“Block Ready To Rock?” Cold Pattern Developing Around Thanksgiving…

Model data continues to suggest a Greenland block will develop as we progress into late-November. This kind of pattern creates a “log jam” of sorts in the weather pattern and is the type pattern notorious for unseasonably cold regimes across our region. The overall agreement between various models raises our confidence in this pattern unfolding as Thanksgiving nears.

Such a pattern illustrated above, per the European ensemble (image 1) and the GFS ensemble (image 2), would help drill a tongue of unseasonably cold air through the northern Plains, into the Mid West, and across the East.

A look at the 00z teleconnections this morning shows 3/4 “big boy” drivers going to that cold look for late-November, as well:

We’ve been discussing early snow cover across Canada and the northern tier for weeks and how models would have to “correct” colder as they realize the air masses traveling over the snowpack won’t be able to modify as they normally would without that snowpack. The differences between this November and last are startling and show how the early snowpack is beginning to “feedback” on itself leading to early-season cold air.

2016 snowpack and temperatures anomalies through the first week of November:

2017 snowpack and temperatures anomalies through the first week of November:

Given the overall look to the pattern downstream, I anticipate the cold will continue to “press” and eventually overwhelm the pattern east as we progress through the second half of the month.

To close, we expect a developing Greenland Block to help drive an unseasonably cold late-November, including the Thanksgiving holiday. This is the type pattern that can also help generate early season wintry “fun and games,” however it’s far too early to be specific with any sorts of potential wintry events that may eventually come in this pattern. Stay tuned.

Bill McMillan November 9, 2017 No Comments AO, Arctic Cold, Autumn, EPO, Forecast Discussion, Greenland Block, NAO, PNA, Thanksgiving, Unseasonably Cool Weather, Unseasonably Warm

VIDEO: Severe Weather Sunday; Wintry Push In The Week Ahead…

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Bill McMillan November 5, 2017 No Comments 7-Day Outlook, Arctic Cold, Autumn, Forecast Discussion, Forecast Models, Hail, Heavy Rain, Severe Weather, snow, T-storms, Tornadoes, Unseasonably Cool Weather, Unseasonably Warm, Weather Videos

Severe Weather Sunday; Much Colder Next Week…

Highlights:

Clouds more bark than bite today
Stormy setup Sunday
Trending colder next week

All Eyes On Sunday…The cold front that passed through the region Thursday night and setup the gorgeous close to the work week is lifting back north this morning as a warm front. This will result in overcast conditions today, areas of sprinkles or drizzle later in the day, and rising nighttime temperatures. Scattered thunderstorms will develop across central Indiana late tonight with a warmer and increasingly moist environment.

Sunday will certainly be a day to remain weather-aware. The overall setup hasn’t changed from what was discussed yesterday with a warm and moist southwesterly air flow in place ahead of an approaching cold front and associated area of low pressure. Additional ingredients in play suggest we need to monitor the threat of large hail, damaging straight line winds, and potentially tornadoes. Individual storms (potential super cells) are expected to fire across central and northern portions of the state Sunday afternoon into early evening. These will be capable of quickly pulsing to severe levels and include potential of large hail, as well as tornadoes (particularly in the vicinity of the warm front which is expected to be draped across north-central parts of the state). Individual cells are anticipated to “morph” into a squall line Sunday evening, including potential of a quick spin-up tornado, as well as damaging straight line winds. With a moisture-rich air mass in place (precipitable water values are expected to approach 2″ Sunday evening), locally heavy rainfall is also expected.

All of our “excitement” will come to an end overnight Sunday and we’ll trend much colder (and calmer) during the new work week ahead. Our next storm system will pass by to our south Tuesday, but may be close enough to spark a light shower across central portions of the state. Drier and colder conditions build in later in the week.

Upcoming 7-Day Precipitation Forecast:

Snowfall: 0.00″
Rainfall: 1.50″ – 2.50″

Bill McMillan November 4, 2017 No Comments 7-Day Outlook, Autumn, Forecast, Hail, Harvest'17, Heavy Rain, Severe Weather, T-storms, Tornadoes, Unseasonably Cool Weather, Unseasonably Warm

Growing Severe Threat Sunday…

We have growing concerns of a severe weather event Sunday afternoon and evening across the state. This morning, the Storm Prediction Center (SPC) has included most of Indiana in an “Enhanced” risk of severe weather. From this distance, all modes of severe weather seem possible, including large hail, damaging winds, and even a tornado or two.

A trough and associated cold front will slice into an unseasonably warm and increasingly moist air mass Sunday. Ahead of the approaching front, temperatures should climb into the lower 70s Sunday afternoon (average high is in the upper 50s) and dew points will reach the lower to middle 60s. While the developing surface low isn’t expected to be terribly strong, as this feature moves northeast, it’ll help drag a cold front into this warm and increasingly unstable air mass late Sunday. From this distance, conditions seem favorable for a couple of super cells to develop Sunday afternoon and evening. We’ll have to keep a close eye on the northward extent of the warm front as this would be the areas of greatest concern for potential tornadic activity Sunday afternoon. Large hail and damaging winds are also included in Sunday’s severe threat. We’re in the second severe weather season, after all, and this kind of event isn’t unusual. Late November 2013 comes to mind.

It’ll be important to remain weather-aware Sunday and stay tuned all weekend for future updates. We’ll transition to a much cooler regime (back to below average) next week.

A cold front will slice into unseasonably warm and moist air Sunday afternoon and evening. A severe weather episode is a growing concern. Remain weather-aware.

Bill McMillan November 3, 2017 No Comments Forecast Discussion, Harvest'17, Severe Weather, T-storms, Tornadoes, Unseasonably Cool Weather, Unseasonably Warm

Not Much Sunshine In This Forecast…

Highlights:

Milder times
Unsettled heading into the weekend
Colder next week and remaining unsettled

Vitamin D Needed…While we’re going through a milder stretch of weather between now and the end of the weekend, it’ll come with considerable cloudiness and periods of rain at times.

Most of today will only feature light passing showers and mist, but a clap or two of thunder can be expected tonight as a cold front passes through the state. The air mass behind the front won’t be particularly cold and a seasonable day is on tap to wrap up our work week Friday.

A warmer southwesterly air flow will return this weekend and this will help boost temperatures to levels as much as 15° above average Sunday. Scattered showers can be expected Saturday into Sunday and we’re monitoring the potential of a stronger storm Sunday afternoon and evening. You’ll want to stay tuned for future updates on Sunday’s storm threat.

As we rumble into a new work week, the active and wet pattern will continue and we’ll add a colder feel to the equation, as well. Monday through Wednesday will feature a “step down” regime: seasonable conditions Monday before turning colder than normal Tuesday and Wednesday.