Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Hastings NE
915 PM CDT Sat Apr 18 2015

issued at 915 PM CDT Sat Apr 18 2015

Ww74 has ended. At this point the threat for severe is over. Even the
threat for a strong storm looks minimal as the atmosphere has been
overturned/worked-over in most areas...decreasing instability.

Summary lsr has been sent. No guarantees we have all the reports
but this is what we have thus far.

We will try to adjust probability of precipitation to reflect what should be the northern
fringe of the commahead rain shield rotating around the upper low.


Short term...(this evening through sunday)
issued at 325 PM CDT Sat Apr 18 2015

Satellite imagery showing the feature of interest through the
short upper level low pressure system...currently
spinning over eastern portions of Colorado. A lobe of shortwave energy
rotating around the main low is starting to spark off
thunderstorms through the plains...with coverage expected to
increase in the coming hours. The surface pattern across the County Warning Area
remains weak...with light and at times variable winds currently in
place for some locations. With MUCAPE values in excess of 1000
j/kg and sufficient deep layer shear...the potential for severe
weather remains in place...especially across roughly the southwestern half of the
County Warning Area...where a Severe Thunderstorm Watch is currently in place through

While the severe potential is expected to wane with time
overnight...higher probability of precipitation remain in lift associated with
that main upper level continues as it finally starts to push
east out of The Rockies.

As we get toward sunrise Sunday and 12z models are in
good agreement showing the main upper level low having shifted
into the western Kansas region...with the trough axis extending north
through western Nebraska and the Dakotas. This system will finally start
pushing its way east across the plains during the daytime
hours...with the main precipitation chances affecting the southeastern
half of the County Warning Area...driven by the deformation zone on the backside
of the upper low. Main change to the forecast was to trend probability of precipitation
up. Accompanying the system is a strong surface cold front...which
models show pushing through the County Warning Area by midday...ushering in gusty
northwest winds for the remainder of the day. Highs are forecast
to top out in the 50s/60s.

Long term...(sunday night through saturday)
issued at 325 PM CDT Sat Apr 18 2015

High temperatures should be near normal to a few degrees below
normal. Will have to watch out for some frost across our northern
and western zones Sunday night...Monday night...and Tuesday
night. Most areas will be dry through Thursday. Some models give
US a good rain event by Friday...but others are nearly dry so a
lot of uncertainty with regard to precipitation chances by
Thursday night through Friday night.

Sunday night...the 12z European model (ecmwf)...GFS...Gem...and NAM all indicate
that the upper storm system will finally have tracked east of
our forecast area by Sunday evening and thus will finally be able
to call for a dry night. Clouds will clear out from northwest to
southeast allowing for good radiational cooling with the wind
becoming lighter as the night GOES on. Therefore...northwestern
zones may see some frost.

Monday trough Thursday...our forecast area will be between storm
systems and therefore expect primarily clear to mostly clear skies
with mild highs ranging from the upper 50s to 60s and cool
nights. Monday night and Tuesday night will be the coolest with
lows in the upper 20s in the Ord area to primarily 30s south of
Highway 92.

Friday and Saturday...the 12z European model (ecmwf) takes a piece of a storm
system currently over Alaska...dives it south into the Desert
Southwest by middle week and then ejects it into the plains by
Friday. The 12z GFS does something similar to the European model (ecmwf) but is
weaker with the system. Confidence in this storm track is very
low. The GFS would give our forecast area very little if any
precipitation while the European model (ecmwf) would result in a rainy period
Thursday night through Friday night. At this point will keep rain
chances at 50/50 or lower and they may be too high if the track
varies much at all. Saturday is currently dry on most forecast
models. Both days currently appear to be heading towards highs in
the upper 50s to lower 60s.


Aviation...(for the 03z kgri/kear tafs through 03z sun evening)
issued at 915 PM CDT Sat Apr 18 2015

Tonight: multi-layered mostly VFR clouds with patchy leftover
rain. A break will occur before another band of rain moves in and
reduces ceilings/visibilities to MVFR. Variable winds will become northwest under 10
kts. Confidence: low due to uncertainty with ceilings/visibilities and

Sun: MVFR ceilings/visibilities in rain during the morning. Rain ends with
ceilings lifting and then clearing late. Northwest winds will gust to 35 kts.
Confidence: medium


Gid watches/warnings/advisories...


short term...adp
long term...wesely

National Weather Service Glossary of Abbreviations