Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 180018

Area Forecast Discussion
National Weather Service Hastings NE
718 PM CDT Thu Oct 17 2019

...Aviation Update...

.SHORT TERM...(This evening through Friday night)
Issued at 337 PM CDT Thu Oct 17 2019

It`s been another quiet but warmer day across the area, with upper
air and satellite data showing ridging working its way east across
the Plains. This ridging is set up between low pressure spinning
over the northeastern CONUS and another disturbance moving toward
the Pac NW, and will continue pushing east with time. There has
again been plenty of sun across the CWA today, but there has been
a bit more in the way of upper level cirrus streaming in compared
to yesterday. At the surface, the day started out with fairly
light winds, but have become more steadily south-southeasterly
through the day, thanks to a tightening pressure gradient across
the area. Sustained speeds this afternoon have generally topped
out around 15 MPH, with occasional gusts closer to 25 MPH.

Overall, no notable changes were made to the short term forecast.
Expecting dry conditions to continue through tonight, with those
southerly winds staying up thanks to that tightened sfc pressure
gradient. Overnight lows tonight are forecast to fall into the mid
40s to lower 50s.

As we get into tomorrow, the main story remains with the passage
of a sfc cold front and preciptiation potential. Models remain
in good agreement showing the upper level pattern turning more
southwesterly with time tonight, as a shortwave disturbance makes
its way through the Rockies. This disturbance passes through the
region during the late tomorrow afternoon through tomorrow night
period. The sfc cold front will push south through much of the CWA
during the daytime hours, but where it ends up by evening time
will determine how much of the CWA sees precipitation. There are
still some minor differences between models with just how far
south it gets, but most agree that at the very least the far
southeast corner of CWA will have the potential to see some
shower/thunderstorm activity. At this point, kept the PoPs
confined to 00Z and on, though it may be a close call whether
anything gets in before that. Have thunder mention only in the
evening hours, models are in pretty good agreement showing CAPE
values topping out around 500 j/kg, and pushing east fairly

Outside of precip chances, it`s looking to be a breezy/windy day
as this front moves in. Ahead of the front, gusty southerly
winds are expected, esp for the eastern half of the CWA. Once the
front passes northwesterly winds will build in, bringing the gusty
conditions to the western areas. Confidence in high temperatures
is not high because of the daytime passage. Mixing ahead of the
front will cause temps to warm...and current forecast highs range
from near 70 in the north to around 80 in the south.

.LONG TERM...(Saturday through Thursday)
Issued at 337 PM CDT Thu Oct 17 2019

The first half of the weekend continues to look dry, with the CWA
sitting under zonal flow aloft in the wake of tomorrow`s system,
and ahead of the next one off to the west. It`s looking to be a
pleasant fall day, with plenty of sun and lighter, generally
westerly winds. High temperatures are forecast to reach the mid-
upper 60s.

The next interesting time frame across the region comes Sunday and
Monday, though at this point the CWA doesn`t look to see a lot in
the way of precipitation. Sat-Sat night, models show the next
upper level disturbance making its way across the Pac NW/Northern
Rockies as an open wave, but by 12Z Sunday is expected to develop
into a closed low, located roughly over eastern WY. This low is
then expected to continue working east along the NE/SD border,
ending up near the SD/MN border by 12Z Monday, before sliding
northeast toward the Great Lakes by Tuesday morning. PoPs across
the CWA during this period remain in the 20-30% range. There are
still some timing/location difference to work out, but in general,
the better chances for precipitation out ahead of the system
itself looks to focus across areas just to the east of the
CWA...and the better chances with the passage of the low itself
look to be focused just off to our north. At this point, model
thermal profiles continue to look to keep things as liquid through
the event. Could again see thunderstorms, mainly Sun afternoon-
early evening. Along with precipitation chances, this system will
bring another round of stronger winds, both Sunday and Monday.
Sustained speeds of 25-30 MPH and higher gusts will be possible.

The forecast for Tue-Wed dries back out in the wake of this upper
level low, with sharper northwesterly flow turning more zonal in
nature with time. Will see how models trend with precipitation
chances for Wed-Wed night. Another upper level disturbance looks
to  work into the region, but timing varies, is it late in the
day Wed or more into Thurs.

As far as temperatures go, 60s are forecast for Sunday, with 50s
for Monday...but confidence in that isn`t the highest with that
strong upper level low in the area. Highs rebound back into mainly
the 60s for Tuesday and Wednesday.


.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 718 PM CDT Thu Oct 17 2019

General overview:
For being a high-confidence VFR forecast (both ceiling and
visibility), this is actually a fairly "complicated" TAF period
thanks mainly to shifting winds associated with a passing cold
front, and also a solid period of low level wind shear (LLWS).
Precipitation-wise, confidence is high in a dry period, with any
possible rain showers Friday evening likely holding off until
beyond the current valid period. As mentioned, high confidence in
VFR, with any clouds of the high-level variety tonight, and a
gradual increase in mid-level clouds Friday afternoon. For those
interested in more wind/LLWS details, please read on...

Surface winds:
This will be a rather breezy period, with the overall-lightest
winds (southeasterly around 10KT) occurring right away this
evening. As the night wears on, winds will turn more southerly
with sustained speeds increasing closer to 15KT/gusts 20KT. During
the day Friday, a passing cold front will result in gradually
veering winds (from southerly in the AM, to southwesterly mid-day,
to northwesterly by mid-late afternoon). Sustained speeds of
15+KT/gusts of 20+KT will be common (with KGRI likely a touch
windier than KEAR overall).

Low level wind shear (LLWS):
Despite breezy surface winds overnight into Friday AM, the
presence of a strong low level jet will promote generally 30-35KT
of overall-shear magnitude within roughly the lowest 1,000 ft. AGL
during the 03-15Z time frame. More specifically, winds at roughly
1,000 ft. AGL will average around 45KT from the south during this
time frame, with even stronger winds of 50+KT found closer to
1,500 ft. AGL.




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