789 
FXUS64 KLUB 230913 CCA
AFDLUB

Area Forecast Discussion...CORRECTED
National Weather Service Lubbock TX
413 AM CDT Fri Apr 23 2021

.SHORT TERM...
07Z analysis indicates a mid-level shortwave trough located near the 
Gulf of California and Sonoran Desert, beneath an intensifying belt 
of 250 mb winds approaching 100-120 kt as per 00Z objective analysis 
and 00Z AMA/MAF RAOBs. Low stratus has invaded the low Rolling 
Plains and Caprock this morning as south-southeasterly flow 
continues to stream through the region, with a pseudo-warm front 
extending orthogonal to the dryline that is currently located across 
east-central New Mexico as per regional METARs. Patchy fog is 
expected to develop now through sunrise as the boundary-layer 
continues to near the saturation point, with a few West Texas 
Mesonet sites recording relative humidity values of 100 percent. 
As the pseudo-warm front shifts northeastward across the CWA later
this morning, moist, isentropic ascent through the 280-300 K 
layer may support the potential for isolated, light rain showers 
across the southeastern Rolling Plains after sunrise as a weak 
impulse moves eastward overhead. 

The aforementioned shortwave trough will begin to dig into central 
Mexico near the late morning and early afternoon hours. Cyclogenesis 
of the surface low is already underway across the northwestern Texas 
Panhandle, with 1-hourly pressure falls at around 1 mb. The cyclone 
is expected to deepen through remainder of the day, and the dryline 
will correspondingly sharpen as static stability in the moist sector 
decreases as it propagates and bulges to the east. A risk for 
isolated thunderstorms (becoming widely scattered just to the east 
of the LUB/OUN CWA border) will exist across the far northeastern 
Rolling Plains late this afternoon with the best focus along the 
northern periphery of the dryline bulge, where low-level convergence 
will be maximized amidst a moderately strong EML characterized by 
MLCAPE at around 2,500 J/kg. Deep-layer flow is expected to veer as 
the left-exit region of the jet streak passes overhead, and the 
steep 700-500 mb lapse rates (L57) observed on the 23/00Z ABQ RAOB 
will have advected into the region by this point in time. 

The combination of intensifying diabatic surface heating and 
steepening of L57 will erode convective inhibition entirely. Where 
exactly convection initiates is uncertain; however, the residence 
time within the northeastern Rolling Plains will be short-lived as 
cold pools mature and convection increases in forward-speed. A 
localized strong wind gust up to 50 mph and small hail will be 
possible before storms surge east. Following passage of the surface 
cyclone, a weak cold front will move through the region from the 
north with slightly cooler temperatures on Saturday morning.

Sincavage


.LONG TERM...
A fairly slow, but increasing amplified, progressive pattern is
expected next week. Flow aloft backs toward zonal as today's upper
level short wave trough exits to the east and is replaced by a low
amplitude ridge. Flow then backs further to the southwest ahead of
the next upper trough that on Monday will be moving onto the West
Coast, then across the 4-corners region on Tuesday, the southern
and central High Plains Wednesday before shearing northeastward
toward the Mississippi Valley. Precipitation chances will be
limited to the period where the latter upper trough approaches
from the west and crosses overhead. Thunder chances ahead of the
trough will depend a great deal on its speed of movement eastward
and the corresponding eastward mixing of the dryline. At this time
a mention across the southeastern quarter of the forecast area
Tuesday night looks reasonable. As the upper trough then passes
overhead on Wednesday more precipitation looks possible. A cold
front at the surface will usher in a cooler air mass limiting
instability, but cooling aloft will still keep the lapse rates
steep enough to consider a slight chance of thunder during the day
Wednesday. The week will finish off on the cool side as the
forecast area will be under deep northerly flow downstream from an
amplifying ridge over the West Coast.

Prior to the rain chances midweek, fire weather will be the main
concern each day from Sunday to Tuesday with an increasingly warm
and dry air mass moving into the forecast area in response to low
level southwesterly flow advecting this air mass off the Mexican
Plateau. Falling heights and pressures will result in breezy to
windy daytime hours on top of the warm temperatures and low
relative humidity.

&&

.FIRE WEATHER...
Elevated to near-critical fire weather conditions are expected this 
afternoon across the southwestern and southern South Plains 
following the passage of the dryline. Surface winds will generally 
remain out of the southwest before shifting to the west as the core 
of the surface low moves through the central South Plains. As a 
result, wind speeds will be slightly offset from peak heating/lowest 
relative humidity values and are, at this time, forecast to increase 
in the late afternoon hours out of the west to around 25 mph with 
localized gusts to 30 mph. Patchy critical fire weather conditions 
will be possible, but given the aforementioned, any Red Flag 
conditions are expected to remain short-fused (i.e. less than three 
hours). Therefore, a Fire Danger Statement will be issued in place 
of a Red Flag Warning.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

09/07