Area Forecast Discussion
Issued by NWS Midland/Odessa, TX

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FXUS64 KMAF 222301

601 PM CDT Fri May 22 2015

See aviation discussion below.


A strong upper level storm system across Arizona is expected to
produce occasional showers and thunderstorms through the TAF
period with occasional MVFR conditions. Southeast winds of 10 to
25 mph and gusty tonight is expected to become south to southwest
by mid Saturday morning.


.PREV DISCUSSION... /ISSUED 254 PM CDT Fri May 22 2015/


Severe thunderstorms are expected to develop over southwest Texas
this afternoon, with more thunderstorms developing late tonight over
the Guadalupe Mountains or southeast New Mexico Plains, if not the
Upper Trans Pecos.  Heavy rainfall will be spotty over southwest
Texas this afternoon/evening, but looks to become more widespread
over the northern CWA tonight, and over the Permian Basin and
Lower Trans Pecos Saturday when another round of convection
appears to be in the offing. Severe storms will also be possible

A large upper low over southern California today will head east this
weekend with southwest flow aloft propagating several shortwave
troughs over the region.  One such shortwave trough just east of the
northern Baja Peninsula will provide a modicum of lift this
afternoon and evening over southwest Texas where SBCAPES will rise
to around 2500 J/Kg over the higher terrain and along a
strengthening surface trough.  Expect thunderstorms to develop over
the higher terrain with 0 to 6Km bulk shear of 30-40kt and steep mid
level lapse rates of 7-8C/Km resulting in organized severe
thunderstorms in and near the Davis/Glass Mountains, Stockton
Plateau, Big Bend region and into the Lower Trans Pecos tonight.
Large hail and damaging winds will be the primary threats, although
a tornado or two is not out of the question.  Storms could
conglomerate into a small MCS and head east/southeastward across the
Lower Trans Pecos tonight.  Heavy rainfall will be a concern, but
convection is not expected to be widespread and localized flash
flooding will be possible.

This evening and later tonight, more thunderstorms are expected to
develop over the Upper Trans Pecos and southeast New Mexico.  A low
level jet will strengthen over the area due to height falls ahead of
the approaching upper low, and provide a modestly unstable airmass
to feed into a  developing cluster of storms over the Guadalupe
Mountains and southeast new Mexico Plains, if not over the Upper
Trans Pecos.  Shortly after convective initiation, instability
and shear will be conducive for organized thunderstorms, and along
with steep mid level lapse rates spreading over these areas, result
in storms capable of large hail, damaging winds, perhaps a tornado
and locally heavy rainfall.  Think these storms will head east/
northeastward, along with the warm front, and move into the northern
Permian Basin as they cluster into another MCS late tonight.  PWaTs
will ramp up to near 1 inch over southeast New Mexico tonight and
closer to 1.5 inch over the northern Permian Basin.  Think if a
complex develops, heavy rainfall could result in flash flooding,
especially over Lea County and the northern Permian Basin, where
there has been heavy rainfall recently.  Since storms could develop
off the Guadalupe Mountains, think Eddy county could also receive
heavy rainfall early on.  Despite Eddy County not having widespread
heavy rainfall recently, will still include them in the Flash Flood
Watch tonight due to high precipitable water, and heavy rainfall

Convection could still be under way Saturday morning over the
northern CWA.  Think the atmosphere will destabilize along and east
of a surface trough, which will reside over the western CWA Saturday
afternoon, as temperatures start to return to closer to normal
values.  Then we could see another round of convection Saturday
afternoon as the base of the upper low extends well south into the
region, enhancing lift over the region into the evening.  Convective
initiation may be altered depending on how widespread convection is
tonight, but will still have to carry a good chance to numerous
thunderstorms in the forecast due to increased synoptic scale lift
over the region.  Some of these storms could be severe too as shear
and lapse rates will be favorable again.  Heavy rainfall will again
be of concern, especially over the western Low Rolling Plains,
central/eastern Permian Basin and Lower Trans Pecos where PWaTs rise
to 1-1.5 inch, or near 2 standard deviations above normal.  Another
cluster of storms could form Saturday night over these areas with
training of thunderstorms enhancing heavy rainfall potential.  Will
go ahead and include all of these areas in the Flash Flood Watch,
which will likely have to be adjusted later tonight, if not again
Saturday afternoon.  Convection may continue Saturday night over the
Permian Basin and Lower Trans Pecos, so the FFA may have to be

Sunday may be a down day as the upper low ejects into the northern
U.S. Plains.  However, another lobe of energy will wheel around the
southwestern periphery of the departing upper low and head for the
region.  Therefore, will include more thunderstorm chances over the
forecast area Monday as this shortwave trough nears the region.
Moisture will spread northwestward into the region, and along with
near normal temperatures, promote an unstable atmosphere along a
sharpening dryline and the potential for more severe thunderstorms
Monday and Monday night.  The ua trough will pass by Tuesday, but
yet another ua trough will deepen over the western ConUS and head
east, so thunderstorm chances could increase again Tuesday over the
east, then further west Wednesday.  Temperatures should be near
normal throughout the extended.


NM...FLASH FLOOD WATCH through Saturday afternoon FOR THE FOLLOWING
     ZONES... Central Lea County...Eddy County Plains...
     Guadalupe Mountains of Eddy County...Northern Lea County...
     Southern Lea County.

TX...FLASH FLOOD WATCH through Saturday afternoon FOR THE FOLLOWING
     ZONES... Andrews...Borden...Crane...Dawson...Ector...
     Mitchell...Pecos...Reagan...Reeves County and Upper Trans




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