Written by Sig Silber
HEADLINES (Updated 4:00 PM EST) –
– Blizzard conditions expected across portions of the north-central U.S. tonight
– Heavy snow possible for the Lower Great Lakes and eastern sections of the Ohio Valley Thursday and Friday
– Heavy rain, damaging wind gusts, and potentially severe thunderstorms to impact much of the East on Christmas Eve and Christmas Day
This article provides continuous updates for a variety of Weather and Weather-Related Threats as well as a general weather forecast. These are “Live” maps that continually update. Please pay attention to the Mesoscale Events maps — Mesoscale Events are potentially life-threatening situations.
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For those interested in longer-term forecasts, we just published the new NOAA Seasonal Outlook and it can be accessed here.
Readers can scan through this article or jump to where they want to go via the links to the right. To get back to the Directory, hit the back arrow at the top of the URL bar on your screen. But in many cases, one of my Editors has graciously inserted a Return to Directory link to click so that is even easier. This is so high tech that I hardly believe it. |
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CONUS Focal Points
Short Range Focal Points
Short Range Forecast Discussion NWS Weather Prediction Center College Park MD – 250 PM EST Wed Dec 23 2020
Valid 00Z Thu Dec 24 2020 – 00Z Sat Dec 26 2020
…Blizzard conditions expected across portions of the north-central U.S. tonight…
…Heavy snow possible for the Lower Great Lakes and eastern sections of the Ohio Valley Thursday and Friday…
…Heavy rain, damaging wind gusts, and potentially severe thunderstorms to impact much of the East on Christmas Eve and Christmas Day…
A powerful surface low pressure system is currently moving across the Upper Midwest today toward the Upper Great Lakes, spreading snow and high winds to the north-central U.S. on its backside. Snowfall amounts of over 6 inches are possible across northern portions of Wisconsin and the Upper Peninsula of Michigan, as well as eastern Minnesota tonight. Heavy snow will then continue for the U.P. of Michigan and western Lower Michigan on Thursday in favored lake effect areas. Additionally, high winds are likely tonight given the depth of the surface low. High Wind Warnings and Wind Advisories are in effect for much of the Plains and into parts of the Mississippi Valley region. In the eastern Dakotas, northeastern Nebraska, much of central and southwest Minnesota, as well as northwestern Iowa, Blizzard Warnings are in place for tonight where the snow and winds could combine to create blizzard conditions, with lowering visibility and treacherous travel likely.
The heavy snow threat will shift into the Lower Great Lakes and eastern Ohio Valley region by late Christmas Eve as the storm system dashes east. Total snowfall accumulations of 4 to 8 inches will be possible from central West Virginia to the southeastern shores of Lake Erie. These amounts will make travel difficult at times between Thursday evening and Christmas morning.
Meanwhile, a strong cold front associated with the aforementioned low will sweep across the Ohio and Tennessee valleys tonight and into the eastern U.S. by Thursday night. Plentiful moisture from the Gulf of Mexico is forecast to stream in ahead of the cold front, leading to increasing rain chances and the possibility for isolated flooding/flash flooding for the Lower Mississippi Valley into the Tennessee Valley tonight. Also, there is a Slight Risk of severe weather in place from the Storm Prediction Center for the central Gulf Coast, where instability will be the highest and could cause strong thunderstorms tonight. Then, as the front tracks eastward Thursday, heavy rain of 1 to 3 inches is forecast for the eastern third of the country through Christmas night. Severe thunderstorms are once again possible Thursday, with an Enhanced Risk of severe weather centered over eastern North Carolina. Damaging winds and isolated tornadoes are possible. However, the potentially most widespread hazard will likely be flooding and flash flooding. A Moderate Risk of excessive rainfall is in place for northeast Pennsylvania, with a Slight Risk surrounding the Appalachians, northern Mid-Atlantic region, and Northeast. For many areas, the rain is expected to fall on top of a deep and relatively fresh snowpack from the nor’easter last week, exacerbating flooding concerns as rain could cause rapid snowmelt. Another concern is the added weight that rain could put on top of snow covered roofs, particularly across regions that still have over a foot of snow on top of buildings from north-central Pennsylvania to Vermont. Winds also remain a threat with this low pressure system as it tracks toward the East Coast. High Wind Watches have been posted for coastal New Jersey to southern Maine.
