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Area forecast discussion 
National Weather Service Hastings NE
559 am CDT Friday Apr 18 2014

Short term...(today and tonight)
issued at 414 am CDT Friday Apr 18 2014

Map analysis indicates an upper tropospheric trough axis extends
from the upper Mississippi Valley to the Southern Plains. A ridge
is noted over the Rocky Mountain range...and another trough axis
exists over the far western Continental U.S.. enhanced upper tropospheric jet
energy extends from the northwestern Continental U.S....northeast into south
central Canada...and then southeast into portions of the northern
and Central Plains...and then northeast into the Great Lakes
region and southeastern Canada. Despite the upper tropospheric jet
axis trying to work into our area...upper tropospheric flow over
our area remains fairly weak only maxing out at around 60kts near
29000ft above ground level per 00z sounding data from klbf and koax. Water vapor
imagery indicates increased upper tropospheric moisture extending
from extreme southwestern portions of the Continental U.S....north into
southwestern Canada ahead of the western Continental U.S. Trough axis. Upper
tropospheric moisture over our area remains fairly meager however.
At the surface an area of high barometric pressure exists over
upper Mississippi Valley...and a trough of low barometric pressure
is noted extending from north to south across the Front Range of
eastern Colorado. The lower tropospheric wind field across our
area remains from the south/southeast as a result.

Guidance from the NAM...operational GFS and ec all suggest the
upper tropospheric ridge axis...currently over the Rocky Mountain
range...will move east through the next 24 hours...positioning
itself over the plains by 00z Saturday...and more into the
Mississippi Valley by 12z Saturday. At the surface...the trough of
low barometric pressure across eastern Colorado is expected to
strengthen...with a closed low expected to develop over
northeastern Colorado by 12z Saturday. The resultant lower
tropospheric wind field across our area is expected to remain from
the south for the most part through the next 24 hours.

An overall lack in Omega should present dry conditions to our
area through the next 24 hours...and such as been presented in the
official forecast.

The strengthening surface trough across eastern Colorado will
help promote a strengthening lower tropospheric pressure gradient
across our area today...with met/NAM and mav/GFS guidance
suggesting a sustained surface wind of 18-24kts...accompanied by
gusts of 25-30kts...will be realized across much of the
area...with the strongest wind expected across western portions of
the County Warning Area. Will go ahead and mention the stiff wind across our west
in the severe weather potential statement.

Southerly lower tropospheric flow and resultant warm air
advection should promote a warmer day today when compared to
Thursday...with afternoon temperature readings in the 70s
currently forecast for most locations across the County Warning Area. Continued
lower tropospheric warm air advection should also promote a warmer
night tonight when compared to early this morning...with Saturday
morning low temperature readings in the lower 50s expected across
much of the County Warning Area.

Long term...(saturday through thursday)
issued at 458 am CDT Friday Apr 18 2014

From an overall-perspective...we are still looking at two distinct
windows of opportunity for showers/thunderstorms...the first
arriving late Saturday afternoon and lingering through Sunday
night but primarily centered on Sat night-Sunday...and the second
during the Tuesday night-Thursday time frame but especially
centered on Wednesday-Wednesday night. Although the latter system
obviously carries even more uncertainty than the first one given
that its farther this point it appears this first system
will generally be fairly slow moving and consist of a number of
low-amplitude embedded shortwave troughs...while the second one
has the potential to barrel through in a more progressive/more
dynamic fashion resulting in a stronger surface low pressure
system...stronger winds...and potentially higher severe
thunderstorm potential. least some limited severe
weather potential is still very possible with this first system
over the weekend.

In terms of forecast changes from previous...the main thing that
truly seems to stand out is that shower/storm chances for Easter
Sunday appear to be on the rise and probability of precipitation have been increased into
high- ND chance 50 to low-end likely 60 territory...but for those
with outdoor interests please note this does not necessarily
equate to an all-day rain out by any means...and we are still a
few days away from having a handle on the more specific details of
morning versus afternoon potential. Secondly...any mention of
low-end thunderstorm chances was pulled from both Saturday morning
and early focusing solely on late-day potential.

