Tonight’s weather across the United States will be a cold one for the majority of us, with more then two-thirds of the country, east of the Rocky Mountains, experiencing significantly below average temperature. Locations in the continental northeast, and as far south as Kansas into Ohio, will be around zero degrees Fahrenheit at midnight, with wind chills into the -20 to -40 degrees. Portions of the Midwest and Northeast are currently under a wind chill warning along with wind chill advisories throughout the night.
The picture above shows the global average temperature anomalies from December 27th until January 3rd. As you can see, the eastern two-thirds of the country will remain well below average temperatures, like it has been for the past few days, with nearly every other portion of earth being well above average.
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ⓒ 2017 Meteorologist Claudia Pukropski
We are nearing the end of 2017, and it’s time to take a look back at this year’s weather events in the United States. From blizzards, to tornadoes, to hurricanes, to wild fires; 2017 left everything out on the table. In no particular order, the following are some of this year’s worst weather events:
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ⓒ 2017 Meteorologist Brandie Cantrell
It’s time to kiss the autumnal warmth of the past few weeks across the Central U.S. goodbye, as arctic air arrives in the U.S. with a vengeance…To read the full story, click here - http://www.weatherworks.com/lifelong-learning-blog/?p=1441
© 2017 H. Michael Mogil
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DISCUSSION: Earlier this year during the spring months, portions of Arkansas and southern Missouri experienced record flooding. Details on this previous event can be found here. Currently, a few months later, these same places are now considered to be in a moderate to severe drought, as shown by the US drought monitor image, but possibly not for long.
Current conditions show an elongated frontal boundary with a weak wave of low pressure moving northeast as the precipitation follows suit. A general 0.5 – 1 inches with up to 2+ inches of precipitation fell yesterday, December 22nd, into the overnight hours across southern Missouri and Arkansas with precipitation stretching into Louisiana as this front brought thunderstorm type activity last night. This precipitation yesterday evening shows up well when looking at the synoptic scale features that were in play alleviating some of these drought conditions.
The 850 mb map shown below, which plots heights (dam), isotherms (degrees C, dotted yellow), and dew point temperatures filled (degrees C), valid 12/23/00Z, shows southerly winds bringing warm air advection, which leads to upward vertical motion, across Arkansas and working its way into southern Missouri. Gulf of Mexico moisture is being advected into the region moistening up the atmosphere enhancing the heavy precipitation threat. Accompanied with this, favorable upper level jet dynamics are present enhancing divergence (yellow contours) in the upper levels (streamlines and isotachs in knots are also plotted) of the atmosphere as shown in the 300 mb analysis valid 12/23/00Z. This enhances the rising air in this region and the chance for precipitation.
These factors come together nicely when looking at the radar imagery from yesterday evening shown below, which illustrates a nice area of precipitation where it was expected in the drought areas based on this synoptic scale analysis.
Stay tuned for future updates here across the Mississippi Valley to see if more drought alleviation is on the way!
©2017 Forecaster Joseph DeLizio
DISCUSSION: As the present national weather pattern stands, there is quite an interesting set-up in place across the United States. One of the first thing atmospheric scientists (i.e., operational forecasters and/or broadcast meteorologists) execute when doing a given forecast is to ascertain a more concrete foundation of what is currently happening at that given time near both the top, middle, and bottom portions of the "active" atmosphere. The "active" part of the atmosphere referring to the portions of the atmosphere within which a large majority of the global weather phenomena occur within the confines of. As you can clearly see in the graphic above (courtesy of the Thermodynamic Solutions Weather Company), there are very different atmospheric flow regimes in place closer to the surface and towards the middle-to-upper portions of the atmosphere.
This is chiefly due to the fact that in the middle-to-upper part of the atmosphere, there is presently a "ridge" (or an area of high-pressure) in place over and across a good portion of Western North America which is shown on the right-hand side of the graphic attached above. To the east of any ridge can often be found a "trough" (or an upper-level region of lower pressure) which is also reflected by the "dip" or "deep left-turning curve" in the deep-blue colored flow shown on the right-hand side of graphic above as well. On the right side of any trough is where you nearly always find a higher probability of there being a greater likelihood of low-pressure formation. This is a combined result of there being stronger cyclonically-turning winds from the surface upwards on the eastern side of a trough which is much more favorable for surface-layer cyclogenesis which can then extend into the mid-levels of the atmosphere as well under the right conditions. Sure enough, very far downstream, there is a strong low-pressure system parked over part of Southeastern Canada which is helping to amplify a good portion of the ongoing lake-effect snow events downwind of Lake Erie, Lake Ontario, Lake Michigan, and Lake Superior. Thus, it is always neat to see how atmospheric science theory works out in real-life application.
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©2017 Meteorologist Jordan Rabinowitz
First Lake Effect Snowfall Event To Impact the Great Lakes Region (credit: NOAA NWS Eastern Region HQ)
DISCUSSION: As a classic Arctic air blast makes it way into portions of the North-Central and the Northeastern United States, this will set the stage for another aspect of winter weather. That particular aspect being referred to is this instance is lake-effect snow. Lake-effect snow occurs as a result of when cold, moist air travels across relatively warmer water contained within the near-surface layer of various spread across the United States (and the world for that matter). In this particular situation, the combination of the cold air and the projected wind forecast will align the larger-scale flow such that areas to the east and east-northeast of both Lake Erie and Lake Ontario will likely get hit the hardest with periods of heavy lake-effect snowfall. As shown in the graphic above, some location may end up being able to measure snow in feet (rather than in inches). Therefore, it is imperative to respect the power of Mother Nature if you are currently situated within any of these forecast areas as trying to travel while under a lake-effect snow-band is quite often a very life-threatening precedent. So, be mindful of that as you plan your travel over the next few days.
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©2017 Meteorologist Jordan Rabinowitz