Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 210545
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1145 PM MDT FRI MAY 20 2016

.UPDATE...
Issued at 637 PM MDT Fri May 20 2016

Just completed an update. The main change was to increase the
cloud cover tonight into early tomorrow. Also considering current
and expected dewpoints...winds...and more cloud cover...raised the
lows a little. Based on the expected cloud cover per a good
agreement among majority of input, I adjusted maxes down a little,
mainly in the eastern portion where stratus and even fog should
persist through the entire day.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 155 PM MDT Fri May 20 2016

Upper ridge axis will persist over the central High Plains through
tonight before moving east tomorrow as the large cut off low over
the Great Basin nudges closer. Isolated thunderstorms will develop
this afternoon in northeast Colorado due to surface heating/weak
to moderate instability. Lack of upper support under the ridge
and loss of surface heating after sunset will combine to limit
eastward progression and not thinking they will impact the local
forecast area. Low clouds will begin to return westward this
evening becoming overcast after midnight with areas of fog and
drizzle due to saturated lower levels. Wind speeds are forecast to
remain in the 10-15kt range which may be enough to prevent
widespread dense fog...but there will be some patchy dense fog
nonetheless.

Similar to what happened today...low clouds will slowly clear
from west to east through Saturday afternoon. Along the western
edge of the clearing line...a narrow axis of moderate to strong
instability is forecast by the models with little to no CIN. 0-6km
shear vectors are near 40kts by 00z in the vicinity of the
instability axis. Synoptic forcing is weak but q-vectors suggest
it will not be unfavorable. Thinking is that coverage will be
isolated but any thunderstorm that develops has the potential to
become supercellular with accompanying threat of large hail, gusty
winds and perhaps a tornado. SREF and NAM place the threat roughly
along a Joes to Burlington to Leoti line...but given inherent
uncertainties in location of the low clouds in this scenario
anywhere west of a Wray to Russell Springs line has at least a
marginal threat of severe weather on Saturday afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 209 PM MDT Fri May 20 2016

The main focus for this period will be the active weather pattern on
Sunday.

Saturday night a stout inversion will persist over most of the Tri-
State area as a warm front moves through. Below the inversion the
environment will saturate, allowing most of the area a chance at
receiving drizzle. Over the west half of the area there will be a
narrow corridor of instability where there is a convergence axis in
the low level jet wind field. Would not be surprised if a few
thunderstorms develop during the evening along this narrow axis. Any
thunderstorm that develops could become severe, but due to the
narrow axis of instability available, am thinking the storms will
not have much time to intensify before heading into a much more
stable environment. If storms do become severe, large hail up to
ping-pong size is possible with the strongest storms.  Meanwhile
isentropic lift will increase over the east 1/3 of the area where
the saturated layer is deepest.  Believe this part of the area will
have the best chance at receiving moisture. The drizzle may lead to
some minor visibility restrictions as well. During the overnight
hours isentropic lift will decline and the saturated environment
will shift east, causing chances for precipitation to decline from
west to east.

Eastern parts of Norton/Graham counties may have some lingering
drizzle during the morning Sunday before the isentropic
lift/saturated environment move east of the area.  The duration of
the cloud cover will influence when storms start to develop in the
afternoon.  The longer the clouds hold, the later into the afternoon
the first thunderstorms will develop, which will also delay the
onset of severe weather to follow and possibly weaken its intensity
once severe storms do develop.

Otherwise a dry line will be progressing east across the area on
Sunday, with the dew point gradient increasing as the day
progresses. Latest consensus of model data has the dry line
somewhere between Highways 27 and 83, with one model as far east as
Highway 283.  See no reason not to side with the majority of the
model output for the dry line position.  During the mid afternoon an
upper level short wave trough develops over the dry line, and
strengthens through the rest of the afternoon, roughly the same time
the CINH is lowest.  Am thinking storms will initially fire along
the dry line, or just east of it, by mid afternoon.  Mean storm
motion is to the north-northeast at 35 MPH.  West of the dry line
the environment will be too dry for storms to develop.

Regarding tornadic development...toward early evening the low level
jet strengthens, causing the 0-1km shear to increase to 25kts, and
LCL`s lower to within the favorable height for tornadic development.
Am thinking the best window for tornadoes to develop will be from
late afternoon to mid evening.   The location of tornado development
will depend on where the dry line will be.  Currently thinking
locations east of Highway 25 will have a chance for tornadoes to
develop, with the odds of seeing a tornado increasing to the east.
After mid evening the low level environment becomes less favorable
for tornadoes to develop as the environment stabilizes.

Early Sunday evening the severe weather activity should be at its
peak.  During the evening the dry line will retreat across the area
as a cold front approaches from the northwest.  The retreating dry
line may allow some storms to develop west of Highway 25.  However
am not expecting much for storm coverage based on the lack of
moisture to work with despite the retreating dry line.  The cold
front will move through the area during the latter half of the
evening and through the overnight hours.  Behind the front dry air
will move in.  There could be some elevated storms along frontal
boundary east of the Colorado border.  The main threat with these
storms would be large hail up to golf ball size.

Monday through Friday several rounds of rainfall are expected across
the area.  During this period the Tri-State area will be under
southwest upper level flow as an upper level trough deepens over the
west coast.  Models disagree with whether the trough moves toward
the area then fills over the upper midwest, or if it fills before
reaching the Tri-State area, and if another trough will deepen over
the west coast later in the week.  Either way, models do agree with
several rounds of rainfall through the work week, accompanied each
time by a quick hitting cold front, as several short wave troughs
move over the area ahead of the main feature.  Have fairly high
confidence there will be rain next week for various parts of the
area, with the best chances for rainfall consistently being of
the northeast quadrant of the area. The best chance for rain for
most of the area will be Wednesday night, as a stronger upper
level short wave trough moves through. Confidence quickly declines
where the rain will fall for the rest of the area aside from the
rainfall on Wednesday night. Am not expecting any severe weather
to develop at this time, due to the dry line remaining east of the
area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1136 PM MDT Fri May 20 2016

For Kgld...through about 15z, lifr/vlifr conditions are expected.
The southeast winds of near 17 knots with gusts to near 25 knots
will decrease about 12z. At 15z the conditions will improve to ifr
then vfr at 18z. At 18z, southeast winds of near 20 knots with
gusts to near 30 knots is expected through 03z. At 03z those winds
will become a little stronger as conditions return to mvfr. Llws
is expected from 03z on as well. Thunderstorms are expected to
develop to the southwest of the site during the afternoon and early
evening. However...since the coverage will be isolated...guidance
hinting that whatever forms will not affect the site...and does
not occur until the end of period...chose to leave any
thunderstorm mention out.

For Kmck...Mvfr conditions will quickly become ifr/lifr early the
period and continue through the remainder of the period. At 18z,
southeast winds will increase into the 15 to 20 knot range with
gusts to near 25 knots. These winds will continue through the end
of the period.

&&

.GLD Watches/Warnings/Advisories...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

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



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