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Area forecast discussion 
National Weather Service Hastings NE
556 am CDT Sat Apr 19 2014

Short term...(today and tonight)
issued at 345 am CDT Sat Apr 19 2014

Map analysis indicates an upper tropospheric ridge axis extending
from the upper Mississippi Valley to the Southern Plains. An upper
tropospheric closed low is noted over the southeastern
Continental U.S....another over northern Montana...and one more over the
southwestern Continental U.S.. enhanced upper tropospheric jet energy extends
along two branches across/near the Continental U.S....with one branch over
southern portions of the Continental U.S....and the other extending from the
northwestern Continental U.S. Eastward into the northern plains and
northeastern Continental U.S.. our area remains in between the two branches
and as a result...upper tropospheric flow over our area remains
fairly weak...only maxing out at around 60kts near 35000ft above ground level per
00z sounding data from klbf and koax. Water vapor imagery
indicates increased upper tropospheric moisture extending from the
Southern Plains...north into the Central High plains and portions
of the northern plains. Much of this increased upper tropospheric
moisture remains west of our area...but is attempting to move
east. At the surface an area of low barometric pressure exists
across northeastern well as across the Dakotas. A
lower tropospheric baroclinic zone is also noted extending from
north central South Dakota into western Nebraska and northeastern
Colorado. The lower tropospheric wind field across our area
remains from the south/southeast as a result.

Guidance from the NAM...operational and sref-mean all
suggest the upper tropospheric low over northern Montana will move
east/northeast into portions of the northern plains and south
central Canada through the next 24 hours. The upper tropospheric
low over the southwestern Continental U.S. Is expected to weaken as it slowly
moves east into New Mexico. At the surface...the area of low
barometric pressure over the Dakotas is expected to move
east/northeast...along with the upper tropospheric low...during
the next 24 hours. The area of low barometric pressure over
northeastern Colorado is expected to weaken as it slowly moves
into western Kansas. The associated lower tropospheric baroclinic
zone is expected to slowly move east/southeast through the next 24
hours...likely moving into far northwestern portions of our County Warning Area by
middle to late this morning...and moving into southeastern portions
of our County Warning Area by 12z Sunday.

An overall lack in Omega should present dry conditions to our
area through mid-afternoon. By late this afternoon however...lower
tropospheric convergence along the baroclinic zone appears as
though it will be sufficient for convective initiation...a
solution supported by quantitative precipitation forecast fields from the NAM...operational and well as simulated reflectivity from
the 4km WRF-nmm. Given the overall lack in synoptic-scale appears any such convective activity will be dependent
upon forcing along/near the baroclinic zone...which means
convective activity will likely be isolated to perhaps scattered
at best this afternoon into this evening. Given all this...went
ahead with 20-30% probability of precipitation across much of the County Warning Area starting 21z...with
the highest probability of precipitation relegated to an area roughly within 25 miles of a
line from Hastings and Phillipsburg which is where
the baroclinic zone is expected to be positioned late this
afternoon into this evening.

Heading into the overnight hours tonight...the NAM...operational and sref-mean all suggest a ~40kt low level jet axis will
develop from southwestern Kansas into southeastern Nebraska. Lower
tropospheric thermal advection along this jet axis will likely
help increase spatial coverage of the convective
activity...especially across the southeastern two-thirds of our
County Warning Area...a solution supported by quantitative precipitation forecast fields from the
NAM...operational and sref-mean. Given this...went ahead
with 30-70% probability of precipitation across much of the County Warning Area 03- 06z. It then appears
chances for precipitation will diminish across our County Warning Area after 06z
as the low level jet axis shifts off to the east...more into the
Missouri River valley. As a result...went ahead and tapered probability of precipitation
across much of our area 06z Onward.

