Area Forecast Discussion
Issued by NWS Albuquerque, NM

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FXUS65 KABQ 222305 AAA

Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
505 PM MDT Sat Jul 22 2017

Dominant upper high center to continue regrouping over the Four
Corners/Great Basin. Sct convection which developed over the
northern and western higher terrain will drift to the west and south
and into the lower elevations while wdly sct tstms over the ern
plains track to the west. Outflow boundary collisions will also
result in erratic cell motion. In addition, short term forecast
models indicate a surface boundary originating from convection over
the north central/northeast to track southward through most of the
ern plains and central portion of NM by 23/09Z. Mts occasionally
obscured in brief MVFR cigs/vsbys in tstms, the stronger of which may
contain small hail and wnd gusts to 45kt. Light showers and isold
tstms to linger aft 23/06Z.


.PREV DISCUSSION...311 PM MDT Sat Jul 22 2017...
Showers and storms with locally heavy rainfall will continue over NM
through the weekend as a weak frontal boundary sags south through
the state. There is an elevated risk of flash flooding with this
pattern along and west of the central mountain chain into Sunday.
High pressure will rebuild over eastern NM for most of next week and
focus the moisture plume over northern and central NM. Not much
change is expected over the state with daily rounds of showers and
thunderstorms, especially around the high terrain. Any direct hit
from storms will be capable of producing heavy rainfall and possible
flash flooding. Temperatures in this pattern will be close to normal.


As can often happen with convective season, there is another shift
in model trends today. The past two or three model cycles favored an
H5 dome centered over NM all of next week with a weakened moisture
plume thinned out over the state. Now, several 12Z runs have more
abundant deep-layer moisture centered over NM while the H5 ridge
drifts from west TX into eastern AZ through next week.

But first, the boundary that models struggled with the past few days
has come to fruition across northern NM and is serving as the focus
for showers and storms with locally heavy rainfall. The 12Z WRF/NAM
and latest HRRR/RAP have caught on and show a robust convectively
aided boundary shifting southward and becoming stationary along the
I-40 corridor overnight into Sunday. Meanwhile, a 35kt speed max at
300mb over the Four Corners region shifts southeast across northern
NM. The main point of uncertainty is how much a 500-400mb layer dry
slot limits convection in the same area where low level convergence
is strongest. Despite this wrinkle in confidence, based on near-term
and hi-res model solutions have raised PoPs along the I-40 corridor
thru Sunday with mention of heavy rainfall. PWAT values are shown to
rise above 1.2" for many areas so the potential for flash flooding
will continue into Sunday.

As noted above, the 12Z model suite has trended wetter again next
week. The H5 ridge builds into eastern NM Monday while an H5 low
center gathers along the CA coastline. A more favorable pattern for
deep-layer, moist southerly flow develops across the area, which has
been lacking on most days this season. This will allow the potential
for flash flooding to continue Monday. The H5 center slowly drifts
west across central NM Tuesday and Wednesday then into AZ Thursday.
This will gradually shift the steering flow throughout the week but
with overall slow storm motions. PWAT values rise to as high as 1.5"
at KABQ Thursday per the 12Z GFS, which would be centered on our
climatological peak for the season. If in fact the wetter pattern
materializes then locally heavy rainfall with recycling of low level
moisture will continue each afternoon through at least next weekend.



Afternoon storms have fired up early today over the northern and
western high terrain. Storm motion will be slow and generally to the
W/WNW through this evening. A mid-level layer of dry air has so far
acted to supress and delay convection over much eastern and central
NM until later this evening. A backdoor sfc bdry will slide S over
the NE NM tonight, with the chance for overnight storms firing up
during its passage as well as producing a modest east gap wind
through the cntrl RGV. The backdoor front also looks to collide with
a remnant sfc bdry currently parallel with I-40, sparking overnight
storm activity over the eastern plains mainly S of I-40.

Sunday will see increased coverage of afternoon storm activity
firing off the higher terrain before moving to lower elevations.
Near record level PWAT values 1.25"-1.40" will be present across the
forecast area, along with Td`s in the mid-upper 50s. Light steering
flow will create ripe conditions for flash flooding potential.

The upper high shifts east over the TX/OK panhandle early next week
with continued rounds of afternoon convection, mainly favoring
western and central NM. With decent monsoonal moisture remaining
over the area, showers/storms will likely persist late overnight
into the early morning hours. A slight downtrend in storm coverage
is expected by mid-week as the upper high transitions back west.
With both the GFS and ECM hinting at another inverted trough passing
to the south of NM, look for an uptick in storm coverage by the end
of next week into next weekend.

Daytime highs will be at or near average through the forecast area,
trending below average where increased cloud coverage from storm
activity is expected. Vent rates trend down as the upper high
transitions back over NM mid-late week, with poor to fair across
much of central NM.



Flash Flood Watch until 9 PM MDT this evening for the following
zones... NMZ508>515-517-526-527.


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