Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 222121
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
221 PM MST Wed Feb 22 2017

.UPDATE...
Issued at 1033 AM MST Wed Feb 22 2017

Critical fire weather conditions will likely be met Thursday
afternoon south of I70 in northwest Kansas and northeast Colorado.
Southwesterly winds will be gusty in the afternoon and the
downslope component will help dew points tank into the single
digits. Along with the warning, issued a watch for the row of
counties to the north, roughly along I70, where there is some
question as to the location and timing of the frontal boundary
which will separate the dryer air from the moist and cooler air
Thursday afternoon.

&&

.SHORT TERM...(This morning through Friday night)
Issued at 247 AM MST Wed Feb 22 2017

Long fetch of W-SW flow extends from Pacific Ocean across the
central Rockies and over the plains. A shortwave trough is over the
Rockies with a region of subsidence over northeast Colorado. Plume
of high level moisture is streaming ahead of this over our CWA.
At the surface a pre frontal trough has shifted over our CWA, with
a cold front moving over the Nebraska Panhandle into northeast
Colorado.

Early this morning: Mixing along surface trough early this morning
has resulted in very dry and warm air mixing to the surface,
while strong LLJ transitions eastward ahead of surface trough.
Interestingly at 1 AM MST (2 AM CST) GLD was at 66F (19F above
normal for highs...much less nighttime temps) and RFW conditions
were briefly reached (not prevailing). Temps are finally beginning
to fall in our west (including at GLD) behind trough axis, but
there is a narrow axis of 10-15% and brief gusts around 25kt
transitioning eastward in region of deeper mixing where LLJ/warm
nose are in place. This may continue to support near critical fire
weather conditions through sunrise or even mid morning for our
eastern CWA.

Today-Tonight: Weak front should move over our CWA by mid morning,
before lee trough rebuilds and WAA redevelops in our SW. Temps are
tricky as our southeast may see near record highs once again ahead
of front (assuming it doesn`t move completely through our CWA),
while locations in our northwest may be closer 60F for highs (still
well above normal). Winds aloft back off this morning over our CWA,
and RH briefing increasing before dropping again this afternoon.
Other than the brief period of concern this morning, RFW conditions
are not expected due to the weaker winds this afternoon.

Thursday-Friday night: Focus continues to be on stronger trough
expected to move across the Rockies into the High Plains during
these periods.

Ahead of strong cold front Thursday our southern CWA could see a
window for near critical or near critical fire weather conditions
(south), but confidence is low as timing of the front is still
uncertain and 3hr seems unlikely if front moves south as fast as
some models are depicting.

Northerly track continues to be favored, while GEM and ECMWF are the
only models currently showing a stronger precip signal in our
northern CWA. NAM/GFS have trended drier. There is a possibility
much of our CWA becomes dry-slotted depending on evolution of
system, and only the north-northwest has the best overlap in precip
signal (mainly Thursday evening). Type should still be rain-snow
favoring a transition Thursday evening, though a faster fropa (still
a possibility) results in a change over Thu afternoon. I still have
high confidence in windy conditions Thu night through Friday and
colder temperatures Friday. I have less confidence in highs, and
precip coverage/timing over our CWA.

Any snow accumulation looks to be on the light side ranging
anywhere from a dusting to 1" on the high end (mainly north) by
time it winds down Friday. I can`t rule out a brief period of
blowing snow Thursday night and Friday, but at this point
confidence is low enough on precip coverage/rates to keep mention
out for now.

.LONG TERM...(Thursday night through Wednesday)
Issued at 212 PM MST Wed Feb 22 2017

Main focus for this period will be the drastic change in temperature
and windy conditions Thursday night and Friday.

The main impact with this storm system will be the abrupt change
from spring-like temperatures to late winter temperatures.
Currently have lows falling to the 20s Thursday night and only
warming into the 30s Friday, which may still be too warm. In
addition wind gusts of 30-40 MPH will contribute to wind chills
falling into the single digits Thursday night and Friday morning.
The northwest winds will increase further on Friday, with gusts of
45 MPH, before becoming light Friday evening.

Thursday evening the cold front will move through the rest of the
Tri-State Area.  There is some difference regarding how quickly the
front will move through, which will determine how quickly the rain
will change to snow behind the front.

Looking at the previous model runs of the
NAM/GFS/ECMWF/Canadian/SREF shows a mixed message.  Some of the
models show a slightly faster cold front while others have shown no
change or a slower frontal speed.  Models do agree that the cold
front will be most if not completely through the Tri-State Area by
late evening.

Ahead of the front am not expecting any precipitation due to the
pronounced dry slot. Along/behind the front the environment
becomes saturated and mixing ratios increase for a brief time.
The mixing ratios show a narrow corridor of higher water content
behind the front before the drier air moves in. Soundings show a
similar trend of saturation with the frontal passage then gradual
drying through the night. However the environment continues to be
saturated due to the CAA. The lower mixing ratios coming in
indicate any snow that occurs will have a lower water content
through the night and into Friday.

The best chance for precipitation will be during the evening when
the best lift moves through behind the front.  Precipitation chances
will mainly be north of I-70 where the environment will saturate
behind the front, although cannot completely rule out some more
isolated chances to the south.  Chances for precipitation decline
after midnight and through Friday due to lift weakening as the storm
system moves further from the Tri-State Area.

Have lower confidence with the current precipitation chances after
Thursday evening due to the weakening lift that may be present over
the northern part of the forecast area behind the storm system.
Thought about removing the chances but cannot ruleout the
possibility of snow lingering into Friday due to some models
keeping weak lift over the north part of the Tri-State Area during
this time. In addition the saturated layer will be in the
dendritic growth zone, so any amount of lift may lead to some
snowfall. With this in mind will leave the lower chances for
precipitation alone.

Snowfall amounts continue to be very low due to the fast moving
nature of the storm system and the low water content of the air.
SREF ensemble plumes continue to support less than two inches of
snowfall accumulation over the Southwest Nebraska counties where
the best chance for snowfall will be. The warm ground temperatures
will also hinder snowfall accumulation. While snowfall amounts
will likely change over the next couple days, confidence continues
to increase that snowfall accumulations will be around an inch or
less.

Friday night into Saturday morning will be the coldest for the
week, with lows falling into the teens. Despite the light winds,
wind chills will fall into the single digits again.

After Friday temperatures will gradually warm, with the warmest
temperatures of the week expected Monday and Tuesday ahead of the
next cold front to move through on Tuesday.  There will be some low
chances for precipitation Tuesday as an upper level trough moves
across the Plains.  However the majority of the lift with this
trough currently will be south of the Tri-State Area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1033 AM MST Wed Feb 22 2017

VFR expected at both KGLD and KMCK through the TAF period.
Surface winds will gradually diminish through this afternoon as
pressure gradient relaxes behind earlier frontal passage. Tonight,
expecting southeast winds to increase after midnight as surface
low begins to strengthen in southwest Kansas and continue to be
gusty through Thursday morning.


&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Red Flag Warning from 11 AM MST /noon CST/ to 6 PM MST /7 PM
     CST/ Thursday for KSZ027>029-041-042.

     Fire Weather Watch from Thursday morning through Thursday
     afternoon for KSZ013>016.

CO...Red Flag Warning from 11 AM to 6 PM MST Thursday for COZ254.

     Fire Weather Watch from Thursday morning through Thursday
     afternoon for COZ253.

NE...NONE.
&&

$$

UPDATE...024
SHORT TERM...DR
LONG TERM...JTL
AVIATION...024



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