Area Forecast Discussion
Issued by NWS Goodland, KS

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000
FXUS63 KGLD 131008 CCA
AFDGLD

Area Forecast Discussion...CORRECTED
National Weather Service Goodland KS
308 AM MST Fri Jan 13 2017

.SHORT TERM...(Today through Sunday night)
Issued at 304 AM MST Fri Jan 13 2017

Forecast focus continues to be on upcoming winter storm and
potential for high impacts across much of our CWA this weekend into
early next week.

Today-Tonight: Upper low is already deepening over central
California with SW flow aloft extending out of the plains. We should
maintain dry and stable conditions through tonight with better
moisture and lift south and east of our CWA. Post frontal air
mass remains in place and with limited diurnal heating expect
highs around or below freezing.

Saturday-Sunday night Winter Storm:

Models continue to support anomalously moist air mass building over
the plains with several upper level waves moving ahead of main upper
low Saturday through Sunday. By Sunday night the negatively tilted
upper trough/closed upper low will swing out of the southern
plains towards our CWA. Latest guidance still puts our forecast
area in line for accumulating ice and snow.

Drier soundings shown by NAM/GFS lower confidence in freezing drizzle
or light freezing rain during the day Saturday possibly delaying
impacts until Saturday night. NAM remains a dry outlier through
this event, though latest 06Z run is beginning to trend towards
other guidance (still drier). Another complication is the amount
of WAA GFS is showing in the BL through the event, with surface Tw
increase to just above freezing at times which could lower total
freezing precip if this verifies. Based on past events this WAA
may be overdone and NAM/ECWMF low level temp profiles were
favored. Depth of near surface subfreezing Tw layer Saturday
through Sunday and final change over to all snow Sunday night will
also make a large impact on ice accumulations and impacts. The
deeper cold layer (ECWMF) would possibly support more sleet in our
southeast and less freezing rain.

There has been a recent trend in the last few model runs to shift
main deformation zone/trowal axis further west Sunday night. ECMWF
continues to advertise much higher snow amounts in our west late
Sunday night, with NAM significantly less. GFS is closer to ECWMF
though not as extreme. Consensus still favors moderate if not
heavy snow accumulations beneath this band in the west late Sunday
night, with the east possibly stuck with freezing rain or sleet.

All of these uncertainties were enough to convince me to hold off
upgrading the ongoing watch, giving us time to fine tune amounts and
make final decision on areas of favored impacts (Ice Storm vs Winter
Storm).

Regarding impacts: This will be a prolonged event and regardless
of precip type or amounts travel will be difficult if not
impossible for most of our CWA. The timing of highest impacts
could vary though, with earliest impacts felt in the south-
southeast. Greatest impacts in north and west may not be
experienced until Sunday night. If higher freezing rain amounts
verify for this prolonged period of time then we could be looking
a potential for crippling travel conditions and widespread power
outages in our southeast.

.LONG TERM...(Monday through Thursday)
Issued at 1253 AM MST Fri Jan 13 2017

Winter storm will still be impacting the area on Monday. The upper
low will be lifting northeast and tracking across eastern portion
of the forecast area. This will place the western area, generally
along and west of a McCook to Tribune line, under the trowal and
in a favorable location for possible heavy snow. Models indicate
an additional 3-6" possible Monday morning in that area, winding
down Monday afternoon and evening as the upper low continues to
lift out. Given the track, eastern areas may see a slower
transition to snow, and a longer period of freezing rain, with
just a short window of light wraparound snow Monday afternoon or
evening.

Tuesday through Thursday should be dry with shortwave ridging
aloft transitioning to zonal flow. Temperatures will gradually
warm allowing some melting of the snow. Models might be too
AGGRESSIVE with the warming if heavy snow falls in western areas,
but won`t get too caught up in the details at this point.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 900 PM MST Thu Jan 12 2017

For KGLD and KMCK, vfr conditions expected through the period. 00z
NAM model doesnt have data til 21z so data prior to then is not
available. Have gone with GFS/RUC/HRRR data for the forecast.

With that said, have backed off on mvfr/ifr cigs for both
terminals from taf issuance through about 21z per model cross-
sections. Winds during this period from the east and southeast
under 10kts. Next shift will need to monitor both terminals for
possibility of above mentioned mvfr/ifr cigs but for now have
removed it from the forecast. From 22z through the rest of the
taf period cigs around 15K ft with winds from the southeast and
south under 10kts. No precipitation or reductions in visibility
expected.


&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Winter Storm Watch from Saturday morning through Monday morning
     for KSZ001>004-013>016-027>029-041-042.

CO...Winter Storm Watch from Saturday morning through Monday morning
     for COZ090>092.

NE...Winter Storm Watch from Saturday morning through Monday morning
     for NEZ079>081.

&&

$$

SHORT TERM...DR
LONG TERM...024
AVIATION...99



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