Click here to go to the Western Water Assessment website. Click through for all the cool graphics. Read ‘em and weep if you’re in Colorado. From the website:
January precipitation was patchily distributed across the region; western Colorado, southeastern Utah, and north-central Wyoming ended up wetter than average, with most other areas drier than average After storms in the last week of January roughly balanced out dry conditions the rest of the month, snowpacks remain below-average across Colorado and southeast Wyoming, and near- or above-average in Utah and the rest of Wyoming The January 1 forecasts for spring-summer streamflow call for below-average flows in nearly all basins in the region; the February 1 forecasts that have been released thus far show a similarly dry outlook
The NOAA CPC seasonal climate outlooks, as well as the “SWcast”, continue to show a slight dry “tilt” for late winter and spring precipitation for the southern half of our region, but the one-month outlook for February has a wet tilt based largely on the storms forecasted for the next week
January Precipitation and Temperatures, and Current Drought
January saw a very uneven distribution of precipitation across our region, in both space and time. The first three weeks of January were quite dry, with two systems in the last week generating most of the month’s moisture. Most mountain areas in western and central Colorado ended up with above-average precipitation, as did eastern Utah and north-central Wyoming. Drier-than-average conditions predominated in southern Wyoming and, yet again, in eastern Colorado. The HPRCC Water Year Precipitation map shows that while January aided some areas, most of the region remains drier than average since October 1. Southeastern Colorado is still the driest area in the region, with less than 50% of average October–January precipitation.
Perhaps the most notable aspect of January’s weather was the cold anomaly over most of Utah and portions of western Colorado, with monthly temperatures more than 10°F below average. Intrusions of Arctic air were followed by upper-level ridging and calm winds, leading to persistent surface inversions. Moab, Utah ended up with a record-cold January monthly average of 8.6°F, or 18°F below normal, and more than 5°F below the previous record. In northern Utah, a particularly strong inversion caused a serious air pollution episode from about the 18th to the 26th.
The latest US Drought Monitor, representing conditions as of January 29, shows very little change in drought conditions since January 1. The vast majority of the region is still classified in severe (D2) or worse drought: Colorado, 100% (up from 95%); Wyoming, 86% (unchanged), and Utah, 66% (up from 64%).
Current Snowpack and Streamflows
The dry first three weeks of January saw regional snowpacks decline with respect to the typical trajectory—especially in Colorado, where this slippage was dramatic. But the final, snowy, week salvaged the month for most basins, bringing conditions close to where they were on January 1 in terms of percent of average. The NRCS Current Basin Snowpack map on February 1 shows that Colorado and southeastern Wyoming basins remain well below to below average. In the rest of Wyoming and in Utah, snowpacks are generally near-average or slightly above average. In Utah’s Wasatch Range, the mountain snowpack slipped to about 85% of average even as the urban areas and foothills experienced above-average snowfall, thanks to “upside-down” storms. The February 1 basinwide snowpack for the Upper Colorado River above Lake Powell was 84% of average, compared to 86% of average on January 1.
In the maps of current streamflows in the three states, most gages are ice-affected and not reporting, as is normal for this time of year. The Green River near Greendale, UT gage, was in the 40th percentile, at 81% of the median flow for February 1.
Spring-Summer Streamflow Forecasts
See the previous briefing for details of the January 1 streamflow forecasts for spring-summer 2013. The general outlook for the region is drier than average, reflecting the snowpack anomalies. The next (February 1) streamflow forecast map should be posted by NRCS (and on the Dashboard) around February 10th; we expect no major changes in the regional outlook from the January 1 forecasts. The Colorado Basin River Forecast Center (CBRFC) has released their official February 1 forecasts here; there are slight improvements in the forecasted flows for the San Juan and Uncompahgre basins compared with January 1, but the forecasts are generally lower elsewhere in the Upper Colorado Basin and eastern Great Basin. IMPORTANT NOTE: While NRCS and NOAA continue to collaborate on streamflow forecasts, the forecast values are no longer being strictly coordinated between NRCS and some of the RFCs, including the CBRFC.
Seasonal Climate and Drought Forecasts
The latest monthly Climate Outlooks for February, released on January 31 by NOAA CPC, shows a wet tilt for most of Utah and western Colorado through February, reflecting the weather model guidance showing a tendency towards troughs (= moisture) over that area in the first half of February. It is also consistent with the wet forecast for our region seen in the 5-day QPF for the February 6–11 period. The latest seasonal Climate Outlooks released on January 17 by NOAA CPC continue to show a slight tilt towards drier-than-average conditions for the late winter and spring in the southern portion of our region, with the area of dry tilt covering more of Colorado and Utah than the previous outlooks. The CPC Climate Outlooks continue to show enhanced odds for above-normal temperatures for the winter and spring seasons, consistent with the long-term trend towards warmer conditions. The latest CPC Seasonal Drought Outlook released January 17 projects that the drought conditions across our region will persist, through at least April 2013, with a slight change from previous outlooks, in that some improvement is expected in far northern Wyoming.
The latest PSD Precipitation Forecast Guidance (“SWcast”), released January 23 for January–March 2013 conditions, continues to forecasts a dry tilt in late winter for most of Utah and Colorado, with the strongest tilt towards dry conditions (>10%) in north-central Colorado—though the model skill is marginal in northern Colorado for this season. A modest tilt towards wet conditions is forecasted for far northern Utah. Overall, this dry outlook for Utah and Colorado is mostly unchanged from the forecast made in November, and is consistent with a continued cold North Pacific (PDO-) in conjunction with a warm North Atlantic (AMO+).
As has been the case since last fall, the seasonal forecasts are not being influenced by ENSO, since the ENSO indicators continue to show ENSO-neutral conditions—though tipping most recently towards La Niña conditions—and the models in IRI’s mid-January ENSO Prediction Plume show a consensus towards ENSO-neutral conditions continuing through next summer.