Written by Sig Silber

HEADLINES (Updated 3:59 PM EST) –

– Critical Fire Weather conditions in Southern California, Air Stagnation Advisories in the Northwest

– Below average temperatures for the eastern U.S., while unseasonable warmth impacts the central to northern Great Plains

– Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great Basin, Sat-Sun, Dec 12-Dec 13.

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.

Directory

CONUS Focal Points

Short Range Focal Points

Short Range Forecast Discussion NWS Weather Prediction Center College Park MD – 250 PM EST Mon Dec 07 2020

Valid 00Z Tue Dec 08 2020 – 00Z Thu Dec 10 2020

…Critical Fire Weather conditions in Southern California, Air Stagnation Advisories in the Northwest…

…Below average temperatures for the eastern U.S., while unseasonable warmth impacts the central to northern Great Plains...

The weather across most of the lower 48 will be fairly quiet through Wednesday but there are a few areas to mention. Out West, a cyclone off of the Southwest coast and strong high pressure over the Great Basin will promote strong offshore flow across southern and central California. Gusty winds and low relative humidities will translate into Critical Fire Weather for portions of southern California through Tuesday night, with an Elevated Risk extending northward into parts of central California. Farther north, poor air quality will be found for parts of the Interior Northwest as winds and mixing remain light near the surface.

Temperatures will be rather warm for the western and central U.S. as well. In fact, high temperatures in the 50s and 60s are expected through Wednesday for the northern and central Great Plains into portions of the Midwest. These numbers are roughly 20 to 40 degrees above average for early December. Above average warmth will also be found into the the western U.S., but departures from average will not be as extreme as forecasts for the central U.S.

In the East, temperatures from the Tennessee and Upper Ohio Valley to the East Coast will be roughly 5 to 15 degrees below average on Tuesday in the wake of a departing but strengthening low in the western Atlantic. Winds will also be gusty along the coast of the Mid-Atlantic and Southeast, with strong winds offshore. Chilly temperatures will linger along the East Coast but a warming trend will spread eastward to the Appalachians for Wednesday.

Regarding precipitation, locally heavy rain ahead of a cold front is expected for the Olympic Peninsula and portions of the Washington Cascades tonight. Mountain snow will be limited due to the influx of relatively warm Pacific air, but some central and eastern locations will see some freezing rain potential. Across the central Appalachians and Northeast, light snow showers will taper off tonight, but a second round of light snow is expected for parts the Northeast on Wednesday ahead of a Canadian disturbance.

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 Thursday December 10 2020 – Monday December 14 2020

Hazards:

– Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great Basin, Sat-Sun, Dec 12-Dec 13.

– Heavy snow across portions of the Central/Northern Great Basin and the Central/Northern Rockies, Sun-Mon, Dec 13-Dec 14

– High winds across portions of mainland Alaska and the Aleutians, Thu, Dec 10.

– High winds across portions of mainland Alaska, Sat-Sun, Dec 12-Dec 13.

Detailed Summary:

Over the medium range period (Thursday, Dec 10 – Monday, Dec 14), periods of precipitation are likely across the Northwest. Precipitation amounts are expected to get heavier by the weekend in the Pacific Northwest and northern California as Pacific moisture increases and a frontal system approaches. Generally higher amounts of precipitation should occur in the terrain of the Coastal Range and Cascades, with higher elevation snow and lower elevation rain. Snow is forecast to spread into the Northern Rockies toward the Wind River Mountains/Tetons early next week, and amounts could be heavy there as well. There is also some chance of gusty winds across the Central/Northern Rockies this weekend into Monday. western Washington during Monday, then diminishing by Tuesday.

Something else to watch during the period is a surface low pressure system deepening in the Plains late week and then track northeastward across the Great Lakes region by the weekend, ahead of an upper-level trough moving eastward across the CONUS. Ahead of the cold front associated with this low, Gulf of Mexico moisture could stream in and interact with the front and cause rain and thunderstorms, with highest rain amounts currently expected in and around the Lower Mississippi Valley. Since the front should be moving fairly quickly, and this area has seen below normal rainfall in the past month or so, the rainfall does not currently appear to pose widespread hazards. Then on the backside of the low track, wintry weather/snow is possible over parts of the north-central U.S., but enough uncertainty in the location and amounts of snow precluded drawing a hazard area there for now. Warmer than average temperatures by 10 to 20 degrees are forecast to push from the central U.S. Thursday/Friday into the eastern U.S. over the weekend ahead of the upper-level trough. Near average temperatures (with maximum temperatures maybe slightly below) are expected for the Intermountain West through Saturday.

Over Alaska, a deep surface low over the Bering Sea Thursday should gradually weaken through the end of the week. But the tight pressure gradient could cause strong southerly winds across portions of the Aleutians and Alaska Peninsula on Thursday, along with some potential for precipitation for that area–model guidance varies with amounts, however. Then, some gusty winds are possible Saturday around the Alaska Peninsula/Kodiak Island area with another surface low, but does not appear to rise to the level of high winds. Areas of interior Alaska also may have a threat for high winds over the weekend with another tight pressure gradient. The winds could cause blowing snow and lower visibility. Below normal temperatures are expected for the western half of mainland Alaska Thursday, spreading into eastern parts of the interior for the end of the week.

(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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