Summary: All of the models are now converging on one scenario regarding the approaching cold front. As I suspected, the model which had projected two surface lows forming along a slower moving cold front, prolonging the rainfall into Saturday, has fallen in line with the other models. The cold front located at the leading edge of the trough in the jet stream, presently located over western NY and PA will approach Berkshire County overnight with increasing clouds with some scattered showers developing in advance of the front after midnight. As the surface low pressure developing along the front rides north, heavier rain will develop toward daybreak and continue through the morning and into the afternoon. After the low passes the steadier and heavier rain should end by mid-afternoon. However, there will still be some lingering showers associated as the cold front moves very slowly through the region through the remainder of the afternoon and evening. Only some sprinkles and a few scattered light showers will persist after midnight. We should receive a pretty good dousing from this system with most of the county receiving between 1.00 and 1.50 inches total rainfall. Skies should at least partially clear on Saturday and there may be a good amount of sunshine in the afternoon as the dry wedge of air between the front and the trailing upper-level low (cold pool aloft) moves through. It will be cooler, and there will probably be more cloudiness on Sunday, particularly during the afternoon as the upper-level cold pool (low) rotates through and generates some instability in the atmosphere. There is even the slight chance of a sprinkle or two but it should remain dry in most locations. It still looks like at least a temporary pattern shift next week with ridging in the eastern U.S. and a large, cold trough diving south over the western U.S.. This should give us a relatively dry and mild week but may result in the first significant snowstorm of the season in the Rockies mid-week.

Thursday Night

Increasing clouds in the evening. Becoming overcast after midnight. There is a good chance of a few scattered showers after midnight with a steadier, heavier rainfall developing toward daybreak. Probability of precipitation 90%. Rainfall totals most likely between 0.25 and 0.50 inches.

It will remain mild for this time of year as the cloud cover prevents much radiational cooling. Low temperatures will be near 50 countywide.

East-southeasterly winds at 5-10 mph.

Friday

Occasional rain and showers, heavy at times, through early to mid afternoon. Probability of precipitation 100%. Additional rainfall between 0.50 and 1.00 inches.

High temperatures in the low 60s for most of the county but only near 60 over elevated terrain and the hilltowns.

East-southeast winds at 8-12 mph.

Friday Night

Some scattered, mostly light, showers are likely in the evening with only a few sprinkles remaining after midnight. Probability of precipitation is 60% early, falling to 20% after midnight. Additional rainfall totals should be less than 0.10 inches. Rainfall totals for this entire event will most likely be between 1.00 and 1.50 inches.

It will remain mild with the persistent cloud cover overnight. Low temperatures in the mid 50s.

Light south-southeasterly winds becoming calm.

Saturday

Mostly cloudy in the morning, becoming partly cloudy during the afternoon. There is the slight chance of an isolated instability shower during the afternoon.

It will remain mild as the air immediately behind the cold front is only slightly cooler. High temperatures in the low to mid 60s.

Winds shifting from south-southeast to southwest and increasing to 8-12 mph.

Summary: A surface high pressure system centered right over New England gave us a beautiful autumn day today with sunshine only occasionally filtered by high clouds and temperatures several degrees above average. This high pressure system will drift SLOWLY eastward as a trough in the jet stream digs down deep into the Midwest. After one more nice day on Thursday, quite similar to today but even slightly milder, the leading edge of this trough will approach our region Thursday night as a surface cold front. As the trough amplifies and partially cuts off from the jet it will slow up considerably. Therefore, it will take quite a while for the cold front to move through our region. A weak surface low will develop along the front and move slowly north along the front. As a result we will have a fairly prolonged period of rain beginning towards daybreak on Friday and extending through the day. We will likely receive upwards of 1.00 inch of rain from this slow moving cold front and its associated developing surface low pressure system. One computer model moves the tough/cut-off low (upper-level) more slowly and generates two waves of surface low pressure with a pause in the rainfall late Friday and then resuming Friday night and continuing well into Saturday. I find the single low and cold front moving through by sometime Friday evening a more plausible scenario at this time. However, I am still concerned about our weekend because the computer models sometimes lift these cut-off lows (the upper-level low/trough, not the surface low along the cold front) out too fast. This situation will become more clear cut in subsequent model runs. For now, I would say that the rain should end by sometime Friday night with a dry day on Saturday and a nice day on Sunday as the trough/cut-off low lifts to the northeast and surface high pressure begins to build back in to our area. A look at the long-range scenario suggests that the jet stream wave pattern may shift early next week and allow a full thickness (all of the troposphere) ridge to build over the eastern U.S.. This means that warmer air at all levels of the atmosphere will move east and push the jet stream and any storms associated with it to the north.

Wednesday Night

Mostly clear, calm and seasonably cold.

Low temperatures in the mid to upper 30s.

Calm winds.

