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Area forecast discussion 
National Weather Service Hastings NE
1216 PM CDT Tuesday Jul 28 2015

Short term...(today and tonight)
issued at 348 am CDT Tuesday Jul 28 2015

While the large-scale message/highlight of these next 24 hours
continues to be the gradual invasion of a slightly cooler and
more-noticeably drier/less-humid airmass that will subsequently
persist through the middle of the week...the much-more uncertain
element of these next 24 hours (and for much of the County Warning Area only the
next 6-9 hours) involves how much (how little?) Shower/thunderstorm
activity will actually develop within the County Warning Area...and whether at
least a storm or two could become strong to severe yet this
morning...and also later this afternoon/evening in the proximity
of the well-advertised surface cold near the far southeastern
fringes of the County Warning Area.

Starting with a look at the here and now:
as of this writing at 240 am...literally the entire County Warning Area still has
remained void of all convection through the entire night...despite
the over-aggressive suggestion of various models that "something"
should have formed by now. As touched on in the 1250 am update
discussion...likely the primary mitigating factors thus far have
been a combination of warm middle level temperatures/capping evidenced by
700mb temperatures around 14c...along with a lack of larger scale
convergence/forcing in the 850-700mb layer. Not
surprisingly...slightly stronger forcing and slightly cooler middle
level air over western/north central Nebraska has allowed a more
widespread coverage of convection thus far tonight in those areas
outside the County Warning Area. All this being said...latest few radar scans
suggest that at least a few showers/weak storms could finally
start flirting with the northwestern edges of the County Warning Area within the
next hour or so. In addition...11-3.9 micron satellite imagery
depicts that at least as smattering of middle level clouds (accas) is
developing within the central/southern County Warning Area...possibly indicative
of additional development in the near future...well- removed from
the ongoing northern Nebraska convection. In the big picture of the
middle-upper levels...water vapor satellite imagery and short term
model data clearly depict an unseasonably strong/closed middle level
low churning over northeast Montana...with the local area residing
along the very southeast fringes of stronger middle-upper level flow
and forcing associated with this primary feature. Closer to home
though...there are hints of a more subtle disturbance working into
the local area on the southwest flow- aloft sandwiched between the
northern rockies closed low and a broad subtropical ridge centered
over the OK area to the south. Meanwhile at the surface...the
entire County Warning Area remains in the warm sector ahead of a pre-frontal
trough and primary synoptic cold front working east-southeast
through western Nebraska. As a result...breezes thus far tonight have
averaged at least 10-15 miles per hour with occasional gusts 20+ miles per hour from
the south...helping keep temperatures well up a few degrees either side
of 80 thus far. Although at least a modest drop should still occur
between now and sunrise...most of the County Warning Area will probably struggle
to drop below the middle-70s for actual lows this morning.

Now turning to the forward-looking forecast...

Early this morning (through around 7am): although precipitation chances
(pops) remain under "likely" levels across the entire County Warning Area...am
expecting at least "some" shower/storm development to take place
within the local area over these next 2-4 hours as the southern
edge of stronger low-middle level convergence/forcing starts to
impinge on the County Warning Area. As mentioned above...could see ongoing
northern Nebraska activity build southward into the area...and could
also see new convective development within The Heart of the
seasonably strong 45-55kt low level jet centered directly over the
area. For now will run with 20-40 probability of precipitation County Warning Area-wide these next few
hours...highest in the north. Warm middle level temperatures may continue to
be a hindrance to things getting going...but even thus-far less
aggressive models such as the usually-reliable 4km NSSL WRF depict
at least isolated to scattered convection developing within the
County Warning Area through sunrise...although it may not be as widespread as more
aggressive models such as the rap13/hrrr suggest. As for any
severe potential early this morning...it is certainly not "zero"
given that elevated cape is averaging up to around 2000
j/kg...although deep-layer shear only on the order of 20-30 knots is
also a limiting factor. Barring any widespread development that
generates a robust low-level cold pool...the main threat with any
strong to severe storms this morning "should" be marginally severe
hail up to around quarter size.

Daytime hours (generally 7am-7pm): obviously whatever does (or
doesn't) get going during these next 2-4 hours will affect what
the first part of the day has in store. At this time...and given
the inherent uncertainty at hand...have only 20-30 probability of precipitation going for
the first part of this morning (highest east)...with these fairly
low chances then gradually decreasing from west-to-east later in
the morning in accordance with the elevated instability axis
diminishing from west-to-east as drier/more stable air gradually
moves in aloft. Of course...these probability of precipitation may need raised
considerably in some areas if more widespread storm development
shows its hand. By this afternoon...have roughly the western 2/3
of the County Warning Area void of shower/storm mention...while leaving 20-30 probability of precipitation
going within mainly the eastern 1/4 of the County Warning Area in closest
proximity to the low level cold frontal zone. As for any threat
for strong to severe storms...while isolated small hail is almost
impossible to rule out mainly in eastern/southern counties...think
the middle part of the day will probably feature a lull in strong-
severe storm prospects in the wake of the main early morning
convection. By late in the day however...a handful of counties
mainly in the far southeast County Warning Area could potentially find themselves
on the fringes of an area of strong to severe storm development
that should "mainly" miss the County Warning Area just to the south and southeast.
Of course...this will be dependent on frontal timing as well. For
now...will carry late afternoon/early evening 20-30 probability of precipitation only
southeast of a Geneva-Plainville line...or roughly the southeast
1/4 of the County Warning Area. With instability values likely upwards of 2000
j/kg and slightly stronger deep layer shear increasing into at
least the 30-35 knots range...this potentially broken line of storms
could easily produce at least marginally severe hail/wind. Agree
with Storm Prediction Center though in keeping southeast parts of the County Warning Area only in a
marginal risk zone...with the slight risk focused farther
east...deeper into the pre-frontal airmass. Speaking of the
surface front...for those not being impacted by convection
today...it is clearly the main weather story as it steadily
invades the County Warning Area from northwest to southeast over the course of the
day...its passage marked by a few hours of breezy north winds
sustained at least 15-20 miles per hour with higher gusts. Although not truly
a "cool" day by any means...have aimed for highs only reaching the
middle 80s in most of the northwest 2/3 of the County Warning Area...with the
southeast 1/3 rising higher into upper 80s/low 90s...and even middle
90s in the Mitchell County Kansas area where the front reaches last.
In fact...there could be a few hours of heat index values around
or just over 100 in the Mitchell/Osborne counties area...which
although a touch short of advisory criteria does at least
necessitate a mention in the severe weather potential statement product. Meanwhile...a gradual
decrease in dewpoints/humidity will invade the County Warning Area from the
northwest...with seasonably comfortable afternoon dewpoints
dropping into the 50s and maybe even upper 40s in some
northwestern counties...while 60s hold on for most of the County Warning Area.

