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Precipitation Discussion

OVERVIEW: Precipitation departures for the month of June thus far has been drier for the interior, and generally near average farther south with thunderstorms this occurred [there] in the middle of last week. Going forward, projections for the month of June were maintained this week for a below average precipitation forecast with a rather dry (overall) next two-week ensembles forecast. In fact, this is one of the rare times that only one precipitation threat is listed in this week's long range chart, and that is with a weak cold front expected Friday 6/14 and scattered thunderstorm activity in the afternoon and evening hours. Aside from that chance, the next 10 days especially looks to be mostly, if not completely dry. For that reason, the projection for June as a whole is for a below average (-1.0" to -2.0") precipitation departure for the month as a whole. The presence of thunderstorms can skew monthly projections of rainfall on a hyper-local basis, and it is important to understand that the monthly projections in storm season are a composite average based on synoptic events, not mesoscale-based activity. Our July projections were maintained this week for a near to slightly above average precipitation departure (0.0" to +1.0") for the month as a whole with the current expectation that while the beginning of the month may start off drier, but may turn around with more precipitation events during the 2nd half of July.

Shorter term, we a cold front moving through the region Friday (6/14) bringing the threat of scattered thunderstorms during the afternoon and evening hours. Given the antecedent very warm and humid airmass in place, storms can take advantage of that environment and could be locally strong or even severe. The NWS Storm Prediction Center does have a slight risk of severe weather today across the heart of our region, and a marginal risk for severe in eastern and southeastern areas. The primary severe mode today is from unidirectional wind gusts that could be locally damaging. While rainfall will certainly be a part of the storm activity today, the heavier rain potential will be largely hit or miss due to the scattered nature of any storm activity, but this will likely represent the lone chance for organized rain chances over the next 10 days with strong ridging moving in next week.

Our projection for the month of June was adjusted this week for a solidly below average (-1.0" to -2.0") precipitation departure, a necessary change due to overwhelming ensemble support of a drier than average next two week period. As temperatures and humidity increase in July, it favors more in the way of thunderstorm activity, most notably during the 2nd half of the month, and for that reason a near to slightly above average (0.0" to +1.0") precipitation departure projection for the month as a whole is currently expected. 

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

June 15th - June 21st: Below average

June 22nd - June 28th: Near average

June 29 - July 5th: Near to slightly below average

July 6th - July 12th: Near to slightly below average

July 13th - July 19th: Near to slightly above average

July 20th - July 26th: Slightly above 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 below is clickable for larger viewing  

 A weak cold front will cross the region Friday 6/14 with scattered afternoon/evening t-storms which have the ability to be locally strong/severe with gusty straight-line winds the primary severe threat
A drier than normal pattern settles in over the next few weeks to coincide with strong ridging in place; aside from the 6/14 cold front, no organized precipitation is expected for the next 10 days

Pattern Discussion

OVERVIEW: After a generally near average first half of June, ridging is expected to arrive early next week, and has some staying power in terms of duration. Widespread 90°F+ temps are expected to dominate all of next week and through at least next weekend. This anomalously strong ridge, which is rather early in the season, has allowed projections for the month of June as a whole to be maintained at an above average (+2.0°F to +4.0°F) projection for the month as a whole. While the temperatures settle somewhat for the final full week of the month, we are still projecting slightly above average temperatures to remain that week. We maintained projections for the month of July this week for a slightly above average (+1.0°F to +3.0°F) temperature departure as we expect a transition from ENSO neutral into a weak La Niña background state at some point in July. The first half of the month looks to be the hottest relative to average, then leaning to the warmer side of average during the back half of July. 

