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Monitoring a fast-moving clipper
system for Saturday night-Sunday

Long Range Outlook

Important information:

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Long range analysis: Technical discussion is below for advanced readers:

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 snow, ice, or rain events, not publicly. To join this discussion and hear the updated thoughts from our team, visit The My Pocket Meteorologist Page by clicking HERE and select the “Premium Weather Forum” option.

Precipitation Discussion:

Precipitation:

OVERVIEW: Precipitation thus far in the month of November is running slightly below average at most locales, and with below average precipitation expected the rest of the way, we raised the confidence level of the near to slightly below average precipitation departures for the month as a whole to VERY HIGH this week. We also maintained near to slightly below average precipitation departures for December with extended range guidance continuing to indicate more of the same type of overall pattern typical of early season weak La Niña. Snow will start figuring into the forecast after Thanksgiving and throughout the month of December, most notably beyond the 2nd full week of December.

Shorter term, a weak wave will cross the region late Saturday night and early Sunday morning with a few light snow showers possible in some areas, followed by trailing upper level energy Sunday PM and overnight. The latter energy will be responsible for more snow shower activity north of I-78, most notably nearest the I-80 corridor in PA. Very minor accumulations are possible with most areas seeing a coating to 1″ of snow on non-paved surfaces, and perhaps an inch or two across the higher elevations. This is likely not a snow map-worthy event, but areas affected will be sent MPM text alerts in areas expecting minor accumulations of snow. A potentially more potent system will likely precede the next trough next weekend, and with warming temperatures out in front of the system and its associated cold front, the primary precipitation type is expected to be in the form of rain. Some areas may end as snow as the system passes and colder air rushes in with the trough if there is any remaining anafrontal precipitation at that time. Ensembles have recently backed off the 8th-12th period for anything significant, but snow will be possible during this period. We have also introduced another period ten days later for a Winter storm signal between the 18th-22nd of December.

The month of November we project will finish with slightly below average (-0.5″ to -1.5″) precipitation departures for the month as a whole, with very high confidence. The remainder of the month from this point forward we project below average precipitation. Snowfall for the month will also likely finish slightly below average, and mainly for the interior/northern locales. Looking ahead to the month of December suggests a near to slightly below average precipitation (+0.0″ to -0.5″) anomaly for the month as a whole, using long range climate guidance and global observational trends. Snowfall in December we expect to be slightly above average.

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

November 28th – December 4th: Slightly below average

December 5th – December 11th: Near to slightly above average

December 12th – December 18th: Near average

December 19th – December 25th: Near to slightly above average

December 26th – January 1st: Near average

January 2nd – January 8th: Near average

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

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

A quick-moving wave brings a few snow showers late Saturday night into early Sunday for some areas, then a trailing upper level low pushes through Sunday PM/night with more snow showers most notably nearest the I-80 corridor.

A potentially more potent system and its associated cold front on the lead of the next trough will arrive next weekend. Given the antecedent airmass expected to be milder, rain will likely be the primary p-type at least initially with this system.

Pattern Discussion:

Pattern:

OVERVIEW: The month of November thus far has seen slightly below average temperatures overall at most locales within our region. Despite the transient warmer shots ahead of troughs and their associated cold fronts, the colder anomalies have outweighed the milder periods. Going forward through the remainder of November, colder than average will continue to be commonplace. December we maintained a slightly below average temperature projections this week for the month as a whole for the 2nd straight month, but not consistently below average until the 2nd half of December. The first two weeks of December will mimic the pattern found in late November with ups and downs fairly well.

The Madden-Julian Oscillation (MJO) is currently in the Circle of Death (COD) nearest the Maritime Continent, and is largely expected to remain there through very early December. The ensemble spread on most guidance shows most members migrating the MJO/KW into the Western Pacific heading into the first week of December, and this will have implications on December temperatures and the overall pattern. A brief stint in phase 6, followed by a propagation into phase 7 through mid-late month is currently projected by most guidance. Phase 6 is a cooler signal in a weak La Niña in December, but given the limited time of just a few days in phase 6, it doesn’t look like it will have a profound effect on the pattern. Phase 7 supports the temperature swings expected in the first half of December, but leans cooler than average overall. The GEFS, Australian BOMM, and EPS camps are in fairly close alignment with this MJO projection in the nearer term through mid-December. MJO waves are monitored going forward from November onward for identifying longer term cold/mild periods and Winter storm signals.

