Area Forecast Discussion
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FXUS64 KLUB 240433

Area Forecast Discussion
National Weather Service Lubbock TX
1133 PM CDT Sun Apr 23 2017

Continued dry and VFR through the period. Upper level westerly
flow expected to increase later tonight and Monday with gradually
deepening of a surface low pressure trough. Winds expected to
become somewhat gusty from the south to southwest Monday along
with a return to very warm temperatures. Mostly thin high clouds
gradually increasing as well. RMcQueen


.PREV DISCUSSION... /issued 620 PM CDT Sun Apr 23 2017/

An upper level ridge axis overhead this evening will shift east
with increasing westerly flow aloft Monday. Surface low pressure
trough will gradually develop overnight maintaining modest 10 knot
or so southerly flow with VFR. Surface trough should edge a
little east into the Oklahoma and northern Texas Panhandles Monday
afternoon while deepening slightly, and leading to modestly gusty
southwesterly breezes. RMcQueen

PREV DISCUSSION... /issued 249 PM CDT Sun Apr 23 2017/

After a chilly start to the day we are in the midst of a terrific
afternoon with light winds, sunny skies and 19Z temperatures
climbing through the middle and upper 60s. The surface and upper
level ridge in place will quickly shift eastward allowing for a
return of southerly surface winds and zonal flow aloft over the
coming 24 hours. WAA and modest southerly breezes overnight will
yield milder conditions than we experienced last night with lows by
Monday morning primarily in the middle to upper 40s. Breezy
downsloping winds will follow and with near full insolation
temperatures will jump back well above average on Monday. By late
afternoon a weak dryline should form up near the edge of the
Caprock. Minimal moisture/instability combined with a firm cap will
keep PoPs nil. However the slightly improved moisture and backed
flow east of the dryline should keep highs in the upper 80s, while
west of the dryline many spots on the South Plains may make it up
into the lower 90s.

Models remain latched onto nearly zonal flow aloft Tuesday through
Thursday before amplification of the pattern occurs with a trough
moving into the intermountain West, closing into a low, then
lifting northeastward across the Plains. The period with the zonal
flow will see a pair of shortwave troughs moving through it, the
first Tuesday night and the second on Thursday. Models continue to
produce some light QPF as far south as the northern zones. This
precip will be associated with elevated instability but into a
post-frontal air mass. This will not be too conducive to much rain
reaching the ground, but it`s also not out of the question. Given
the persistence of the models and the WRF-NAM joining the party,
we will introduce a sliver of slight chance PoPs across the
northern tier of the forecast area. At this point Thursday`s
trough looks even less likely to produce precipitation. In
between, the cold front will bring what is looking to be a better
quality cool air mass than expected a couple days ago with highs
dipping back below normal on Wednesday.

The latter part of the period will be focused on the developing
low to our west. The models continue to struggle to a degree but
seem to be coming toward a solution that closes the low near the
4-corners Friday night-ish then lifts it across the
central/northern Plains states Sunday. Questions persist about the
quality of low level moisture that will be available and how much
upper forcing/support there will be, so will in general keep rain
chances in the 20-30 percent range. Currently see a window for
precip Friday night with a developing warm conveyor belt
downstream from the developing low with another window Saturday
night as the low ejects over the Plains and a Pacific front moves
into the region.

Warm, dry and breezy conditions will develop across the Caprock,
behind a weak dryline, Monday afternoon. RH values will dip to at or
below 10 percent west of the dryline while southwesterly winds
increase to 15 to 20 mph. This will create a period of elevated fire
weather. However the recent robust greenup across the South Plains
region will tend to mitigate the overall fire danger.

Wind speeds Tuesday should be higher than Monday, likely
surpassing 20 mph at the 20-foot level. Cooler temperatures across
the northwest and higher dew points off the Caprock will leave the
southwestern third of the forecast area as the best chance of
reaching critical conditions, although as mentioned above, greenup
will tend to mitigate the danger.




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