Flood Potential Outlook
Issued by NWS Albuquerque, NM

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Probabilistic Hydrologic Outlook
National Weather Service Albuquerque NM
1055 AM MST Thu Mar 1 2017

...NORMAL FLOOD RISK FOR THE CANADIAN RIVER BASIN...

...BELOW NORMAL SPRING FLOOD RISK EXPECTED OVER THE REMAINDER OF
NORTHERN AND CENTRAL NEW MEXICO...

...EXISTING CONDITIONS...

To date, the main story of the 2017-2018 Water Year over the
Southern Rockies has been one of La Nina and drought. La Nina
conditions developed during Fall 2017 which established a dry
weather pattern over the Southern Rockies. This dry pattern has
produced seasonal precipitation totals well below normal over the
majority of New Mexico.

The 2016-2017 Water Year was very beneficial for New Mexico with
above normal snowpack values during the winter and a robust monsoon
season. This surplus allowed for the recharge of soil moisture
conditions throughout most of the region and an increase in
reservoir storage from previous seasons. As La Nina developed,
precipitation came to a halt in mid-October 2017. As the 2017-2018
Water Year has progressed, the impacts of La Nina have continued
with well below normal precipitation totals. This has been
especially true of the mountain regions that receive the bulk of
their precipitation during the winter season. Simultaneously,
temperatures have been above normal for the water year, leading to
increased evapotranspiration rates and water demand. Over portions
of the Eastern Plains, soil moisture in the upper layers continues
to decrease, thus erasing the beneficial late monsoon burst.

The weather pattern has become more active since mid-February as the
Madden-Julian Oscillation has produced a short term pattern change.
This has provided a much needed burst of precipitation over the Land
of Enchantment, but 90-120 day departure from normal values remain
low at near record or record levels.

...PRECIPITATION...

The 2017-2018 Water Year had a very active start over much of New
Mexico with a robust monsoon burst that produced flooding over
portions of the Pecos and Middle Rio Grande Valleys in early
October. However; the western one-third of New Mexico missed most of
the active monsoon and saw below normal precipitation values by the
end of the 2016-2017 Water Year. By mid-October, the stereotypical
pattern of La Nina began to appear over the Southern Rockies with a
sudden decrease in precipitation. This trend has continued through
the start of meteorological spring with several weather stations
seeing the driest water year on record. Overall, for the last 90
days, most weather reporting stations have received less than 25% of
their normal precipitation.

The most impacted regions have been the mountain areas and the
Eastern Plains of New Mexico. Areas of the Eastern Plains have seen
less than 20% of their normal precipitation for the last 90 days.
Percent of normal values are equally as low over portions of the
middle and upper Rio Grande Valley as well as the Four Corners
region.

In the shorter 30-day time frame, the recent pattern shift has
produced some above normal precipitation anomalies for portions of
the lower Rio Grande Valley. This is primarily due to a single
weather system in mid-February which produced widespread totals of
0.40-0.50 with some localized totals slightly over 1.00. Normal
monthly precipitation during this time for this region is in the
0.35-0.50 range, thus short term percent of normal values are
skewed when compared to long term deficits.

...SNOWPACK...

In a typical year, mountain areas in New Mexico tend to see the
majority of their precipitation during the winter in the form of
snow. As La Nina conditions have settled firmly over the region,
snow water equivalent (SWE) values for basins that impact New Mexico
are below normal. In Colorado, the headwaters of the Rio Grande, San
Juan, and Animas basins are nearing 60% of normal. In New Mexico,
most basins are less than 50% of normal with the Rio Chama and Rio
Hondo basins nearing 50-60% of normal SWE. The highest SWE for New
Mexico is in the Rio Hondo due to a single storm event and the fact
the basin is nearing its climatological peak.

Climatologically, basins in southern New Mexico tend to see their
peak SWE values by early-March while basins further north reach
their climatological peak later in March or the first half of April.

...RESERVOIR SUMMARY...

Due to the above normal runoff and precipitation in the 2016-2017
Water Year, reservoir conditions throughout the state are in fair
condition. Many reservoirs (especially on the Pecos River) benefited
from the late monsoon burst, which helped to bring reservoirs to
their seasonal average levels. Navajo Dam is near normal storage
with the Rio Grande below normal, but above recent seasonal trends.
All reservoirs in New Mexico have adequate flood storage space.

