Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 231843

Area Forecast Discussion
National Weather Service Hastings NE
143 PM CDT Sat Sep 23 2017

.SHORT TERM...(This evening through Sunday)
Issued at 141 PM CDT Sat Sep 23 2017

Extend and timing of rainfall across the CWA the
primary forecast concern along with temperatures.

Current water vapor imagery along with 12Z upper air analysis
showing high amplitude flow with riding in the eastern half of the
CONUS and troughing in the west. GOES-16 7.34 um water vapor channel
has a closed low spinning over SE Nevada. This system has been slow
in movement with little in the way of 500 mb height falls/rises in
the past 24 hrs. At the surface, a stationary front was bisecting
Neb from northeast to southwest, just clipping our NW CWA. This
front has lifted just a bit northward today. In addition to the
typical wind pattern associated with the front, dewpoints ranged
from the upper 60s south to near 50 just north of the front. These
were even lower in the Neb panhandle, upper 30s to lower 40s.
Similar differences noted in the surface temps. We did have a few
showers pop up in the eastern part of the CWA during the mid
morning, but coverage was isolated at best with no lightning noted.

Starting late this afternoon and into the evening, expect isolated
thunderstorms to pop up across the CWA. Would think the better
chances will still be across the western half of the CWA, closer to
the surface front. It does appear that there will be adequate CAPE
and deep layer shear to allow for a few strong/severe storms,
especially prior to sunset. However the best CAPE is in the warm
sector, aways from the better forcing to the west. Best effective
shear is west. Overnight all signs are pointing to the bulk of the
rain staying west of our CWA. the upper level system is progged to
move very little with several models taking the 500 mb low from SE
NV today to the UT/WY/CO border area by Sunday evening, then
gradually filling and lifting the trough northeast, with its
influence on us ending Tues evening. Under this scenario much of the
precip should be along and just behind the surface front. Starting
times for the persistent rain should be around sunrise Sunday in the
far western CWA and not until Sunday evening in the east. Of course
there will be pop up warm advection type showers/tstms ahead of the
main system but this should not be as widespread. Severe storms are
not anticipated with the main precip shield Sunday into

.LONG TERM...(Sunday night through Saturday)
Issued at 141 PM CDT Sat Sep 23 2017

Continuing on with the short term discussion, expect
rain to continue into Tuesday, with the best chance across the CWA
Sunday into Monday afternoon. Again this is all tied to the upper
level system which has continued to slow a bit from what was
expected 5 days ago. Given the anticipated movement of the upper
level system, the surface front should begin moving east during the
day on Sunday and exit the CWA before sunrise Monday. However, the
post frontal rain should continue Monday, slowly ending from west to
east Tuesday.

After that, surface high pressure will move into the Plains drying
things out. Cooler air is expected to remain over the region and
highs for the rest of the work week with highs some 5 to 10 degrees
below normal for this time of year.


.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Sunday)
Issued at 1210 PM CDT Sat Sep 23 2017

Warm advection showers have developed the past few hours just
south and southeast of the GRI terminal and these could affect
both terminals this afternoon. Additional showers and a few
thunderstorms have also popped up west of the EAR terminal. Expect
the brunt of these to remain west this afternoon and evening.
Otherwise south winds should pick up as the afternoon wears on
with gusts up to 20 kt. Main precip area should move in along and
behind a surface cold front from west to east after sunrise
Sunday, but for the most part expect area to remain VFR until
after 18Z Sunday. Other item that was noted in previous aviation
section of the AFD is the chance for LLWS overnight as low level
jet ramps up.




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