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Area Forecast Discussion (AFD)

Issued by Goodland, KS (GLD)

FXUS63 KGLD 222018

Area Forecast Discussion
National Weather Service Goodland KS
218 PM MDT Wed May 22 2019

.SHORT TERM...(This evening through Thursday)
Issued at 215 PM MDT Wed May 22 2019

Clouds will continue to increase through tonight, with low chances
for precipitation during the late overnight hours towards early
Thursday morning south of Interstate 70. Low temperatures will
range from the upper 30s in northeast Colorado to the upper 40s 
in north central Kansas. Despite northeasterly surface winds, 
models not producing any fog, probably due to rather high dew 
point depressions to start which will be difficult to overcome. 

Vorticity lobe will pivot northeastward on Thursday around the 
main upper low over the Great Basin as the entire system gradually
lifts into the northern Rockies. Appears convection will 
initially develop along the surface front in southwest Kansas and 
move northward, becoming elevated as they move away from the 
surface boundary. Some question on how far north that boundary 
will get on Thursday, but the GFS appears to be too far north 
compared to the rest of the model guidance. As long as it stays 
south, storms will most likely be elevated and primarily pose a 
risk for large hail and heavy rainfall. The eastern six counties 
will see the best chances for those hazards, with storms 
developing a little earlier than typical, by mid to late morning, 
and continuing through the afternoon and evening hours. 
Precipitation will finally exit to the northeast by around 06z 
Thursday night. Cooled off temperatures for Thursday to the 10th 
percentile of model suite with expected clouds, easterly winds and
developing precipitation, with highs in the 50s.

.LONG TERM...(Friday through Wednesday) 
Issued at 135 PM MDT Wed May 22 2019

Synopsis... Unsettled weather is expected across the Tri-State area 
throughout the forecast period. Chances for showers and 
thunderstorms persist Friday evening through Tuesday. Widespread 
heavy rain will be possible for the Central High Plains this weekend 
into early next week. In addition, some marginally severe weather 
with large hail and damaging winds cannot be ruled out at times with 
the stronger thunderstorms, especially Friday night through Saturday 
evening and Sunday afternoon and evening. Temperatures should be 
relatively mild this weekend with highs in the 70s and 80s before a 
slight cool down is possible early next week as highs dip into the 
60s and 70s. Lows will generally be in the 40s and 50s throughout 
the long term forecast period with warmer temperatures towards 
central Kansas.

Discussion... As an upper-level trough progresses northeast past the 
Central High Plains, precipitation chances will diminish for Friday 
during the day as skies will clear up a bit. There is a chance for 
some convection to develop mainly over northwest Kansas late Friday 
night and persist into early Saturday morning. There will be a large 
amount of deep-layer shear on the order of 50 to 60 kts in addition 
to CAPE values on the order of 1000 to 1500 J/kg as a weak surface 
low moves from southeast Colorado into northwest Kansas. 

Precipitation chances will increase during the day on Saturday as a 
strong upper-level trough strengthens over the southwest United 
States. This trough will create increased synoptic-level support for 
ascent leading to repetitive showers and thunderstorms for much of 
the Tri-State area through the upcoming holiday weekend and into the 
first half of next week. The axis of that upper-level trough will 
finally progress eastward through the Central High Plains by 
Wednesday, so some clearing skies are expected Wednesday as 
precipitation chances decline.

While showers and thunderstorms will be possible throughout the day 
and night essentially from Saturday afternoon through Tuesday for at 
least some portions of the Tri-State area, Sunday in particular 
stands out as a day that could potentially see severe weather. Even 
though it is still 4 to 5 days out at this time, several global 
models are hinting at a peak in instability Sunday afternoon and 
evening as southerly surface winds draw in rich moisture from the 
southern United States and the Gulf of Mexico. That moisture will be 
co-located with great upper-level support for ascent from the strong 
trough in the southwest United States. From a jet streak dynamic 
perspective, there may even be double support for rising motion from 
the left exit region of the jet streak associated with the 
aforementioned trough as well as the right entrance region from a 
jet streak associated with an upper-level low over northern Canada. 
A surface-based frontal feature also appears to be evident across 
east-central Colorado and northwest Kansas Sunday afternoon, and 
with relatively strong upper-level winds there will be deep-layer 
shear on the order of 50 to 60 kts. Both the GFS and the ECMWF 
models have highlighted a peak in instability Sunday afternoon and 
evening in the Tri-State area with CAPE values on the order of 2000 
to 3000 J/kg. 

With all of the necessary ingredients for severe weather - shear,
lift, instability, and moisture, Sunday could be our best bet for
severe weather in the Tri-State area in the long term. Those in 
the Tri-State area this weekend should monitor future forecasts 
for updates and more information as we get closer to this weekend.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1135 AM MDT Wed May 22 2019

Vfr conditions are anticipated at both KGLD and KMCK terminals
through this afternoon and evening. As a low pressure system digs
into the desert southwest, cloud cover will increase overnight 
into Thursday morning, with mvfr ceilings anticipated. With the
cloud cover comes the potential for rain showers which will be
looked at for the upcoming 00Z TAF issuance. Northwesterly winds
decrease by this evening and shift to the north/northeast
overnight. East/northeast winds strengthen tomorrow morning back
into the 10 to 15 knot range with gusts near 20 knots.