Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Goodland Kansas
933 am MDT Thursday Jul 24 2014
issued at 924 am MDT Thursday Jul 24 2014
Current near term forecast concerns focus on how warm things will
get this afternoon combined with magnitude of dewpoint falls as
dryline develops this afternoon.
Latest rap and hrrr and to a lesser degree the NAM are supporting
a well mixed very warm pattern across the County Warning Area pushing highs above
105 in several locations. Not totally sold on this as models are
aggressively mixing things faster than current observations. GOES
sounder data does indicate an area of low precipitable waters nosing into the
western County Warning Area as of 14z...which would support a layer of drier air
off of the surface which could potentially dilute surface dew points this
afternoon. Have lowered both the dew point and raised temperatures a few degrees
based on latest data and will closely monitor trends to see if
much warmer temperatures are needed.
Given dry air and increasing southwesterly winds...fire weather may
become a large concern this afternoon especially near recently
harvested or ready for harvest wheat fields. Currently widespread
critical fuels are in question though so not sure a rfw is valid
at this point in the green up cycle. For the time being...plan on
highlighting potentially critical local fire danger in Special Weather Statement for now
until fuel information becomes more apparent.
Update issued at 630 am MDT Thursday Jul 24 2014
Small area of low stratus and minor fog has developed to the east
of surface trough stretching from Garden City to russel Springs.
This is not a particularly wide area and think Morning Sun should
help mix out fog and lower clouds fairly quickly.
Short term...(today through Saturday night)
issued at 324 am MDT Thursday Jul 24 2014
Forecast problems will be chances of precipitation and how hot does
it get. Satellite showing an amplified pattern from the eastern
Pacific into the western Atlantic. Strong ridge centered to our
southwest is starting to be pushed south by a strong upper system
that is now moving into the Pacific northwest. Stalled frontal
boundary is near the western end of our area.
At middle levels...models tended to be a little too far east...
especially with the Pacific northwest system. Overall the European model (ecmwf) was
doing a little better than the GFS and UKMET. At low levels...the
European model (ecmwf) and sref were doing the best. The European model (ecmwf) was doing a little
better on the low level thermal field.
Today/tonight...surface trough and shortwave trough move into the
western portion of the forecast area later this afternoon. There is
a deep dry layer shown by the model soundings with 700 mb
temperatures greater than +15. Will keep a slight chance of
precipitation but pull the slight chance back further west toward
the lift. This also matches with gefs probabilities. New guidance
supported only making slight adjustments to the high temperatures.
Question then becomes how far east does it go during the night.
Initially most of the lift aloft GOES across the northwest half
during the evening. However...the surface trough and remainder of the
shortwave GOES across during the night. Since lift does not look that
strong right now and there is a deep dry layer will continue what the
day shift put in which is the slight chance across the northwest half
during the evening. This also matches with the probability forecast
which does keep measurable a little further west as well.
Friday/Friday night...models now appear a little slower with the
cold front...being pushed by northern system. In fact most of them
stall the front over the central/southeast portion by late in the
afternoon. This then looks to pull back to the north during the
evening before coming through in the later half of the night.
Also a weaker shortwave will move across where the front will be in
the afternoon. After that a much stronger shortwave moves in from
the west during the night. Complicate that with 700 mb temperatures
near or above plus 15 and a deep dry layer in the bottom half of
the atmosphere. Storm motions will be very slow as well. So could
possibly have thunderstorms develop near/just west of the boundary
and/or come off the higher terrain to the west due to the shortwave
and some upslope flow. Will put some slight chance probability of precipitation with the
front in the afternoon.
Question once again is how far east does the convection go and how
long it GOES into the night. Model quantitative precipitation forecast and probability forecasts
tend to favor the western portion of the area and to our north. Right
the current forecast in the evening looks reasonable and only made a
slight adjustment. However with the boundary and decent lift moving
through in the latter half of the night...will insert a slight chance
in the southeast half.
High temperatures will be interesting depending on the speed and
position of the front. Since models are slower with the front...
model temperatures are warmer than they were yesterday...especially
in the southeast portion of the area. So ended up raising maxes...
especially in the southeast half.
Saturday/Saturday night...at this time it looks like the front is
through the entire area...not by much...by early afternoon. So air
mass will be cooler with some weak upslope occurring. This front
continues to move south and east through the night. With the front
through the area believe initially that the precipitation will be
tied to it with the main area south and east of the forecast area.
It will be possible that the far west will see some storms with the
next shortwave trough approaching the Post frontal upslope air
mass. So reduced probability of precipitation to just that area in the afternoon.
Shortwave trough moving through during the night. But models
disagree on where the best lift and how much instability will be
present. Overall setup and probabilities support the southwest half
of the forecast area at this time. So left the current forecast
Even though most of the area is behind the front by shortly after
18z...models disagree on how much cooler air to bring into the
area. Once again the further north and west you go...the less hot it
will be. Again the southeast will see the hottest temperatures.
Made only minor adjustments to ongoing forecast.
Long term...(sunday through wednesday)
issued at 150 am MDT Thursday Jul 24 2014
For the extended period...region will see pattern shift as models
begin to strengthen 500 mb/700 mb ridges over the western portions of the
country...counteracted with a deepening trough/upper low setting up
over the Great Lakes/northeast regions. Upper flow as a result will
be northwest over the area for the entire extended time frame. At
the surface...a series of weak waves will move off the eastern
portion of The Rockies for Sunday into Monday night...followed by a
stronger Lee-side trough that sets up on Tuesday...settling south of
region early Wednesday and then converting to inverted trough and
meander of the region through Wednesday. The result of the synoptic
setup will bring chance for thunderstorm/rain shower almost every day with best
chances being Tuesday into Wednesday and this is where highest probability of precipitation
(30-40) are highlighted...before things wind down Wednesday night
into Thursday. As a result of the broad northwest upper flow and expected
cloud cover...temperatures will be generally a few degrees below
normal with highs in the 80s to low 90s in spots. Overnight lows will
range in the low/middle 60s and will be hampered at times if any
residual clouds remain from convection during the afternoon/evening
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 515 am MDT Thursday Jul 24 2014
VFR conditions are expected through the period. Some thin and
shallow may be around for a very short period of time after 12z.
Once enough heating takes place the southerly winds will be gusty
with kgld having the strongest winds. Some isolated thunderstorms
are possible late this afternoon into this evening. Since it is
late in the period...and coverage looks very spotty...will not
include any mention in the tafs.