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000
FXUS64 KEPZ 222103
AFDEPZ

Area Forecast Discussion
National Weather Service El Paso Tx/Santa Teresa NM
303 PM MDT Tue Aug 22 2017

.SYNOPSIS...
Somewhat drier air has moved into the Borderland pushing the
deeper moisture to the east. Enough residual low level moisture
will remain to fuel some isolated thunderstorms this evening
mainly east of the Rio Grande. On Wednesday and Thursday, the
interaction between increasing subtropical moisture, some
disturbances aloft, especially Wednesday night, and a weak push
of easterly surface winds will result in increased shower and
thunderstorm coverage. Again, there will be a risk of locally
heavy rainfall with potential flooding of low lying areas.
Moisture should retreat eastward By Friday and Saturday but
sufficient moisture should will remain for isolated thunderstorms.



&&

.DISCUSSION...
Drier southwest flow at the surface and aloft has moved into the
CWA as evidenced by the water vapor imagery and surface obs.PW
was down to 1.17 inches on the 12Z KEPZ run. Surface Dewpoints
should are generally in the 40`s and 50`s west of the rio Grande
and 60`s east of a ELP-ALM line where most this evenings isolated
convection should take place.

Wednesday and Thursday...Things get a tad more a tad more
interesting as an upper high over Mexico is forecast to drift
north and elongate into a ridge as trough aloft over the western
U.S. erodes the ridge with short wave impulses. This will in
in turn draw in more subtropical moisture into our CWA from
Mexico along with destabilizing our atmosphere. As of now the
03Z-12Z timeframe on Thursday shows the best potential for heavy
rain with capes up to 1300 j/kg and PW`s to 1.3 inches. I would
not call it a backdoor but there also will be an increased push
of surface easterlies (starting wednesday) to enhance the process
with some low level convergence. Nam has it`s greatest UVV in the
03-12Z Thursday timeframe. All 3 major models are in good
agreement with increasing layered moisture from eastern
Pacific/Gulf of California feed. WPC has put southern NMex into a
slight risk for excessive rainfall particularly for later
Wednesday into Thursday thus there will be a potential for some
flash flooding (again). Forecast soundings hit of high cape
(1000-2000 j/kg) with increasing speed shear but weak
directional shear Wednesday into Thursday suggesting a strong
storm of so in this time frame also.

By Friday through the weekend we the forecast continues in that
2-3 day sinusoidal pattern with drier air returning and
convective activity decreasing to to an isolated level. The
Eastern Pacific high eventually builds back up over the Great
Basin by Saturday. Though developing Gulf of Mexico tropical
system is not able to make much inroads west towards us, it does
combine with the upper high to produce the dreaded user
unfriendly northerly flow aloft over the area. Though not adding
much moisture, the northerly flow can often bring down
disturbances or cold pools aloft which can briefly increase a
strong thunderstorm threat.

Finally, it does not appear at this time that the possible
resurrection of Harvey back into a TC of Hurcn state in the Gulf
of Mexico will affect us as it is forecast to hit the Texas coast
around BRO to CPR this weekend then go north and stall and
passably curve back into SE Texas before exiting to the NE. If
true. considerable rainfall and flooding will be most likely in
areas least needing it. If there is any good news here it is
this...should not be our problem.



&&

.AVIATION...Valid 23/00Z-24/00Z...High pressure aloft centered over
the International border will maintain ISOLD-SCT MTN TSRAGS/WND
VRB25G45KT/LCL VIS 1-3 SM/CIGS 030-050 AGL thru 02Z.  ISOLD LOWLAND
-TSRAGS/WND VRB30G50KT/LCL VIS 2-4 SM/CIGS 070-090 AGL thru 03Z.
More widespread storm activity is expected over the mountains aft
23/18Z...under influence from a weak frontal boundary expected to
approach from the east. Winds generally variable under 10KTS through
08z...then shifting east southeast under 10 kts along and east of
the Rio Grande.


.FIRE WEATHER...
High pressure aloft centered over the international border...will
maintain a typical scattered mtn/isold lowland storm distribution
through early this evening. Wednesday and Thursday look more
active. On Wednesday...as a weak back door frontal boundary
approaches and introduces more focused lift over southern NM/far W
TX for more numerous storms. Heavy rain...strong downburst winds
and frequent lightning will be the main impacts from this
activity. On Thursday the upper level low now off the California
coast...will weaken and begin to move northeast into the inter-
mountain west as an open wave. A shortwave aloft ahead of this
feature will move across northern and central NM later in the day.
This is expected to touch off another round of scattered storms
for most areas...with hail possibly more of a threat during
daylight hours Thursday.

Concurrently...the high over area will slowly migrate north while
phasing with a high aloft west of Baja California. Result will be
development of a large area of upper level high pressure over the
southwest states.  Circulation around its eastern periphery will
induce a northerly flow over New Mexico/west TX by this weekend.
This will generally mean a downturn in storm activity...however the
lightning/hail/severe wind threat will go up as a consequence.

Min RH this afternoon will range from the upper 20s SW lowlands...to
lower 50s Sacramento mountains.  Values increase roughly 4-8 percent
each day through Friday...then fall back 7-15 percent by Sunday as
the drier continental air moves south over the region.


&&

.PRELIMINARY POINT TEMPS/POPS...
El Paso                 72  93  69  89 /  20  20  40  30
Sierra Blanca           67  89  64  86 /  20  20  30  30
Las Cruces              68  92  64  87 /  20  20  40  30
Alamogordo              66  90  64  86 /  20  40  40  40
Cloudcroft              50  69  50  64 /  30  50  60  60
Truth or Consequences   68  91  64  86 /  20  30  30  40
Silver City             58  85  57  81 /  20  40  40  30
Deming                  66  92  63  87 /  20  20  40  30
Lordsburg               68  92  63  86 /  20  30  40  30
West El Paso Metro      72  93  68  88 /  20  20  40  30
Dell City               69  91  66  89 /  20  30  30  30
Fort Hancock            72  93  69  90 /  20  20  40  30
Loma Linda              65  88  62  84 /  20  20  40  30
Fabens                  72  94  68  90 /  20  20  40  30
Santa Teresa            69  93  65  88 /  20  20  40  30
White Sands HQ          69  91  65  86 /  20  20  50  40
Jornada Range           67  92  64  86 /  20  20  50  40
Hatch                   68  94  65  87 /  20  30  40  40
Columbus                69  92  65  87 /  20  20  40  30
Orogrande               69  91  66  86 /  20  30  40  40
Mayhill                 55  77  54  74 /  30  50  50  60
Mescalero               54  78  54  74 /  30  50  50  60
Timberon                55  77  53  73 /  30  50  60  60
Winston                 58  83  54  80 /  20  60  50  50
Hillsboro               62  88  59  84 /  20  50  50  50
Spaceport               67  91  64  85 /  20  30  40  40
Lake Roberts            57  84  52  80 /  20  40  50  50
Hurley                  61  87  58  83 /  20  40  40  30
Cliff                   61  90  59  84 /  20  40  40  30
Mule Creek              61  89  59  83 /  20  40  40  30
Faywood                 62  87  58  84 /  20  40  50  30
Animas                  67  92  63  86 /  20  30  40  30
Hachita                 66  91  62  86 /  20  30  40  40
Antelope Wells          66  91  62  86 /  20  30  40  30
Cloverdale              62  87  60  84 /  20  50  40  30

&&

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

$$

20/22  NOVLAN / TRIPOLI



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