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Spring-like temps to come to an end;
t-storms Saturday break the warmth
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Long Range Outlooks

DatesThreatsSignificanceConfidence
2/25TemperatureWell above averageVery high
2/26TemperatureNear averageVery high
2/27-3/1TemperatureAbove averageVery high
3/2-3/6TemperatureNear to slightly above averageHigh
3/7-3/10TemperatureSlightly below averageModerately high
3/11-3/15TemperatureNear to slightly above averageModerate
3/16-3/20TemperatureAbove averageModerate
3/21-3/26TemperatureNear averageModerate
2/25PrecipitationA strong cold front will move through the region Saturday afternoon/evening, bringing with it scattered showers and thunderstorms. Some storms could be locally strong with locally damaging wind gusts greater than 50mph.Very high
2/28-3/1PrecipitationA warm front will move through with showers on Tuesday, followed by a 2nd cold front a day later than could be accompanied by scattered showers and thunderstorms.High
February as a wholeTemperatureWell above average (+7°F to +10°F)Very high
February as a wholePrecipitationSlightly below averageHigh
February as a wholeSnowfallBelow averageVery high
March as a wholeTemperatureAbove average overall with transient cold shots most notably March week 2Moderately high
March as a wholePrecipitationNear to slightly above averageModerate
March as a wholeSnowfallBelow averageModerately high

Outlook table last updated: Thursday February 24th, 1:30pm. Next update: Friday March 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/my-pocket-meteorologist/ 

*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 Hi/LoEPAWA projection
February 25th46°F/30°FWell above average
March 4th49°F/31°FNear to slightly above average
March 11th51°F/33°FNear to slightly above 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.

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

Technical discussion below will feature two (2) subcategories: Precipitation, and Pattern Discussion. Wintry possibilities will be discussed exclusively in the Premium Forum with intense model analysis leading up to any Wintry 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 Discussion:

Precipitation:

Two precipitation events to speak of this week. The first will be a strong cold front passage on Saturday afternoon and evening that will effectively end the exceptional warmth that we have been seeing currently. This cold front will be accompanied by strong to perhaps isolated severe thunderstorms ahead of the front Saturday afternoon and early evening farther east into New Jersey. The main threat from this line will be strong to isolated severe straight line winds. With the strong low-level jet modeled to be in excess of 55-60 knots at the 850mb level, it won’t take much to transport some of that to the surface, resulting in winds over 50mph, and isolated over 60mph. Widespread severe weather is not expected, but be alert for sudden changes, and adhere to any severe thunderstorm warnings that are issued by the National Weather Service. My Pocket Meteorologist alerts will be sent as needed in realtime to those subscribed, which will detail expectations of any individual threats as they are headed toward a particular county/area.

The 2nd event is a warm front that will move through the region on Tuesday, which will be accompanied by rain showers, and then followed by a cold front later in the day or evening on Wednesday. This cold front will have the ability to produce thunderstorms once again, but currently not modeled to be as potent as its predecessor front this Saturday.

All public/freely available maps will be updated when the threat is imminent for severe weather and snow threats 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 4km NAM shows the line of showers and perhaps strong thunderstorms moving from west to east across PA during the afternoon. Image is for 3pm Saturday.

nam2

The GFS shows the next chance of thunderstorms along a cold front on Wednesday. This will be preceded by scattered showers on Tuesday prior (not pictured).

gfs1

Pattern Discussion:

Pattern:

We are currently in a very abnormally warm pattern for late February, and we are seeing temperatures more normal for late May. This warmth is setting records, and in some ways is unprecedented in that regard. We spoke in previous outlooks about how this pattern going forward will be more of the transient variety, which means nothing sustainable for a long period of time. If you don’t like the weather today, just wait a few days, it will likely be different. And that is what is reflected in the table above, a lot of short-lived shots of warmth, followed by colder for a few days, then warmer, then colder. Wash-rinse-repeat. This pattern is expected to continue for much of the month of March into at least the first half of April. But at the end of the day, or in this case, month… the warm will outweigh the colder periods. Does this mean we will not see anymore Wintry weather? Not necessarily. But odds exponentially decrease with time, as we introduce two more negating factors not seeing in the heart of Winter, like during the month of January. Those two factors are:

  1. Climatology. The daily highs and lows are steadily increasing just about every other day. The longer into the future one ventures, the higher the average temperatures.
  2. Sun angle. As not seen in January, the sun angle is steadily increasing in the sky. This means if you do see a fluke snowfall, it will likely disappear very quickly, and will have to be timed right. Starting overnight vs. middle of the day makes a difference.

