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:

We will see the active precipitation pattern continue through the end of the month. The first system we’ll be dealing with will move in Saturday late afternoon/evening and continue into the overnight period, and into Sunday morning. This is a far interior heavy snow, a snow to mix to rain situation in the middle, and heavy rain farther SE. For the latest map/call regarding this system, please visit the Weather Alerts page by clicking here:  http://epawaweather.com/weather-alerts/.

The next system comes in early next week, and is tied to a frontal boundary moving through on Wednesday. Rain showers are expected for all areas with the front, then most modeling hangs up the front and stalls it over the region on Wednesday night as it runs into ridging to the east and southeast. A low pressure center will form along that boundary and move northeastward, bringing periods of rain most likely Wednesday night and Thursday, and some could be heavy. This is the true pattern changing storm, and sustainable cold air locks in afterwards through February with no transient warm-ups in between. There is a chance the front is a bit more progressive and a wintry aspect will be brought into the equation, but odds are against that happening at this time. We will monitor it closely.

Another system looks to affect the region next weekend, but it is too early to speculate on that one to closely. Models are showing a clipper system moving through the Great Lakes, and then some show possible redevelopment near the coast. If no redevelopment occurs, this is a light snow event. If it does redevelop, it could be a much larger system. Regardless of evolution, this time period is outlined as the next winter storm signal, and will be snow as the precipitation type. We will revisit this one next week in daily local forecasts and forecast videos. Further storm signals are expected in early February, and we will outline those next week.

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Meteorologist Bobby Martrich [EPAWA] on Twitter:  https://twitter.com/epawawx

YouTube channel/daily forecast video: https://www.youtube.com/user/eastpaweather

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

January 21st-January 27th: Slightly above to above average

January 28th-February 3rd: Near average

February 4th-February 10th: Near average

February 11th-February 17th: Near to slightly above 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

The latest HRRR 3km simulated radar at 11:00pm Saturday shows heavy snow in the northern interior, changing to ice in the central areas, and rain farther south. The ice/rain line continues to move northward in the overnight.

A storm that will likely usher in the long-awaited pattern change is due to arrive this Friday. Unfortunately for snow lovers, this one is rain for most before the change. But there are several winter storms in the pipeline.

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently in the phase 4 octant, and the best forcing is expected to move through phases 5 and 6 thereafter. Beyond an extensive time spent in the circle of death. Stratospheric warming and a change in wind direction from west to east in the stratosphere occurred near New Year’s Eve, and the well-advertised subsequent stratospheric vortex split is observed as doing such. Strong stratospheric warming episodes disrupt the Polar Vortex (PV) away from the polar regions, and displaces the cold air farther south to lower latitudes. We do think we will see these changes and subsequent downwelling to the troposphere affecting our sensible weather beginning on January 20th briefly, then it relaxes and reloads on the 23rd/24th, then is here to stay thereafter. Stratospheric split vorticies that do successfully downwell to the troposphere will generally last 45-60 days from start, which takes us at least through the entire month of February. Once the pattern changes, it likely locks in for quite some time.

Through late Fall and early Winter, the pattern has been very similar to a Nov/Dec 2014 look, which featured colder than average in November 2014 (with a significant pre-Thanksgiving snow storm that year) followed by a mild and rainy December 2014. The mild bled into early January of 2015 before a flip into winter mode occurred, and the colder than average temperatures and above average snowfall followed through March 2015. We will not see this flip as early as we saw in January 2015, but do think we will see a turnaround this winter, beginning around January 24th.

Will we still see above average snowfall and make up for lost time? 

Yes, we still think so. We were never on the snowy December kick that some expected, and argued that December 2018 would mimic a December 2014 milder pattern. We also figured January would start off mild, then flip. While we were previously a few days early on that flip projection, it still will come. As such, with our expectations low for the early part of winter, our snowfall projections for an above average winter as a whole is still on track. Might be an active and wild 6-8 week period, but still winter nevertheless.

The January outlook is for a slightly above average month (+1.0°F to +3.0°F) as a whole with moderately high confidence. The milder start to the month will be offset somewhat once the pattern changes around the 20th of January, but with 2/3rds of the month prior remaining largely above average, the colder periods in the late month period will be difficult to completely offset the month as a whole. Our forecast for February suggests a well below average month (-5.0°F to -9.0°F) with well above average snowfall once the cold locks in from late January onward.

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

The GEFS show the transient milder period on the 23rd/24th prior to the pattern change expected on 1/24. Accompanying this milder period will be a pattern changing rain storm in the Wed. night/Thurs. period.

This is the GEFS agree with our take that January 24th will be the pattern flip date. Cold air previously locked up in Canada is will settle over our region from Friday 1/25 onward, and remain in place through February.

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.

The My Pocket Meteorologist text alert program is a year-round program, and seasonal options for Spring/Summer will be available soon. Click on the image below for more information.

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated:  Saturday January 19th, 2:50pm