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Area forecast discussion 
National Weather Service Hastings NE
638 am CDT Tuesday Sep 1 2015

Update...
issued at 638 am CDT Tuesday Sep 1 2015

Cloud tops have been warming over the past 2 hours and the line of
showers is rapidly dissipating as it approaches Highway 183. However...
we have noted a slight uptick in reflectivity with some new showers
between northern-hlc over north-central Kansas. We'll be making some minor
adjustments to short-term probability of precipitation over the next 3-6 hours here
shortly. Thunder has also been withdrawn from the forecast through 20z.

A quick look at the 06z NAM suggests a cap will minimize thunderstorm
potential this afternoon. Would prefer to keep mention of rain out
of the forecast after morning sprinkles/showers are gone. Suggest
reading the forecast as an 80% chance of staying dry at any one
location.

&&

Short term...(today and tonight)
issued at 330 am CDT Tuesday Sep 1 2015

Aloft: broad/low amplitude west-southwest flow will prevail over the Central
Plains through tonight. A pv streamer extended from Hudson Bay west-southwest
through the Dakotas to Southern California. There were a couple embedded very weak
pv anomalies...but it's arguable if they will have any influence
on shower/thunderstorm activity. One is forecast to move through early this evening and
the other toward dawn Wednesday.

Surface: the tail end of a weak Pacific cool front bisected central Nebraska
into northwest Kansas. Frontolysis will occur today with the forecast area
basically remaining in the warm sector...with high pressure over the
eastern USA and the Lee trough just to the west.

Today: given minimal synoptic forcing...confidence is very low in
what transpires with this shower/thunderstorm activity. Current expectation
is that it will weaken/dissipate this morning leaving plenty of
multi-layered middle-high clouds today. However...skies will average
p/cloudy...allowing for temperatures to warm close to what occurred
yesterday. Highs are largely continuity with the prvs forecast...but
did lower a couple degrees S of Highway 6.

Breezy S winds will gust 20-25 kts.

As far as rain potential today...am not expecting much. Just not
enough forcing.

Tonight: p-M/cloudy and mild. Breezy at times. Lows close to 10f
above normal. As for precipitation chances...a few thunderstorms will probably
erupt well west of the forecast area late this afternoon. Probably not
enough activity to form a cold pool and make it east into the forecast
area. A 40 knots low-level jet is forecast to redevelop. Model quantitative precipitation forecast
clustering and the 12 hour quantitative precipitation forecast probabilities from the 03z sref mean
suggest the best potential for convective initiation will be over
eastern Nebraska at the terminus of the low level jet. But there is a chance western edge
of this activity could develop over the eastern half of the forecast area.

For what little thunderstorm activity might develop through tonight...am not
expecting any strong/severe thunderstorms at this time.



Long term...(wednesday through monday)
issued at 330 am CDT Tuesday Sep 1 2015

Overview...after numerous dry days...portions of our forecast
area will finally start to see a chance of showers and
thunderstorms...but those chances will likely be rather low. At
this point do not see any thunderstorm chances above 20 to 30
percent. Temperatures will average 5 to 10 degrees above normal
through Sunday. Highs through Sunday will range from the upper 80s
to lower 90s and lows will range from the upper 60s to lower 70s.
Confidence on the timing of a cold frontal passage around Labor
Day if rather low. Labor Day could be noticeably cooler if the
cold front passes through Sunday night or Monday morning or it
could be yet one more hot day if the front is slow in getting
here.

Wednesday through Sunday...the overall pattern does not change
much with a large upper trough over the Pacific northwest middle to
late week that will ever so slowly edge into the northern plains
by Sunday. The upper ridge from the Southern Plains into the Ohio
Valley will also move very little through the period. Consequently
..we can expect continued warm southerly flow keeping our
temperatures 5 to 10 degrees above normal. The only chances for
showers and thunderstorms will depend on weak subtle little
disturbances riding up through the plains in the southwesterly
flow aloft out ahead of the main system. Some forecast models
indicate periods of isolated convection and others do not.
Confidence in timing these subtle little waves more than a day or
two out is not overly high. Overall...most areas will likely be
dry through this period.

Sunday night into Monday...this will be the period most in
question as a cold front will eventually swing through once the
main upper wave enters the northern plains. This will likely
result in a little better chance of precipitation...but too far
out to nail down areas that will be most favored due to timing
questions with the frontal passage. The European model (ecmwf) has slowed things
down and the cold front may not even come through until Monday
night in some areas...which would result in Monday being
potentially one last warm/hot day before the cooler weather moves
in.

&&

Aviation...(for the 12z kgri/kear tafs through 12z Wednesday morning)
issued at 638 am CDT Tuesday Sep 1 2015

Significant weather issues: low level wind shear ending 14z and then again tonight.

No crosswind issues through tonight on gri rwy17 and ear rwy18.

Today: low level wind shear ends by 14z. VFR with multi-layered scattered to
occasionally broken clouds at or above 11k feet. There could be a
couple clouds around 7-8k feet before 17z. S winds increase and gust
20-25 kts after 17z. Confidence: medium

Tonight: VFR. Scattered clouds at or above 12k feet. S winds diminish to
around 10 kts. Low level wind shear. Confidence: medium

&&

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

$$

Update...halblaub
short term...halblaub
long term...wesely
aviation...halblaub

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