Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 222023

Area Forecast Discussion
National Weather Service Hastings NE
323 PM CDT Thu Jun 22 2017

.SHORT TERM...(This evening through Friday)
Issued at 317 PM CDT Thu Jun 22 2017

The main focus in the short term is the chance for thunderstorms and
the potential for a strong/severe storm this evening.

Flow aloft across the Central Plains was fairly zonal with a high
pressure ridge in the desert southwest, tropical depression Cindy
along the TX/LA border and an upper low in Manitoba. At the surface,
a cold front was advancing southeast across central Nebraska and
western Kansas early this afternoon. The cold front combined with a
lead shortwave trough translating southeast across the plains around
the northern upper low will provide the focus for shower and
thunderstorm development into the evening.

By late afternoon, the front will be oriented across the southeast
third of our cwa and models are in decent agreement with development
initiating across north central Kansas and potentially filling in to
the northeast into Nebraska along the baroclinic zone. There is a
few hour time frame where strong to severe storms may occur with
instability near 3kj/kg along the boundary with shear in the 20 to
30kt range and storms will be capable of producing large hail,
damaging winds as well as locally heavy rainfall with
precipitable water values averaging an inch and a half.

The cold front moves out of our cwa during the evening with
instability decreasing north/south and a period of dry weather is
expected before precipitation chances increase again overnight or
early Friday as convection which develops along the high plains
works eastward before dissipating by midday Friday.

The big news for Friday is the pattern change we see behind this
system/cold front. We tap into a cooler Canadian airmass behind this
front with the pattern transitioning to northwest flow for our
region as an upper trough deepens across the plains and Ohio
valley region. Mid level temps which were near 30C during our heat
spell earlier this week drop a solid 15C or more by Friday and
temperatures will be noticeably cooler with highs in the low/mid
70s. Conditions will also be less humid as dewpoints drop into the
40s. Friday will also see breezy/windy conditions as model
forecast soundings indicate mixing above H85 and winds at the top
of the layer average 25 to 30kts.

.LONG TERM...(Friday night through Thursday)
Issued at 317 PM CDT Thu Jun 22 2017

After what looks to be a rather breezy day on Friday, winds should
begin to diminish as we head into the evening hours. Any lingering
light showers will have since dissipated or moved out of the area
and things should remain dry overnight.

The seasonably cool temperatures will continue into the weekend as
the upper level trough sinks a bit further south into the central
plains helping to sustain this period of below normal temperatures.
Overall am expecting highs in the 70s Saturday and Sunday with winds
generally out of the north and west. A few scattered rain showers
are possible along a semi-stationary boundary in our southwestern
zones as a weak wave drifts around the southern end of the trough.
Overall am not expecting much in the way of widespread
precipitation. With the cooler temps and limited to no CAPE in the
area, have not included any mention of thunder through Sunday.

As we move into the beginning of the work week, the ridge that has
dominated the southwestern CONUS this past week quickly builds back
north and east into the plains. Southerly flow returns ushering in
more seasonable temps with highs in the 80s and low 90s by Thursday.
Another trough from the northwest gradually shifts eastward
supporting an increase in precipitation chances as a series of
shortwaves push off the Rockies. This will bring periodic chances
for thunderstorms Monday through Wednesday.


.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Friday)
Issued at 1208 PM CDT Thu Jun 22 2017

Just before the onset of the TAF period a cold frontal boundary
was located just to the west of KEAR. As the front progresses,
winds will shift northerly behind the boundary in the first couple
hours of the taf period, with gusts near 25kts possible. The
boundary will be the focus for afternoon and evening convection
which will primarily be south of the terminals. Cannot completely
rule out precipitation chances tonight or early Friday as
additional convection works east from the high plains, but chances
do not appear great enough to include at this time. Look for
northwest winds to increase again by mid morning Friday with gusts
over 20kts expected.





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