Area Forecast Discussion
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FXUS64 KEPZ 152242
AFDEPZ

Area Forecast Discussion
National Weather Service El Paso Tx/Santa Teresa NM
342 PM MST Fri Dec 15 2017

.SYNOPSIS...
Sunny skies and seasonal temperatures are on tap for Saturday, but
an upper level storm system will bring scattered lowland rain and
high elevation snow showers to the area on Sunday. Higher
elevations of the Gila Region and Sacramento Mountains,
especially above 7500 feet, could see several inches of snowfall
by Monday morning. Drier conditions and a slow warming trend is
expected through the middle of the week, with more unsettled
weather possible late in the week.

&&

.DISCUSSION...
Active pattern is on the near and far horizon, but it`s still a
bit early to get worked up about the things that are over a week
away.

To start with, the upper trough that affected us (barely)
yesterday as closed off an upper low centered over the southern
Gulf of California. It`s about ready to kick out to the NE,
tracking over Big Bend on Saturday, but bringing little more than
some high or mid clouds grazing SE Hudspeth County. For most of
the area, expect seasonal highs with Mostly Sunny skies.

Our next weather maker is a trough currently just off the Pacific
Northwest coast. This system will quickly drop down into southern
California by Saturday afternoon as the ridge over the Great Basin
breaks down. It will almost "replace" the outgoing upper low but
won`t dig quite as far south. By Sunday morning, we should see a
closed 500mb low somewhere around southern Arizona, hopefully
no further south than Puerto Penasco, moving slowly to the east.
There is still an unfortunate amount of variation in the models
and ensembles (GFS Ens and SREF anyway) with the evolution of this
system...which has a direct impact on the QPF amounts.

Here`s what we have moderate-to-high confidence in at this point.
A deep trough with closed upper low moving into southern Arizona
on Sunday, with deep SW flow tapping into some moisture (though
not a super-rich subtropical tap (PW`s get up around 0.60 inches
over us, which about 2x the mean for Dec 15). This will result in
widespread lowland rain showers and higher elevation snow showers
Sunday. Snow levels look to hover between 6500 and 7500 feet in
both the Gila Region and Sacramento Mountains, dropping lower as
precip moves out Sunday night.

QPF amounts are low to medium on the confidence scale. Liquid QPF
amounts look to be in the 0.25 to 0.50 inch range (possibly some
0.75" bullseyes), highest in the mountains with SW upslope flow,
with the Gila favored a little more than the Sacramentos. Snowfall
amounts could be in the 3 to 6 inch range for the highest
elevations of the Sacramento Mountains, 1 to 2 on the west slopes,
around 1 inch on the east slopes (downslope region). Without a
backdoor cold front, we shouldn`t expect to see the lopsided
snow levels. For the Gila, it`s looking like 3 to 6 in the Black
Range and Pinos Altos Range (elevations above 7500 feet), with 1
to 3 inches down to 6,000 feet (highly dependent on timing).

These amounts could easily change with slight variations in storm
evolution, but the risk of lowland snow appears low. The 18z NAM
and 12z ECMWF deterministic runs hint at the upper low really
slowing down over Arizona, limiting Sunday precip to areas near
and west of the Rio Grande until Monday night...but this is an
outlier solution and still unfavored.

In the longer range...still going with drying on Monday with
slightly below-normal temperatures recovering to near normal by
Tuesday, and a few degrees above normal by Wednesday (upper-50s in
the lowlands)

Later in the week, confidence is growing for an "unsettled"
pattern with a high amplitude trough moving into the Great Basin
Thursday. Sharp ridging off the west coast favors an Arctic
outbreak dropping down the Great Plains, with a potentially strong
backdoor cold front pushing into southern New Mexico Thursday
night or Friday morning. There`s a chance this trough could follow
the recent trend of cutting off somewhere in Arizona or Sonora,
and giving us a classic overrunning precip event next Friday or
into next weekend. Snowfall for the lowlands is not impossible,
but despite the 12Z deterministic GFS, it is still far too early
to get excited over this. Lowland snowfall events are almost
always decided by minute spatial and temporal details with various
features (like upper lows and backdoor front), not to mention
variations in temperature and moisture. The amount of skill we (or
computer models) have in reliably resolving such details in the
Day 7 to 10 timeframe is MINIMAL. Given the busy travel time ahead
of Christmas, it is wise to keep abreast of changes in the
forecast, but anyone who posts a snapshot of the 12Z GFS post-
processed snowfall totals for Day 10 deserves a lump of coal in
their stocking come Day 10 morning.

&&

.AVIATION...Valid 16/00Z-17/00Z...
P6SM SKC-FEW250 through period. Winds will be variable under 10KTS
through 18Z then become S to SW at 5-15KTS.


&&

.FIRE WEATHER...
After a cooler day today, temperatures will warm about 3 to 6
degrees for Saturday before cooling slightly as another upper low
develops along the AZ/MX border region. This system will spread
precipitation across the region with lowland rain and mountain snow
likely into at least early Monday. Several inches of snow are
possible in the mountain zones with rainfall amounts of around a
quarter inch.  After this system exits the region early next week,
westerly flow will setup and warm temperatures back to about 5
degrees above normal.  Winds will generally be light during forecast
period with breezy conditions possible Sunday. Another storm system
is expected the later part of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
El Paso                 54  28  56  42 /   0   0   0   0
Sierra Blanca           51  29  55  38 /   0   0   0   0
Las Cruces              50  24  55  38 /   0   0   0   0
Alamogordo              48  25  51  37 /   0   0   0   0
Cloudcroft              44  19  40  26 /   0   0   0   0
Truth or Consequences   50  27  54  34 /   0   0   0   0
Silver City             50  26  50  34 /   0   0   0  20
Deming                  52  22  55  39 /   0   0   0  10
Lordsburg               54  23  57  38 /   0   0   0  30
West El Paso Metro      51  28  55  41 /   0   0   0   0
Dell City               51  25  57  36 /   0   0   0   0
Fort Hancock            53  28  59  38 /   0   0   0   0
Loma Linda              48  26  51  39 /   0   0   0   0
Fabens                  52  23  58  37 /   0   0   0   0
Santa Teresa            50  26  55  39 /   0   0   0   0
White Sands HQ          51  28  54  39 /   0   0   0   0
Jornada Range           50  16  54  34 /   0   0   0   0
Hatch                   53  25  56  37 /   0   0   0   0
Columbus                52  24  56  41 /   0   0   0  10
Orogrande               50  28  53  39 /   0   0   0   0
Mayhill                 47  22  49  31 /   0   0   0   0
Mescalero               45  21  47  29 /   0   0   0   0
Timberon                43  20  43  29 /   0   0   0   0
Winston                 50  14  54  28 /   0   0   0   0
Hillsboro               52  27  56  33 /   0   0   0   0
Spaceport               51  19  52  33 /   0   0   0   0
Lake Roberts            53  12  51  28 /   0   0   0  10
Hurley                  50  18  52  33 /   0   0   0  20
Cliff                   54  19  54  32 /   0   0   0  20
Mule Creek              52  18  52  34 /   0   0   0  30
Faywood                 51  25  52  34 /   0   0   0  10
Animas                  54  20  58  40 /   0   0   0  30
Hachita                 53  22  59  39 /   0   0   0  20
Antelope Wells          52  26  59  39 /   0   0   0  30
Cloverdale              53  24  54  40 /   0   0   0  30

&&

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

$$

25-Hardiman / 26-Grzywacz



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