Tonight: (generally 7pm-7am wednesday): by the middle-evening hours
and beyond through the rest of the overnight...confidence is
rather high that the vast majority of the County Warning Area will remain
shower/storm-free under mostly clear to partly cloudy skies.
However...will hold onto some low probability of precipitation in far southern zones just
in case some overnight convection lingers or develops in that
area. In the large-scale picture...the strong forcing from the
vigorous closed low decreases as it heads northeast toward the
Manitoba/Ontario border by sunrise Wednesday morning.
However...the elevated instability zone stalls out very near the
southern fringes of the County Warning Area during the night as it becomes more
west-east oriented. Although some models (such as the 6z nam)
suggest that even our far southern zones in Kansas should be void of
convection by midnight or so...it could be a very close call...and
thus have opted to just broad-brush a low pop through the entire
late-night period...but only within our far southern counties of
Rooks/Osborne/Mitchell. Although small hail would not be out of
the question...would be rather surprised if any legitimate severe
threat existed beyond midnight or so. Meanwhile...for the vast
majority of the County Warning Area that should not be affected by showers/storms
tonight...a seasonably cool and less-humid night is in store. In
the presence of light north breezes generally only averaging 5-8
miles per hour as surface high pressure builds in from the northwest...have
low temperatures aimed from the middle-upper 50s through roughly the
northwest 1/2 of the County Warning Area...and low-middle 60s in the southeast half.
This represents a minor...generally 1-2 degree downward nudge
from previous forecast. Dewpoints late tonight should drop into
the upper 40s northwest to middle-upper 50s southeast...but raised
these values slightly from previous forecast...as it is difficult
to really tank dewpoints this time of year.

Long term...(wednesday through monday)
issued at 348 am CDT Tuesday Jul 28 2015

Wednesday will be one of the cooler more pleasant days of the week
with dewpoints much lower behind the Tuesday cold front.
However...we will warm right back up to around normal high
temperatures on southerly winds for Thursday and should remain near
normal with our temperatures right through the weekend. Most
locations will likely see dry conditions through the extended
forecast period with primarily just some slight chances for
thunderstorms.

Wednesday and Thursday...will continue to call for dry conditions
all across our forecast area with the first slight probability of precipitation working back
into our southwest zones Thursday night as low level moisture
increases on the southerly flow. This Thursday night rain chance is
very slight and was only hinted at in a few models. After highs in
the middle 80s with low dewpoints on Wednesday...dewpoints will be
climbing back up on Thursday and highs will be back into the upper
80s to around 90.

Friday through the weekend and into Monday...the upper ridge that
has been centered over the Southern Plains will retrograde back to
the west and should be centered over the Desert Southwest giving US
a transition from zonal flow to more northwesterly flow. Although
the ridge will have moved...we will still be on the edge of this
upper ridge and capable of catching ridge running short waves and
possible mesoscale convective system events. Forecast models struggle with accurately
depicting northwest flow thunderstorms more than a day or two out
and thus confidence in precipitation chances next weekend is still
low. At this time...there does not appear to be any big systems
coming through and thus will just carry the occasional slight probability of precipitation
in portions of the extended when a few models possibly bring weak
troughs through our area. Overall...this is a pretty normal pattern
for this time of year and we can also expect rather normal high
temperatures in the upper 80s to lower 90s in most locations.

&&

Aviation...(for the 18z kgri/kear tafs through 18z Wednesday afternoon)
issued at 1212 PM CDT Tuesday Jul 28 2015

The main feature across the area today...a passing surface cold
front...has pushed through both terminal areas as of midday.
Expecting the gusty northerly winds to remain in place through the
rest of the afternoon hours...with VFR conditions in the forecast.
Not expecting the MVFR bases at kgri as of 17z to stick around
long. As surface high pressure settles into the area this
evening/overnight...winds will diminish in speed...remaining
northerly. As the continues to move in from the west...potential
will be there for to be more light/variable winds.

&&

Gid watches/warnings/advisories...
NE...none.
Kansas...none.
&&

$$

Update...pfannkuch
short term...pfannkuch
long term...wesely
aviation...adp

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