As for non-thunderstorm hazards/potential hazards during this
6-day time frame...there are at least a few periods that could be
candidates for approaching or meeting Wind Advisory sustained
speeds of 30+ miles per hour. Early on...will have to keep an eye on Saturday
daytime south of the frontal zone mainly in the far
southern/southeastern County Warning Area for southerly speeds that could flirt
with advisory if forecast winds trend up any farther. Then later
in the long term...will have to keep an eye on southerly wind
speeds for Wednesday as they also could eventually become an
advisory candidate out ahead of a strong surface low. In
addition...a dryline setting up near the western edge of the County Warning Area
on Wednesday could promote at least near-critical fire danger as
long as vegetative fuels remain favorable for fire growth by
then...but of course this is still several days away. Lastly and
of lowest confidence/probability...although not reflected in any
forecast grids yet will have to keep an eye out for at least
patchy fog potential mainly on Saturday/Sunday nights especially
if winds become light for a time in places that receive rainfall.

Getting back into more meteorological specifics and taking it in
24-48 hour blocks...

Saturday/Saturday night...low pressure system number 1 makes it
initial arrival. In the middle-upper levels...flow will not be
particularly strong as the Central Plains remains in between the
main northern/southern jet branches...but the first batch of low-
amplitude shortwave energy will track into the local area in
southwest flow aloft...out ahead of the main parent wave still
hanging back over Colorado/nm at sunrise Sunday morning. At the
surface...the day will start out rather breezy out of the
south...and remain so all day in southern zones...while in
northwest areas a southwest-northeast oriented cold front will
gradually sag into the area...turning breezes northeasterly in its
wake. This boundary will be attached to a modest low pressure
center along southern portions of the Kansas/Colorado border. As for precipitation
chances...despite meager elevated instability...various models
suggest that any weak morning convection should remain outside the
County Warning Area...but possibly brushing parts of western/north central Nebraska.
Meanwhile...low level capping should hold any local convection at
Bay well into the day...and in fact some models including the 00z
4km WRF-nmm show little to nothing happening even later in the
day. However...others such as the 06z NAM still insist that a
likely fairly narrow corridor of storms will break out in the
4pm-7pm time frame within the surface frontal zone across The
Heart of the County Warning Area...and thus the continuation of modest 30-40 probability of precipitation
to cover this possibility. Turning to the evening/overnight
period...precipitation chances increase whether anything happens before
then or not...mainly due to a modest nocturnal increase in the low
level jet as it accelerates into the fairly sharp 850 millibar
frontal zone. Thus have continued likely 60-70 probability of precipitation across most of
the County Warning Area during the evening/night...but did lower a good chunk of
the Kansas County Warning Area below likely territory as most convection should remain
fairly closely tied to the low-level front farther north. As for
thunderstorm intensity...this is certainly not a high-end severe
threat...but with the latest NAM calling for generally 500-1000
j/kg of mixed layer cape in the presence of modest 25-30kt knots deep
layer shear...could easily get a few strong to marginally
severe...slow-moving storms especially during the evening. As a
result...will continue this thinking in the local hazardous
weather outlook...despite the official Storm Prediction Center day 2 outlook still
somewhat surprisingly not even advertising token 5 percent severe
probabilities. Depending on how focused storms are along the
boundary could even see some decent rains...but obviously the
ground is primed to handle a fair amount of water before Hydro
issues would arise. Temp-wise...made only minor tweaks to
highs/lows...aiming highs from low 70s northwest to low 80s
south...and lows mainly low-middle 50s.

