Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 252110
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
410 PM CDT Tue Jul 25 2017

.SHORT TERM...(This evening through Wednesday night)
Issued at 358 PM CDT Tue Jul 25 2017

The main concern in the short term is the potential for
thunderstorms overnight tonight through Wednesday night.

Overall today has panned out as expected with highs in the 90s and
dewpoints in the upper 60s to low 70s. Heat indices are beginning to
reach above 100 for a few sites and should peak between 100 and 105
across much of the area late this afternoon. Winds have been gusty
at times out of the south at 15 to 25mph which will hopefully

Thunderstorm chances return tonight with a line expected to move in
from the west around midnight. Severe potential is somewhat in
question, but the initial line has the potential for strong to
severe wind gusts and small hail. The latest NAM NEST is hinting
at some spotty shower/tstorm development ahead of the line across
areas south of I-80 but currently have things dry until the main
line comes through.

Rain showers will linger through the overnight hours, with a narrow
but strong low level jet developing overnight ahead of the
advancing cold front that should help keep precip around into the
early morning hours. Models are recently hinting that things may
clear out for a few hours allowing for more destabilization to
occur allowing for the potential for redevelopment Wednesday
afternoon especially across our southeastern zones. Any storms
that do develop have the potential to be strong to severe,
although we are currently not outlooked. These will then track off
to the southeast out of the area by late Wednesday night.

.LONG TERM...(Thursday through Tuesday)
Issued at 358 PM CDT Tue Jul 25 2017

General overview of this 6-day period: It`s probably somewhat of a
good news/bad news situation depending on one`s viewpoint, as while
it will be trending somewhat cooler it also looks to remain
relatively dry with no "big soakers" for those wanting/needing
decent rains.

By far the number 1 story is temperatures: In contrast to the
slightly above to occasionally well-above normal heat/humidity that
has defined most of July so far, the last several days of the month
into the first day of August should actually average near- to-
slightly-below average for a change. We are not talking
"refreshingly cool" by any means, but we are talking several
consecutive days withs highs "only" in the 80s across the majority
of our county warning area (CWA), with perhaps some low 90s
occasionally brushing into a few of our typically-hotter
southwestern counties at times. Low temperatures look to follow a
similar trend, with most nights at least cooling into the low-mid
60s, as opposed to the upper 60s- mid-70s lows that have defined
much of July so far in many areas. And last but not least in this
department, dewpoint temperatures and resultant humidity levels look
to be more tolerable as well with more in the way of low-mid 60s
instead of the more oppressive 70s much of especially the northeast
half of the CWA has endured on many recent days.

Precipitation-wise: Technically speaking, this latest forecast
package now features more in the way of pesky/small/fairly uncertain
rain/thunderstorm chances (PoPs) than the previous one did, as at
least some portion of the CWA features at least a 20 percent (slight
chance) during each day/night period from Friday night through
Tuesday. At this time, the very highest PoPs are only 30-40 percent
(and limited in area at that), so certainly nothing that looks
overly widespread/soaking for beneficial rains at this point (beyond
tonight/tomorrow`s halfway decent chance outlined in the Short Term
section above). The same goes for severe thunderstorm chances. While
this type of summer pattern is certainly conducive to at least
isolated/occasional strong to severe storms, there does not appear
to be anything very organized/widespread in the Friday-Tuesday time
frame. Backing up to the nearer-term Thursday daytime-Friday daytime
periods, these 36 hours look to be about as "guaranteed dry" as July
can possibly get, as we catch a glancing blow of Canadian high
pressure, also responsible for our aforementioned slightly cooler
and drier airmass.

Briefly covering the large-scale weather pattern, the vast majority
of this time frame will be dominated by a large-scale ridge over the
western/southwest CONUS and a large-scale trough over the eastern
states, placing our region under fairly persistent/consistent
northwest-flow aloft, featuring the passage of intermittent/fairly
weak disturbances.

With the main points covered, will conclude with some day-to-day
specifics for those interested...

Thursday daytime-night: Although there is probably the slightest
chance that a rogue sprinkle/shower could linger slightly past
sunrise in our extreme southeast CWA behind the departing system
from Wednesday night, have maintained a dry forecast CWA-wide for
now. Overall, the day should feature plentiful sunshine and
northeast winds around 10 MPH. Did nudge up high temps very slightly
from previous, but still "only" talking 83-87. Weak high pressure
will dominate the region Thursday night, and as long as skies remain
clear, lows temps should make it all the way down into the 59-62
range most areas, which would mark the overall-coolest night most
places (including the Tri Cities) have seen in at least 2 and a half
weeks!

Friday daytime-night: Breezes transition to out of the east-
southeast behind departing surface high pressure, but high temps
look very similar to Thursday with mainly mid-upper 80s. While
confidence remains high in a dry day and probably evening too, the
late night hours feature the return of some "iffy" small
shower/thunderstorm chances.

Saturday daytime-Sunday night (the weekend): Don`t get too concerned
about the fairly persistent small PoPs, as "most" of the weekend
should remain dry in most areas, with continued high temps mainly
mid-upper 80s and lows in the low-mid 60s. The latest GFS especially
is suggesting perhaps a somewhat better chance of rain mainly late
Saturday night, but this has fairly limited support from the ECMWF.

Monday-Tuesday: Overall much the same story as the weekend as we
head into August, so again: highs mainly mid- upper 80s and some
intermittent low rain chances. There are hints (especially per the
GFS) that a somewhat stronger mid level wave could bring a more
promising hope for more widespread rain just beyond the current
official 7-day forecast around next Wednesday, but this scenario
currently has very little support from either the ECMWF or Canadian
at this time, and appears to be somewhat of an outlier.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Wednesday)
Issued at 1242 PM CDT Tue Jul 25 2017

Overview: Breezy this afternoon with LLWS possible overnight.
Thunderstorm chances increase across the area after midnight and
last through much of the day Wednesday. Currently keep things VFR
through the TAF period with a prevailing VCTS mention... however
MVFR to near IFR conditions will be possible under any showers and
thunderstorms that move directly overhead.

Winds: Currently have gusty south winds this afternoon around 15
to 20kts with gusts of 20 to 25kts possible. These should
gradually diminish tonight with low level wind shear developing
overnight as the low level jet sets up ahead of an advancing cold
front. Although winds could be quite variable and gusty under any
convection, generally expect winds to begin shifting to out of
the east and northeast as the front moves through the area during
the day Wednesday.


&&

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

$$

SHORT TERM...Petr
LONG TERM...Pfannkuch
AVIATION...Petr


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