Highlight: Heavy rain with severe storms into the Great Plains, rainfall pattern change in South America and an evolving cold air source region east of Europe.
Fig. 1-2: Mega-cluster ensemble percent of normal precipitation forecasts for the next 10 days across North America.
Discussion: Widespread Winter Weather and Wind Advisories for snow and gusty wind are spread across much of the Interior West U.S. as a potent upper-level Pacific low-pressure trough arrives. The upper trough spawns heavy rain and severe storms across the southern Great Plains and Texas beginning tomorrow and lasting into the weekend. Wet weather stretches northeastward into the Upper Midwest in the 5-day forecast (Fig. 1). The upper trough persists in the 6-10-day period causing more wet weather with mountain snows across California northeastward to the North-central U.S. and into Ontario (Fig. 2). Cold air moves into the northwest Great Plains late in the 6-10-day period causing rain to snow change. Tropical showers and thunderstorms approach the Southeast U.S. Coast during the period. The expanding and deepening snow in Western Canada extending to the Interior Northwest allows a very cold air mass to develop.
In South America, the north and northeast push of wet weather from Southeast to Northeast Brazil remains in the 15-day outlook according to most models including the ECM ENS (Fig. 3). Some models indicate a chance of showers returning to Southeast Brazil in the 11-15-day period. However, the overall look is a precipitation pattern change. In the short-term there is chilly air in Southeast Brazil as low temperatures drop into the 30’s this morning and tomorrow morning Interior Southeast Brazil (Fig. 4).
Fig. 3-4: ECM ENS 15-day rainfall anomaly forecast across South America and the 5-day temperature anomaly forecast across Southeast Brazil.
In Europe, the never-ending warmth continues especially across the western half. However, in the extended range there are signs that an evolving cold air source region will develop centered on the Caspian Sea region (Fig. 5). The cold could become vigorous in this region by the 11-15-day period. In the 11-15-day period, the Europe warm pattern eases.
Fig. 5: ECM ENS 15-day temperature anomaly forecast for Europe/Russia.
In Australia, the extreme rain pattern has eased. Although GFS indicates patchy wet areas in the 15-day outlook, the 24-hour trend is much drier across the eastern half of the continent (Fig. 6-7).
Fig. 6-7: GFS 15-day percent of normal rainfall forecast across Australia and the 24-hour change.