Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Goodland Kansas
538 PM MDT Wednesday Oct 1 2014

Short term...(this evening through thursday)
issued at 114 PM MDT Wednesday Oct 1 2014

18z water vapor imagery/rap analysis indicated strong trough
moving into northern Colorado. At the surface...fairly dry airmass in
place across the tri state area with front draped from klbl to
kmci.

Main forecast concern for the period will center around
approaching short wave trough and development of precipitation as
it moves into the area. While seeing current dry air in the area
does cause some concern on precipitation development...bulk of near term
models all indicate a tap of moisture originating near surface front
and interacting with elevated frontal zone this evening. Mixing
ratios in this plume are high and with some elevated instability
expect a decent response to period of strong frontogenesis.
Somewhat surprised by consistency of quantitative precipitation forecast output from available
data sources and am comfortable increasing general amounts to 0.25
to 0.75 at most locations. Chose not to go on the high end of
precipitation though...due to aforementioned concerns over
moisture quality. Forcing will diminish towards sunrise as deep
cold air advection takes over. Surprisingly...some low topped instability does
exist through the morning hours so a few lingering showers appear
warranted.

Other concern for the near term will be winds behind strong cold
front advancing across the area tonight. 12z NAM and to a lesser
degree the rap indicate strong 3 hour pressure rises in excess of
6mb as front passes. This could lead to a period of near advisory
level gusts for an hour or two behind the front. Played up winds a
bit in the forecast...but until strong pressure rises/gusts become
more apparent in observational data plan on holding off on any
highlights.

Long term...(thursday night through wednesday)
issued at 149 PM MDT Wednesday Oct 1 2014

Thursday night-Friday night...

A second cold front will move across the region late Thursday night
along with front end of 300 mb jet on back side of upper level trough.
With strong frontogenetical and upper level forcing I decided to
keep 20 probability of precipitation across northwest part of County Warning Area Thursday night despite limited
moisture profiles. Strong pressure rises behind the front should
allow a brief period of near advisory or advisory winds (45 mph)
as pressure gradient tightens overnight. NAM in particular shows
6hr pressure rises in excess of 10mb which is concerning and could
indicate possibility of brief warning criteria winds. If there is
virga or light showers this may also help mix stronger winds to
the surface. Will hold off for now on headlights...but this needs
to be monitored.

Gradient relaxes from the west to the east as upper level jet and
trough axis move east...however there are still strong winds aloft
over the eastern County Warning Area through the day Friday. Profiles would limit
mixing to below where strongest winds aloft are Friday despite
sunny conditions...so advisory level winds seem unlikely during
the day Friday. Should still be windy...especially Friday
afternoon.

Very cool air mass settles into region Thursday night and Friday. If
it wasnt for increasing cloud cover and windy conditions this air
mass would have supported a hard freeze (looks like well Luck out).
Clear skies...low dew point...and light winds will support good radiational
conditions Friday night. At the same time temperatures aloft will be
moderating as a ridge over the SW US begins to build east. Most of
the County Warning Area should stay above freezing...though patchy frost will
certainly be possible in the north and northeast where overnight
lows in the 33-35f range are expected.

Saturday-Wednesday...

Guidance in decent agreement on ridge building across western US
with main upper level jet stream shifting well north and east of
County Warning Area. European model (ecmwf) is showing a weak shortwave trough rotating around close
upper low over Great Lakes possibly bringing showers/thunderstorms
back to northern plains...possibly as far west as our County Warning Area. There
isnt a lot of consistency on this weak feature between deterministic
and ensembles so I kept sun/Sun night dry. Temperatures will
moderate through these periods with high temperatures in the upper 70s
lower 80s by early next week and persistent dry conditions.
Consensus/model blend seemed appropriate...so little change from
previous forecast.

&&

Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 531 PM MDT Wednesday Oct 1 2014

VFR conditions will continue at kgld and kmck for the next few
hours. However, a line of storms will move into both sites this
evening with ceilings coming down to the MVFR level by middle evening and
continuing through early morning. Conditions should improve to VFR
by middle day and continue through the afternoon.

&&

Gld watches/warnings/advisories...
Kansas...none.
Colorado...none.
NE...none.
&&

$$

Short term...jrm
long term...Dr
aviation...fs

National Weather Service Glossary of Abbreviations