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12/07/2018, 1:53 pm EST

Daily Feature: Arctic Air Brief

Arctic Air Brief Fig. 1: The Siberia to North America arctic air connection the past 30 days. Fig. 2: The GFS OP identifies warming of the Siberian arctic air source region forcing the previous cold southward into China Dec. 7-12. Meanwhile the cutoff arctic air into North America allows Canada to warm while remnant cold is released the Southeast U.S. Fig. 3: In the 6-10 day period the Canadian warmth expands into the U.S. There is no arctic air in the northern hemisphere. Fig. 4: Dec. 17-22 finds a stratospheric warming event over Northeast Asia causing the Siberian region to go extremely cold – a new arctic air mass. While that cold is redeveloping North America is very warm. But will the Siberian chill which is much colder this time flow cross-polar into North America (and the U.S.) in late DEC/early JAN? CLOSE ATTENTION required to this potential scenario.
12/02/2018, 12:44 pm EST

Daily Feature: The Next U.S. Storm

Fig. 1: U.S. snow depth chart as of Dec. 2, 2018. Summary: A dominant player in the late autumn/early winter North America climate is the much above normal snow cover across the northern U.S. (Fig. 1) causing cold air masses to evolve more quickly, last longer and promote snow over rainfall. The latest storm is easing slowly over Nebraska to (where 2 feet occurred) while new expansive snow cover has emerged in the Interior West. Based on the 12Z GFS where are additional snow storms over the next 10 days? One storm raises havoc in the 10-day forecast. A strong low pressure area approaches the California Coast Tuesday and stalls while ejecting waves of heavy rain and high elevation heavy snow into the California Coast. The storm stays offshore drifting slowly southeastward to just off the southern California Coast by Thursday. Persistent waves of heavy precipitation affect the immediate coast while well inland amount is light. By Friday the storm is inland and moving across northern Mexico. The 5-day precipitation forecast by the GFS OP indicates excessive amount just offshore the California Coast with spotty excessive amount reaching coastal areas in the San Francisco Bay area, Santa Cruz and farther south into San Diego (Fig. 2). Quickly, the storm regenerates intensity once reaching Texas later Friday propelling a heavy rainfall across Texas to Louisiana next weekend. The 12Z GFS OP indicates potential for 5-10 in. of rain across eastern Texas (Fig. 3). The northern fringe of this storm will feature heavy snow. The 12Z GFS indicates potential for 1-2 feet of snow from Oklahoma to Arkansas Friday night through Saturday night (Fig. 4). The storm moves to the Carolina Coast next Sunday night taking a swath of heavy snows across the Appalachians and into the interior Mid-Atlantic States where another 1-2 feet of snow could occur. The storm moves northeast while offshore the East Coast early next week backing potentially heavy snow into New England. Last night’s ECMWF model was heavier with snow in the Carolinas and Virginia. All of this rain and snow is caused by one storm moving across southern U.S. beginning the next 2-3 days and lasting into early next week. Fig. 2: A storm approaches the California Coast this week and stalls keeping heaviest precipitation just offshore. Fig. 3: The storm crosses Mexico late this week and reorganizes off the Texas Coast causing 5-10 in. of rain in eastern Texas. Fig. 4: The northern fringe of the storm produces heavy snow with 1-2 feet in Oklahoma to Arkansas next weekend and similar amount into the Interior Mid-Atlantic early next week.