Written by Sig Silber

HEADLINES (Updated 4:37 PM EST) –

– Lake Effect snow for the Lower Great Lakes

– Rain and higher elevation snow for parts of the Pacific Northwest

– Critical risk of fire weather in Southern California, Air Stagnation Advisories continue in the North Intermountain Region

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 – 257 PM EST Tue Dec 08 2020

Valid 00Z Wed Dec 09 2020 – 00Z Fri Dec 11 2020

…Lake Effect snow for the Lower Great Lakes...

…Rain and higher elevation snow for parts of the Pacific Northwest…

…Critical risk of fire weather in Southern California, Air Stagnation Advisories continue in the North Intermountain Region…

Upper-level energy and cold air flowing over the relatively warm Great Lakes will aid in producing Lake Effect snow over the Lower Great Lakes through Thursday. The snow will aid in creating hazardous driving conditions over the region.

Meanwhile, a front moving into the Pacific Northwest will move inland to the Upper Mississippi Valley/Central Plains by Thursday. Moisture associated with the boundary will help produce rain and higher elevation over parts of the Pacific Northwest and snow over parts of the Northern Intermountain Region through late Wednesday night. The snow will aid in producing unsafe driving conditions over the area.

Next, an upper-level low will move into Northwestern Mexico/Southwestern U. S. overnight Wednesday that will weaken while moving to the Southern Rockies by Thursday. The energy will produce rain over parts of the Southwest into the Southern Rockies on Thursday. Furthermore, upper-level energy and associated moisture will help create rain over parts of the Pacific Northwest and Northern California on Thursday evening. In addition, moderate to strong Santa Ana winds are forecast to be ongoing across Southern California. The strong wind will be due in part to the strong surface pressure gradient associated with the Great Basin’s high pressure. On Wednesday, the widespread elevated and locally critical fire weather conditions from remnant offshore winds will become increasingly local through the day as low-level flow and the offshore pressure gradient weakens. Due to these conditions, Red Flag Warnings have been issued across parts of Southern California.

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 Friday December 11 2020 – Tuesday December 15 2020

Hazards:

– Heavy precipitation from portions of northern California into the Pacific Northwest, Sat-Sun, Dec 12-Dec 13.

– Heavy precipitation across northwestern Washington, Tue, Dec 15.

– Heavy precipitation from portions of northern Illinois to lower Michigan, Sat, Dec 12.

– Heavy precipitation across portions of northern Maine, Sun, Dec 13.

– Heavy rain from across portions of lower Michigan down across the Midwest, the mid-Mississippi Valley, and to the west of the lower Mississippi Valley, Fri-Sat, Dec 11-Dec 12.

– Heavy snow across portions of the higher elevations of northeastern Washington, Idaho, and the northern Rockies, Sun-Mon, Dec 13-Dec 14.

– High winds across portions of interior Alaska, Sun-Tue, Dec 13-Dec 15.

Detailed Summary:

An active pattern in the northeastern Pacific will continue to send low pressure/frontal systems toward the Pacific Northwest into the medium range period (Friday, Dec 11 – Tuesday, Dec 15), with the next wave of precipitation likely reaching the coast by Friday night. Lower-elevation rain and mountain snow will likely become heavy through much of the weekend as they will likely spread well inland across Idaho and into the northern Rockies such as the Wind River Mountains/Tetons on Sunday into Monday. Generally higher amounts of precipitation should occur in the terrain of the Coastal Range and Cascades. Gusty winds will likely accompany the passage of a warm front followed by a cold front across the Pacific Northwest this weekend into Monday. By next Tuesday, there appears to be decent model agreement on the arrival of the next wave of moisture across northwestern Washington.

Meanwhile, an upper trough exiting into the central Plains will likely evolve into a deepening surface low pressure system that will track from the central Plains to the lower Great Lakes Friday into the weekend. Ahead of the cold front associated with this low, Gulf of Mexico moisture will likely be lifted to result in a quick round of heavy rainfall Friday night to the west of the lower Mississippi Valley, and then across the Midwest toward the lower Great Lakes on Saturday. In the mean time, cold air from Canada is forecast to settle southward and then wrap around the backside of the cyclone. This will likely change the precipitation from rain to snow near and just north of the cyclone track. A heavy precipitation area is indicated for this changeover where the 24-hour QPF amounts are an inch or higher. There is still some uncertainty regarding the storm track but the models appear to have settled into the present forecast track. The system will also bring a decent amount of wintry precipitation for northern Maine on Sunday. Finally, it is worth mentioning that the ECMWF has introduced the possibility of a rapidly intensifying cyclone early next week across the Southeast to the Mid-Atlantic. This scenario has not been incorporated into the current hazards map.

Warmer than average temperatures by 10 to 20 degrees are forecast to push from the central U.S. 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 persistent high pressure system centered in the Arctic Ocean will be contrasted with deep cyclones moving across the northeastern Pacific to create a tight pressure gradient over mainland Alaska. Interior central Alaska will likely see the highest threat for high winds late in the weekend into early next week. The winds could cause blowing snow and lowering of visibility.

(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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