Sunday/Sunday earlier mentioned this period seems to be
trending Rainier/ least for portions of the County Warning Area for
some part of the day. In the middle/upper levels...the final and
largest piece of the slow-moving low will lumber across the
Central Plains...while at the surface most models track a fairly
weak surface low across Kansas in some west-to-east fashion. Although
deep-layer shear will remain quite weak especially by late-April
standards...the moist airmass should support low-level cape on the
order of 500-1000 j/kg again as the day wears on...which should
result in a general uptick in at least scattered shower and maybe
even strong marginally severe thunderstorm activity as the day
GOES on...especially in roughly the southeast 1/2 of the
County Warning Area...where probability of precipitation were raised to low-end likely 60 percent.
Although instability fades Sunday night...lingering convection is
likely at least through the first half of the night...and probability of precipitation
were raised into the 30-50 percent range in much of this area but
kept below likely territory at least for now. Temperature-
wise...confidence in Sunday highs are somewhat low as so much will
depend on the extent of clouds and precipitation coverage...but based on
a model consensus nudged up values a few degrees but ranging from
upper 60s northwest to middle 70s in Kansas zones.

Monday daytime through Tuesday daytime...this 36-hour period was
left void of any precipitation mention and confidence remains fairly high
this should remain the case in future a fairly
pronounced period of middle-upper ridging translates eastward across
the Central Plains in the wake of the departing weekend system and
ahead of the next...larger and stronger one that reach the
West Coast/intermountain west by Tuesday afternoon. At the
surface...Monday could be a bit breezy out of the north...but
changed highs little with generally low 70s. Monday night then
features a passing weak surface ridge axis before winds pick up
out of the southeast on Tuesday in response to High Plains
pressure falls. Highs Tuesday low-middle 70s.

Tuesday night through Wednesday night...system number 2 becomes a
player as what should be a fairly organized/large scale trough
makes its way eastward from the western Continental U.S.. however...there are
still an abundance of differences between the European model (ecmwf)/GFS solutions
regarding how this system moves in...with the latest European model (ecmwf) much
more progressive and in fact at least 12-18 hours faster with the
progression of the large-scale trough axis. At the surface...and
as mentioned previously...Wednesday could be quite windy out of
the south as strong low pressure deepens over the Nebraska/KS/co border
area before a cold front passes through Wednesday night and turns
direction more westerly/northerly. It is far too early to
pinpoint severe weather potential...but it certainly is a
possibility given the likely presence of much stronger deep-layer
shear and stronger instability than system number 1 has. As for
probability of precipitation/thunderstorm chances...have a smattering of 20-30 probability of precipitation across
much of the County Warning Area Tuesday night-Wednesday...with Wednesday
afternoon/evening bearing some watching for a surface-based severe
threat off of a north- south dryline. Then Wednesday night there
is the potential for a more widespread coverage of storms...but
left probability of precipitation capped at only 40 percent for now. Temp-wise...Wednesday
is still looking like the overall warmest day of the week...and
have upper 70s-low 80s all areas.

Thursday daytime...kept most of the County Warning Area void of probability of precipitation but
introduced some slight 20s in eastern zones mainly to account for
the slower departure of the system per the GFS solution. The European model (ecmwf)
however would suggest just dry and breezy out of the
northwest...potentially with dewpoints falling far enough to bring
fire concerns into play. High temperatures mainly upper 60s-low 70s.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 559 am CDT Friday Apr 18 2014

VFR conditions to continue through the next 24 hours...but
significant low level wind shear is looking likely tonight into
early Saturday morning.

Periodic clouds near 15000ft above ground level will remain possible through
mid-morning...with clear skies otherwise expected. The surface
wind will remain from the south/southeast during the taf
period...intensifying to around 21kts with gusts near 29kts by
this afternoon. The development of a ~50kt jet streak just above
the boundary layer will likely promote significant low level wind
shear at gri tonight into early Saturday morning...and such has
been presented in the taf 05z Onward. Visibility restriction is
not expected at gri through the next 24 hours.


Gid watches/warnings/advisories...


Short term...Bryant
long term...pfannkuch