The Madden-Julian Oscillation (MJO) is currently in the Circle of Death and likely remains there through at least the middle of July. The prolonged stretch in the Circle of Death is very typical of summer pattern where the overall flow is rather weak in the Pacific subtropical regions. Ridging will return just after the middle of June and very hot temperatures are expected for the entirely of next week through at least the weekend. As we head into July as we expect a transition from ENSO neutral where we are currently, to a weak La Niña background state at some point during the month. July as a whole should be a relatively hot month overall...which means hotter than it typically is even for July, one of the hottest months of the year. Although we limit the long range outlooks purposefully at a 5-6 week lead time with accuracy in mind, our preliminary thoughts for August and September are to see a continuation of at least slightly above average temperatures.

Average high temperatures are currently in the 80-83°F range from north to south across our coverage region, which is about 2 degrees higher than at this time last week. Temperature climb will continue at that same general rate of increase throughout June of about +1-2°F per week, with that rate of increase maintaining through early July. 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, the above to well above average temperatures listed between next Monday and the 24th of the month generally features highs in the 90-100° range across the region, coming at a time when average highs are generally in the lower to middle 80s. Use the average highs/lows chart below that provides a point of reference for what average is for each corresponding date through early August.

Our projection for the month of June is for an above average (+2.0­°F to +4.0°F) temperature departure, and that is largely due to the expected ridging that will take over just after the middle of the month, and still remaining at least slightly above average for the final week of June. July projections were maintained this week for a slightly above average (+1.0°F to +3.0°F) temperature departure expectation, using longer term climate guidance and global observation trends, and we are expecting a transition from ENSO neutral to a weak La Niña background state at some point during the month.

Note:  Any image below is clickable for larger viewing`

Very slightly cooler than average temperatures will be in place over the weekend, but we anticipate strong ridging to dominate next week, bringing hot temps and humid conditions to the region
Average temperatures over the next 6 weeks are shown below at our major climate sites throughout the region, with a steady increase of average temperatures as we move through Spring/Summer

Long Range Outlook Table

 

Date(s)ThreatsSignificanceConfidence
6/15-6/16TemperatureNear to slightly below averageVery high
6/17-6/23TemperatureAbove to well above average High
6/24-6/30TemperatureSlightly above averageModerately high
7/1-7/7TemperatureSlightly above averageModerate
7/8-7/14TemperatureSlightly above averageModerately low

7/15-7/21
TemperatureNear to slightly above averageLow
7/22-7/28TemperatureNear to slightly above averageVery low
6/14Cold frontA weak cold front crosses the region Friday afternoon and evening with scattered thunderstorms, some locally strong possible with gusty straight-line windsVery high
June as a wholeTemperatureAbove average (+2.0°F to +4.0°F)High
June as a wholePrecipitationBelow average (-1.0" to -2.0")Moderately high
July as a wholeTemperatureSlightly above average (+1.0°F to +3.0°F)Moderate
July as a wholePrecipitationNear to slightly above average (0.0" to +1.0")Moderate

 

Outlook table last updated: Friday June 14th, 11:00 AM. Next scheduled update: Friday June 21st.

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.

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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 Hi/Lo (°F)Current EPAWA projection
June 15th83°F/64°FNear to slightly below average
June 22nd85°F/66°FAbove to well above average
June 29th87°F/68°FSlightly above average
July 6th88°F/69°FSlightly above average
July 13th88°F/70°FSlightly above average
July 20th88°F/70°FNear to slightly above average
July 27th88°F/70°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.

Climate Prediction Center (CPC) Graphical Products

These products are from the NOAA Climate Prediction Center (CPC) and do not necessarily reflect the EPAWA forecast which is detailed above. All images below update automatically as the CPC releases new graphical products

CPC 6-10 day temperature outlook
CPC 6-10 day precipitation outlook
CPC 8-14 day temperature outlook
CPC 8-14 day precipitation outlook
CPC weeks 3-4 temperature outlook
CPC weeks 3-4 precipitation outlook
CPC next 3 months temperature outlook
CPC next 3 months precipitation outlook

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.

US drought monitor (NE US)

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Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday June 14th, 11:00 AM