Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Lubbock Texas
329 PM CDT Tuesday Sep 30 2014

Short term...
20z surface analysis shows a diffuse dryline located across the
northwestern South Plains with low to middle 40 dewpoints on the west
side and low 60s on the east side. Mixing zone was fairly broad
across the northern South Plains but has tightened up a bit across
the western and southwestern South Plains. Visible satellite loop
shows cumulus field starting to develop along and east of the moisture
discontinuity at the surface. Biggest problem is the discrepancies
between the models on timing and location of any possible convection
for late this afternoon through tonight. NAM has been the most
aggressive and furthest west with storm development. This is due to
an axis of approximately 2000 j/kg SBCAPE across the rolling plains
while the rest of the models are anywhere from 700-1400 j/kg across
the same region. Next issue is cap strength which also varies from
model to model. For the most part...forecast soundings across the
area show a pretty substantial cap to overcome with a lack of
forcing aloft to help erode the cap. With surface flow pretty much
parallel to the dryline...also have little in the way of surface
forcing to help storms initiate. Both the higher-res ttu-WRF and
hrrr hold off on initiation until around 02z and have been fairly
consistent with this time line over the last several runs. With this
in mind...kept probability of precipitation favored across the northern rolling plains where
the best instability will be located. Main severe weather potential
will be for hail approaching one inch and wind gusts to 60 miles per hour.
Rain chances will taper off pretty fast as you head west with slight
chance ending along the I-27 corridor. Late timing of initiation
will also hinder coverage due to the loss of surface-based heating
and instability.

After another morning fairly similar to this morning across most of
the region...expect to see the dryline shift a little further west
as the axis of the surface pressure trough also shifts east. Models
mix the atmosphere out a bit more which should limit rain chances.
Opted to pull probability of precipitation out for tomorrow afternoon for the rolling plains
as a result.



Long term...
the approach of an upper air shortwave trough translating southeast across
the southern rockies and nearing the Southern Plains tomorrow
evening/night...will cause its cold frontal boundary/retreating
dryline to be located across the far rolling plains. This boundary
coupled with lingering middle-level moisture will be the focus for
precipitation development. Will need to keep an eye on storms possibly
nearing strong levels given steepened lapse rates and prognosticated MUCAPE
of at or above 1700 j/kg. Attention quickly turns to the aforementioned upper air
shortwave...which is anticipated to propagate across the Southern
Plains on Thursday. Its associated cold front will commence to
impinge on the region late tomorrow night/early Thursday morning
from northwest to southeast...and perhaps renew precipitation chances
mainly across the Low Rolling Plains where adequate middle-level
moisture will reside. However...most solutions maintain best
rainfall chances just east of the County Warning Area. Pressure rises of 4-8 mb per
6 hours could lead to a brief period of breezy nearly wind speeds
during the daytime hours on Thursday /aoa 20 mph/...where by the
evening the surface ridge will settle near the forecast area and pose a relaxing
gradient and thus lighter wind speeds. The cold front will also
advect in a cooler airmass...with highs ranging from the lower 70s
across the SW Texas Panhandle to the middle 80s across the Low Rolling
Plains on.

Thereafter...upper air ridging amplification will take shape across the western
Continental U.S....leading to dry northwest flow aloft across the Southern Plains
Friday through early next week. Hints of a weak embedded impulse in
the flow aloft will move across the County Warning Area Sunday...though atmospheric
levels appear too dry for any significant weather /other than perhaps a
brief wind shift to the north/ to come to pass. Temperatures will gradually
warm from the 70s on Friday to the 80s by late weekend into early
next week. Model guidance continues to show cool morning/S on Friday
and Saturday /lower to middle 40s across the SW Texas Panhandle to
lower 50s across the Low Rolling Plains/ due to the presence of a
nearby surface ridge.


Preliminary point temps/pops...
Friona 54 81 52 71 44 / 0 0 0 0 0
Tulia 56 84 55 73 46 / 20 0 10 0 0
Plainview 57 84 55 73 47 / 20 0 10 0 0
Levelland 58 84 56 75 48 / 10 0 10 0 0
Lubbock 59 85 57 75 48 / 20 0 10 0 0
Denver City 60 85 58 77 49 / 10 0 10 0 0
Brownfield 60 86 58 77 50 / 10 0 10 0 0
Childress 62 93 59 79 50 / 30 10 10 10 0
spur 64 90 63 81 51 / 30 10 10 10 0
Aspermont 67 93 67 85 53 / 20 10 20 10 0


Lub watches/warnings/advisories...



National Weather Service Glossary of Abbreviations