Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Hastings NE
1158 am CDT sun Jul 5 2015
Short term...(today and tonight)
issued at 314 am CDT sun Jul 5 2015
Finally starting to see convection develop early this morning along
our southwest County Warning Area where the low level jet has strengthened to near 40kts.
The area of convection is aligned fairly well with the 315k
isentropic surface as depicted by the nam12 and if model trends hold
true...the area of convection should gradually work east and
eventually wane this morning. Cannot rule out a hit or miss strong
storm in presence of decent shear/instability.
The weather pattern will begin to undergo changes during the next 24
hours as an upper low in Manitoba translates southeast with the
southern extent of the upper trough reaching the northern
plains/Dakotas tonight. This system will break down and shunt the
western ridge over the central rockies south to the Southern Plains
with an airmass change moving into our region late tonight and early
Monday as the upper trough and associated cold front arrive.
Until this time however...we are looking at quite a hot day
temperaturewise ahead of the approaching system. Forecast models are
pretty consistent with 850 mb temperatures in the 25c to 31c range east/west
with forecast soundings indicating mixing well above this level.
Resultant high temperatures are expected to top out well into the
90s this afternoon but this will also be dependent upon the degree of
high clouds around. Gusty south winds will be an issue in the
deep mixing and tightening surface gradient and wind speeds shld
average 20 to 25 miles per hour this afternoon with gusts over 30 miles per hour.
After any morning convection...the daytime and really the evening
hours are looking to remain dry with warm middle level temperatures in the 12
to 15c range. Chances for thunderstorms increase after dark and more so after
midnight as the cold frontal boundary approaches from the northwest.
The front will focus showers and thunderstorms and cannot rule out a strong
to severe storm however not looking for widespread severe weather
with the late timing of the front and better instability focused
north of our County Warning Area. Low temperatures will remain quite mild tonight with
steady south winds carrying into the nocturnal hours ahead of the
boundary and not looking for that airmass change until the front
moves through more so on Monday. Generally looking for lows to range
from the upper 60s to low 70s.
Long term...(monday through saturday)
issued at 314 am CDT sun Jul 5 2015
High temperatures each day along with precipitation chances will be
main concerns in the extended.
Starting out Monday at 12z...upper air pattern looks to have the
southern end of a Canadian trough swinging through the Dakotas and
northern Nebraska. A slow moving northeast to southwest oriented cold
front will be somewhere in our County Warning Area. Taking an average of the latest
NAM...GFS and ec operational model runs would place the surface wind
shift line somewhere from Greeley to Kearney to phillpsburg...but
this could be 50 miles one way or the other depending on the actual
speed of the system. Best forcing will remain north of our County Warning Area but
still expect a chance for some precipitation across the County Warning Area with
surface convergence near the cold front and some support aloft.
Enough instability for thunder but do not expect any severe weather
on Monday as the front will pass through the area overnight and
during the morning hours...which should keep severe storms at Bay.
Of course if the front slows down and does not exit the southeast
part of the County Warning Area until middle/late afternoon...then stronger storms are
possible in that part of the County Warning Area.
If things pan out as currently prognosticated...Monday will be much
different than what we will see today as very cool air for July
plunges south behind the cold front. Highs Monday could be 20
degrees lower than sundays highs. In addition to morning rain
chances and cooler conditions...it will also be windy. All in
all...not a nice day.
Tuesday into Wednesday should be dry with lighter winds as a surface
high pressure drops in from the north. With the cooler airmass in
place high temperatures should remain 5 to 10 degrees below normal on
Tuesday and Wednesday before a slow warming trend arrives for the
end of the week and into next weekend. There will be several small
chances for thunderstorms Wednesday night through next Saturday. At this
time the best chance appears to be Wednesday night into Thursday as both
the GFS and ec models slide a middle level wave through the region.
These models diverge after that. By next weekend...the ec is
building a middle level ridge into the High Plains while the GFS
dampens the ridge with another trough through the northern plains.
24 hours ago the solutions were just the opposite...so will have to
monitor to see how it plays out. It may be hot and dry...or warm
with at least small chances for thunderstorms.
Aviation...(for the 18z kgri/kear tafs through 18z Monday afternoon)
issued at 1149 am CDT sun Jul 5 2015
Strong southerly winds will continue through the afternoon and
evening hours before slightly decreasing overnight. However...a
cold front approaching from the northwest will aide in keeping
wind speeds above 10 kts from the south. Although timing of the
frontal passage is not quite certain...winds will begin to shift
from the south to west by the early morning hours before finally
shifting to the north by middle morning. Lowered ceilings are
expected with this frontal passage as showers and possibly
thunderstorms are likely to be in the vicinity if not over the
taf site by middle morning.