Holiday Weather Event Dill

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The forecast for Wednesday morning shows a broad southerly flow along the east coast that will bring heavy rain. Behind the low pressure system, it will be cold enough to snow in Wisconsin and Michigan. Forecast courtesy of NOAA.

The forecast for Wednesday morning shows a broad southerly flow along the east coast that will bring heavy rain. Behind the low pressure system, it will be cold enough to snow in Wisconsin and Michigan. Forecast courtesy of NOAA.

A few people may go over the river and through the woods in a sleigh this week. But many more will be traveling by car or airplane to get to grandmother’s house.

The American Automobile Association estimates that 98.6 million people will travel more than 50 miles from home this holiday period, 89.5 million of them by car.

The weather pattern is active, and though it does not reach the threshold for a vegetable-named extreme event, Decoded Science considers this week’s weather worthy of a name because of its potential effect on holiday travel and outdoor activities.

We’ve chosen the name Dill — not a full-fledged vegetable, but a spice that flavors the food, as undulations in the jet stream will flavor this week’s weather.

Travel Disruptions Will Mar Air And Road Travel Coast To Coast

Once ensconced with family or friends at a chosen destination with a seasonal beverage, you won’t really care what the weather is like outside.

But getting there will be an issue in much of the country. Dill will be unusual for its extent, with almost every part of the US affected by disruptive inclement weather at some point during the week.

This map shows that most of the country will receive precipitation in the next week, with hotspots in the south, northeast, and midwest. Analysis courtesy of NOAA.

This map shows that most of the country will receive precipitation in the next week, with hotspots in the south, northeast, and midwest. Analysis courtesy of NOAA.

  • Gulf Coast: Bouts of heavy rain with some thunder and even the outside possibility of a tornado will cause delays at major airports, but flights should eventually take off. Roads will often be slick, and there could be some local flooding of urban streets.
  • Midwest: A sprawling low pressure system across the eastern half of the country will bring mostly rain as far north as Montreal. However, the back side of the storm will be cold enough to produce snow; significant amounts could fall in Wisconsin and Michigan on Tuesday, and the rest of the midwest on Wednesday.
  • Eastern Seaboard: A powerful low-level jet will bring large amounts of moisture to the big cities of the east coast. Several inches of rain are possible in New York, Boston, and Washington. Driving will be difficult, and with heavy traffic expected, any minor collision will block traffic and cause long delays. Airports will probably be able to continue near-normal operations, but passengers should expect delays.
  • West Coast: Extreme Weather Event Cucumber is officially over. The remnants of the last system which hit the northwest with heavy rain, wind, and mountain snow is now in the Rockies and moving east. More rain will fall today through Wednesday, but nothing unusual for the season. California will go back to a dry pattern after a couple of weeks of drought-alleviating rain and mountain snow.

Omega Block May Re-Emerge Over Eastern Pacific

Last winter’s weather pattern featured a persistent high pressure area in the jet stream over the west coast and the eastern Pacific Ocean. When this high became very pronounced, it formed an omega-like shape (Ω) that blocked the normal flow of weather systems from west to east. The polar vortex dropped into the central US and caused persistent cold and snowy weather in the eastern two-thirds of the country.

Last winter’s pattern returned in November, but for the last few weeks the block has been broken and storms hit the west coast as far south as southern California. The storms produced a southerly flow ahead of them which pushed warm air into the midsection of the country.

This is the forecast for the jet stream for next Sunday. This pattern is conducive to the formation of a storm on the east coast. Forecast courtesy of NOAA.

This is the forecast for the jet stream for next Sunday. This pattern is conducive to the formation of a storm on the east coast. Forecast courtesy of NOAA.

Currently the ridge is off the west coast, and the trough is over the Rockies and the Intermountain West. Indications are that the trough will move to the middle of the country by next weekend, and the ridge will intensify close to the west coast. Longer-term forecasts show the pattern persisting into next week.

Waves ripple along the jet stream, and as they come around the trough and reach the east coast, the temperature structure of the atmosphere is conducive to storm development; cold air over the continent lies next to warmer air over the water, and this is a state of high potential energy.

A coastal storm — a nor-easter — is likely to develop next weekend or during the following week. Whether this storm is mostly snow or rain depends critically on the position of the jet stream and the temperature of the air several thousand feet above the ground.

Avalanche Warning For Northern Rockies

Warming temperatures, increasing winds, and new snow have prompted the National Weather Service to issue avalanche warnings for the northern Rockies from Colorado to Montana. Anyone planning to travel into the back country in these areas is advised to check local conditions. The warmer weather weakens the old snowpack, and the new snow and wind may be enough to dislodge the snow and cause an avalanche.

A Messy Week Weather-Wise

The entire week will offer a variety of bad weather to travelers, but particularly on the heavy travel day of Wednesday in the east and midwest. Wherever you go, drive carefully, check airline schedules, and when you get to your destination, enjoy that seasonal beverage.

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