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Area forecast discussion 
National Weather Service Lubbock Texas
349 PM CDT Monday may 4 2015

Short term...
the bulk of evidence continues to point towards a valid threat for
flooding or flash flooding mainly on The Caprock tonight. Moist
southeasterly low level inflow will increase through the late
afternoon and evening as southwest flow aloft increases while lead
disturbances swing through early this evening and again later in the
night. Forecast precipitable water values later tonight have
increased to around 1.3 inches over the central South Plains with
both WRF/NAM and GFS solutions...or more than double the average for
this time of year. Early evening convection appears likely to mature
into one or more convective systems over the southwestern or western
South Plains...that should persist and edge east or southeast into
the low level inflow during the night....perhaps along an
increasingly well-defined southwest-Northeast Boundary.

More solutions are producing large rainfall totals during the night
as convective systems work slowly eastward...with highest totals
mostly in the 3" to 5" range...although a few solutions even higher.
This is consistent with our previous forecast. Pinpointing exactly
where highest totals will fall remains somewhat elusive though we
are starting to see better signals of the maximum moisture
convergence stretching from the southwest into the central and
eastern South Plains. As such we have expanded the Flash Flood Watch
one additional row of counties to the east. The possible high total
rainfall will continue to justify potential for a flashy nature to
the flooding threat although areal flood threat overall probably
will dominate for most locations. Urban areas in particular will be
at risk for very rapid runoff. There may not be much opportunity for
discrete rotating cells this evening...and shear is rather weak
anyway except near the New Mexico border. We may see a few strong or
severe storms mainly this region though a brief rogue severe cell
could occur almost anywhere as convective energy levels increase
close to 1000 joules per kilogram.

Should rain event unfold overnight as in the above scenario...a cool
moist airmass should shove south and westward early Tuesday...though
still may see on-going rain and heavy rain threat at daybreak
especially northeastern zones. The stronger approaching upper trough
late Tuesday will tend to tighten surface trough and solutions are
consistent indicating a dry-line push along the New Mexico border if
not a little further east in the afternoon. This zone may be at risk
for severe storms by late Tuesday although additional forecast
details will have to await tonights outcome. Rmcqueen

Long term...
ongoing widespread convection Tuesday evening will continue into
the early hours of Wednesday until upper level trough axis shifts
NE across West Texas into Oklahoma. Weak ridging behind the
departing wave will provide a brief lull in precipitation chances
through the early afternoon on Wednesday...until an upper level
wave pushes across the dryline in our south/southeastern zones
providing enough upper level instability to coincide with
convergence along the dryline and deeper moisture off The Caprock
to expect strong to possibly severe storms to initiate in our area
and exit eastward as Wednesday evening progresses.

Guidance suggests dryline convection chances continue Thursday...
Friday and into the weekend as the Pacific low slowly plods across
The Four Corners into West Texas through the weekend...not exiting
east until early Monday. Maintained chance/slight chance probability of precipitation for
the end of the week into the weekend especially east of The
Caprock as the mean dryline position seems to favor The Divide
between the South Plains and rolling plains.

Temperatures will remain right around normal..to possibly a tick
below...through the forecast period. Increased low level
moisture...cloud cover and potentially significant rainfall from
previous couple of days will all help to keep maximum temperatures at Bay.
Guidance hints toward another similar system setting up for next
week with multiple days of dryline convection.

&&

Preliminary point temps/pops...
Friona 55 69 51 78 / 90 70 30 0
Tulia 57 67 55 80 / 90 80 60 10
Plainview 58 68 56 80 / 90 80 50 10
Levelland 57 72 57 81 / 90 70 20 0
Lubbock 58 70 59 82 / 90 70 30 10
Denver City 57 77 57 81 / 90 50 20 10
Brownfield 58 74 58 82 / 90 60 20 10
Childress 61 70 62 83 / 80 80 60 30
spur 58 69 60 83 / 90 70 50 40
Aspermont 61 73 63 82 / 60 70 50 40

&&

Lub watches/warnings/advisories...
Flash Flood Watch through Tuesday morning for txz021>024-027>030-
033>036-039>042.

&&

$$

05/55

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