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Area forecast discussion 
National Weather Service Hastings NE
428 am CDT Monday Apr 21 2014

Short term...(today and tonight)
issued at 426 am CDT Monday Apr 21 2014

Surface front buoyed by 3mb pressure rises is not making quick
progress into/across south central Nebraska. Cluster of showers
and isolated thunderstorms have been along for the ride.
Unfortunately most of the rain has been/and will be light...but at
least it rained. With the precipitation band moving into a more
stabilized area as seen by complete disintegration of rainfall
across north central Kansas...would expect the coverage to
gradually wane with time. Attempted to push the precipitation
south with hourly grids and move it out of the region by 9-10 am.
Look for northerly winds to quickly take hold and with good
mixing/downward momentum the area will be breezy to windy for much
of the day. That will put a little cooler edge on the temperatures
for the morning hours. Clearing just about to enter Dawson
County...which is about on schedule.

This afternoon...attention turns to fire weather parameters and
winds and relative humidity approaching critical levels. Current
surface dewpoint forecast is to quickly dry out behind the surface
front..and bottom out in the lower 30s. Those depoints yield
late afternoon relative humidity levels of 20 to 25 percent most
areas. Concern is the sub-30 dewpoints already coming into north
central Nebraska...and how far south/how much mixing of those will
occur. This will have to be watched...as temperatures rise above
normal...this could yield some sub-20 percent relative humidity
levels. Despite recent rainfall...such low relative humidity
values could spark some fire concerns as gusty north winds prevail
nearly all day.

Tonight...all is clear weatherwise. Light winds will set up as a
ridge of surface high pressure slowly slides west to east
overnight. Will be noticably cooler than recent nights...with
many locations likely touching the 30s for overnight lows.

Long term...(tuesday through sunday)
issued at 426 am CDT Monday Apr 21 2014

Primary forecast concern lies with midweek thunderstorm
potential...then the next weekends temperatures and precipitation chances.

Dry conditions remain in the forecast at the start of the long
term period /the daytime hours on Tuesday/...with models in
pretty good agreement with the upper level pattern across the
Continental U.S.. the eastern rockies and plains are under the influence of
ridging...at 12z Tuesday is set up between low pressure/troughing
originating in Ontario...and another system moving onto the West
Coast. There isnt a lot of change during the daytime hours...the
ridge slides east but remains over the plains/cwa. At the
surface...a weak pressure gradient to start the tightens up as low
pressure better organizes over the northern rockies...with a trough
axis extending along the High Plains. This is going to result in
gusty S/southeasterly winds across the County Warning Area...speeds of 15 to 25 miles per hour are
expected. Only minor adjustments were made to temperatures...with daytime
highs forecast to reach the Lower/Middle 70s. Even with that
direction/speeds...models in good agreement showing moisture
return being weak...with dewpoints only looking to climb into the
upper 30s to near 40 degrees.

The first active time frame of the long term period comes Tuesday
night through Wednesday night...with the main focus being
Wednesday afternoon/night. Tuesday evening...upper level flow is
transitioning to southwesterly over the plains...as the upper
level trough axis swings from the West Coast into The Rockies. Out
ahead of the main axis...there is the potential for a piece of
shortwave energy to slide on through...and combined with an
increasing low level jet developing...will bring a chance for precipitation. There
are some questions...mainly with the positioning of the low level jet and
the better zone of convergence to help drive precipitation...with some
models not showing a lot going on across the County Warning Area due to the
corridor of strong winds being right overhead...thus pushing the
better convergence to other areas. Models showing instability
being pretty meager as this is going on...so have thunder in as
isolated.

