Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 212342

Area Forecast Discussion
National Weather Service Hastings NE
642 PM CDT SAT MAY 21 2016

.SHORT TERM...(This evening through Sunday night)
Issued at 307 PM CDT Sat May 21 2016

The primary forecast concern will center around the chance of
precipitation, both light drizzle at times tonight into Sunday
morning as well as the possibility of severe thunderstorms by
Sunday evening.

Tonight...Elevated instability will be on the increase through
the overnight hours and can not rule out an isolated elevated
thunderstorm...especially across southwestern zones.
However...most forecast models are in pretty good agreement that
thunderstorms this evening will form across west central Kansas
and should pass to the south of our forecast area later tonight as
they weaken. We are seeing the forecast models generating light
QPF tonight into Sunday morning in what is most likely a light
drizzle or a few sprinkles out of the stratus deck. Again not
expecting much and most areas will likely see little or no
precipitation through Sunday afternoon.

Sunday evening into Sunday night...This is where things get more
interesting. The 12Z and 18Z NAM and GFS along with several WRF
models try to initiate scattered thunderstorms in the warm sector
near the dry line across southwestern Nebraska into western Kansas
between 6 to 8 pm. MLCAPE values by late afternoon from Lincoln
county down to Frontier county could be up into the 3500-4000 J/KG
range. Deep layer 0-6 km shear is not overly impressive at 30-40
kts...but there is increasing low level shear (0-1km) values of
20-30 kts by 00z and 30-35 kts by 03z as the low level jet
strengthens. The combination of instability and shear is more than
sufficient for severe thunderstorms should forcing be sufficient
for initial storm development. Have added isolated tornado
wording to our HWO due to the strong low level wind shear in that
23-03z (6-10 pm) time frame. Although storm may form just west of
our forecast area, they will likely quickly move into our forecast
area. There is still at least some uncertainty as to if there
will be enough forcing in the warm sector with the upper trough
still so far to the west for thunderstorms to actually develop
Sunday evening, but if they do develop keep an eye out for severe

Confidence in the potential widespread nature of thunderstorms
tracking across the region late Sunday night has actually
decreased some with more models showing what would be a more hit
and miss scattered nocturnal thunderstorm event for our forecast
area being largely supported by the strengthening low level jet.
Will continue to keep Sunday night POPs at 60-70 percent.

.LONG TERM...(Monday through Saturday)
Issued at 307 PM CDT Sat May 21 2016

Monday...The front appears to be slowing down, which would put
eastern areas more under the gun for thunderstorms Monday
afternoon and evening. The GFS began showing this yesterday but
now the 12z and 18z NAM have slowed down and are also showing
decent thunderstorm potential from the Tri-Cities eastward. There
is little if any cap so expect thunderstorms could develop rather
early on Monday. The CAPE is very high Monday afternoon with
MLCAPE values of 3000-3500 J/KG and 0-6 km shear values around 40
kts. Therefore, am also going to start calling for the possibility
of severe thunderstorms on Monday especially across the eastern
half of our forecast area.

Tuesday...We continue to be under the influence of southwesterly
flow aloft with high instability and at least modest deep layer
shear. Forcing may be a bit more lacking, but there is still
certainly the possibility of strong to severe thunderstorms by
afternoon and evening.

Wednesday through Saturday...Am not going to talk much about this
period at this time. There is just too much uncertainty with the
specifics. Overall we will continue to have a large upper trough
across the western CONUS with short waves tracking through the
broader upper trough across the plains. Consequently, there will
be at least a threat of thunderstorms pretty much any day through
the period and would not be surprised to see some additional
severe thunderstorms on a few of these days.


.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday evening)
Issued at 642 PM CDT Sat May 21 2016

Low stratus will dominate the forecast with a chance for showers
and isolated thunderstorms overnight. Patchy drizzle is possible
throughout the evening and early overnight hours. Because
confidence in precipitation impacting the terminals is low, have
kept the mention out of the TAF for the most part. Will amend as
necessary.  Winds are generally out of the southeast and gusty.
Expect the winds to stay breezy overnight and be stronger than
today during the day Sunday. Ceiling heights are expected to
deteriorate throughout the evening and overnight hours before
rising during the day Sunday. Ceilings will be MVFR and possibly
drop to IFR overnight.


.GID Watches/Warnings/Advisories...


LONG TERM...Wesely
AVIATION...Billings Wright is the U.S. government's official web portal to all federal, state and local government web resources and services.