Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 221132
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
632 AM CDT Fri Sep 22 2017

...Aviation Forecast Discussion...

.SHORT TERM...(Today and Saturday)
Issued at 300 AM CDT Fri Sep 22 2017

An area of surface low pressure currently over western Nebraska
is forecast to move to the northeast into South Dakota. Behind
this, we will be left with a weak dryline and subtle wind shift
stretching across west-central Nebraska. This means another very
warm day for the region with high temperatures in the 90s. Winds
should gust to around 30 to 35 MPH during the afternoon for most
of the area. The good news is that increased moisture should keep
us from reaching critical fire weather conditions in our CWA, but
still may be near-critical along and west of a line from
Lexington to Stockton (RH in the 20 to 25% range and wind gusts 30
to 35 MPH).

By late afternoon, the HRRR and NAMnest are developing scattered
diurnally-driven thunderstorms along the aforementioned boundary.
This should be west of a line from Cambridge to Greeley. With 30
to 40 kts of bulk shear, there is a marginal risk for severe
weather, but low-level moisture will be a limiting factor. Without
much upper-level support, I expect that any thunderstorms will
start to wane by late evening and re-focus across northern
Nebraska and South Dakota along the edge of an increasing 850mb
low-level jet.

Heading into Saturday, a strong upper-level cutoff low will start
to push eastward across the Rockies. This will start to impart
some upper-level forcing into our area as well as gradually nudge
a surface cold front closer to the area. This will make rain and
thunderstorms likely across western and northern parts of the CWA,
but will take until at least Sunday before most of the CWA sees
appreciable precipitation.

.LONG TERM...(Saturday night through Thursday)
Issued at 300 AM CDT Fri Sep 22 2017

The long term forecast is dominated by widespread rainfall
expected Saturday night through Monday evening, followed by cooler
and mainly dry weather Tuesday through Thursday.

Well advertised, multi-day rain event still appears on track
although its progression eastward across the forecast area is
methodical. Its all about high rain chances from Saturday night
through Monday, just gradually spreading east. Best shot for rain
from Highway 281 west is Saturday night through Sunday night. Most
likely rain chance from Highway 281 east is Sunday night and
Monday. Several models show multi-inch rainfall totals and we area
currently forecasting rain amounts ranging from 1.50" in Mitchell
and Jewell counties, to nearly 3" in Valley county. The western
half of the area still appears to be the most likely area for
heavier rain amounts although developing a secondary southwest to
northeast rain axis further east not uncommon and certainly
possible. Localized 4"+ rainfall is possible with feed of moisture
into the region (2+ standard deviations above normal precipitable
water), but even with the heavy amounts, recent dry weather and
the slower nature of the rainfall should keep flooding concerns
minimal (if any) at most.

The slow moving surface front doesn`t really make great progress
until later in the day Sunday, which keeps the best rain chance
along or behind the front. Some MUCAPE along and ahead of the
front warrants T-storm chance, but sketchy mid-level lapse rates
averaging about 6 deg. C/KM should keep strong storm risk at bay
and coverage more isolated. Obviously the extreme warmth leading
up to this event will be squelched with the copious cloud cover
and expected rainfall with highs in the 60s for some areas Sunday
and Monday.

Have gone with a dry forecast for Tuesday through Thursday in the
wake of the main upper trough. ECMWF is settling more of cut off
system in the intermountain west and all the models are consistent
to some degree with surface pressure moving across the Central
Plains. Believe this trend will result in mainly dry conditions
with low dewpoints, cool mornings and afternoon temperatures
roughly 5-7 degrees below normal, but still some pleasant early
fall weather.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Saturday)
Issued at 624 AM CDT Fri Sep 22 2017

Surface winds remained elevated all night with frequent gusts of
20 to 30kts. This has limited the LLWS a bit, but the vertical
wind profile is still showing 50 kt winds at around 2000 ft.
Therefore I included LLWS in the TAFs for the next couple hours.

Windy conditions will continue today, with southerly wind gusts
of 25 to 30 kts for most of the day. Any thunderstorms are
expected to remain north and west of the terminals late this
afternoon and evening. Winds will taper off a bit tonight into
Saturday morning. There is a chance that we approach LLWS criteria
again, but this will depend on how much the atmosphere decouples
overnight. With this uncertainty, I didn`t include it with this
issuance.

&&

.CLIMATE...
Issued at 456 AM CDT Fri Sep 22 2017

Record warm minimum temperatures will likely be broken today,
September 22nd. Low temperatures will only fall into the low to
mid 70s this morning and should only drop to around 70 degrees by
midnight tonight. Current records are:

Grand Island: 67 degrees (1936)
Hastings: 65 degrees (2008,1969, 1945)

We may also approach new record warm minimum temperatures for
tomorrow, September 23rd. The current record is 70 degrees at both
Grand Island and Hastings, set in 1930 and 1945, respectively.
Currently, a low temperature of 70 degrees is expected for both
Grand Island and Hastings.

&&

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

$$

SHORT TERM...Mangels
LONG TERM...Moritz
AVIATION...Mangels
CLIMATE...Mangels


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