Flash Flooding in New Mexico, July 21, 2022

Area Forecast Discussion
National Weather Service Albuquerque NM
1146 AM MDT Thu Jul 21 2022

.AVIATION...
18Z TAF CYCLE
High pressure retrograding further west will bring SHRA/TS to the
nrn and sw mts this afternoon, as well as hot temperatures in the 90s
and low 100s. Given relaxed flow aloft, convective activity will
continue to have slow and erratic motion in addition to the typical
hazards of small hail, gusty downburst winds, and locally heavy
rainfall. Prevailing motion will move storms slowly south to
southeast at around 10 kts. Any direct hits to terminals will be
capable of MVFR vsbys due to heavy rain. Convective activity will
persist into the late evening hours before tapering off overnight.

12

&&

.PREV DISCUSSION...324 AM MDT Thu Jul 21 2022...
.SYNOPSIS...
Daily rounds of showers and thunderstorms are expected for the next 7
days with a continued risk of locally heavy rainfall. Scattered to
numerous storms are forecast to track to the south and southeast off
the high terrain again today. Storm motions will become slow and
erratic Friday and Saturday, then cells will track more to the north
and northeast during the first half of the coming work week as a
more traditional monsoon flow sets up. High temperatures will fall a
few to several degrees today from yesterday's hot readings, but
highs will remain a few to around 9 degrees above normal through the
end of the week. Temperatures are forecast to fall below normal over
northern, central, and especially western areas during the first half
of next week, when the risk of locally heavy rainfall will increase.

&&

.DISCUSSION...
SHORT TERM...(TODAY THROUGH FRIDAY)...
Today, the upper high will remain parked over northern AZ with
geopotential heights reducing by 2-4 decameters across NM, and this
will allow temperatures to cool a couple to a few degrees in most
central to eastern zones. This will not be the case over the
northwest plateau that will be closer to the dome of high pressure
and hence hotter with triple digit temperature readings expected
again. Therefore, another Heat Advisory will be issued for this lone
zone. Dry air will continue to wrap into the northwestern quadrant
of NM, where a dearth of storms is expected. The best moisture
across the state will be found along and east of the central
mountain chain where rising PWATs of roughly 1.0 to 1.2 inch will be
common. This moisture combined with less subsidence from the weaker
presence of high pressure will make the eastern half of NM a favored
area for storms, initiating along the high terrain before eventually
expanding to some of the high plains and regenerating along
mesoscale cold pools in these lower elevation areas. With the Sangre
de Cristos being the prime initiation point, and cells drifting
south southeastward into a steady low level inflow from the south
southeast, it seems prudent to issue a Flash Flood Watch for the
eastern slopes to account for Hermits Peak-Calf Canyon burn scar
flooding possibilities. High moisture will be present over the Gila
and southwestern high terrain where a secondary focus for storms is
expected, but confidence in any flooding is lower there. High
resolution models and CAMs indicate the Jemez could also see a
scattered cells too this afternoon, but storms will likely have
difficulty filling into the middle Rio Grande valley again.

The eponymous upper high will wobble closer to it regional Four
Corner’s origin on Friday with minimal changes in the height fields
over NM. Therefore, the heat will persist over the northwestern
plateau zone which looks to be the hot spot in the forecast area
with remaining zones not trailing too far behind. The spatial
distribution of moisture will not alter too much on Friday with the
northwestern zones remaining dry. Numerous storms are expected to
initiate over the southwestern, south central and northern mountains
Friday afternoon with isolated to scattered cells being common in
most remaining zones (outside of the northwest).

52

LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)...
Scattered to numerous showers and thunderstorms will redevelop each
afternoon and evening this weekend, favoring the east slopes of the
central mountain chain westward. The 500 mb high pressure center is
forecast to weaken some this weekend while shifting gradually
eastward from over the Four Corners Friday night to over OK and AR by
Sunday night. Some models also depict a somewhat moist backdoor
front dipping into northeast areas on Saturday night. PWATs are
forecast to climb some this weekend in the process, generally varying
around 0.8-1.20 inches, which will increase the risk of locally heavy
rainfall. Storm motions will be slow and erratic until Sunday, when
the upper high may shift far enough east for general cell movement
toward the northwest and north across the forecast area. After
another hot day Saturday with high temperatures a few to around 10
degrees above normal, readings are forecast to fall a few to around 7
degrees over all but the southeast plains on Sunday.

A more traditional monsoon moisture stream is forecast to track north
and northeastward mainly over western and north central NM during
the first half of the coming work week as the main upper high remains
centered east of NM, and a weaker high pressure lobe forms over the
Great Basin. Models depict some embedded disturbances tracking
northward within the monsoon flow enhancing instability at times,
especially along and west of the continental divide. The NBM depicts
some storms spreading over central and northeast parts of the
forecast area each day as well, with the southeast plains least
favored for precipitation. PWATs are forecast by the GFS to climb
around 1-1.3 inches Monday and Tuesday, when there will be the
greatest risk of locally heavy rainfall and flash flooding. With all
the moisture in place, high temperatures are forecast to fall from a
few to around 8 degrees below normal each afternoon during the first
half of the work week, except for readings a few to around 8 degrees
above normal on the far eastern plains.

44

&&

.FIRE WEATHER...
High pressure will stay in northern AZ today before moving into the
Four Corners on Friday and eventually over the Colorado-New Mexico
border by the weekend. This will keep drier and hotter conditions in
place over northwestern NM today and Friday where high Haines
indices and low afternoon humidity of less than 15 percent will be
present. Elsewhere, scattered areas of wetting rain will be common,
especially along the central mountain chain and southwestern
mountains with lesser chances in the eastern plains and even more-so
into the Rio Grande valley. The moisture will slowly start to feed
into northwestern zones this weekend and into early next week while
drier air begins to slide southward into the plains. Amid the dry
conditions, the plains will stay hot into next week, but the added
moisture will act as a moderator to the temperatures in central and
western zones. Overall, prevailing wind speeds will stay light to
moderate over the next few days, but thunderstorm outflows can of
course produce abrupt disruptions with brief and locally strong
gusts. Good to excellent RH recovery is expected to continue each
night and early morning period, even in areas that will succumb to
lower afternoon humidity.

52

&&

.ABQ WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM MDT this evening for the following zones...
 NMZ201.

Flood Watch until 10 PM MDT this evening for the following zones...
NMZ215.

&&