pressure was over the OK panhandle, while a
warm front extended east from the low toward the MO/OK/KS border
area. Dewpoints in the 50s F were streaming northward south of the
front. Closer to home, a weak surface ridge was over eastern NE
and western IA with temperatures in the 40s and dewpoints in the
upper 30s/lower 40s.

Tonight...we should see an increase in showers into the southern
parts of the forecast area. Trend from previous forecast was good,
just modified timing, northward extent of POPs and also increased
those POPs a little near the KS and MO borders. A fair amount of
weight was given to the RAP, experimental HRRR and NAM output.
General consensus is that amounts should be mostly less than 0.25
inches, although the 12Z GFS suggested there could be some
amounts higher than that. Convective potential seems best south of
our area, so did not mention thunder at this time.

Showers should linger in the southeast part of the forecast area
Monday morning, then we look for a dry period from Monday
afternoon into Tuesday morning. By 12Z Tuesday, a new mid level
closed system should have moved into the four corners region, with
modest diffluent flow over the central Plains. That low is
expected to track into western Oklahoma by Wednesday evening.
Increasing moisture and forcing should result in development of
light rain or showers over our western counties by late Tuesday
afternoon. The 12Z GFS was just a bit faster than the 00Z ECMWF,
so there are some timing differences that will need to be resolved
the next few shifts. But by Tuesday night, most model guidance
brings rain into our area. Right now, think that precipitation
amounts from Tuesday Night into Wednesday should be from 0.25 to
0.75 inches. The ECMWF does show a bit more than that though.

.LONG TERM...(Wednesday night through Sunday)
Issued at 305 PM CDT Sun Mar 26 2017

Rain should linger Wednesday night and then decrease from west to
east on Thursday as the mid level system moves east and the
deformation zone weakens. Heaviest rain, potentially over an inch,
should be across southeast NE into southwest IA. Most if not all
of the precipitation should be in liquid form, but did allow for a
very short window of a rain/snow mix west of highway 81 in
northeast NE late Wednesday night into mid morning Thursday.

The period from Thursday night into Friday evening looks mainly
dry, but another system could bring rain for at least parts of
the area next weekend. Model agreement is not great by that time,
so confidence does drop to normal or below normal by Day 7. The
ECMWF is a bit wetter than the GFS, especially Saturday into
Saturday Night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1221 PM CDT Sun Mar 26 2017

Mesoanalysis at 17z depicts surface lows over the northern TX
panhandle and northwest IL with the forecast area in light north
to northwest winds. Moisture wrapping around the IL cyclone is
resulting in continued IFR ceilings which should gradually lift to
MVFR (FL010-012) as the boundary layer deepens this afternoon. A
weak inverted trough noted from KBIE-KOFK-KONL has been the focus
for lingering fog, and visibilities in these locations should
improve over the next couple of hours.

The northeastward advance of the southern Plains cyclone will
maintain a moist low-level air mass in place across the region
with MVFR conditions prevailing through the remainder of the
forecast period.

&&

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

$$

SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Mead


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