As we get into the daytime hours Wednesday...kept some lingering
probability of precipitation going through the morning to account for the overnight
disturbance and low level jet...but expect that activity to slide off to the
east of the County Warning Area...giving the area a lull for part of the day.
Expecting another breezy day...especially for the southeastern half/two thirds of
the County Warning Area...as the pressure gradient remains fairly tight...and
speeds in the 25 to 30 miles per hour range are in the forecast. Models
remain in pretty good agreement showing the main upper level low
sliding into the northern rockies/far southern Canada area through the
afternoon hours...with additional energy swinging around the base
of the low and onto the plains. A surface cold front will also be
making its way south into the region during the day...and this
front will serve as a focus for afternoon thunderstorm
development. Latest models vary a touch on how far into the County Warning Area
the front gets...but the general consensus has it in the the northwestern
quarter to third of the County Warning Area by late afternoon. Activity is
expected to increase in coverage during the evening hours...as the
main upper level trough axis is starting to move through...and the
low level jet jet ramps back up into the area...increasing to anywhere from
50 to 60 kts depending on the model. 50 to 70 probability of precipitation are widespread
during the evening...but after 06z...trimmed probability of precipitation back in the
west...keeping the higher probability of precipitation in the east/southeastern third of the County Warning Area.

Deep layer shear is certainly better with these thunderstorm
chances than the batch this past weekend...but again there is
some question with the magnitude of instability that develops.
While there is srly flow across our County Warning Area already Tuesday...models
in pretty good agreement showing winds not really tapping into
better Gulf moisture until possibly Wednesday morning...so then it
becomes an issue of how much can really get this far north by Wednesday
aftn/evening. Think dewpoints at least in the middle 50s not out of
the question...though some models would suggest lower 60s in
place...with MUCAPE values reaching into the 15-2500 j/kg range as
temperatures climb well into the 70s to near 80 in some locations.

Still looking at the potential for strong/severe thunderstorms with
this set up shown by models...and Storm Prediction Center has the entire County Warning Area in a
slight risk on the day 3 outlook. Agree with the thinking that
the lack of more significant low level/surface dewpoints would keep
this primarily a hail/wind threat. Will see how upcoming models
trend with features.

By 12z Thursday...models in good agreement showing the main upper
level low having shifted into the northern plains/Canada border
region...but the main trough axis has swung through the
County Warning Area...pushing precipitation chances off to the east. Kept the forecast
dry through Friday night...with zonal/nwrly flow on Thursday
giving way to some shortwave broad ridging through Friday ahead of
yet another system moving onto the west. A cooler air mass moves
into the region with the frontal passage Wednesday night...but
models show a reinforcing shot of cooler air moving in Thursday
night/early Friday. Forecast highs for Thursday current range from
the middle 60s north to near 70 south...with Friday ranging from near
60 in the north to upper 60s south...so not a significant drop
off.

For the upcoming weekend...quite a few questions in place...but it
will present the next chance for precipitation to the region.
Timing is a bit up in the air...the European model (ecmwf) is showing a more open
pattern at 500mb compared to the wound up low pressure system
shown by the GFS/Gem through the day on Saturday. Do the precipitation
chances come more in waves through the weekend as suggested by the
European model (ecmwf)...or in one big shot mainly on Sunday as the low moves
through the central/Southern Plains shown by the GFS /which is also
much colder and would support inserting a mention of snow/. Not
buying into the GFS solution...but will be interesting to see how
things trend. Did not make significant changes to the period being
this far out...though did taper back thunder mention to
isolated...and considered pulling it all together...but will what
upcoming model runs show. Either way...cooler temperatures are in the
forecast...especially across the northern County Warning Area. Stuck close to allblend for
both Sat/sun...with highs in the middle 50s to lower 60s Sat and
Lower/Middle 50s for sun.

&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 1217 am CDT Monday Apr 21 2014

VFR conditions are forecast for the Grand Island Airport but
there area a weather changes. The main changes will occur with
an advancing frontal boundary slated to pass by around just prior
to sunrise. Ahead of and along the front...some isolated showers
may be in the area but not confident enough to say for sure the
Airport will actually measure any rainfall. Have including the
showers in the vicinity. Once the front GOES through...north
winds will pick up dramatically and gust over 25kts by late
morning and during the afternoon. Middle level ceilings will give
way to some scattered high clouds by late morning.

&&

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

$$

Short term...NOAA/NWS/Moritz
long term...ado
aviation...NOAA/NWS/Moritz