Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 221101
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
601 AM CDT MON AUG 22 2016

.SHORT TERM...(Today and tonight)
Issued at 313 AM CDT Mon Aug 22 2016

Breezy conditions have developed across the region overnight as
the pressure gradient continues to tighten in response to an area
of low pressure deepening on the lee side of the Rocky Mountains
with and an area of surface high pressure slowly sliding eastward
across the Mississippi River valley. As a result...do not expect
much of a rest-bit from the breezy winds today...as the local
area will remain caught between these two system...and mixing of
even stronger winds aloft should result in gusty winds to 30 mph
or greater at times. With this strong southerly flow...expect some
warm air advection across the local area...with high temperatures
generally running 5-7 degrees above yesterdays readings. This
will result in most location reaching the mid to upper 80s...or
just a few degrees above normal for late August.

While occasional mid/high level cloud cover will stream across
the region from time to time today...skies will be mostly
sunny...with no precipitation currently in the forecast. Late in
the day and into the evening hours...expect the remnants of an
upper level wave to lift northeastward out of the Colorado
Rockies...bringing slightly thicker cloud cover the the region
this evening. While some models are tying to squeeze a few light
showers out of this disturbance overnight...there is very limited
elevated instability to work with and the focus of tonights
nocturnal jet is expected to be well northeast of the local area.
As a result...maintained a dry forecast overnight...with continued
mild temps...as sustained southerly breezes of 10 to 15 mph will
keep the atmosphere fairly well mixed near the surface and prevent
temperatures from bottoming out much below the mid 60s...even in
the coolest spots Tuesday morning.

Overall...dry...breezy and seasonably mild weather is expected
across the region for the next 24 hours.

.LONG TERM...(Tuesday daytime through Sunday)
Issued at 503 AM CDT Mon Aug 22 2016

General overview of this 6-day period:
One sentence summary: Although it won`t rain/storm each and every
day and night in all areas, we will certainly be trading in our
recent quiet weather/taste of fall for an off-and-on more active
late summer weather pattern that will probably feature at least a
few risks for strong to severe storms.

This forecaster just doesn`t have enough time this morning to
give this 6-day period the "proper justice" it deserves, as quite
frankly it has the potential to be rather active convectively at
times, but am already running a little behind (my apologies) so
will get right to it: Of greatest forecast concern, I am starting
to think that maybe previous/recent forecast products weren`t
"hitting the throttle" quite hard enough regarding the halfway
decent potential for at least isolated/scattered severe storms
especially within our northern/eastern CWA for Tuesday
afternoon/evening...and now that the latest SPC Day 2 outlook has
maintained at least a Marginal Risk for the entire CWA and
upgraded most Neb counties along/east of Highway 281 to a Slight
Risk, have attempted to bring a little more attention/detail to
this setup in our latest Hazardous Weather Outlook (HWOGID).
Although not as concerning overall, SPC also assigned roughly our
southeast 1/4 to a Marginal Risk on the latest Day 3 outlook, and
although there are still plenty of question marks at this time
range this does seem reasonable. Looking farther ahead, while most
of the Thursday-Friday daytime periods still look "mainly" storm-
free, another round of potentially widespread convection looks to
focus perhaps around the Friday night/Saturday time frame and
would also not be surprised to see this time frame carry at least
some marginal strong/severe storm potential as it gets closer.

Temperature-wise, no major changes were made versus the previous
forecast package, although in the nearer-term, high temps for
Tuesday were nudged up generally 1-3 degrees (especially in
southwestern zones). Tuesday is clearly the warmest/hottest of
these 6-days, and technically now again looks a few ticks warmer
than Monday for parts of the CWA (which day truly ends up being
warmer has gone back-and-forth a bit lately). Then, temps cool
down somewhat for Wed-Fri in the wake of a modestly-strong cold
that passes through Tuesday night, with highs only averaging
between the upper 70s-low 80s for the most part with lows Wed
night and Thurs night back down in the 50s. At least for now, the
weekend looks to warm back up a notch with highs more solidly back
into the 80s, although right in line with late August norms.

With the main themes covered, will finish up with some rather
sparse day-to-day details:

Tuesday daytime-night:
By far the main focus is the aforementioned, mainly
afternoon/evening risk for at least a few legitimate severe
storms. Compared to the seasonably-dry airmass currently in place,
some rather substantial warming/moistening will take place over
the next 36 hours. Assuming that skies don`t really cloud up more
than expected, afternoon temps climbing into the mid 80s-mid 90s
range teaming with dewpoints jumping back up well into the 60s
most areas (perhaps low 70s east) should yield some fairly
impressive instability values with the more conservative GFS
advertising mixed-layer CAPE of at least 1500-2500 J/kg and the
NAM roughly 1000 J/kg higher (although possibly overdone). With
modest (not necessarily strong) west-southwest flow aloft and
pretty good model agreement of a shortwave trough passing directly
over the region, the setup could be ripe for at least a few severe
storms developing ahead of the incoming cold front, especially
between 4-10 PM and generally favoring northern/eastern zones
versus other areas. While multicell storm mode is most favored,
the instability/shear combo could yield at least a brief/transient
supercell risk as well. Even at this closer time range though,
there is still some uncertainty on how early/late storm potential
might start/end. For now, the highest PoPs (including a limited
area of 60+ "likely" percentages in our northeast) are focused
during the evening period, but some models suggest the late
afternoon coverage could be just as high. Most models also agree
that most storm activity should depart east/southeast of the CWA
for the post-midnight hours, so late night PoPs were lowered
accordingly. In other departments, although not as windy as today,
it looks to be another breezy day from the south with sustained
speeds generally 15-20 MPH with higher gusts.

Wednesday daytime-night:
In the wake of the surface cold front, slightly breezy northerly
winds will overtake the CWA along with cooler temps. However,
enough elevated instability (perhaps even some surface-based?)
could linger in southeast zones along with another disturbance in
the flow aloft to foster a marginal severe threat mainly during
the afternoon/early evening. The higher "chance" PoPs are clearly
focused in southern zones with less potential for rain/storms in
the north.

Thursday daytime-night:
For days now we have advertised a dry/storm-free forecast for
Thursday, and although this is looking slightly questionable
especially in our far southern KS zones, have maintained it dry
for now as the area looks to be under a fairly stable/coolish
airmass. Have maintained some low-confidence slight PoPs in
southern zones for Thursday night but this could be pretty
"iffy".

Friday daytime-Sunday:
Not going to dive into much detail for this 3-day period, but the
bottom line is that thunderstorm chances again increase during at
least 1 if not more periods as the flow aloft remains seasonably-
active from the west-southwest with embedded, passing
disturbances. For now, the overall highest PoPs in the 40-50
percent range are focused on Friday night, but this could easily
shift by 12 hours given inherent uncertainty at this Day 5-7
range.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Tuesday morning)
Issued at 540 AM CDT Mon Aug 22 2016

Strong southerly winds are expected at both terminals by late
morning as a tight pressure gradient in place combined with some
vertical mixing will result in wind gusts this afternoon to near
30kts. Ahead of this mixing...the VWP is still indicating upwards
of 50KTS of southerly winds just under 2kft...so kept some LLWS in
the 12Z TAFS for the next couple of hours. While this differential
will decrease during the mid-morning through afternoon
hours...expect LLWS to return this evening as the winds decouple
again but remain elevated aloft. Other than a few passing mid/high
level clouds...no obstructions are anticipated with VFR
conditions forecast through the valid TAF period.

&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.
&&

$$

SHORT TERM...Rossi
LONG TERM...Pfannkuch
AVIATION...Rossi



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