Written by Sig Silber

HEADLINES (Updated 3:16 PM and 5:14 PM EST) –

– Significant Winter Storm for New England as rapidly-intensifying Nor’easter moves from the Mid-Atlantic to New England; heavy snow possible across portions of New England

– There is a Slight Risk of severe thunderstorms over parts of Coastal North Carolina

– Critical Fire Weather risk along the Coastal Ranges of Southern California today, Air Stagnation Advisories in the Northwest

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.

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CONUS Focal Points

Short Range Focal Points

Short Range Forecast Discussion NWS Weather Prediction Center College Park MD – 353 PM EST Fri Dec 04 2020

Valid 00Z Sat Dec 05 2020 – 00Z Mon Dec 07 2020

…Significant Winter Storm for New England as rapidly-intensifying Nor’easter moves from the Mid-Atlantic to New England; heavy snow possible across portions of New England…

…There is a Slight Risk of severe thunderstorms over parts of Coastal North Carolina…

…Critical Fire Weather risk along the Coastal Ranges of Southern California today, Air Stagnation Advisories in the Northwest…

A significant winter storm will develop over New England as the rapidly-intensifying Nor’easter moves from the Mid-Atlantic to New England on Saturday into Sunday. The storm will produce heavy snow across portions of the Northeast on Saturday and Sunday. The snowfall totals will be 12-18 inches locally higher for interior NH and Maine, and 6-12 inches for central Massachusetts and, just inland of I-95, from eastern Massachusetts to the central Maine coast. There is the potential for heavy snow extending south from central Massachusetts into CT. The system will start as an area of low pressure over the Southern Appalachians on Friday evening, which will move northward along the Mid-Atlantic and the Northeast Coast, advancing to the Canadian Maritimes by Sunday evening. The SPC has issued a Slight Risk of severe thunderstorms over parts of North Carolina through Saturday morning. The significant hazards associated with severe thunderstorms are frequent lightning, severe thunderstorm wind gust, and a couple of tornadoes. The storm will produce periods of heavy rain over parts of the Mid-Atlantic and Northeast Coast. In addition to the rain, the wind speed will increase, with the strongest wind felt along the New England Coast, where high surf, coastal flooding, and beach erosion are possible.

Elsewhere, weather throughout the Western United States will remain relatively quiet due to an expansive area of high pressure. The lone exception is Southern California, where gusty offshore winds will to continue across the region. These winds, combined with dry air, will allow for any wildfires to spread rapidly. The SPC has issued a Critical Fire Weather area from the San Diego County Mountains northward to the higher elevations of eastern Ventura and western Los Angeles counties. Elevated Fire Weather conditions are likely to persist in these areas on Saturday. Red Flag Warnings and Wind Advisories are also issued for much of Southern California. Much of the Northwest is under Air Stagnation Advisories through Sunday due to the large dome of high-pressure overhead and poor air quality at low levels.

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 Monday December 07 2020 – Friday December 11 2020

Hazards:

– Heavy precipitation across portions of the Pacific Northwest, Tue, Dec 8.

– Flooding possible across portions of the Southern Appalachians, the Mid-Atlantic, the Northeast, and the Central Appalachians.

– High significant wave heights for coastal portions of the Pacific Northwest, Mon, Dec 7.

– Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Tue, Dec 7-Dec 8.

– High significant wave heights for coastal portions of the Alaska Panhandle and mainland Alaska, Mon, Dec 7.

Detailed Summary:

It looks like much of the lower 48 will experience relatively dry weather for much of next week. The only really notable exception will be the Pacific Northwest, where a cold front and associated onshore flow will support some moderate to isolated heavy precipitation (upwards of 1-2 inches) across the Olympics and northern Washington Cascades later Monday into Tuesday. This is a warm system for early December, so snow levels will range higher than average for this event. In addition, a long fetch of southwesterly flow associated with a powerful low tracking south of the Aleutians will support waves up to 20 feet offshore of western Washington during Monday, then diminishing by Tuesday.

Otherwise, there’s the potential for Santa Ana winds in central/southern California early next week as an upper level low tracks south-southwest from the Great Basin through southern California. At this time, this doesn’t appear to be a significant event (unlike the conditions earlier this week), so opted not to outline a hazards area. Farther east, upper level ridging and downslope flow will result in an unusually mild stretch of days across the Plains and upper Midwest. High temperatures Monday-Wednesday will range up to 15-25 degrees above normal before cooler weather returns later next week.

Over Alaska, onshore flow associated with a large and deep area of low pressure tracking into the Gulf of Alaska will bring widespread moderate to heavy precipitation Monday into Tuesday into south-central Alaska (mostly east of the Kenai Peninsula) and across much of the Alaska Panhandle. Precipitation amounts will range up to 1-3 inches each day over south-central Alaska, but likely somewhat lighter over the Panhandle. However, given the recent very heavy rainfall, any additional amounts could exacerbate flooding. In addition, as mentioned above, a large area of significant wave heights of around 20-25 feet are expected Monday across coastal sections of the same general region impacted with heavy precipitation. Elsewhere, there are indications of a potentially strong low developing and tracking near or across the western Aleutians toward the latter part of next week. There are still notable discrepancies among the models, but it’s something to monitor over then next few days.

(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

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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

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
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

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