Guidance from the NAM and operational GFS suggest 0-1km MLCAPE
values of around 1000j/kg will be in existence across portions of
our area along and head of the advancing baroclinic zone late this
afternoon and evening. These same sets of guidance also suggest
deep- layer bulk shear values of 20-30kts will be in existence
across the area. Given all appears possible a few of the
updrafts late this afternoon into this evening could be strong
enough to promote a threat of large hail...with resultant
downdrafts perhaps promoting an occasional strong to severe wind
gust. Given the anticipated position of the low level baroclinic
zone by late this afternoon...will go ahead and outlook locations
along and southeast for a line from Grand Island and
Osceola for strong to severe thunderstorm activity between 21z and
03z. Loss of diabatic heating Post-sunset should promote a
significant drop in potential instability and even with the
presence of the low level seems unlikely strong to severe
convection will be observed beyond 03z tonight.

An increasing lower tropospheric pressure gradient ahead of the
approaching baroclinic zone will likely promote a stiff surface
wind across portions of the County Warning Area today. That being said...the
surface wind will likely diminish quite a bit across all areas by
middle-afternoon as the baroclinic zone moves into the area.
Still...met/NAM and mav/GFS guidance suggest a sustained wind of
around 24kts...along with gusts near 32kts...will be possible
across portions of Osborne and Mitchell counties between late this
morning and early this afternoon. Given all this...will go ahead
and outlook strong wind in the severe weather potential statement for extreme southeastern
portions of the County Warning Area.

Continued southerly lower tropospheric flow and resultant warm
air advection will provide very warm day for those locations ahead
of the baroclinic zone today...which will basically be the
southeastern two-thirds of our County Warning Area where highs in the upper 70s to
lower 80s are currently forecast. Farther northwest however...back
behind the baroclinic zone...a cooler lower tropospheric air mass
will likely promote temperature readings in the lower 70s.
Continued southerly lower tropospheric flow...along with
increasing cloud cover and precipitation...will likely keep
temperature readings from falling off all that far across the
southeastern one-half of our County Warning Area tonight...with overnight lows in
the upper 50s to near 60 currently forecast. Once again
however...locations farther northwest back behind the baroclinic
zone in a cooler lower tropospheric air mass...can expect
overnight temperature readings in the upper 40s to middle 50s.

Long term...(sunday through friday)
issued at 451 am CDT Sat Apr 19 2014

The forecast tale remains very similar to thinking of the past few
nights regarding this time frame...with Sunday/Sunday night
featuring the second act of low pressure system number 1 and its
associated shower/limited severe storm chances...while the
Tuesday night- Thursday daytime time frame features system number
2 and its potentially...repeat potentially...higher threat of
severe weather. At least for the time being...the Monday
daytime-Tuesday daytime periods remain void of precipitation chances. In
addition...Thursday night-Friday daytime remain dry at the very end
of the official forecast period. Temp-wise...readings will average
at least slightly above late-April averages...with highs on most
days across the majority of the County Warning Area somewhere in the 65-75
range...with any 80s most favored in southwest zones on Wednesday.

As for non-thunderstorm related hazards/potential hazards...and
going in order: 1) Monday afternoon is starting to trend toward
at least near-critical fire danger mainly within the northwest 1/4
of the County Warning Area as drier air works southward on somewhat gusty
northerly breezes and pushes relative humidity values down to
around 25 percent or slightly lower...but given this is still 3
days out and also that vegetation could get a decent soaking over
the weekend in parts of the area am not sure there is too much
fire weather concern yet and will abstain from a hazardous weather
outlook (hwo) inclusion for now. 2) barring pretty significant
changes in the large-scale synoptic pattern for middle-
week...Wednesday is looking like a fairly solid candidate for
sustained south winds at least near-advisory levels...and this
potential will be added to the severe weather potential statement as at least limited sections of
the County Warning Area already have advisory-level winds officially advertised in
the forecast...which is a bit unusual for 5 days out. May also
have at least near-critical fire weather concerns mainly in the
far western County Warning Area...but this is highly uncertain and hinges on the
exact position of a north-south dryline 3) although still a long
ways out and subject to plenty of fine-tuning...will also have to
keep an eye on Thursday/Friday afternoons for another dose of at
least near- critical fire danger as dewpoints crash in the breezy
west- northwest wind regime behind the departing system number 2.

