Area Forecast Discussion
Issued by NWS Albuquerque, NM

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FXUS65 KABQ 211743 AAB

Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
1143 AM MDT Fri Jul 21 2017

Two distinct mesoscale vortices along the NM/AZ border will have a
large influence on the focus for convective development today. SHRA/
TSRA already developing over the high terrain will increase thru 20Z
and become fairly widespread along and west of the Cont Dvd thru at
least 02Z. Storm motions will be generally toward the north around
10kt. The central mt chain will also see SHRA/TSRA before tapering
to SHRA thru the evening. Storms will produce gusty/erratic outflow
winds and any direct hits will produce brief MVFR cigs/vsbys from
heavier rainfall. Precip may linger well into the evening west of
the Rio Grande Valley before tapering to mid level cloud decks thru
sunrise Saturday. The eastern plains will remain mostly cloud free
with very hot temps.



.PREV DISCUSSION...310 AM MDT Fri Jul 21 2017...
High pressure will linger in a weakened and evolutionary state east
and northwest of New Mexico today. Temperatures will run slightly
below normal in western New Mexico and slightly above in eastern
parts of the state while thunderstorms favor the west central,
southwestern, and south central mountains. Increasing thunderstorms
are expected over the northern mountains of New Mexico Saturday with
an active storm pattern then spreading to many remaining areas of the
state into Sunday and Monday. Locally heavy rainfall will be
possible, as storms move very slow over the next few days.


Upper level winds will be very light across NM today as high pressure
undergoes an imbalance with a new, but very weak, centroid starting
to take shape northwest of the Four Corners. A modest flux of
subtropical moisture began to invade south central and southwestern
portions of NM yesterday, and this will inch a bit farther north
today. Attention will also be turned toward Colorado where a weakness
in the height fields, and perhaps a deformation zone will set up and
initiate a healthy swath of convection over the Rockies just north
of NM. This could produce a relatively deep mesoscale cold pool that
could be a focal point for new convection tonight and more-so into
Saturday. Otherwise, for this afternoon expect temperatures to be
within 3 to 5 degrees either side of average for mid to late July
with the eastern zones running slightly above normal and the west
hovering just beneath.

As alluded to above, the convectively driven cold pool/outflow from
Colorado should drive a notable wind shift into north central to
northeastern NM on Saturday with new and presumably vigorous storms
initiating as it propagates southward. This will be an area of
concern for locally heavy rainfall. At this time, have not opted for
a flash flood watch, but as things begin to evolve tonight, there may
be high enough confidence to issue one for some north
central/northeastern zones Saturday and possibly in central to east
central zones Saturday night. Not to be forgotten, the southwestern
and south central mountains will still have ample subtropical
moisture to work with as PWATs hover in the 1.1 to 1.3 inch range
which would roughly be in the 85th to 95th percentiles. Temperatures
will take a drop of a few degrees in north central to northeastern
zones where the wind shift and attendant convection will first hit.

As the wind shift sags farther south over NM on Sunday, forecast
models peg the northeastern to east central zones with hefty QPF.
Through this time, the upper high will encompass the NV/UT/AZ
vicinity, and steering flow will be light with slow-moving storms
keeping the heavy rainfall forecast justified. The high PWAT
environment will continue to reside southwestward into the Gila,
Mogollon Rim, and lower Rio Grande where decent rains will also be
possible. With prevalent cloud cover and widespread precipitation,
temperatures on Sunday would drop a couple to a few more degrees in
many zones, falling most just below normal.

By Monday, the high will leave the Colorado River basin and shift
east, somewhere between the Four Corners and the Rockies. While
winds aloft will remain light, the predominant surface component
would be a southerly one for much of western and central NM. This
would keep boundary layer moisture intact, possibly with a slightly
better influx of moisture into middle parts of next week as the high
nudges a bit farther east toward the front range.



Favored area for afternoon thunderstorms will once again be across
western NM today. Scattered to numerous thunderstorms spread areawide
over the weekend as the Four Corners high redevelops over the
southern Great Basin, resulting in a moist southeasterly low level
flow and north to northeasterly flow aloft. Both GFS and ECMWF
continue to keep scattered convection going well into Sunday night.

Four Corners upper high lives up to its name Monday, shifting ewd
over the quad-point in response to a closed low moving newd through
northern CA. Low level flow remains moist sely with a near to
possibly above average crop of storms most areas Monday afternoon
and evening. Both GFS and ECMWF indicating a downtrend in activity
Tuesday as the upper high shifts ewd over northeast NM. GFS is
generating widespread nocturnal convection Tuesday night, seemingly
due to upper level stretching (deformation) but it seems overdone.
Models then elongate the upper high over the state Wednesday and
Thursday for perhaps below average thunderstorm coverage. The low
levels will remain plenty moist both days, however, resulting the
potential for heavy rain given slow storm motion.

GFS and ECMWF differ on the position of the upper high beyond
Thursday but both models keep low level moisture advection going
either from the east or southeast for near average rounds of
thunderstorms each afternoon and evening through next weekend.
Temperatures are expected to be near to slightly below average for
late July through next weekend.





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