Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 191959
Area Forecast Discussion
National Weather Service Goodland KS
159 PM MDT Wed Oct 19 2016
.SHORT TERM...(Today through Friday night)
Issued at 221 AM MDT Wed Oct 19 2016
Early morning WV imagery and RAP upper level analysis shows a
shortwave trough over Wyoming and Colorado, with a region of
subsidence/dry air moving northeast out of south central Colorado.
At the surface Lo pressure is in place with a surface trough axis
extending north across eastern Colorado. A cold front is over then
Northern plains, moving into northeast Wyoming and approaching
southern South Dakota.
The shortwave trough will move east and pass over our CWA today
and tonight. Region of subsidence may remain in place over our
southern CWA limiting chances there. Moisture profiles will be
slow to saturate, and dry lower levels may limit potential for
precip to reach the surface. Limited instability and a slow
increase in moisture depth/moisture profiles could eventually
allow light showers to develop. Guidance is still showing an
overlapping weak precip signal in our north and northeast today
and tonight, with dry conditions elsewhere. By Thursday the trough
will be east, and subsidence ahead of building ridge in the west
will overspread our CWA. Very dry/stable air will then remain in
place through the rest of the week.
Regarding temperatures: The cold front in the northern plains
should pass over our CWA this morning and Canadian high pressure
will slide out of the Rockies towards the Central High Plains
tonight, then eastward through Thursday night. The air mass change
will support cooler temperatures Today and Thursday (upper
50s/lower 60s), before the flow aloft shifts and WAA brings above
normal temps back to the region Friday (mid 70s).
A frost (or freeze) is possible Thursday and Friday
mornings. As surface high pressure remains just west, we may see
enough of a gradient that winds around 10 kt could limit peak
radiational conditions to all but the far west tonight. There is
also a small chance that stratus develops along forward edge of
ridge ahead of low BL Tds, and this could hold overnight lows up.
On Thursday night/Friday morning radiational conditions may
better better, but the air mass will also begin to moderate
lowering confidence in lows. Ultimately a frost advisory may be
needed (06- 15Z) tonight/Thursday morning and Thursday
night/Friday morning for our west. There is enough uncertainty
that after coordination, the decision was made to hold off for
.LONG TERM...(Thursday night through Wednesday)
Issued at 123 PM MDT Wed Oct 19 2016
A weak short wave trough moves through the apex of the initial
upper ridge that moves east of the Rockies and across the high
plains Thursday night and early Friday. The subsequent broad major
ridge axis moves past the Rockies and over the Plains States on
Friday and Friday night with another weak upper short wave trough
moving through the apex of the ridge on Saturday. The weak short
wave trough moves east with the ridge reamplifying over the
Rockies and High Plains Sunday through early Monday. The whole
pattern gets shifted east as a low pressure area dives south into
position off the Pacific Northwest by Tuesday morning with
southwest flow aloft and weak embedded short waves lifting out
across the Central High Plains region Monday and Tuesday.
The forecast area appears to remain mostly dry and warmer than
average through the extended period. High Temperatures should be
well into the 70s with lows mostly in the upper 30s to the upper
40s. The exception is the precipitation possible Tuesday night as
the upper short wave trough lifts out across the forecast area.
The issue that far out is the ECMWF and GFS have solutions that
become increasingly divergent between Tuesday and Wednesday. The
ECMWF strengthens the initial trough more than the GFS while the
GFS latches on to the second trough more and deepens it further
than the ECMWF over the southwestern U.S.
Do not have enough confidence in either model scenario at this
time to vary from the Superblend solution of producing isolated
to chance POPS with light QPF across portions of the GLD forecast
area during the Tuesday night time frame.
One upcoming coordination issue may be the possibility of frost
across portions of the forecast area on Thursday night/early
Friday morning. Skies are expected to be initially clear, but low
temperatures may be affected by increasing clouds. Am not
confident at all in issuing a frost/freeze highlight for that
period at this time. Also have a possible frost/freeze highlight
for tonight/early Thursday morning and don`t want to confuse the
issue at this point.
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1059 AM MDT Wed Oct 19 2016
VFR conditions expected for the TAFs. Clouds will clear by late
afternoon then return tonight as the corridor of clouds over
southern Wyoming moves over the TAF sites. Winds will shift from
the north to northwest as the clouds return tonight.