Area Forecast Discussion
Issued by NWS Hastings, NE
FXUS63 KGID 221602
Area Forecast Discussion
National Weather Service Hastings NE
1102 AM CDT SUN MAY 22 2016
.SHORT TERM...(This afternoon through Monday)
Issued at 1102 AM CDT Sun May 22 2016
Aloft: Moderately amplified flow was over the CONUS. Today began
with a ridge over the Plains...but it has departed to the E. A
large trof was over the Wrn USA and a shortwave trof was lifting
out of its base and was over UT. This trof will cont NE
tonight...crossing CO/WY into the Dakotas by daybreak Mon. The
mean Wrn trof will retrograde a bit...but low amplitude SW flow
will remain over the Plains.
Surface: A Pac cool front extended from the Wrn Dakotas thru the
Neb Panhandle then SW thru CO/UT/NV. A dryline intersected the
front over Ern CO. The cool front will cont E across the Nrn
Plains tonight with its more Srn portion moving slower to the E.
Present indications are that the front will enter the fcst area
around dawn Mon. It is expected to stall over the fcst area...with
alterations possible due to tstm outflows.
Now: Most of the WAA-induced tstms from this morning have
weakened...but we have seen a little renewed development within
the past hr. Subsidence in the wake of these storms has resulted
in some decrease in cloud cover over parts of the fcst area. We
won`t be able to completely rule out additional but limited tstm
development E of hwy 281 this afternoon as ascent is fcst to cont
in the 4-6K ft layer.
Overall...am not expecting much additional tstm activity to
affect the fcst area this afternoon/eve. Isolated tstms will
develop over Wrn Neb and KS close to the dryline/cool front. Can`t
rule out one or two of these storms affecting areas W of hwy 183.
Tstm coverage will be more significant well N and W of the fcst
area this afternoon/eve...closer to the vort max. This activity
should grow upscale into one or more MCSs from SD into the Neb
Sandhills this eve. One of these MCSs could move in after
midnight. Strength/ severity is uncertain. Time of day argues
against severe and it should be weakening/cold pool-dominant...but
it can`t be ruled out with MUCAPE 1500-2000 J/kg.
Mon: Tstms may be over/exiting part of the fcst area during the
morning. What happens thereafter is highly uncertain. We could be
socked in with stratus in the wake of the storms. Despite the
presence of the cool front/dryline and possibly outflow boundaries
...there will be a lack of synoptic forcing. So late afternoon/eve
tstm coverage should be rather minimal. That doesn`t mean no
chance and it doesn`t mean no svr. With dwpts well into the
60s...any persistent heating could trigger convective initiation
and any storm that do occur could be svr.
.LONG TERM...(Monday through Saturday)
Issued at 439 AM CDT Sun May 22 2016
The long term is an active pattern littered with thunderstorm
chances everyday. The most notable day for this forecast period is
definitely Tuesday due to the high confidence for severe weather.
Confidence beyond Tuesday dwindles for severe weather. That being
said, Tuesday will be the focus of this discussion.
In the upper levels we will be under southwesterly aloft with no
dominant feature to really speak off besides small embedded
impulses ejecting out over the plains. At the surface, a low will
develop across western parts of the Central Plains and nose its
way into/near the forecast area Tuesday afternoon. The placement
of the surface low and the associated boundaries will be the
biggest factor in severe weather development and coverage across
our forecast area. Current thinking is it will nose up across
western/southwestern portions of the forecast area. There is
significant instability around in the afternoon across the
forecast area where the NAM and GFS indicate most unstable values
around 5000 J/Kg. Bulk shear (0-6 km) values are around 45-50
knots. The ingredients for strong rotating updrafts are going to
be in place. Low level (0-1 km) helicity values are not overly
impressive, but with the surface low so close and the chance for
boundaries (warm front) over the forecast area, a tornado threat
cannot be ruled out at this time. However, the main threats will
likely be significant hail (2+ inches) and damaging wind speeds.
Depending on where the surface low and associated boundaries end
up, the threat for tornadoes could be more of an issue. There is a
good chance there will be at least a few supercell thunderstorms
around the forecast area on Tuesday, and severe weather will
likely be a threat. This is a day to watch as we move forward
because the forecast can change, but the ingredients are currently
there which warrant the mention for severe weather at this time
with high confidence.
Normal temperatures for this time of year range around the mid to
upper 70s, while lows range around the low to mid 50s. Overall,
temperatures are going to be near or above normal everyday in the
.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Monday)
Issued at 559 AM CDT Sun May 22 2016
One concern is low-level wind shear for the first couple of hours.
Also, some storms are possible overnight, but ceilings are low
confidence. Overall a low-confidence forecast for ceilings as
models have been poor for the past several days. Lower ceilings
should nudge east this morning, but as in the past, could have
some trouble getting farther east.