Winter Seasonal Text Alerts and forum
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*Indications of above or below average temperatures in the table above are relative to what is considered “normal” using data collected over the long term for a particular date. This is collected and maintained by the National Climatic Data Center in conjunction with the National Weather Service actual data from previous years collected at official ASOS/climatology stations across our coverage area. Also note that as time moves forward into a different period as shown above, average temperatures for those dates will also change. See the example below using Philadelphia, PA as the climo station:

The departure from normal uses the average temperature for the date, averaging temps over 24 hours for any given location, using both high and low temperatures hourly during any particular day. This outlook determines warm vs. cool periods relative to normal temperatures.

Technical discussion below will feature two (2) subcategories: Precipitation, and Pattern Discussion. Storm possibilities will be discussed exclusively in the Premium Forum with intense model analysis leading up to any major rain or severe events, not publicly. To join this discussion and hear our updated thoughts from our team, visit The My Pocket Meteorologist Page by clicking HERE and select the “Premium Weather Forum” option.

Precipitation:

After a wet start to the month and an unprecedented (in some cases) Winter storm that occurred a full week before Thanksgiving, we now look to a drier pattern in the week ahead. Snow melt will gradually occur over the next week, in spite of the colder temperatures expected through at least Thanksgiving.

Two areas of precipitation to keep an eye on, the first is a weak reinforcing cold front that moves through Sunday night/early Monday morning. A few light snow showers will be possible with that front for mainly far interior areas, and perhaps an isolated rain shower farther SE. Right now this looks like no big deal for most of the region, and no real impacts to worry about.

The 2nd comes late week or the start of the weekend, and will be in the form of showers for the entire region, since it comes at a time where temperatures are sufficiently warmer to prevent frozen precipitation. We need a perfect set-up this time of year for big snows, and while we had that Thursday, a similar set-up is not there Friday and Saturday. This is all in association with an offshore coastal system, which will be far enough away most likely to keep the showers threat light. We’ll monitor throughout the week.

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Breakdown of precipitation departures from normal over the next several weeks:

November 19th-November 25th: Slightly below average

November 26th-December 1st: Near average

December 2nd-December 9th: Near average

December 10th-December 16th: Near average

Public/free available maps will be updated when a threat is imminent for significant weather or snowfall on the weather alerts page throughout the Winter:  http://epawaweather.com/weather-alerts/

Note:  Any image in the outlook is clickable for larger viewing

A weak cold front moves through late Sunday night and early Monday bringing light snow showers to the far interior, and light rain showers farther SE. This appears to be an insignificant frontal passage at this time.

An offshore coastal system will have to be watched closely at the end of the week, but the GFS shown below keeps most of the rain offshore. Euro is more showery over the entire region, but it is rain this time, not snow. 

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently in the circle of death, and the best forcing is expected to propagate eastward into the Western Pacific afterwards in the coming weeks. The trend has been to keep the signal weaker and not as strong as best tropical forcing moves eastward with time. This likely means that although there will be some noted milder risks just after Thanksgiving, likely the milder periods are transient in nature and associated with synoptic warmth ahead of systems. In part this is tied to the influence of warm Sea Surface Temperatures in the Gulf of Alaska. As we near the end of the month, the signal is becoming more clear with the GEFS and EPS at no longer at odds with tropical forcing propagation, showing it moving into a colder phase 8/1 look. A slight dip into negative AAM anomalies in the subtropics during the post Thanksgiving time frame lend credence to the milder period, but we have seen guidance trend colder as we head towards the end of November and early December with +AAM anomalies returning, and the MJO reaching more favorable phases.

The pattern begins with higher than normal amplification that is partly responsible for the amped heavy rain and snow systems we dealt with in the first half of the month. We now turn more zonal, which will allow for both less precipitation overall, and milder risks to enter the picture after Thanksgiving, although transient. We opted to abandon the warmer look to start December as indicated by the Euro weeklies (week 4) last week, and follow the pattern and analogs that suggest different. That appears to have been a good choice, as the long range weeklies have since adjusted and trended colder. Another weaker polar vortex (PV) disruption as projected by the GFS that also would lead to the cooler risks returning late month and early December.

Snowfall in November will remain well above normal due to the anomalous pre-Thanksgiving snow storm seen on Thursday 11/15. Monthly normals were by far exceeded in that one storm, and in some cases, were the highest snow totals from any November storm, on any November date, in recorded history. The analogs chosen in the Winter Outlook for 2018-2019 would suggest slightly above average snow to fall in the month of December, and perhaps an impactful event within the first two weeks of December.

It is important to understand that average highs/lows will be steadily dropping as we move deeper into Autumn, and any indications of slightly above average temperatures at that time are relative. For example, normal average high in Philadelphia on November 24th is 53°F, so any slightly above average high temperatures expected are likely to be in the mid to upper 50s.

The November outlook suggests a near to slightly below average month (-2.0°F to +0.0°F) as a whole. Early look at the month of December, using top analogs chosen for the 2018-2019 Winter Outlook and climate models, suggest another near to slightly below average month as a whole (-2.0°F to +0.0°F) and slightly above average snowfall.

Note:  Any image in the outlook is clickable for larger viewing

GEFS ensembles show the below average temps across the region next week continuing as the deep trough in the Central Plains moves eastward, especially midweek.

After Thanksgiving, we see the temperatures rebound as milder air found across the Central US moves eastward. Still slightly above average here, and transient.

Images below are clickable for better viewing

Days 1-5 – confidence VERY HIGH

Days 6-10 – confidence HIGH

Days 11-15 – confidence MODERATELY HIGH

Days 16-20 – confidence MODERATE

Below is a look at the latest Soil Moisture Anomaly for the Contiguous United States. This is used by NOAA/CPC for the purpose of drought monitoring and drought outlooks.

This image will automatically update daily.

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Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated:  Friday November 16th, 1:10pm