Two separate systems to bring heavy
rain and breezy conditions this week

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: A very dry month of October relative to average 22 days into the month will end on a slightly wetter note over the final 9 days, mostly centered around next Monday night and Tuesday, and again next Thursday. As we move deeper into Autumn and turn the calendar to November, an uptick in overall precipitation departures relative to normal is currently projected for the month as a whole, but generally back to near average precipitation. Snowfall projections also become part of the long range forecast beginning in November, and our current projection is for near average snowfall for that month, but it should be noted that most areas don’t see much snow accumulation in November. Realistically even with an earlier start to the snow season anticipated this year, accumulating snowfall even if minor typically waits until the 2nd half of November for most locales. Tropical systems will still need to be monitored through the end of Atlantic Hurricane season (November 30th) for possible direct or indirect remnant impacts to our region locally, and have the ability to skew projected monthly precipitation departures from normal.

Shorter term, we’re expecting a few light showers/sprinkles Saturday AM for some areas as weak energy rounds the base of a trough to our north. A warm front lifts northward through the region Sunday evening and overnight, with overrunning showers ahead of it. Next Monday night and Tuesday a potentially more impactful system is likely to bring periods of steady rainfall with low pressure moving from the Midwest through the Ohio Valley and eventually the DelMarVa by Tuesday morning. Another area of low pressure and its associated cold front moves through the region next Thursday with more showers likely as it does so.

The month of October we project will finish with below average (-1.50″ to -2.50″) precipitation departures for the month as a whole, with high confidence. A relatively dry month thus far will likely see an uptick during the final 9 days of the month. Looking ahead to the month of November suggests a near average precipitation (-0.5″ to +0.5″) anomaly for the month as a whole, using long range climate guidance and global observational trends. The caveat to the precipitation projections listed will be any tropical systems or remnants thereof that have the ability to skew projections higher in that instance. Projections for monthly precipitation departures considered this possibility, but assume no tropical remnants in order to paint the bigger picture of monthly precipitation.

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

October 23rd – October 30th: Slightly above average

October 31st – November 6th: Near average

November 7th – November 13th: Near average

November 14th – November 20th: Near to slightly below average

November 21st – November 27th: Near to slightly above average

November 28th – December 4th: 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 warm front moves through Sunday night with showers, then clears to the north Monday. A more potent area of  low pressure follows Monday night/Tuesday with periods of rain.

As one potentially impactful system exits, another area of low pressure and its associated cold front will work through the region next Thursday, bringing another round of showers.

Pattern:

OVERVIEW: The month of October has been very warm overall, with the majority of the first half of the month seeing above average temperatures. The past week saw up and down temperatures with a battle between cool Autumn days and warmer temperatures more typical of mid-late September. Going forward through the remainder of October we expect temperatures to remain very close to average or very slightly below average on a few of those days. November we feel will remain slightly below average overall, with strong ensemble agreement for a cooler than average month after the unusually warm October. The coolest periods relative to average look to be centered around the middle two weeks of the month, in part due to expected tropical forcing/wave propagation. A weaker than normal stratospheric polar vortex continues to be shown by the GEFS and ECMWF in late October/early November making it susceptible to splits/displacements, which has the ability to change the pattern in the late November through December period.

The Madden-Julian Oscillation (MJO) is currently in the Circle of Death (COD) and is expected to remain there through early next week…then emerging into phase 8/1 in early November. Both the GEFS and EPS camp are in fairly close alignment with this MJO projection in the nearer term, but these two diverge on their individual projections beyond the first few days of November. MJO waves are monitored for possible favorable periods of tropical cyclone development in the Atlantic. Climatologically speaking, August and September are typically the most active months for Atlantic tropical cyclone development, but October has produced some memorable tropical cyclones and remnants thereof locally. Currently in the Atlantic there are no credible threats to our area for a direct or indirect hit from any system or potential system to the US. Going forward from November onward, MJO activity is also monitored for identifying longer term cold/mild periods and with time, Winter storm signals. Phase 1 in November as most ensemble members suggest would support the cooler than average temperatures projected in our long range chart.

Average highs and lows are continuing a slow and gradual drop-off week to week. Normal high temperatures are currently in the 61-65°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 a 2-3° per week drop in November. 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, near to slightly below average temperatures listed for the next several days will generally feature highs on either side of 60° 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 October we project will finish with above average temperatures (+3.0°F to +5.0°F) when the dust settles October 31st with high confidence, largely due to a much warmer than average first half. Early look at the month of November as a whole suggests a slightly below average month (-1.0°F to -3.0°F) using long term climate models and seasonal/global observation trends.

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

A trough will influence our weather over the weekend with slightly cooler than average temperatures, but no extremes expected as the broad trough largely remains to our north.

After a few days of near average temperatures just before the end of the month, another cooler than average stretch is expected to begin the month of November.

Outlook table last updated: Friday October 22nd, 12:50 PM. Next scheduled update: Friday October 29th.

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/ 

*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 October 22nd, 12:50 PM