Saturday is Chase Day!

FINALLY... After two days and 1,200 miles of traveling, chase day has arrived!

Here's what we're tracking:

There is a Slight Risk for severe t-storms from Central Nebraska, south across Kansas and Oklahoma.  The StormTrackerWx Team arrived in Junction City, Kansas early this evening.  Our position is just west of where storm initiation will likely occur Saturday afternoon.  This means we'll likely have to travel a few miles west to Salina, Kansas and wait for development to begin there.

There is a large amount of CAPE (Convective Available Potential Energy) present across much of Central Kansas and Oklahoma.  Think of a lid on a boiling pot of water.  This same scenario holds true in nature.  When a temperature inversion is present (warmer air aloft), it "caps" the environment, suppressing energy needed for storm development near the surface.  When large amounts of CAPE are present- on the order of 2500 j/kg or more, this adds buoyancy to the atmosphere.

Under the right conditions, this cap can break transferring energy upward.  This momentum is what aids in thunderstorm development.  The more momentum, the more energy that is transferred.  Long story short, this is what we'll be looking for tomorrow afternoon and early evening.

The other big factor we'll be looking for is a highly sheered environment.  For this, we look at helicity, which is simply the amount of rotation found in a storm's updraft.  Lots of rotation and momentum transfer are key ingredients for tall storm structure and rotating updrafts favorable for tornadic super cells, all of which will be available in minute amounts for tomorrow.

How you can track us:

Pay attention to our status buttons, which are posted on our home page at StormTrackerWx.com.

NO SVR: Severe t-storms are not forecasted or if they are, then A) The probability is less-than 15% or B) They are just outside our chase window.  Streaming Weather Content will remain offline.

STAND-BY: Severe t-storms are possible, and deployment is likely within the next 24 hours.

ACTIVE: Severe t-storms are likely to occur within the next 24 hours, and the StormTrackerWx Team has already deployed.  Streaming Weather Content is online.

Keep in mind that as long as we are in transit, the tracker map will always be available online at live.stormtrackerwx.com.

Stay-tuned!

Forecast in Two Words: "Death Ridge!"

The forecast for storm chasing over the next 4-8 days can be summed-up in basically two words... "death ridge!"

By that, I mean a broad area of high pressure, which will firmly anchor itself across much of the eastern two-thirds of the country.  Infact, models indicate the jet stream will remain north of the contiguous U.S., which will keep any significant troughs from emerging from the Pacific Northwest, possibly through the remainder of May.

If you are a storm chaser, you crave these troughs of low pressure, because they introduce shots of cooler Canadian air to the Plains, where a warm and moist airmass is typically present this time of year.  With a ridge in place, you have large scale subsidence- sinking air, unfavorable for lift and thus, thunderstorm development.

Infact, an anticyclonic flow is expected for much of the western third of the country through atleast Wednesday.  This will cause winds along the Gulf Coast to be offshore, preventing any moisture return from the Gulf of Mexico.

There is hope, however.  By Friday, a trough will build south and east from Southern Canada, transitioning winds aloft from east to a more southwesterly flow.  Models are already eluding towards the potential for strong storms, with numerous embedded waves of energy ejecting across the Northern Plains through Saturday.

While it remains too early to precisely pinpoint where storms will develop, it appears the StormTrackerWx Team may deploy a couple of days later than originally planned, with sights set on the Northern Plains states.

Stay-tuned!

To Snow, or Not to Snow: That is the Question

Following this most recent cold snap, I was asked whether or not it would snow again.  Do not swap out your snow tires for lawn mowers just yet.  If the roller coaster transition from winter to spring has taught us anything, it is that Mother Nature still has a few tricks left up her sleeve.

It is in the Climatology

The National Weather Service begins calculating snowfall totals in July.  Why?  It is that past occurrences have proven it can still snow in May.  It also means that statistically, we have a lesser chance of seeing significant snow as we approach the month of July.  As is normally the case, there are a few wild cards in the mix.

By March, most of the Great Lakes are covered with ice.  This year however, the lakes are largely ice free, with temperatures in the 40s.  To produce lake effect snow, you need on average a -13° differential between the lake water and air temperature aloft.  You also need ample low level moisture and instability.

The Lake Breeze Front

As we move further into spring, the northern hemisphere turns towards the Sun, increasing the angle of solar radiation in direct contact with the earth's surface.  The warming landmass in return radiates some heat back into the surrounding atmosphere.  One thing to keep in mind here is that water warms more slowly than land.

This is why the lake shore is typically cooler in the daytime during the late spring and summer months.  Cooler, more dense air produces areas of high pressure over the lake.  Simultaneously, the Sun warms inland areas more quickly, producing lower pressure.  Weather 101 tells us wind flows from areas of high pressure to lower pressure, since the atmosphere is always trying to reach a state of equilibrium.

