Severe Thunderstorm Warning 76, NWS El Paso, TX

Area Forecast Discussion
National Weather Service El Paso Tx/Santa Teresa NM
320 PM MDT Tue Aug 27 2019

.SYNOPSIS...
Tuesday afternoon has likely brought us our last 100 degree day
for a while, and is also bringing an uptick in thunderstorm
activity. Wednesday will bring slightly cooler temperatures, with
lowland highs in the 90s, and one of the more active thunderstorm
days of the summer. Slow moving thunderstorms will result in
highly localized heavy rainfall during the afternoon and evening.
We will remain in a moist and unstable pattern all the way through
Saturday, with some drier and warmer air aloft expected to
diminish thunderstorm activity early next week.

&&

.DISCUSSION...
Surface analysis and visible satellite imagery suggests the
backdoor cold front has stalled out just east of the Sacramento
and Guadalupe Mountains, but a prefrontal trough or wind shift
line, with increased moisture behind it, has pushed up to the Rio
Grande. Behind this boundary, dewpoints are in the 50s, while 40s
are more common further to the west (except in the NM Bootheel).

RAP analysis shows moderate to strong instability behind the
boundary, with MLCAPE values of 1500-2500 J/Kg over parts of
Otero, El Paso, and Hudspeth Counties. However, strong capping
remains in place, as suggested by the lack of significant cu
development on satellite imagery, and supported by RAP analysis
CIN values of -20 to -60 J/Kg.

However, there has been some minor development in the past hour
over parts of southern Hudspeth County and nearby mountains south
of the border, and stronger storms over parts of Presidio County.

A few of the CAMS models which are handling on-going convection
well, notably both the 12Z NAM and GFS-initialized UofAZ WRF runs,
suggest convection will break the cap over Hudspeth County in the
next couple of hours, perhaps aided by outflow from stronger
storms over Presidio County. The models then suggest outflow from
these storms, aided by a further westward push of the backdoor
cold front early this evening, will interact with weak outflow
from sparse convection N and W of ELP and LRU, triggering more
widespread thunderstorms over south-central NM and Far West Texas
early this evening. Given that the wind shift line/prefrontal
trough is sitting over the Rio Grande Valley, this solution is not
entirely far-fetched.

Low level East to SE flow will continue to advect low level
moisture into the region overnight, and by late morning tomorrow
(Wed), PW values look to range from about 1.15 inches in the far
western reaches of the CWA, to around 1.40 inches along and east
of the Rio Grande. The GFS suggests 500mb temperatures around -6
to -7C, increasing instability with SBCAPE values over 2000 J/Kg
east of the Rio Grande, and a weak shortwave trough rounding the
eastern edge of the subtropical ridge during the afternoon. Expect
the usual diurnal trend of orographic showers and thunderstorms,
with weak to moderate capping in the lowlands limiting lowland
thunderstorm development until late afternoon and early evening as
outflow boundaries interact in the lowlands. Convection may be
further aided by the weak shortwave trough. Overall Wednesday
looks like one of the more active days of the season so far.

The overall pattern will remain unchanged on Thursday, with the
subtropical ridge focused off to our west. While the E to SE low
level flow is cut off, plenty of recycled moisture will remain in
place, with PW values ranging from 1.15 to 1.25 inches. Mid-level
temperatures look to moderate somewhat, due to widespread
convection the previous day. Overall thunderstorm chances will be
closely limited by leftover convective debris/stabilization from
the previous day's thunderstorms, but should still be fairly
active.

Similar conditions will persist on Friday, with recycled moisture
remaining in place. As the upper ridge shifts back towards the
Four Corners, we'll end up in E to NE flow aloft. Thunderstorm
coverage still looks to be fairly active, aided by slightly cooler
mid-level temps moving into the area.

Drier and warmer air aloft still looks like it will filter into
the area Sunday and Monday, diminishing overall thunderstorm
chances, but not eliminating them entirely (higher elevations will
still be favored).

Towards mid-week, the crucial details remain fuzzy, but there's a
chance that a trough digging into the west coast and an eastward-
shifting ridge will try to pull up some additional moisture into
some part of the Desert Southwest, but areas west of the
Continental Divide will likely be more favored.

&&

.AVIATION...Valid 28/00Z-29/00Z...
P6SM FEW-SCT080-100 SCT-BKN150-200 through period.  Isolated to
scattered VRB25G40KT 1-3SM TSRA BKN030-040 through the night, then
storm coverage increasing to scattered lowlands to numerous
mountains after 18Z. Winds generally east to southeast 5-15KTS but
variable and gusty near thunderstorms.

&&

.FIRE WEATHER...
Low and mid level moisture has started to move into the region
behind a weak boundary moving westward.  Enough moisture will remain
over the area into the weekend to bring a daily chance for showers
and thunderstorms. The best chances for widespread wetting rains for
the lowlands and mountains looks to be tomorrow. Storms are not
expected to be severe but will have the potential to produce locally
heavy rain and flooding.  Temperatures for the remainder of the
forecast period will be dropping to near normal with minimum
relative humidities remaining above 20 percent for the lowlands and
above 25-30 percent in the mountains. Winds will remain under 15 mph
except gusty near thunderstorms.

&&

.PRELIMINARY POINT TEMPS/POPS...
El Paso                 74  95  71  93 /  40  30  50  10
Sierra Blanca           69  90  67  90 /  30  40  40  10
Las Cruces              70  93  67  92 /  40  30  60  10
Alamogordo              69  95  67  94 /  30  40  40  20
Cloudcroft              53  72  53  71 /  40  70  40  40
Truth or Consequences   71  94  67  94 /  30  50  40  30
Silver City             65  89  62  88 /  20  60  50  60
Deming                  70  96  67  93 /  20  30  60  20
Lordsburg               70  96  67  94 /  20  30  50  20
West El Paso Metro      74  97  71  94 /  40  30  50  10
Dell City               70  93  68  96 /  30  30  40  10
Fort Hancock            75  98  72  96 /  30  30  50  10
Loma Linda              69  88  66  88 /  30  40  50  10
Fabens                  75  96  71  93 /  30  30  50  10
Santa Teresa            71  95  68  93 /  40  20  50  10
White Sands HQ          73  94  70  94 /  40  30  60  10
Jornada Range           69  94  67  93 /  40  30  60  10
Hatch                   70  95  66  94 /  40  40  60  20
Columbus                72  96  69  93 /  20  20  60  10
Orogrande               70  93  68  92 /  30  30  50  10
Mayhill                 58  79  57  81 /  40  70  40  40
Mescalero               56  81  55  81 /  30  60  40  30
Timberon                57  78  55  79 /  40  60  50  30
Winston                 59  87  57  86 /  20  70  50  60
Hillsboro               66  93  63  92 /  30  60  60  50
Spaceport               67  93  64  93 /  40  40  50  20
Lake Roberts            59  89  56  88 /  20  70  50  70
Hurley                  64  91  62  89 /  20  50  60  40
Cliff                   63  98  61  96 /  20  60  50  50
Mule Creek              66  93  65  90 /  20  50  50  50
Faywood                 67  91  64  90 /  20  50  60  40
Animas                  69  97  67  95 /  20  40  60  20
Hachita                 68  96  66  93 /  20  30  60  10
Antelope Wells          68  95  65  92 /  30  50  70  30
Cloverdale              67  90  64  87 /  20  60  70  40

&&

.EPZ WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&

25-Hardiman / 26-Grzywacz