Written by Sig Silber

HEADLINES (Updated 6:29 PM EST) –

– Heavy snow possible over parts of the Northern Mid-Atlantic and patches of freezing rain over parts of the Appalachians and Piedmont region of Virginia and North Carolina on Wednesday

– A series of fronts will move into the Northwest, producing rain and higher elevation snow

– Snow to develop over parts of the Central Rockies to parts of the Central/Southern Plains Monday evening into Tuesday

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 – 333 PM EST Mon Dec 14 2020

Valid 00Z Tue Dec 15 2020 – 00Z Thu Dec 17 2020

…Heavy snow possible over parts of the Northern Mid-Atlantic and patches of freezing rain over parts of the Appalachians and Piedmont region of Virginia and North Carolina on Wednesday…

…A series of fronts will move into the Northwest, producing rain and higher elevation snow…

…Snow to develop over parts of the Central Rockies to parts of the Central/Southern Plains Monday evening into Tuesday…

Low pressure over the Southern Rockies will move southeastward to the Central Gulf Coast on Tuesday evening. The storm will produce snow over parts of the Great Basin and the Central Rockies on Monday evening. On Tuesday, the snow will move into parts of the Central/Southern Plains, ending over the Central Rockies by Tuesday afternoon. On Tuesday evening, the snow will move into parts of the Middle Mississippi Valley. The system will produce one to four inches of snow over the portions of the Rockies and Central/Southern Plains. Rain will also develop over parts of the Western Gulf Coast/Southern Plains and the Lower Mississippi Valley on Tuesday afternoon into the evening. Overnight Tuesday, the rain will move into parts of the Southern Ohio/Tennessee Valleys and parts of the Southeast by Wednesday morning. Snow and isolated pockets of rain/freezing rain will develop over parts of the northern edge of the precipitation shield over parts of the Ohio Valley overnight Tuesday and Wednesday. The system will continue to produce rain over parts of the Southeast on Wednesday into Wednesday evening. The snow and freezing rain will help in creating hazardous driving conditions over the region.

On Tuesday evening, another area of low pressure along the Southeast Coast will move northward along the coast to the Northern Mid-Atlantic by Wednesday evening. The storm will produce rain over parts of the Southern Mid-Atlantic on Wednesday, with snow developing over parts of the Central Appalachians. In addition, rain and freezing rain will develop over parts of the Piedmont and Appalachian region of Virginia and North Carolina on Wednesday. By Wednesday afternoon, snow and coastal rain will develop over parts of the Northern Mid-Atlantic. The storm will produce significant snowfall accusations over parts of the Central Appalachians and the Northern Mid-Atlantic on Wednesday. The snow will start to move into parts of the Northeast by Wednesday evening. The snow and freezing rain will help create hazardous driving conditions over the Central Appalachians and the mid-Atlantic on Wednesday.

Elsewhere, a series of fronts will move into the Northwest, producing coastal rain and higher elevation snow over parts of the Pacific Northwest and Northern California, as snow develops over parts of the Northern Intermountain Region/Northern Rockies through Wednesday evening. The snow will produce hazardous driving conditions.

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 17 2020 – Monday December 21 2020

Hazards:

– Heavy snow across portions of the Northeast, Thu, Dec 17.

– Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great Basin, Sat-Mon, Dec 19-Dec 21.

– Heavy snow across portions of the Northern/Central Rockies and the Northern/Central Great Basin, Thu, Dec 17 and Sat-Mon, Dec 19-Dec 21.

– High winds across portions of the Central Great Basin, the Northern/Central Rockies, and the Northern/Central Plains, Sat-Sun, Dec 19-Dec 20.

– Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu-Sat, Dec 17-Dec 19.

– High winds across portions of mainland Alaska, Thu, Dec 17.

– Much below normal temperatures across portions of mainland Alaska, Thu-Mon, Dec 17-Dec 21.

Detailed Summary:

Throughout the medium range period (Thursday, Dec 17 – Monday, Dec 21), the main area of concern for hazards is the northwestern quadrant of the U.S. as multiple frontal systems approach and move through the region. On Thursday, one round of potentially heavy snow is forecast for mountainous areas of the interior West, including the Northern Rockies, Wind River Mountains/Tetons, and Wasatch associated with a front and an upper-level trough. Then on Friday, precipitation amounts in the West should lessen, but chances of heavy precipitation once again increase for the weekend as westerly flow increases, bringing in Pacific moisture. The Pacific Northwest and adjacent northern California can expect coastal rain and higher elevation (Coastal Range and Cascades) snow through early next week. Heavy snow is also likely to spread farther inland across the Northern Rockies and Wind River Mountains/Tetons again over the weekend and Monday. Additionally, gusty winds are possible across Washington and Oregon over the weekend, but even higher winds could be hazardous across northern/central portions of the Rockies and the northern High Plains.

Elsewhere, the nor’easter impacting the Mid-Atlantic and Northeast on Wednesday will be pulling away from the CONUS on Thursday, but snow should continue across eastern New England into Thursday before the low pressure system exits. Locally high/gusty winds are not out of the question either. Temperatures are forecast to be warmer than average by 10 to 25 degrees across the north-central U.S. through the period, with Sunday likely to be the warmest day, but hazards are not expected from these mild temperatures.

For Alaska, a low pressure system moving through the Gulf of Alaska through the latter part of the week may spread high winds to areas near the Cook Inlet, such as portions of Kodiak Island, the Bristol Bay region, and the Kenai Peninsula on Thursday. As the low tracks slowly eastward, it should spread borderline heavy precipitation across Southcentral and likely heavier amounts across the Panhandle through the end of the week. A round of precipitation may affect the Alaska Peninsula by early next week, but precipitation amounts are still in question at this point. Temperature-wise, much of the mainland is likely to see near to below average temperatures especially in terms of highs through the period. A hazard area was delineated for the eastern Interior, where low temperatures are predicted to be the most below normal, with dangerously cold temperatures in the -30s and -40s.

(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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