The strong cold front will be a dividing line between temperatures 10 to 20 degrees below normal behind the front in the western and central U.S., with much above normal temperatures ahead of it in the Ohio Valley and Great Lakes region this evening and eventually across the East Thursday. The warm temperatures (and dewpoints) in the Northeast Thursday should be another contributing factor to flooding there, since it could cause rapid snowmelt into nearby rivers and streams. Temperatures on Christmas morning will struggle to dip below the mid-40s across New England, potentially setting daily records. The cold temperatures behind the front will support rapid freezing of any standing liquid.
Elsewhere, fire danger is a concern across portions of Southern California this evening and Thursday, where the Storm Prediction Center has outlined a Critical Risk. Red Flag Warnings are in effect as well. Dry conditions and gusty winds could also cause elevated risks of fire weather in the Southern Plains.
We try to keep this up to date but if is not you can find the updated version here.
When you click on this image it takes you to the SPC Fire Warning Page and you get a set of maps for Days 1, 2, 3 – 8, etc. You can then click on those for more detailed information. The map is a bit blurry as I tried to make it a bit larger than the map provided by NOAA but should be able to see where the current wildfire risks are. But if you click on this map, you will get to see three maps that show the risk for different time periods.
Thunderstorm Risk
This should play out something like shown in this 60 Hour Forecast Animation
Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color-coding.
The two maps below break it down by day and may be easier to read.
Now, the Day One and Two CONUS Forecasts: These Maps Update Daily.
Day One CONUS Forecast | Day Two CONUS Forecast |
These graphics update and can be clicked on to enlarge. You can see where the weather will be | |
During the winter much of our weather originates in the Pacific. That is why we pay attention to the near-term history of storms arriving.
Temperature
A version that shows a 20 hour animation and some other views can be found here
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Day 3 – 7 Hazards
Valid Saturday December 26 2020 – Wednesday December 30 2020
Hazards:
– Heavy precipitation across portions of the Pacific Northwest, Sat-Sun, Dec 26-Dec 27, and Wed, Dec 30.
– Heavy precipitation across portions of California, Sun-Tue, Dec 27-Dec 29.
– Heavy snow across portions of the Northeast, Mon, Dec 28.
– Heavy precipitation across portions of the Central Plains and Middle/Upper Mississippi Valley, Tue, Dec 29.
– Heavy Rain across portions of the Central/Southern Plains and Middle Mississippi Valley, Tue, Dec 29.
– Heavy Rain across portions of the Southern Plains, Middle/Lower Mississippi Valley, Tennessee Valley and Southeast, Wed, Dec 30.
– Heavy snow across portions of the Northeast, Mon, Dec 28.
– Flooding possible across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the Central Appalachians, and the Ohio Valley.
Detailed Summary:
Parts of the Northeast, central and western U.S. will experience hazardous weather during the medium range period (Saturday, December 26th – Wednesday, December 30th). An upper-level low will tilt negatively as it moves into the eastern seaboard on Friday (Christmas day). Flooding remains a concern over parts of the Northeast as rising temperatures and a new low pressure system generate rapid snowmelt through the weekend. Meanwhile, in the west, another deep upper-level low will generate heavy snowfall over the Olympic mountains and rainfall over the surrounding lower elevations. This disturbance will weaken to a mere shortwave as it crosses the lower 48 over the weekend before restrengthening and developing a potent area of surface low pressure. This low pressure system may go on to produce heavy snowfall over interior portions of the Northeast on Monday, particularly over the Adirondacks, but current guidance may trend a bit farther south with the highest precipitation amounts. Heavy snow remains a threat downwind of lake Ontario. Another low pressure system will enter the West coast on Monday, bringing with it the chance for heavy snowfall to the Sierra and rain for the surrounding low elevations. This system is also forecast to restrengthen and produce a strong low pressure system over the Southern Plains. Heavy precipitation is possible over the Central Plains and Middle Mississippi Valley while heavy rain is expected across the Central/Southern Plains and into the Middle Mississippi Valley. The focus for heavy rain is expected to shift eastward into the Lower/Middle Mississippi Valley and Southeast on Wednesday. Heavier snow may shift into the Midwest on Wednesday, but models haven’t reached a consensus on this at the moment.
