Area Forecast Discussion
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FXUS64 KLUB 191518 AAA

Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
1018 AM CDT Mon Jun 19 2017

Updated the forecast to remove mention of fog and drizzle this
morning. The low cloud deck will slowly break up through early
afternoon with mostly sunny skies for the remainder of the day.


.PREV DISCUSSION... /issued 640 AM CDT Mon Jun 19 2017/

MVFR conditions are in place at KCDS and KLBB with KPVW bouncing
back and forth between MVFR and VFR. There will be a window over
the next couple of hours where IFR conditions could develop at
KLBB. Expect low clouds to gradually increase into the VFR range
through late morning before becoming a few to scattered VFR deck
this afternoon. Once VFR conditions do develop, expect to remain
there until possibly early Tuesday morning but confidence is not
high enough to include at this time.


PREV DISCUSSION... /issued 402 AM CDT Mon Jun 19 2017/

Unexpected showers and storms were well underway at 330 AM
across the far SW Panhandle. This activity was tied to a subtle
trough in NW flow shown best in the 00z RAOB plots from 700-500
mb. Diffluence from 300-250 mb was also apparent over the western
Panhandle, so background ascent is sufficient for this activity to
continue SE through the early morning. We suspect this elevated
convection may expand in coverage as the trough impinges on an
elevated Fn layer across the southern half of the forecast area.
This Fn layer has already saturated with stratus in response to
rich, easterly isentropic flow, so certainly more pros than cons
exist for some storms to continue progressing SE across the CWA
this morning. Elevated CAPE peaks to 2000 J/kg near and south of
Highway 380 which may foster some rowdy cells in the coming hours
if convection can be maintained. Otherwise, storms will wane by
late A.M. as the trough departs to our SE, followed by a slow
erosion of stratus. Moist easterly upslope flow remains intact
all day which favors keeping max temps below normal for a second

Stratus is likely to return overnight as even richer dewpoints
advect westward, but this improved moisture is a moot point for
precip chances as NW flow weakens considerably within a burgeoning
upper ridge. A cool surface ridge meanwhile is progged to translate
out of the region on Tue resulting in milder thicknesses locally.
This heat will only amplify through Thursday as a toasty 700 mb
thermal ridge arrives from the Colorado Plateau along the periphery
of a 500 mb high over Arizona. Even with the heat, many models
indicate convective temps are reached each afternoon on Tue, Wed and
even Thu from northeast NM through the western Panhandles. These
areas reside just north of the main upper ridge axis oriented W-E
over the South Plains, so PoPs were boosted across our NW zones
particularly on Wed night when NW flow convective signals appear
greatest. Otherwise, high temps were ramped up considerably on Thu
with the arrival of the aforementioned thermal ridge which has 850
mb temps not too dissimilar from what we saw this past Saturday.

Fortunately, Thursday`s intense heat looks to be in a state of decline
by Friday as heights slowly decay in response to broad troughing
emerging across the eastern 2/3rds of the CONUS. How fast this
trough unfolds remains the biggest challenge at present, with no
signal of preference evident on 00Z models. Cold FROPA timings
range from Friday (GFS), to Saturday (ECMWF), to even early
Monday (Canadian). Opted to keep a warm bias for Friday and
Saturday given WPC`s inkling for non-GFS guidance by this time.
Models do at least share good agreement in less anticyclonic flow
from Fri through Sun, so 20-30% PoPs were inserted each day with
enhancement preferred whenever the cold front arrives.




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