Hydro-Climate Dashboard

Severe Thunderstorms, Heavy Rainfall and Dangerous Heat

Severe thunderstorms are expected today and Friday from the upper Midwest, central Great Lakes into the Ohio and mid-Mississippi Valley's. In addition, heavy rainfall threat increases on Friday across the Ohio Valley. Meanwhile, early summer-like heat wave across portions of southern Texas with new daily records are forecast today and through the weekend; The heat spreads across the Gulf States. Read More >

Hydro-Climate Dashboard

Hydro-Climate Context for December

Updated November 26, 2014, Text valid for Nov 26 - Dec 22, 2014

The peak of the rainy season is upon us.

December is the first of three consecutive months with peak rainfall in the West, especially across northern CA and the Sierra (Figure 1). History shows us that flash floods occur mainly in southern CA and southern NV (Figure 2) during December, while mainstem river flooding (Figure 3) and subsequent FEMA disaster declarations (Figure 4) have occurred throughout the region.

Fall storms moving through the Pacific Northwest brushed across northern CA bringing near to slightly below average rainfall (70-100% percent of average) to that region (Figure 5). A few storms reached down into central CA bringing a small amount of rain to a few locations, which was climatologically above average. With a multi-year drought in place across the region, the near-average rainfall soaked into the soil and only ameliorated the long-term drought and did little to improve reservoir conditions overall (Figure 8). Meanwhile, once again little to no rainfall fell across the rest of the southwest U.S. during November, further adding to the drought stresses in that region of the country.

While currently still in ENSO neutral, NOAA’s Climate Prediction Center (CPC) continues to forecast a weak El Niño to emerge during the winter months and continue through Spring 2015 (Figure 10). The latest 3-month outlook for precipitation favors above-average precipitation for Arizona, central/southern CA, and southern NV during the Dec-Jan-Feb season. Equal chances for above-, near-, or below-average precipitation is forecast across the northern third of CA and NV (Figure 11). Climatologically, El Niño does increase the risk of above-average rain and snow (and thus flooding) in the winter season. With a weak El Niño this is especially true across mainly AZ and parts of southern CA (Figure 9).

Historical Averages: Background Climate Risk

Figure 1. Precipitation Climatology	Figure 2. NWS Flash Flood Climatology	Figure 3. NWS Flood Climatology	Figure 4. FEMA Flood Disaster Climatology
Figure Updated: Last Thursday of the month Figure Source/Data: NOAA-CPC	Figure Updated: Last Thursday of the month Figure Source/Data: NWS Local Storm Reports	Figure updated: Last Thursday of the month Figure Source/Data: NWS Local Storm Reports	Figure updated: Last Thursday of the month Figure Source/Data: FEMA

Interpretation All Months

Current Conditions: Conditioning Climate Risk

Figure 5. Precipitation in Previous 30 Days	Figure 6. Snow Pack Conditions	Figure 7. Streamflow Conditions	Figure 8. Reservoir Conditions
Figure updated: Daily Figure Source/Data: WRCC	Figure updated: Daily Figure Source/Data: NRCS	Figure updated: Daily Figure Source/Data: USGS	Figure updated: Last Thursday of the month Figure Source/Data: USGS

Interpretation

Climate Outlooks

Figure 9. ENSO Composite Odds	Figure 10. ENSO Forecasts	Figure 11. Precipitation Forecast	Figure 12. Seasonal Flood Forecasting
Figure updated: Last Thursday of the Month Figure Source/Data: CPC and CLIMAS	Figure updated: 1st/3rd Thursday of the Month Figure Source/Data: IRI	Figure updated: 3rd Thursday of the Month Figure Source/Data: CPC	Figure updated: Daily Figure Source/Data: NWS

Interpretation All Months

Interpretation

Interpretation Future Maps

Interpretation