Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 290853
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
353 AM CDT MON AUG 29 2016

.SHORT TERM...(Today and tonight)
Issued at 328 AM CDT Mon Aug 29 2016

The timing and placement of thunderstorms is the main forecast
challenge in a complex weather pattern.  Convection developed
earlier in the evening and has persisted into the overnight hours
across our central CWA, and significant rainfall amounts in the 3 to
5 inch range have been common across southern Adams and northern
Webster Counties where a flash flood warning is in effect.
Although convection has weakened to some degree we continue to see
new development early this morning primarily across our western
counties.

Patternwise the Central Plains is in weak flow in between a closed
low pressure system in New Mexico and ridging to the east in the
Tennessee and Ohio valleys. A plume of subtropical moisture is
streaming into our region with subtle embedded shortwave troughs
providing sufficient lift to generate convection. We will remain
in this pattern through the short term periods and cannot rule out
storms at any given time, although pinpointing the coverage and
location is challenging. Models are having a difficult time
resolving what to do with the desert southwest low and attempt to
phase it across the plains and with the progression of this system rain
chances are looking fairly promising. Weak jet streaks around
50kts lift thru our region into tonight will provide additional
periods of lift. The mean flow actually weakens even more so by
tonight to under 10kts. Any storms which develop will move very
little and are expected to be efficient rain produces in the
presence of high lowlevel moisture with dewpoints in the middle
and upper 60s and precipitable water values averaging an inch and
a half to two inches. Once again we could see some hefty rainfall
totals in excess of two inches, and the majority of our area is
outlined in the excessive rainfall outlook. Since overall
conditions have been dry with heavy rainfall has been isolated to
this point, will hold off on hydro related watches, but could see
some rises in rivers and lowland flooding if significant rainfall
materializes especially in locations which just saw heavy rain.

Have kept afternoon temperatures conservatively cool due to the
expected cloud cover and the potential for convection. Then tonight
readings are expected to be mild again in the 60s with clouds and
lowlevel moisture in place.

.LONG TERM...(Tuesday through Sunday)
Issued at 328 AM CDT Mon Aug 29 2016

Primary forecast concern will continue to revolve around
precipitation chances.

At the start of the long term period Tuesday morning, shortwave
troughing in the upper level is set up across the Central Plains,
sitting between areas of high pressure over the central Rockies and
Midwest region. At the surface, a weak pattern is expected to be in
place, with light/variable winds, with high pressure spread from
central Canada southeastward into the Great Lakes region. Precip
chances remain in the forecast across the entire CWA on Tuesday with
this mid/upper level trough axis around, with lift also aided by an
SW-NE orientated upper level jet streak. These features remain a
player across the area into Tuesday night and Wednesday, with models
actually in decent agreement with the southward shift, pushing much
of the better chances south of the CWA by the end of the day
Wednesday. As it does so, well amplified ridging gradually slides
into the High Plains region. The light/variable winds starting off
the period becomes more east-northeasterly, driven by better
organized high pressure sliding across southern portions of Canada.
PoPs for much of the Tues-Wed period are in the 30-50% range, and
maybe scattered in nature. Shear/instability parameters continue to
suggest severe is not likely. Temps were cooled a bit with the
higher PoPs going and plenty of cloud cover expected, with mid 70s
to lower 80s forecast.

Compared to the past few days, models have come into better
agreement with showing the potential for some dry periods, coming
during the Thurs-Fri time frame. Do have some lingering slight
chances PoPs clipping far south-southwestern areas, sitting closer
to the better upper level forcing. Otherwise, the upper level
ridging builds further east onto the Plains through Friday, with the
main axis looking to be near the Missouri River area by 00Z Sat. At
the surface, those easterly winds through mid week will turn more
southerly, as that larger area of high pressure builds further south
into the Great Lakes/Midwest. Should see a bump up in temps of at
least a few degrees if things remain dry.

Into this next weekend, the system pushing the upper level ridging
east through the region is storm system moving onto the West Coast,
resulting in more southwesterly flow across the Plains. Models
showing that while the main trough axis looks to remain off to the
west of the area through Sunday, shortwave disturbances ejected out
ahead will once again bring periodic thunderstorm chances to the
area. Highs look to climb into the mid 80s.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Monday night)
Issued at 1226 AM CDT Mon Aug 29 2016

Main concern for the tafs is the potential for convection which
has already developed near the terminals and activity looks hit or
miss through the next 24 hours. Cloud cover is expected to be
prevalent primarily at mvfr or vfr levels.


&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.

&&

$$

SHORT TERM...Fay
LONG TERM...ADP
AVIATION...Fay



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