Most of Alaska will remain relatively quiet throughout the medium range period, while the Aleutians and mainland west coast may experience some high winds on Saturday and Sunday as a very deep area of low pressure moves itself into the Bering Sea.
(This is updated only during the week) Note the first list is weather highlights, this list is hazards. Not sure there is that much of a difference but they come from two different parts of NOAA. The Day 3 – 7 Hazards List does not update on weekends. But it is still useful as it remains valid for the period of time it covers. Of course, all forecasts are subject to change. Later we show a map of the hazards. Perhaps we should show them together.
Click here for the latest complete Day 3 -7 Hazards forecast which updates only on weekdays. It includes the full discussion which I do not update in this article but only present the highlights.
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Ski Snow Reports
New Feature – Ski Reports. (We may be a tad premature but not by much). It is difficult to find reports that auto-update on-screen (and they are very long) but these links will get you to them – If you have additional suggestions make them in the comments section after every GEI Article and we may add those links. We will try to not have too much overlap as that can add to the confusion.
We will update the above map weekly but more frequent updates can be obtained here.
Snow Forecasts.
Day 1
Day 2
Additional snow information can be found here and here.
We also include drought information in this section.
New December Drought Outlook
Seasonal Outlook Issued November 19, 2020
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Tropical Events
I am replacing the large with three small maps but you can click on them to get larger versions. Even though they are small maps you should be able to tell if there is activity and If I see activity I will make the map where there is activity full size and when available add other related maps.
the Central Pacific. | the Eastern Pacific | the Atlantic and the Gulf of Mexico |
Atlantic and Gulf of Mexico
And the Eastern Pacific
Updates on individual named storms can be obtained here.
And the Western Pacific
Weekly Tropical Forecast
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Intermediate-Term Weather Forecast
And shifting to the Alaska and CONUS Intermediate-Term Weather Forecast showing from left to right, Days 1- 5, 6 – 10, 8 – 14 and Weeks 3 – 4 You can click on these maps to have them enlarge, there are larger versions in the Addendum (More Weather the link is shown at the end of this section, and there are larger versions of these maps in the Addendum. Also, the discussions that go with these forecast maps can be found here (first two weeks) and here (Weeks 3 and 4).
First Temperature
And then Precipitation
For those interested in more detail, there are additional weather maps and information in the MORE WEATHER Addendum. The link to the Addendum is here. |
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Mesoscale Events
The following map shows where mesoscale events are occurring or forecast. If you do not see any areas highlight on this map than there are no mesoscale events taking place or forecast. A mesoscale event is a very serious situation for a very small area and detailed information is provided for these events when they occur or are forecast. If a mesoscale event is shown, click on the map and more detail on the event will be shown.
Two different parts of the NWS issue this map and they are not always in agreement although they are pretty close. They (Norman Oklahoma and College Park Maryland) issue the alerts when they realize the need, so it is best to look on both maps and click one or both if you see areas highlighted.
This next map showing where “Headlines” have been issued for convection (and an animation of the recent movement of storms) should update and you should be able to click on to get additional details but if it does not update when you click on it, click here.
There is a slight difference between convection and thunderstorms. The below map shows where “Headlines” have been issued for Thunderstorms. You should be able to click on the map to get additional details but if it does not update, you can click here.
The map below shows the current wildfire risk which becomes more significant as we move into Summer. When you click on this image it takes you to the SPC Fire Warning Page and you get a set of maps for Days 1, 2, 3 – 8, etc. You can then click on those for more detailed information. The map is a bit blurry as I tried to make it a bit larger than the map provided by NOAA but should be able to see where the current wildfire risks are. But if you click on this map, you will get to see three maps that show the risk for different time periods.
