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Interesting AFD from NWS DDC From May 17th

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  • USA Weather Inc, President/CEO

WOW! This is an interesting evening across the DDC CWA! Here's the AFD text.. focus on the short term wording! There was some destructive tornadoes across the area!


FXUS63 KDDC 180446

Area Forecast Discussion
National Weather Service Dodge City KS
1146 PM CDT Fri May 17 2019

...Updated Aviation Discussion...

Issued at 1021 PM CDT Fri May 17 2019

Well, clearly the cap eroded. Long track tornadic supercells have
caused widespread damage across SW Kansas (refer to the latest
LSRs issued by DDC). The most impressive supercell has tracked
from the Oklahoma state line near Meade, and is still producing a
dangerous tornado approaching Lewis. Tornado damage has occurred
occasionally all along this track.

Cancelled tornado watch behind the supercells.

Cold front/dry line combination is now progressing through US 83
corridor, with new thunderstorms expected to develop along this
boundary as it intersects moisture/instability. These are not
expected to be supercellular, but still large hail/damaging wind
may occur with this activity into the early morning hours.

UPDATE Issued at 536 PM CDT Fri May 17 2019

Capping inversion of warm air aloft appears to be winning the
battle across SW Kansas. HRRR has been one of the last holdouts
calling for supercell initiation, originating from the Oklahoma
panhandle. A recent attempt at initiation in Beaver county,
Oklahoma on radar/satellite has failed. Pronounced dryline is
clearly visible on radar, from just west of Scott City, to just
west of Liberal. Its eastward momentum is ending, and will begin
retreating soon. With the loss of convergence and strong capping,
reduced pop grids for the next several hours. Kept a 20% mention
out of respect for the extremely unstable airmass east of the
dryline, but it appears convection will struggle or fail to
initiate. Towards midnight, HRRR shows a rapid explosion of
convection from near Dodge City to near Hays, as the cold
front/dryline combination collide with the moisture/instability
axis. This seems reasonable, and large hail is possible from this
activity overnight.


.SHORT TERM...(This evening through Saturday)
Issued at 100 PM CDT Fri May 17 2019

Depending on the strength of a capping inversion, thunderstorms will
be possible this evening as short range models continue to show a
strengthening field of southwesterlies aloft spreading eastward
across the Western High Plains downstream of a negatively tilted
upper level trough shifting across the Great Basin. As an upper
level shortwave perturbation lifts northeast across the Colorado
Rockies into western Nebraska, a deepening surface low in eastern
Colorado will begin to lift northeast into southwest Nebraska.
Meanwhile, a sharpening attendant dryline near and along the
Colorado border will edge slowly eastward across west central and
southwest Kansas. Ahead of the dryline, a prevailing southerly
flow will draw ample moisture into the area with surface dewpoints
climbing up into the lower/mid 60s(F), providing substantial
instability as low/mid level lapse rates steepen. Although the
strength of the cap remains an issue in regards to timing of
initiation and coverage, isolated to potentially widely scattered
thunderstorms will be possible early this evening in vicinity of
the dryline as it advances across western Kansas. The better
chance for development looks to be further north toward the I-70
corridor. Based on model soundings, favorable deep layer shear and
instability with SBCAPE values in excess of 3000 J/kg suggest a
significant severe potential with any storm that develops. Large
hail and damaging winds will be the main threats initially with
isolated tornadoes also possible.

The focus for thunderstorm chances shifts east late Saturday
afternoon as the main upper level trough axis moves out of the
Colorado Rockies into the Western High Plains, nudging the dryline
further east into central Kansas by Saturday afternoon. Meanwhile,
there is fair agreement between the NAM/GFS/GEM/ECMWF of a
secondary surface low developing generally across extreme
southwest Kansas into the panhandles of Oklahoma and Texas by
early afternoon with a convergence zone setting up along a
developing attendant boundary extending northeast into
central/north central Kansas. Dependent on recovery time from any
convection the previous 12-24 hours, thunderstorms may develop in
vicinity of a surface trough/dryline more toward central Kansas,
then later Saturday evening in west central and portions of
southwest Kansas as a cold front begins to push southeast into the
area out of northeast Colorado and southwest Nebraska.

As for temperatures, a drier and slightly cooler air mass will
spread southeast into western Kansas tonight in wake of the
advancing surface trough/dryline. Look for lows well down into
the 50s(F) by early Saturday morning with a few 60s(F) still
possible in south central Kansas. Expect highs only up into the
70s(F) Saturday afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 205 PM CDT Fri May 17 2019

Drier conditions will prevail Sunday as an upper level trough
quickly lifts northeast out of the Central Plains into the Upper
Midwest. Drier and cooler air will filter into the high plains
behind a departing cold front limiting highs to the 70s(F) across
much of the area Sunday afternoon. A few upper 60s(F) will be
possible further north in west central and central Kansas.

Rain chances return Monday into early Tuesday as an easterly upslope
flow sets up across the Western High Plains ahead of yet another
upper level low pushing eastward across the Intermountain West. With
sufficient lift and moisture present, showers/thunderstorms will be
possible by late Monday afternoon as a series of H5 vort maxima
begin to eject out of the Desert Southwest into the high plains of
western Kansas. Medium range models are in fair agreement showing
stronger QFP signals, more specifically across central Kansas where
the ground remains fairly saturated from heavy rainfall in the last
week or so, resulting in potential flooding impacts.

Easterly upslope winds will do little to erode a cooler air mass
settled across the high plains to kick off the work week.
Considering likely increased cloud cover and potential areas of
rain, highs are expected to remain well below normal Monday before
beginning to slowly recover through the middle part of the week.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1141 PM CDT Fri May 17 2019

VFR conditions will prevail for all TAF sites during this period
with showers in the vicinity of HYS for the first two hours as the
cold frontal boundary pushes through in wake of the severe storms
exiting the CWA to the east and northeast. Weaker westerly winds
behind it under a loose pressure gradient with scattered high
clouds through the morning and afternoon hours. Increasing clouds
after 20Z with thunderstorm development firing back up across the
CWA for DDC and HYS and after 21Z for LBL and GCK lasting through
02-04Z. Improving sky conditions with weak northeasterly winds to
end the period as induced ridging pushes back across the high
plains from the Colorado Rockies.


DDC  54  79  49  72 /  60  30  30   0
GCK  49  76  46  71 /  20  30  20   0
EHA  50  75  45  75 /   0  20  10  10
LBL  52  77  47  75 /  10  10  10   0
HYS  56  77  49  69 /  70  30  60   0
P28  64  79  53  74 /  30  40  50   0




LONG TERM...JJohnson


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