Highlight: Heavy rains/mountain snows West next 10 days. Now adding East/Southeast heavy rains days 6-10.
Fig. 1: ECM 10-day precipitation forecast across the West U.S.
Fig. 2: The NEW water year percent of normal precipitation so far in the West is about to receive great improvement.
Fig. 3: ECM indicates a NEW heavy rain forecast for the East/Southeast U.S. centered on days 6-10.
Discussion: Forecast models continue to indicate excessive precipitation across the West U.S. in the 10-day outlook according to ECM (Fig. 1). The ECM indicates widespread 5-15 in. during that time with feet of snow in mountain areas. Heavy precipitation begins tomorrow in northern California with the second wave of heavy precipitation striking central and northern California on Sunday. Third wave arrives early next week for Washington/Oregon. The new water year began October 1st. Of course, much of the West is very dry although the Great Basin to central Rockies have over-achieved (Fig. 2). Relief is on the way for northern California, Oregon and Washington while excessive amount in the Great Basin will increase.
New to the forecast is a developing heavy rainfall regime developing in the East/Southeast centered on the 6-10-day period according to ECM (Fig. 3). Most of the rainfall is mid-to-late period as a Pacific trough arrives and regains strength while entraining Gulf of Mexico moisture. Heavy rain causing flash flooding is possible from the Tennessee Valley to the Mid-Atlantic States and Southeast also featuring severe thunderstorms during October 27-29.
The gas population weight HDD forecast continues to indicate extremely low early season heating demand nationally although following the West storms a cool-to-cold period is likely there. The GFS is the lone model indicating normally cool weather for late OVT/early NOV (Fig. 4).
Fig. 4: The gas population weight HDD forecast continues to indicate LOW heating demand and the consensus forecast is similar to yesterday except a little cooler due to the GFS influence for Oct. 29-Nov. 4.