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Now the Day 3 – 7 Hazards Outlook Maps
The orange and red outlined areas are what is most concerning of the forecasted Day 3 – 7 Hazards. This graphic does not update during the weekend. There is a discussion that goes with this graphic and you can access that discussion here.
The following is provided to help the reader relate the maps to how NWS will describe an area of the U.S.
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Now to our More Detailed Weather Report
This graphic is about Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events.
500 MB Mid-Atmosphere View
The map below is the mid-atmosphere 3-Day chart rather than the surface highs and lows and weather features. In some cases, it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA’s latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Thinking about clockwise movements around High-Pressure Systems and counterclockwise movements around Low-Pressure Systems provides a lot of information.
Day 3 Above, 6 Below | Day 4 Above,7 Below | Day 5 Above. |
Here are the precipitation forecasts. First the cumulative for Days 1 – 3
Then cumulative for Days 1 – 5
Then cumulative for Days 1 – 7
Now we look at the forecast for the Maximum Temperature three days out.
Looking ahead to next week.
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Additional Tools to Obtain Watches and Warnings
Current watches, warnings, and advisories issued by the agencies of the National Weather Service. Hazards should show up in the various maps but the below links will take you to all outstanding watches and warnings in each category which may include some categories not covered in the various maps or difficult to find. So if there is a category of interest, click on the appropriate link below. |
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Below you will see a number of different maps that are updated in real-time, making this a “live” report. If a part of one or more of the maps shows an area that is highlighted, you can click on it and get the full current report. By having the reader click on these active situations rather than having GEI do so, you will not miss any events in which you might have an interest and which we had not noticed and the page will not get cluttered with warnings, etc that have since expired.
Our focus here is events that are likely to last in the range of six hours but there can be longer or shorter events that are addressed by the Storm Prediction Center which is the main source of the information in this article. Long-term major events like a Hurricane are more likely to be in a separate article. But that may not always be the case. Since in general, all the links on this page transfer you into the NOAA system, in order to get back into this article you need to either close the tab to which you were transferred or click back on the tab that has this article.
Live Warning Maps which If Severe Weather is Shown can be Clicked on to get more detail about these events. If there is a current warning shown on the map, click on the map for additional information related to the event. | These maps are updated as risks are identified. |
This is the current graphic showing any mesoscale discussions (MD’s) which are in effect over the contiguous United States. Please read the description of the purpose of our MD’s for further information. Details on all valid MD’s may be found on our Current Mesoscale Discussions page. | |
Convective Outlooks | |
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This is today’s forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. You may find the latest Day 1 Outlook available as well as all Outlooks issued today online. | Today’s Outlook |
This is tomorrow’s forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. The latest Day 2 Outlook is available as well as all Outlooks that have been issued today. | Tomorrow’s Outlook |
This is the day after tomorrow’s (day 3) forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. The latest Day 3 Outlook is available as well as all Outlooks that have been issued today. | Day 3 Outlook |
This is the day 4-8 forecast for organized severe thunderstorms over the contiguous United States. The latest Day 4-8 Outlook is available as well as all Outlooks that have been issued today. Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms (e.g. a 30% chance that a severe thunderstorm will occur within 25 miles of any point). | Day 4-8 Outlook |
The Thunderstorm Outlooks depict the probability of thunderstorms across the contiguous United States in 4 or 8 hour time periods. The probabilistic forecast directly expresses the best estimate of a thunderstorm occurring within 12 miles of a point. The three probabilistic forecast thresholds are 10, 40, and 70 percent. | Thunderstorm Outlook |
Fire Weather Outlooks | |
This is today’s forecast for organized wildfires over the contiguous United States. Please read the description of the risk categories for further information about this product. | Today’s Outlook |
This is tomorrow’s forecast for organized wildfires over the contiguous United States. Please read the description of the risk categories for further information about this product. | Tomorrow’s Outlook |
This is day 3-8 forecast for organized wildfires over the contiguous United States. Please read the description of the risk categories for further information about this product. | Day 3-8 Outlook |