Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Goodland Kansas
1138 PM MDT sun may 3 2015
issued at 534 PM MDT sun may 3 2015
Issued minor forecast update to account for latest trends with
probability of precipitation...winds and sky. Slow moving thunderstorms have developed
south of Interstate 70. Due to slow movement...rains have been
heavy at times. Will need to refine quantitative precipitation forecast and qpe shortly.
Storms have been sub-severe so far but a few have approached
severe limits. Main threats with these storms is damaging winds
and large hail if they were to become severe.
Short term...(this evening through monday)
issued at 224 PM MDT sun may 3 2015
Early afternoon WV imagery and rap upper level analysis show
westerly flow in place across the plains with a shortwave trough
upstream over the central rockies. At the surface a trough is
currently in place over the County Warning Area...with a cold front near Imperial
Nebraska extending into northeast Colorado. Regional radar shows
scattered thunderstorm activity already moving off the higher
terrain in Colorado and moving off the Palmer Divide towards the
western part of our County Warning Area.
This afternoon-tonight...window for severe weather appears to be
mainly ahead of cold front where models had been advertising
moderate instability developing by 00z (mainly east of surface
trough). So far rap analysis shows ml cape generally around 500 j/kg
likely due to much lower dew point values ahead of cold front than
previously anticipated. Hrrr/rap have been showing isolated
development along surface trough axis where cap has been weakened.
There is a window for increasing sheer as cold front moves south and
depending on strength of updrafts we could see some organized
cells...otherwise it appears to be an environment favoring pulse
type thunderstorms through most of the night. Dcape values in excess
of 1000 j/kg do raise concerns for microburst potential ahead of
cold front so even weaker updrafts could produce near severe or
severe winds as they collapse.
Shower and thunderstorm coverage will increase late this evening
along/north of cold front with increasing moisture return and
elevated cape in place. By late tonight instability begins to
wane...while large scale forcing starts to shift north and east of
the region. This is where models diverge with NAM continuing to
indicate and lull or dry period while European model (ecmwf)/GFS indicate possible
overrunning or stratus/fog/drizzle development along/north of the
front. Tough call and while I hedged toward the dry NAM at 12z...I
could see in this type of pattern a light precipitation/drizzle even
evolving by Monday morning.
Monday...upper low over the southwest US begins to deepen and
move east with better large scale forcing spreading over the County Warning Area
by late afternoon. Depending on what happens to possible stratus
during the day we may or may not have a window for severe
thunderstorms in the eastern part of our County Warning Area where models show warm air advection
and increasing tds/instability. Further north and west stratus is
more likely to linger...holding temperatures down in and any instability
would be elevated and weaker. Depending on choice in model
showers/thunderstorms could be possible through the day...however
better chances should be tied to stronger large scale forcing
later during the day Monday.
Long term...(monday night through sunday)
issued at 224 PM MDT sun may 3 2015
Southwest flow will precede an upper trough that will affect the
Central Plains Tuesday through Wednesday. Surface high pressure
will shift east across the Central Plains Monday night as low
pressure moves into Colorado Tuesday. Low pressure will remain over
Colorado and western Kansas through Wednesday.
Probability of precipitation will increase from Monday evening to overnight as better
dynamics and moisture move north into the forecast area. Plan to go with
chance probability of precipitation across the western portion of the forecast area during the evening
with likely probability of precipitation over the southeast zones closer to the surface
boundary. Likely probability of precipitation will spread north across the forecast area overnight as
very favorable moisture and lift move into the forecast area. Likely and
definite probability of precipitation will be used across the entire forecast area Tuesday and Tuesday
evening as good dynamics and moisture continue to stream northward
across the forecast area. Precipitable water values are around an inch so will
include moderate rain in the grids Tuesday. Probability of precipitation will start
decreasing to chance probability of precipitation after 06z Wednesday as the upper trough
starts to lift out of the area. Some likely probability of precipitation will still exist
across the northern forecast area Wednesday afternoon as instability increases.
Min temperatures Monday night should cool to the middle 40s in eastern
Colorado and the middle 50s in the eastern forecast area. Min temperatures Tuesday
night will range from the lower to middle 50s. Maximum temperatures Tuesday
should range from 65 to 70 and 70 to 75 Wednesday.
In the extended...(wednesday night through sunday)...the upper
trough lifts northeast Wednesday night with southwest flow following
through Saturday. The next upper trough moves into the plains
Saturday night and Sunday. Shortwaves moving through the flow and
increasing dynamics with the next trough Saturday night and Sunday
will keep at least a chance of thunderstorms across the forecast area each day.
Min temperatures through Saturday night should range from 45 to 55.
Maximum temperatures will generally range from the middle 60s to the middle
Aviation...(for the 06z tafs through 06z Monday night)
issued at 1138 PM MDT sun may 3 2015
Overall thinking for stratus/fog remains largely unchanged. Have
grown less confident MVFR fog will be observed at kgld so have
removed fog mention. Forecast guidance became more optimistic
towards ceilings so feel that IFR ceilings are unlikely now. MVFR
ceilings between 1000-2000 feet are the most likely scenario.
Short term threat of thunderstorms at kmck has become the more
significant issue. Elevated storms continue moving to the north.
Storms could contain gusty winds...small hail and heavy rains.