Mostly dry weekend, but more
clouds than sun will dominate

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:

OVERVIEW: Relatively dry conditions for most of the region through the first half of the month to date will likely continue in the week ahead, with just a few minor impulses in the vicinity Sunday-Monday, followed by two separate cold fronts midweek and next weekend. At present time compared to seasonal norms, even with a possible uptick in precipitation to end April (final week) it doesn’t look like it will be enough to overcome the below average precipitation departures currently running 0.5-1.0″ below average observed across the region through April 16th. May continues to look a bit wetter at least during the first half of the month, with a closer to average outlook for the 2nd half of May.

The first chance for precipitation in this outlook is not very noteworthy, as back to back weak impulses move through the region on Sunday and Monday. A stray shower cannot be ruled out on either occasion, however recent modeling trends have been to limit this chance to just Monday. A better chance for scattered showers presents itself on Wednesday as a cold front moves through the region, but precipitation does not look to be a lot with a quarter inch or less for most areas. Another reinforcing cold front is due to arrive next weekend, with the GFS suggesting Saturday, and the European guidance pushing that chance off until Sunday. Scattered showers will again be possible along and ahead of the boundary.

The month of April we project will finish with slightly below average (-0.5″ to -1.0″) precipitation departures for the month as a whole with moderately high confidence. Snowfall is unlikely from this point forward, and we are likely past the point that accumulating snowfall will occur. Our opening bid for the month of May we project slightly above average precipitation (+0.5″ to +1.0″) anomaly for the month as a whole, using long range climate guidance and global observational trends. Best chance for above average precipitation favors the first half of the month.

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

April 17th – April 23rd:  Slightly below average

April 24th – April 30th:  Near to slightly above average

May 1st – May 7th:  Near to slightly above average

May 8th – May 14th:  Slightly above average

May 15th – May 21st:  Near average

May 22nd – May 28th:  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  

Using the 06z ECMWF simulation loop during the Sunday-Monday time frame, a few spotty showers will be “in the vicinity” on both occasions with weak impulses moving through. Most areas are dry.

The first of two cold fronts expected in the next 7-10 days will arrive on Wednesday, and will be accompanied by scattered showers ahead of the boundary. Cooler temps follow behind the front.

Pattern:

OVERVIEW: Slightly milder temperatures relative to average thus far in April will likely turn cooler overall on several occasions during the 2nd half of the month. This will likely allow the monthly mean temperature departures, which are currently +2.0°F to +3.0°F across the region to finish near to slightly above average, or +0.0°F to +2.0°F by months end. Most notable cooler stretches will be found between next Wednesday and the following Tuesday, but nothing extreme. A rebound in temperatures is expected to close out the month, and we follow with another near to slightly above average May. The Madden-Julian Oscillation (MJO) is currently phase 7 in the Western Pacific, and is expected to maintain in phase 7 for much of the next 7-10 days. Phase 7 combined with a global relative +AAM  (Atmospheric Angular Momentum) supports the near to slightly below average period expected between April 21st-27th. The longer term ensembles show eventual movement into phase 8 past day 10, but this time of year phase 8 results in a near to slightly above average temperature pattern.

Through the first half of April, temperatures are generally slightly above average, and despite the unseasonably cold temperatures to begin April, we have since overcome that deficit and are currently observing +2.0°F to +3.0°F departures. Several days of a near to slightly below average stretch is expected from the 21st-27th, then rebounding to end the month of April. During the cooler stretch, temperatures will be largely on either side of 60° with a couple days perhaps not escaping the 50s next Wednesday and Thursday to begin that cooler period. More consistent 70s are expected to appear in May given the average highs nearing the 70° mark at that time and a near to slightly above average temperature expectation for the month as a whole.

Average highs and lows are continuing to slowly rise every 2-3 days, and normal high temperatures are currently in the 59-64° range from north to south across our coverage region. Any above or below average stretches listed in the outlook will be relative to seasonal norms at that time. It is important to note that cooler/warmer periods will be relative to the time of year we are talking about. For example, near to slightly below average temperatures listed between the 23rd-27th likely results in high temperatures in the upper 50s to lower 60s (north to south) with respect to the normal/average highs at that time. Use the average highs/lows chart above that provides a point of reference for what average is for each corresponding date, with the examples used for the Philadelphia region.

For the month of April, we expect near to slightly above average temperatures (+0.0°F to +2.0°F) when the dust settles April 30th with high confidence. Looking at the month of May as a whole suggests another near to slightly above average month (+0.0°F to +2.0°F) using long term climate models and seasonal/global observation trends.

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

Cooler than average temperatures found Friday and Saturday will begin to moderate to near average Sunday and Monday, and then will spike Tuesday to slightly above average ahead of a cold front.

Thanks largely to MJO phase 7 and +AAM, the Plains will be unusually cold, and our area will be on the eastern periphery of that between April 21st-27th with a slightly below average temperature stretch.

Outlook table last updated: Friday April 16th, 10:45 AM. Next scheduled update: Friday April 23rd.

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:

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.

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.

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday April 16th, 10:45 AM