Thus, the lake breeze:


Diagram illustrating the Lake Breeze Circulation.  Areas of low pressure form inland ahead of colder, more dense air. Similar to cold fronts, the lake breeze acts as a lifting mechanism, resulting in clouds and precipitation.

Where am I going with all of this?  Simply put:  This boundary between cold, more dense air and warmer air is referred to as the lake breeze front.  Similar to synoptic (large scale) cold fronts, these fronts serve as lifting mechanisms for precipitation during the late spring and summer months.

To Snow or Not to Snow

Which brings me to the focus of this blog entry: The graphic below was generated by the European forecast model (ECMWF), and is a temperature forecast for 8 PM Tuesday, April 3.

We all known the jet stream is the boundary between cold and warm air. As the polar jet retreats north, so do colder temperatures. Often times however, lobes of energy will break-off from the jet stream, forming what are known as cut-off or "cold core" low pressure systems across the contiguous U.S.

One would think lake temperatures in the 40s and air temperatures in the 20s would generate a significant lake effect snow storm for the Great Lakes.  Not so fast!  Remember key ingredients to produce lake effect snow include, among other things instability and ample low level moisture.

While there can be a -13° difference between the lake and air temperature this time of year; unlike winter-time low pressure systems, these cut-off lows lack upper level support and are typically not as strong.  While these systems can produce lake effect precipitation, significant snowfall is less likely.

On the other hand, if a trough developed to the lee of the Rockies, we could potentially see a significant late winter storm develop in the Southern Plains.  This type of scenario is more commonly reserved for winter months, however.

Visible satellite image showing cumulus clouds, associated with lake effect precipitation, developing downwind of Lake Ontario. These clouds are the result of the lake breeze front, a common feature in the late spring and summer months.

In other words, while the term "significant" can be used increasingly less to denote snow events during the months of April and May, accumulating snow is still climatologically possible for the Great Lakes.  Those areas- especially in the snow belt, still have a chance of snow, at least through mid April.

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The StormTrackerWx Store: Coming Soon

Here's a look at just some of the apparel that will be available in the StormTrackerWx Store, coming soon!

March Madness: Severe Weather and Record Breaking Heat

After a week of record contending highs, Mother Nature has decided to revert back to normal or near normal temperatures. Highs for Monday and Tuesday will be some 20-30 degrees cooler than those of just a week ago.

Why the Heat?

Two weeks prior to the June-like warmth, a broad ridge of high pressure had anchored itself across the contiguous U.S. Areas of high pressure move slower than low pressure. High pressure also acts as a giant lid, capping the atmosphere aloft and trapping air at the surface. With little or no wind, the atmosphere can become stagnant for days if not weeks on end.

March saw a blocking pattern that typically develops across the southeast states during the mid to late summer. This type of pattern- known as the "Ring of Fire", occurs when a portion of the Bermuda-Azores high becomes affixed in the same general area for days. The longevity of the event is attributed to a lack-of Canadian cool fronts, which aid in eroding the cap and breaking down the high pressure ridge.

"Summer in March"

Record smashing high temperatures numbered in the thousands- the most for any spring since record keeping began in the late 1800s. Perhaps nowhere was the record breaking heat most noticeable than International Falls, Minnesota. The city known as the "Nation's Icebox" set their first and second consecutive hottest temperatures for the month of March at 78° and 79° (42-43 degrees above average). Coincidentally, their low temperature of 60°F tied the previous record high for that date.

Map illustrating global temperature anomalies (departure from normal) for the month of March. Note the orange and red shading for the eastern two-thirds of the contiguous U.S. denoting warmer than average temperatures.  This area represents about 10% of global temperatures.  Source: Poclimate/ http://policlimate.com/climate/ncep_cfsr_t2m_anom.png

Return to Seasonable

While much of the eastern two-thirds of the U.S. was experiencing above average temperatures, the west was locked under a low level trough that brought persistent rain and snow to the Pacific Northwest.  The trough eventually became too extreme and unstable, breaking off from the jet stream and forming a "cut-off low" that would bring severe weather and cooler temperatures to much of the lower 48.

The return of near seasonable readings means highs in the 40s Monday and Tuesday.  As a result of high pressure, overnight lows Monday night are forecast to drop well below freezing for much of the Great Lakes and Midwest.  Unfortunately, Mother Nature's revert to winter comes at a time when many fruit trees are in full bloom.  The combination of clear skies and calm winds has prompted Freeze Warnings, which could come at a cost for Lake Erie vineyards and orchards.

Unlike its predecessor, this weather regime will be short lived.  Highs are forecast to be in the 60s by mid week.

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