December 10, 2013

Highlights

  • A major storm on a southerly track in late November led to much-above-average monthly precipitation for southeastern and west-central Utah and western and south-central Colorado.
  • Snowpacks are above normal across nearly all of the three-state region, with the wettest basins (>140% of median) in northern Wyoming, southern Utah, and the southern half of Colorado, and the driest basins (80–100% of median) in northern and central Utah and far southwestern Wyoming.
  • The NOAA CPC climate outlooks show a wet tilt for Wyoming over the next three months, with a slight dry tilt for southern Colorado and Utah for late winter (January–March). The NOAA PSD ‘SWcast’ is more pessimistic, showing a dry tilt for most of Colorado and Utah for late winter.                                  

 

Click on the thumbnail images in the text below to bring up the full-sized graphic
 

November Precipitation and Temperatures, and Current Drought

While the storm tracks in October favored the northern part of our region, in late November a major storm took a southerly path, resulting in above-average precipitation for the month  in southeastern and west-central Utah, and in western and south-central Colorado. Nearly all of Wyoming, northern Utah, and eastern Colorado were drier than average. The mountain areas in Colorado and in southern Utah generally received above-average precipitation.  

Temperatures in November were slightly warmer than average, by 0–2°F, across most of the region except for those areas with the most precipitation, which were slightly cooler. (The still-lingering severe cold wave that moved into region starting December 2–4 will be covered in the January briefing.)

The latest US Drought Monitor, representing conditions as of December 3 , shows improvement since early November in areas of southern Utah (from D1 to D0) and southwestern Colorado (D0 to drought-free) that received much-above-average precipitation in November. The proportion of the region in D2 or worse drought remained steady, with Utah at 16%, Colorado at 12%, and Wyoming at zero.

Snowpack
The Current Basin Snowpack map from NRCS  indicates above-normal SWE in nearly all basins in our region—a welcome change from early December conditions in the previous two winters. The largest positive anomalies, with over 140% of median SWE for the date, are in northern Wyoming, southern Utah, and the southern half of Colorado, reflecting the very wet October in Wyoming, the wet November in the southern mountains, and a generally wet start to December. Snowpacks are below normal in several basins in northern and central Utah and far southwestern Wyoming, but no basin has less than 80% of median SWE as of December 9.

Current Streamflows

The maps of current streamflows for Colorado , Utah , and Wyoming show an increasing number of ice-affected gages with no data, and other data may be unreliable as the cold wave of early December is affecting lower-elevation gages unusually early. The Colorado River near Cisco, UT gage was just beginning to freeze up on December 6, with flows in the 44th percentile (96% of median flow).

Seasonal Climate and Drought Forecasts

The latest monthly Climate Outlook released on November 30 by NOAA CPC shows a wet tilt for precipitation for Wyoming for December , but no tilt elsewhere. The seasonal outlooks released November 21 show a slight tilt towards wetter conditions for most of Wyoming, but no tilt elsewhere in the region, for the December–February period . For the January–March period, a slight dry tilt is shown for southern Utah and Colorado . The latest CPC Seasonal Drought Outlook released November 21  projects that most of the areas of drought conditions (D1 or worse) in our region, mainly in Utah, will persist through at least February, except for improvement along Utah’s Wasatch Front and in east-central Wyoming.

The PSD Precipitation Forecast Guidance ("SWcast") released November 13 for January–March 2014  shows a dry tilt over nearly all of Utah and Colorado, with the strongest dry tilt (-10%) over north-central Colorado. Even so, the non-ENSO indicators in the Pacific Ocean, and in the Atlantic Ocean, are not as suggestive of drought as they were last year at this time.

The experimental January 1 SWE forecast for Colorado released in early October has the median (50th percentile) forecast  calling for above-average January 1 snowpack (109–117% of average) for all basins except the Yampa (93%) and Rio Grande (98%).

ENSO indicators   are still showing ENSO-neutral conditions, though with a warming trend over the past few months.The models in IRI's mid-November ENSO Prediction Plume once again indicate a consensus towards ENSO-neutral conditions continuing through the winter, though both the dynamical and statistical models are tending towards the warm side of neutral, with several models calling for El Niño conditions by spring.

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