Omega Block Weather Pattern Impacting Weather From Coast to Coast (FORECAST)

Chris Dolce
Published: April 17,2016

You may have never heard of it, but an "omega block" weather pattern is having a big impact on weather in the U.S., resulting in warmer conditions for parts of the Midwest, Northeast and West Coast, while the Plains is targeted by several rounds of thunderstorms and the Rockies are pounded with snow.
The term omega block is not new — it's often first taught in basic meteorology courses.
Here's how it works: an area of high pressure aloft has anchored itself near the Great Lakes. This high is sandwiched between two southward dips in the jet stream, one over the western Atlantic Ocean, and the other over the western United States. Now, notice how the weather pattern described above and depicted in the image below resembles the greek letter omega shown here: Ω.

Omega High Centered Over Ohio Valley Into Early Week

The impacts of this omega block weather pattern where we live at the surface of the earth are far reaching through early this week. We step through those impacts below from the East Coast to the West Coast.

Omega High Brings Warmer Conditions to Midwest, Northeast

After seeing record cold temperatures and even snow in parts of the Midwest and Northeast in the first week of April, conditions have changed for the better in much of those regions.
(MORE: Cold Air Infiltrates Northern States)
Above-average temperatures will dominate many cities into Monday thanks to the area of high pressure associated with the omega block.

Forecast Highs Early This Week

Widespread 70s and low 80s are in the forecast through Monday in parts of the mid-Mississippi Valley, Ohio Valley, Great Lakes and the Northeast. However, locations near the Canadian border from northern Minnesota to Upper Michigan and northern New England will be substantially cooler on Monday compared to Sunday.
Minneapolis-St. Paul is expected to continue a 70-plus degree streak through Monday, which is 10 to 20 degrees above mid-April averages. The Twin Cities reached 80 degrees on Saturday for the first time this year. Chicago, Detroit and New York City could all see their first official 80-degree day of 2016 on Monday.
A few record highs were set on Sunday including Marquette which reached 78 degrees, which was 5 degrees warmer than the previous record and La Crosse, Wisconsin set a new record with 83 degrees
(FORECAST: Cleveland | Syracuse | Philadelphia)
Temperatures will cool down somewhat by midweek, but still remain several degrees above average.

Heavy Rain, Severe Weather, Snow in the Central States

In the Plains, heavy rain and severe thunderstorms are the result of this weather pattern into early in the week ahead.

The omega high over the Great Lakes is blocking the forward progression of an area of low pressure that has formed in the upper atmosphere over the western states. That low is interacting with moisture returning north from the Gulf of Mexico, leading to the development of widespread rain and thunderstorms in the Plains.

Rainfall Forecast

Repetitive rounds of rain will lead to flooding in some locations, while snow falls on the central and southern Rockies.
For full details on the severe weather, flooding and snow, click on the links below.

(MORE: Severe Threat Continues | Flooding Take Aim on Plains | Winter Storm Vexo)

Record Heat in the West

To the west of the area of low pressure bringing heavy rain to the Plains is a northward bulge in the jet stream along a sliver of the West Coast.
This is allowing warmer than average temperatures to take over the Northwest and California through Wednesday. In some cases, highs will be up to 25 degrees above average.
Highs may reach the 80s in Seattle and Portland, Oregon, through Tuesday. Daily record high temperatures are likely to be toppled in the Pacific Northwest. Here are some of the potential record highs each day (current record to beat is shown):
Monday: Medford, Oregon (87 degrees); Portland, Oregon (80 degrees); Seattle (80 degrees)
Tuesday: Portland, Oregon (80 degrees); Seattle (79 degrees)
Record highs were set on Sunday including: San Diego which climbed to 86 degrees; Newport, Oregon which soared to 86 degrees which is 9 degrees warmer than the previous record; Santa Barbara, California reached 81 degrees; Portland, Oregon climbed to 81 degrees beating the previous record of 73 degrees.

Forecast Highs Compared to Average Monday

MORE: Summer in Every State