Now for more meteorological detail and taking it in 24-48 hour
blocks of time...

Sunday daytime/night...again this 24 hours features the
continued influence of system number 1 and associated precipitation
chances. Want to continue to emphasize that despite the likely
60-70 probability of precipitation advertised across much of the County Warning Area later in the day on
Easter Sunday...this is by no means an all-day rain-out and
higher-resolution models such as the 00z 4km WRF-nmm and also the
latest 06z NAM are strongly suggesting that the greatest coverage
of showers/storms should favor the later afternoon hours with
things much more hit-and-miss or outright dry during the first part
of the day. However...even for only being 24-36 hours away there
is still quite a bit of uncertainty here. In the middle-upper levels
the main story involves the slow passage of a fairly low-amplitude
shortwave trough that lumbers through the central/Southern
Plains...with the larger-scale trough consisting of several
smaller ripples of middle level energy. This slow-moving system is a
result of rather weak upper level flow especially for late-April the area remains in a flow-magnitude minimum
between the split branches of the northern/southern stream jets.
At the surface...the daytime hours will feature fairly light and
potentially variable breezes...but generally prevailing from some
variation of southerly or easterly...while Sunday night a stronger
push of northerly breezes generally 10-20 miles per hour will drop into the
County Warning Area on the backside of a broad surface low pushing east into
IA/MO. As for shower/thunderstorm chances...attempted to add some
3-hourly resolution detail to Easter daytime probability of precipitation...generally
downplaying the morning hours and holding off the highest 50-70
probability of precipitation for the afternoon in the southeast County Warning Area...while keeping probability of precipitation
below likely range in the northwest. Admittedly though...given the
moist airmass and presence of multiple small scale least brief passing showers cannot be ruled out
at any time. As for thunderstorm strength...forecast soundings
reveal a fairly tall/skinny cape profile that is typical of a
fairly deep moist airmass with fairly weak middle level lapse
rates...and as a result the latest NAM generally keeps 0-1km mixed
layer cape down in the 500-1000 j/kg the presence of
very weak deep layer shear on the order of 20kt or less. As a
result...although the vast majority of storms should not be all
that strong let alone severe...will have to keep an eye on the
afternoon hours especially in the southeast half of the County Warning
any breaks in cloud cover just to the northeast of the primary middle
level low pressure center moving east across Kansas could spark
clusters of multicell storms with at least small hail/gusty wind
potential...along with locally heavy rainfall...and especially
during the 3pm-10pm time frame. By sunset Sunday evening and
especially later in the night...whatever meager instability is
left starts to diminish and push out from northwest-to-southeast
as the parent system departs eastward...and although probability of precipitation were
boosted into likely territory in the evening across mainly eastern
portions of the County Warning Area...especially western areas should dry out by
later in the night. High temperatures Sunday are admittedly fairly low
confidence and will be highly dependent on whether any at least
brief sunshine breaks out...but based on a consensus of various
models/guidance actually boosted values a few degrees getting most
of the County Warning Area into the 71-74 range...with Sunday night lows then
generally ranging from upper 40s far northwest to middle 50s

Monday/Monday night...although confidence is pretty high that the
majority of the County Warning Area remains dry this entire time...there are
various models starting to suggest that at least a brief period of
lingering showers/weak storms could still be affecting the far
southeast County Warning Area on Monday morning before forcing departs...and the
next few shifts may need to consider adding a lingering Monday
morning pop in these areas. Otherwise...its a dry 24 hours thanks
to the arrival of a fairly broad/expansive middle/upper level ridge
axis that overspreads the plains in the wake of system number 1
and still well-downstream from system number 2...that should just
be coming onshore the western Continental U.S. By sunrise Tuesday. At the
surface will be a bit breezy out of the north most of
the day at sustained speeds up around 20 miles per hour before subsiding by
late afternoon as high pressure centered to the north exerts
greater influence. Breezes overnight will then become
light/variable and eventually more easterly. Assuming at least
mostly clear skies...temperatures should easily fall into the low-middle 40s
and these values represent a slight drop from previous forecast.
Daytime highs were changed little with most areas low 70s.

