FXUS63 KGLD 190340

Area Forecast Discussion
National Weather Service Goodland KS
940 PM MDT Thu Oct 18 2018

.SHORT TERM...(This evening through Friday)
Issued at 1204 PM MDT Thu Oct 18 2018

18Z Water vapor imagery/RAP analysis indicated closed low
circulation centered over UT. PV fields did not indicate much in
the way of large scale forcing for ascent and actually may be
suggesting a low amplitude shortwave ridge. Precipitation
continues to drift to the north along the 305 K isentropic
surface. While forcing looks somewhat weak, instability looks
sufficient enough to maintain showers for the next several hours.

Aforementioned precipitation will continue to lift to the north
and east through the afternoon and early evening hours until
saturated layer begins to dry out as winds aloft gradually shift
more towards the west. Once showers depart, main forecast concern
will be fropa moving in after 06z. Not expecting too much of a
wind threat given the strong inversion that will be forming behind
it. Given the saturated/humid airmass ahead of the front, may
actually see a bit of fog develop across southwestern zones
although it will be short lived.

Despite front approaching from the north, airmass behind it warmer
and drier than today. Expect temperatures to rebound into the mid
and upper 60s with gusty northerly winds. Current data supports
afternoon humidities around 25 percent, but do have concerns that
deep mixing may drive humidities down closer to critical values.
At this time, confidence too low for any potential fire weather
highlights, but will have to monitor upstream moisture profiles
through tomorrow.

.LONG TERM...(Friday night through Thursday)
Issued at 129 PM MDT Thu Oct 18 2018

Fairly docile pattern in store for the long term forecast.
Temperatures are very stable with highs in the 60s Saturday, Sunday
and Monday, then a slight drop into the upper 50s for Tuesday,
Wednesday, and Thursday. A high pressure center descends
southeastward out of Canada over the Central Plains by Sunday
evening guaranteeing pleasant weather conditions until it pushes
southeastward over the Gulf Coast by Monday evening.

A decaying low pressure center over the great lakes pushes
northeastward off of the Eastern Seaboard, placing the Tri-State
area in an area of troughing in between two high pressure centers.
Warm air advection due to southerly flow associated with the
boundary which will have pushed off to the northeast extends
directly into the Plains States bringing ample moisture. By this
time leeside troughing is firmly in place and instability will
give way to rain showers for most of Wednesday and Thursday. As
the 850 mb easterly flow brings downslope flow and dry air
advection, the moisture leaves the area by Thursday morning. Cloud
cover will accompany the rain showers and the clear skies
which will have dominated the first half of the forecast give way
to overcast skies with cloud cover moving in from the southwest
and completely covering the Tri-State area by Tuesday afternoon.
Skies remain overcast until Thursday with clouds breaking up and
sun should be peaking through the clouds by the end of the
forecast period.

The GFS and the ECMWF show notable discrepancies in the placement
of the decaying low pressure center over the Eastern Seaboard,
thus affecting the position of the ridging and subsequently the
areas of moisture advection on the backside of the ridge. The
ECMWF wants to place the moisture swath farther west covering as
far as Western Arizona and as far east as central Kansas. The GFS
keeps the swath farther east covering the entire state of Kansas.
The GFS has southeasterly 850 mb winds while the ECMWF has
southerly winds in place over the region which will affect
temperatures and moisture availability. As next week approaches,
the models will likely come into better agreement. At this time
the GFS seems to be more realistic, so this was the model of
choice for the forecast.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 940 PM MDT Thu Oct 18 2018

For KGLD and KMCK, sub vfr cigs expected from taf issuance through
about 08z-09z before southwest winds start to veer to the west
ahead of an approaching sfc trough and wind shift. Cigs are
expected to quickly improve to vfr by 09z or at the latest 10z and
continue through the rest of the period. Northwest then north
winds gusting to 30kts or so expected during time of peak heating
before falling below 12z around 23z-00z. For tomorrow evening
winds slowly decrease while backing to the northwest.




Back to Main Forecast Discussion Page