With that being said, the outlook for snow going forward isn’t that great. In order for this to occur, it would have to be a perfectly timed, thread-the-needle type of event, to coincide with one of the colder shots listed in the table, and favors the far interior locations and areas of elevation. Far interior is defined as north of I-78 in Pennsylvania and New Jersey, and north/west of I-287 in New Jersey. That doesn’t mean something can’t happen farther south, but that is where the best chance for something to occur would be. Best odds. The GFS has been hinting at one or more snow events in the extended range, but that would have to coincide with colder shots to work out. Most notably, the 2nd week of March. Currently there is a small window of opportunity there, which would be remarkable after this recent exceptional warmth, but nothing to get excited about yet or threats to take seriously.

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

GEFS (GFS ensembles) show propagation of the MJO into favorable phases of 2 and 3 before collapsing into the circle of death. If ensembles are correct with a blocking signal over Greenland, this has the opportunity to produce at least slightly below average temperatures for a time.

mjo2

Euro/EPS also agrees with the GEFS of a relatively quick propagation through phases 2 and 3 before collapsing into the circle of death. Best forcing is still shown to be on the Maritime Continent at this point, however, which means warmer weather should arrive for a time by mid-month.

mjo3

EPAWA 1-5 day temperature departure outlook

1-5

EPAWA 6-10 day temperature departure outlook

6-10

EPAWA 11-15 day temperature departure outlook

11-15

EPAWA 16-20 day temperature departure outlook

16-20

Our 2016-2017 Winter Mea Culpa

It largely appears like the culprit this lackluster Winter comes down to a combination of three things… this was outlined in the “what can go wrong” section of the Winter Outlook as the very first bullet point. Those three things are:

(1) QBO (Quasi-biennial Oscillation) remained too far positive, and didn’t decline as suggested by leading analog years that matched this year well. In other words, it is an unprecedented year to see the weak La Niña combined with low solar and a ++QBO around +15. Never happened that I know of. QBO is a measure of the strength of equatorial stratospheric zonal winds, positive is westerly, negative is easterly. If the zonal winds are too strong (outside of +/- 8) then it keeps the Polar Vortex (PV) too strong. If the PV is too strong, it remains over the North Pole, and is very difficult to displace. Without it being displaced, cold is locked up over the polar regions, including most of Canada, but has a difficult time reaching the lower latitudes aside from transient cold shots.

(2) Uncooperative Pacific and La Niña base state. This also has a derived effect from the QBO and strong PV. Despite being a weak La Niña headed toward neutral, this winter behaved like a stronger La Niña, where the SE ridge flexes and allows storms to cut more frequently. Had the PV been weaker, it could have easily offset this effect, but this base state was allowed to dominate since November with no splits or displacements of the PV since then. This led to a very fast Pacific jet at times that allowed much of the country to flood with milder air, and the Madden-Julian Oscillation (MJO) never really was able to get the best tropical forcing away from the Maritime Continent as a general rule.

(3) Taking the words of Michael Molda, one of the moderators on our premium forum, “The Pacific Decadal Oscillation (PDO), or complete lack thereof. We have had several years to start this decade with a very beneficial north Pacific warm Sea Surface Temperatures (SSTs) promoting/nudging that ridge (PNA+) that helped regardless what the other pattern pieces are. No help this year, at all.”

So lack of Winter really ultimately came down to the ++QBO that didn’t drop as analogs suggested, and this is a new analog that we will be able to study for the years to come. There is NO WAY to predict the QBO accurately… any forecaster that says the opposite is fooling you and themselves. There are things like low solar and snow cover in Siberia in early Fall that typically contribute to a weaker QBO, but not always. This is obviously a year where the QBO didn’t behave as expected, and henceforth, an incorrect Winter forecast. I refer to the QBO as the “grim reaper” of outlooks, because largely of its unpredictability, has the ability to take a perfectly good and well researched Winter outlook and shred it apart. As a result of this, it is clear that seasonal outlooks – namely Winter – are a waste of time and energy. We will still offer our seasonal thoughts in the premium forum, but the public outlooks have been discontinued. We will continue the weekly/public long range outlooks like we have been every Friday, but those outlooks will be limited to 2-3 week leads, outlining the cold/warm periods and precipitation.

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

The QBO since August has not dropped like anticipated, instead stayed above +10 through January 2017. Ideally you want this to be between +/- 8.

qbo1

The Stratospheric Polar Vortex (PV) remained strong since after November, largely due to stronger westerlies/+QBO.

strat1

PDO also declined a bit more rapidly than anticipated, leaving little room for the -EPO to save the day as it did in years prior.

sst

Current U.S. Snow Cover

My Pocket Meteorologist

My Pocket Meteorologist Winter-only seasonal text alert options now available at a 50% off mid-winter discount! Simply click on the product description image below to sign up!

mpm2

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated:  Friday February 24th, 1:30pm