Average highs and lows are continuing a slow and gradual drop-off week to week. Normal high temperatures are currently in the 47-52°F range from north to south across our coverage region, which is about 3°F lower than last week at this time. Average highs and lows will continue to gradually decline over the next few weeks which maintains about a 2°F per week drop through December. Any above or below average stretches listed in the outlook will be relative to seasonal norms at that time, and it is important to note that cooler/warmer periods will be relative to the time of year we are talking about. For example, slightly below average temperatures listed over the next several days will generally feature highs of 40-45° from north to south. Use the average highs/lows chart below that provides a point of reference for what average is for each corresponding date, with the examples used for the Philadelphia region.

The month of November we project will finish with slightly below average temperatures (-2.0°F to -4.0°F) when the dust settles November 30th with very high confidence. Early look at the month of December as a whole suggests another slightly below average month (-1.0°F to -3.0°F) using long term climate models and seasonal/global observation trends. Those recent trends for December have been for favoring more of the same type of pattern we have seen recently in the first half of the month, followed by a more consistent slightly below average 2nd half.

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

Cooler temps to end November will yield to a transient warm-up for a few days late next week and weekend, then back to colder temperatures afterwards.

Average snowfall for the next two months at our major stations are listed below, with not much overall expected in November. Snowfall increases in December.

This week's long range table

Date(s)ThreatsSignificanceConfidence
11/27-12/1TemperatureSlightly below averageVery high
12/2-12/4TemperatureNear to slightly above averageHigh
12/5-12/10TemperatureSlightly below averageModerately high
12/11-12/17TemperatureNear averageModerate
12/18-12/24TemperatureSlightly below averageModerately low
12/25-1/2TemperatureSlightly below averageLow
1/3-1/9TemperatureNear to slightly below averageVery low
11/27-11/28Snow showersA weak clipper system brings some snow showers later Saturday night, then more snow showers are possible Sunday PM/night as the upper level energy swings through with very minor accumulations possible nearest the I-80 corridor and mainly north of I-78 on Sunday.High
12/4-12/5RainPotent low pressure and its associated cold front on the lead of the next trough will move through the region next weekend, with the potential for rain that may end as snow for some areas.Moderately high
12/8-12/12Winter Storm SignalA winter storm signal has been identified during this period using longer range ensembles and global observational trends. A Winter storm signal is a favorable period from a probabilistic standpoint, but does not guarantee accumulating snow at any given location.Moderate
12/18-12/22Winter Storm SignalA winter storm signal has been identified during this period using longer range ensembles and global observational trends. A Winter storm signal is a favorable period from a probabilistic standpoint, but does not guarantee accumulating snow at any given location.Moderate
November as a wholeTemperatureBelow average (-2.0°F to -4.0°F)Very high
November as a wholePrecipitationSlightly below average (-0.5" to -1.5")Very high
November as a wholeSnowfallSlightly below averageVery high
December as a wholeTemperatureSlightly below average (-1.0°F to -3.0°F)Moderately high
December as a wholePrecipitationNear to slightly below average (+0.0" to -0.5")Moderate
December as a wholeSnowfallSlightly above averageModerate

Outlook table last updated: Friday November 26th, 11:30 AM. Next scheduled update: Friday December 3rd.

This is a weekly updated public long range guidance product from EPAWA. For daily long range updates and more detailed updates M-F, please join the EPAWA forum. More information/sign-up at: http://epawaweather.com/mpm/ 

Climatology

*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:

DateAverage High/Low (°F)EPAWA projection for temperature departure from normal/average
November 27th52°F/36°FSlightly below average
December 4th49°F/34°FNear to slightly above average
December 11th47°F/32°FNear average
December 18th45°F/31°FSlightly below average
December 25th44°F/29°FSlightly below average
January 1st42°F/28°FSlightly below average
January 8th42°F/27°FNear to slightly below average

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.

Next 3 weeks of US temperature departures

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

Current U.S. Soil Moisture Anomaly

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.

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday November 26th, 11:30 AM