Omega Block Weather Pattern Develops This Weekend; Will Impact Weather From Coast to Coast (FORECAST)

Chris Dolce
Published: April 15,2016

You may have never heard of it, but an "omega block" weather pattern is about to have a big impact on weather in the U.S. The omega block takes shape late this week into the weekend, resulting in warmer conditions for parts of the Midwest, Northeast and West Coast, while the Plains is targeted by several rounds of thunderstorms and possibly even some 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 will develop and anchor itself near the Great Lakes. This high will be 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 Midwest This Weekend

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

Omega High Brings Warmer Conditions to Plains, Midwest, Northeast

After seeing record cold temperatures and even snow in parts of the Midwest and Northeast last week into this past weekend, conditions will change for the better in much of those regions through the weekend.
(MORE: Cold Air Infiltrates Northern States)
Above-average temperatures will dominate many cities in the days ahead thanks to the area of high pressure associated with the omega block. An exception to this may be the Northeast coast where onshore winds from surface high pressure may hold off the warmth until late weekend or early next week.

Forecast Highs This Weekend

Widespread 60s and 70s are in the forecast through this weekend in parts of the Plains, Upper Midwest and Great Lakes. Minneapolis-St. Paul is expected to see multiple days in the upper 60s and low 70s through Sunday, which is 10 to 15 degrees above mid-April averages. The Twin Cities only reached 70 degrees twice this year so far through April 12 but has seen highs already climb into the low to mid 70s on April 13 and 14.
(FORECAST: Bismarck | Omaha | Green Bay)
After parts of the Northeast reached the 60s on Friday, it will turn even warmer this weekend. This weekend it will turn even warmer with highs in the 60s overspreading New England, while the mid-Atlantic sees 70s. For many areas temperatures may be 10 to 20 degrees above average from Pennsylvania to Maine by Sunday.
(FORECAST: Cleveland | Syracuse | Philadelphia)
The area of high pressure will also keep much of the East dry through this weekend.

Heavy Rain, Severe Weather, Snow in the Central States

In the Plains, heavy rain and severe thunderstorms will be the result of this weather pattern through this weekend and possibly beyond.

The omega high over the Great Lakes will block the forward progression of an area of low pressure that forecast to form in the upper atmosphere over the western states. That low will interact 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 could eventually lead to flooding in some locations, while snow falls on the central and southern Rockies.
Not only that, it may be cold enough for snow to pile up in the Rockies and parts of the adjacent High Plains.

For full details on the severe weather, flooding and snow this  weekend, click on the links below.

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

West Coast Heats Up

To the west of the area of low pressure that will bring heavy rain to the Plains will be a northward bulge in the jet stream along a sliver of the West Coast.
This will allow warmer than average temperatures to take over the Northwest and California Saturday to Wednesday. In some cases, highs will be 10 to 25 degrees above average.
Highs in the 70s will return to Portland, Oregon, this weekend, with Sunday possibly topping out near 80 degrees. Seattle may make a run at 80 degrees by Monday.
Portions of California's Sacramento Valley along with southern Oregon will see 80s. A few locations could top out near 90 degrees this weekend.

Forecast Highs Compared to Average Sunday

MORE: Summer in Every State