Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 181313
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
813 AM CDT Fri May 18 2018

.UPDATE...
Issued at 813 AM CDT Fri May 18 2018

Just published a substantial update thru noon for POPs/sky/wx to
better reflect the latest radar trends. Also lowered temps thru
the AM and into the afternoon N and W of the Tri-Cities.

The best cores are now at the Srn fringe of the MCS where new
cells cont to initiate. Can`t completely rule out an isolated
rumble of thunder N of Hwy 6...but thunder is mostly done there.

&&

.SHORT TERM...(Today and tonight)
Issued at 338 AM CDT Fri May 18 2018

The forecast turns more active with wet/stormy weather especially
tonight and again on Saturday.

The overall pattern features an upper trough from the Pacific
Northwest through the central Rockies, with southwest flow across
the central plains, while another trough was located to the east
across from the MO/TN valleys to the gulf. At the surface, the
pattern was a little messy with ongoing convection across western
Nebraska, however a cold frontal boundary was located in MT, with
a surface trough extending along the high plains to the surface
low in eastern CO, with another boundary associated with the
convection stretching from southwest Neb to central SD.

The western Nebraska convection has held together early this
morning, mainly affecting the northern half of our cwa and points
north on the nose of the low level jet. Occasional wind gusts of
45 to 50 mph have been observed with the line of storms. As the
low level jet weakens, the area of convection will gradually
spread farther south into central Nebraska this morning before
ending around mid day. Decent rainfall will accompany the stronger
storms and KLBF has already picked up just over an inch of rain.

A lull in convection is expected through the afternoon and evening,
with the next round of storms initiating to our west again along a
boundary from southwest to north central Nebraska, with additional
storms firing along the cold front advancing southeast from MT/WY
while a piece of the western upper trough lifts out of CO. Storms
are expected to organize to our west with the timing of
convection for our area favoring after dark, and even more so
after midnight through the overnight hours aided by a strong llvl
jet while the upper wave edges onto the plains. Elevated
instability around 2000 j/kg and decent shear favor more of a
hail/wind threat with the storms and locally heavy rainfall may
also occur as precipitable water values averaging near an inch,
and particularly if storms train.

.LONG TERM...(Saturday through Thursday)
Issued at 338 AM CDT Fri May 18 2018

Saturday is still looking rather wet with rounds of showers/storms
either ahead of the closed upper system per slower models (GFS/NAM)
or as the upper low moves across Neb (ECMWF). Of more concern is
the severe weather potential especially across our southern zones
from north central KS to far southeast Neb (Thayer County) in
proximity to the warm frontal initially prior to the arrival of
the cold front in the evening. Moisture pooling along the boundary
will lead to high instability with models suggesting a corridor
of 3000 J/KG (or higher) along our southeast zones and 30kts of
effective shear, which will combine to support supercell
development with large hail, damaging winds and tornadoes all
possible. Agree with the latest SPC Day 2 outlook which has
upgraded Thayer County to an enhanced severe risk and will need
to monitor trends of boundary location.

By Sunday, the severe weather threat diminishes behind the cold
front and the rain will be winding down. When all said and done,
rainfall amounts Friday through Saturday night are expected to be
plentiful with many areas seeing totals in excess of one and two
inches, with locally higher amounts realistic in the strong
storms, and these high rain totals may lead to areas of flooding.

To round out the weekend on Sunday, cloud cover and cooler air
behind the front will hold temps primarily in the 60s for highs.
Heading into next week, the pattern remains unsettled with
intermittent chances for showers/thunderstorms as a potent upper
trough and closed low meander along the west coast and intermountain
west, with pieces of energy lifting out of the western trough across
the plains. Monday into the first part of Tuesday favor drier
weather in brief shortwave ridging with precip chances trending up
thereafter. Of note is that each day is not a rain out, but not
necessarily dry either.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Saturday)
Issued at 625 AM CDT Fri May 18 2018

Thunderstorms have been expanding farther south early this
morning, with the individual storms tracking to the northeast
while the entire area of storms/complex works eastward. The storms
will intermittently affect the terminals this morning, with dry
weather forecast during the afternoon/evening. Storm chances
increase again after dark and more so after midnight, with strong
to severe storms possible.


&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

UPDATE...Kelley
SHORT TERM...Fay
LONG TERM...Fay
AVIATION...Fay



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