Tuesday/Tuesday night...the latest 00z European model (ecmwf)/GFS runs are in
pretty darn good agreement through this time-frame on the big the large/highly-amplified western trough heads
inland and reaches an axis from the Pacific northwest-southern
rockies by sunrise Wednesday morning. High confidence in dry
weather during the day as the local area as The Heart of the
middle/upper ridge axis translates overhead...but then by Tuesday
night have maintained 20-30 percent storm chances County Warning Area-wide to
cover the possibility of convection firing along a strong low
level jet axis. At least for now...even elevated instability does
not appear all that impressive to support a decent overnight
severe threat. Prior to the night storm chances...breezes during
the day will increase out of the southeast at 10-20 miles per hour with
higher gusts...and have highs low-middle 70s.

Wednesday/Wednesday night...this is potentially the most
interesting 24 hours of the upcoming week...but we are still
several days away from having a decent handle on the magnitude of
any severe thunderstorm threat. As mentioned the
very least the daytime is shaping up to feature rather strong
south winds as a strong surface low deepens to around 990-995mb
somewhere within the central Continental U.S....and a generally north-south
dryline sets up shop somewhere within the western halves of
neb/KS. If in fact the European model (ecmwf) solution remains fairly consistent
going forward...then its possible that severe storms could fire
along this dryline and affect parts of the County Warning Area during the
afternoon/evening hours. Although instability values are still in
question...undoubtedly deep-layer shear will be much stronger than
with this weekends system...likely on the order of 40-50 knots
which would obviously support organized supercells. All that being
said...its far too soon to get overly concerned despite the
presence of the new day 5 severe risk area that covers the
majority of the County Warning Area on the latest Storm Prediction Center day 4-8 there
are a ton of details left to be resolved on exactly what portions
of the central Continental U.S. Realize the main severe threat versus those
that are spared. Part of this uncertainty lies in the fact that
these deep systems often have a habit of coming in at least 12-24
hours slower than models currently depict. At any rate...the
highest probability of precipitation in the extended periods...although still no higher
than 50 percent...are advertised Wednesday night as the main batch
of strong upper level forcing and the associated strong surface
dryline/cold front crosses the local area. Made very little change
to high temperatures Wednesday with mainly upper 70s-low 80s.

Thursday/Thursday night...again the European model (ecmwf)/GFS remain in pretty good
agreement on the large-scale both show the main
vorticity maximum closing off as it departs east-northeast across the South Dakota/Minnesota
area...with the strong surface taking a similar path. This leaves
the local area in breezy to windy west-northwest winds and drier
air in its wake. Pop-wise...lingered a slight chance of showers
within the northeast half of the County Warning Area Thursday as the system
departs...and then dry Thursday night. Highs generally 65-70.

Friday daytime...reasonable confidence in a dry day at this time low- amplitude shortwave ridging moves in behind the
departing system. Temperatures preliminarily looking a touch cooler than
preceding days with most areas aimed between 60-67.


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 556 am CDT Sat Apr 19 2014

VFR conditions forecast through the next 24 hours...but
significant low level wind shear will continue through sunrise and
convective activity is expected this evening.

Little in the way of cloud cover will be observed at gri to start
the taf period...but increasing high-level clouds near 15000ft above ground level
will be observed during the day today...with a scattered but
shallow cumulus field near 5000ft above ground level also expected by late
morning or midday. Increasing high-level cloud cover near 10000ft
above ground level...likely the result of deep convection across the area...will
then be noted this evening...with stratus near 3500ft above ground level possible
to finish the taf period. The surface wind will start the taf
period from the south/southeast at 15kts. The approach of a lower
tropospheric baroclinic zone will allow the surface wind to become
light and variable by 21z...with the wind then becoming
northeasterly Post-frontal passage by 02z. A ~50kt jet streak just above the
boundary layer will continue to promote significant low level wind
shear at gri through 15z...and such has been presented in the taf.
Dry conditions are expected at gri through middle to late afternoon.
The approach/passage of the aforemen