Area Forecast Discussion
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FXUS64 KLUB 182050

Area Forecast Discussion
National Weather Service Lubbock TX
350 PM CDT Wed Apr 18 2018

Compared to the last several days, today is a nice reprieve from
the hot, windy, and dusty conditions we have seen. North to
northeast wind has kept the cool airmass in place with
temperatures currently about 20 to 25 degrees cooler than
yesterday. Heading through tonight into tomorrow, the surface
ridge will shift off to the east with time allowing surface winds
to gradually veer to the east or southeast by sunrise Thursday. At
the same time, low-level moisture return will start to develop
during the day Thursday to the southwest of the forecast area with
weaker moisture advection over the Rolling Plains. Better and
deeper moisture levels will remain across Mexico and far western
Texas through the day but we should finally start to see some of
this moisture mix into the far western South Plains by Friday
morning. Depending on how quickly moisture can return to the area,
we could see some isolated thunderstorms late Thursday night into
Friday morning near the Texas/New Mexico state line but these will
be somewhat elevated in nature. Coverage of showers and storms is
expected to increase through the day Friday, especially late in
the day.

Two things will happen on Friday that will help increase chances
for thunderstorms across the forecast area. The first is the
approach of a strong closed low that will have it`s center near
or just east of the Four Corners by Friday evening. Through the
day, a very strong jet streak will swing around the base of the
low and start to push towards the region late Friday. Diffluent
flow will develop ahead of the jet streak and the track of the
core will place the left exit region of the streak overhead late
in the day. Unfortunately, cool surface temperatures generally in
the upper 60s through the day Friday and warm temperatures between
700 and 600 hPa will keep both surface-based and mid-level
instability low through the day. As the low and jet streak
approach, increasing synoptic-scale lift should help to cool the
mid levels but only result in meager increases in the amount of
instability available for storm development. Models continue to
keep the amounts of MUCAPE at or below 1000 J/kg with most models
between 500-750 J/kg late in the day. How things may unfold Friday
afternoon remain uncertain as the balance between weak
instability available for convective growth and the increasing
shear values through the day opens up a wide range of possible
outcomes. 0-6km bulk shear values will increase into the 60-80 kt
range by Friday evening and with strong forcing moving over the
area, it will likely be convection developing along the dryline in
eastern New Mexico then pushing into our area as a line or broken
line of storms. QLCS development cannot be ruled out either
thanks to the strong bulk shear and vectors perpendicular to the
dryline. Hail is looking a bit less likely but we could still see
damaging winds and and isolated tornado if the convective mode
goes into QLCS.

Precipitation chances will linger into Saturday morning as the
upper-level low starts to swing out across the area through the
day. The dryline will take it`s time moving east through the
morning so additional development east of the boundary is still
possible through late afternoon. A cold front will swing south
behind the departing low with a triple point developing somewhere
east or southeast of Lubbock early in the day. The NAM wants to
try and develop precipitation along the cold frontal zone on the
caprock Saturday afternoon but much of the low-level moisture will
have already been pushed south and east of the region so have kept
Saturday evening dry for now across all but the far northeastern
Rolling Plains. Cool conditions will continue through Tuesday
before models start to diverge by that point; the GFS is pushing
another strong cold front into the region by Tuesday morning
while the ECMWF is 12 to 18 hours behind the GFS with the front
arriving Tuesday evening. Enough residual moisture may be around
to produce some precipitation on Tuesday evening but have gone
well under the blends until the timing differences are figured
out. Precipitation chances may linger through the end of next week
depending on how mid-level flow pattern develops but have kept
mention of precipitation out for Wednesday through the end of this
forecast package. Temperatures will remain seasonable even behind
the front early to middle part of next week; the bulk of the cold
air will be well east of the area.





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