Of note, long term averages for reservoirs use data from the
19812010 period. During this time, reservoirs along the Rio Grande
had higher storage values due to a wetter period that impacted the
first half of the 30-year period. Therefore, the 30-year average is
statistically skewed to a higher value and may not be reflective of
reservoir storage trends for the previous 15 years.

...STREAMFLOW CONDITIONS AND RUNOFF FORECASTS...

Streamflow conditions over northern and central New Mexico are
reflective of the wet 2016-2017 Water Year as well as the recent
hydrometeorological trends. Natural flowing basins in the western
one-third of New Mexico have mostly experienced below-normal
streamflow conditions due to the below normal monsoon season. Moving
eastward, most natural flowing basins in the remaining two-thirds of
the state have trended above normal with regards to streamflow.
However; as the lack of precipitation and above normal temperatures
have persisted, the overall trend for natural basins has been
downward as the abundant soil moisture from the previous water year
has been exhausted.

NWS River Forecast Centers, in conjunction with our partners in the
NRCS, USACE, and the USBR, produce seasonal streamflow forecasts for
selected river locations and basins in New Mexico. These forecasts
are based on hydrologic conditions as of the first of the month and
may not reflect current trends and forecasts.

Overall, current seasonal runoff forecasts are below normal for all
rivers within New Mexico. This is based on the available SWE within
the river basins and climatologically-expected conditions at runoff.

...DROUGHT...

Drought over New Mexico has continued to develop over the last
several months with virtually all of the state in some state of
drought on the US Drought Monitor. Most of the state is in Severe
Drought (D2) with portions of the Northern Mountains, the Four
Corners, and Catron County in Extreme Drought (D3). The seasonal
drought outlook issued by the NWS/Climate Prediction Center
indicates that drought is likely to persist through Spring 2018.

The drought status for New Mexico is re-evaluated weekly and can be
found at the National Drought Mitigation Center website at
http://droughtmonitor.unl.edu.

...CLIMATE OUTLOOK...

The NWS/Climate Prediction Center anticipates that La Nina
conditions will continue through early Spring 2018 and will begin to
return to an ENSO-Neutral condition by late Spring 2018. Climate
outlooks for March through May are reflective of the expected
impacts of La Nina.

The temperature outlook for March through May for all of New Mexico
as well as the Southern Rockies indicates that above normal
temperatures are likely. Precipitation outlooks are typical of a
waning La Nina with normal to below normal precipitation likely.

These outlooks are issued monthly with the next outlook to be issued
on March 15th. Outlooks can be found at the NWS/CPC website at
http://www.cpc.ncep.noaa.gov.

SPRING FLOOD OUTLOOK

Taking into consideration of all current hydrometeorological
factors, most basins in northern and central New Mexico have a below
normal risk of spring flooding. For the Canadian River basin, the
flood risk this year is normal.

Spring flooding related to snowmelt is uncommon in New Mexico and
the low snowpack to date and expected below normal precipitation
through Spring 2018 are the primary factors in this assessment.
The Canadian River typically does not see flooding due to spring
runoff and normally experiences flooding related to heavy rainfall,
thus the normal flood risk is expected.

The NWS Albuquerque Hydrologic Service Area (HSA) is serviced by
three River Forecast Centers: West Gulf RFC (Fort Worth, TX),
Arkansas-Red Basin RFC (Tulsa, OK), and the Colorado River Basin RFC
(Salt Lake City, UT). These RFCs issue a variety of hydrologic
forecast products during the year. Further products and current
information can be found at the following locations:

https://www.weather.gov/wgrfc https://www.weather.gov/abrfc
https://www.cbrfc.noaa.gov

You can also find additional weather and water products and
forecasts at the NWS Albuquerque website at:

https://www.weather.gov/abq

For questions or comments about this outlook, you can contact Royce
Fontenot, Senior Service Hydrologist, at 505-244-9150 x 228 or via e-
mail at royce.fontenot@noaa.gov.

$$

54/Fontenot



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