Thursday

Mostly sunny and unseasonably mild. There may be an increase in high clouds late in the afternoon.

High temperatures in the mid 60s in Pittsfield and North Adams, high 60s in Great Barrington and low 60s over elevated terrain and the hilltowns.

South-southeast winds at 10-15 mph.

Thursday Night

Increasing clouds in the evening, becoming overcast after midnight. Not as cold. Rain will likely develop by daybreak. Probability of precipitation is 70%. Rainfall totals most likely between 0.10 and 0.25 inches.

Low temperatures in the low 50s.

Winds shifting from south-southeast at 5-10 mph in the evening to the east-southeast and increasing to 10-15 mph after midnight.

Friday

Rain, moderate to heavy at times. Rainfall totals will likely exceed 1.00 inch. Probability of precipitation near 100 percent.

High temperatures in the low 60s for most of the county, near 60 for the elevated terrain.

Southeast winds at 10-15 mph.

Summary: The weather scenario has not changed much since yesterday. A surface high pressure system is building into the region behind last night’s cold front passage. This has resulted in clearing skies this afternoon. It will become clear and calm, ideal for radiational cooling as high pressure crests over the region tonight. Wednesday and Thursday we will receive warmer south-southwesterly flow around the back side of the high as it moves off the Atlantic Coast. Therefore, it will become much milder than today. It will be generally fair both days although predominantly high clouds will filter the sun (angle dropping as we move through autumn) somewhat. An upper-level trough (southward dip in the wave pattern of the jet stream) will dive south into the Midwest over the next few days and its eastern edge will approach our region as a cold front on Thursday Night. As the front edges through the region we will experience a bout of fairly significant rainfall sometime later Thursday Night into Friday. The amplification of the jet stream wave pattern will be fairly pronounced but, at this point, it does not appear to be amplified enough to cause the wave to break and the upper-level low (cold pool) to become “cut-off” from the jet. If that were to occur we could experience an extended period (several days) of unsettled weather and the weekend would end up relatively cool, cloudy and somewhat showery. Fortunately, it appears more likely that this trough will lift back to the northeast and out of the region relatively quickly and the weekend will end up fairly decent. More on this tomorrow…..

Tuesday Night

Clear and cold with winds lightening in the evening and becoming calm after midnight.

Low temperatures in the low 30s in most regions although it could reach the upper 20s in some of the colder valleys.

Northwest winds diminishing in the evening and becoming calm after midnight.

Wednesday

It will be mostly sunny in the morning. Skies should average out partly cloudy (25-50% cloud cover) during the afternoon. However, the majority of the clouds will be high clouds and therefore, we should see the sun for most of the afternoon although it will be filtered at times. It will be much milder than Tuesday.

High temperatures in the low 60s in Pittsfield and North Adams, mid 60s in Great Barrington and near 60 over elevated terrain and the hilltowns.

Winds light and variable in the morning, becoming south-southwest at 5-10 mph in the afternoon.

Wednesday Night

Some high clouds, otherwise, mostly clear. Not as cold as Tuesday Night.

Low temperatures near 40.

Calm winds.

Thursday

Mostly sunny for most of the day with an increase in clouds late. Unseasonably mild.

High temperatures will likely reach the mid 60s in Pittsfield and North Adams, there may be some upper 60s in South County. Highs will be in the lower 60s in the usually cooler elevated terrain.

South-southeasterly winds at 8-12 mph.

Summary: The secondary coastal low pressure system developing along the passing cold front is tracking closer to Berkshire County than originally anticipated. Therefore, rainfall will be heavier this evening and rainfall totals will likely reach or exceed 0.50 inches. There may be a few lingering light showers overnight and again in the early morning as the upper-level low tracks over the region. High pressure will then build into the region for Tuesday through Thursday and we will experience dry and fairly clear weather for that period. It will be cooler on Tuesday as the winds blow from the northwest in advance of the high and it will then warm up on Wednesday and Thursday as the high tracks to our east and the return flow around the high brings milder air in from the southwest (note: wind flows clockwise around high pressure in the Northern Hemisphere). The next cold front will approach the region with another round of rain or showers for Thursday night into Friday.

Monday Night

Rain, moderate to heavy at times through the evening hours. The steadiest rain should end by midnight. There is the chance of a few lingering light showers after midnight. Probability of precipitation 100%. Total rainfall for this event will likely reach or exceed 0.50 inches. It will be overcast for most of the night but there may be some partial clearing toward daybreak.

Temperatures and dewpoints will drop significantly after the cold front passes with low temperatures reaching the low to mid 40s countywide by morning.

South-southwesterly winds will shift to northwesterly after midnight as the front passes. Wind speeds will average 8-12 mph.

Tuesday

Mostly cloudy during the morning with a chance of scattered light rain showers. There may be some snowflakes mixed in, particularly at the higher elevations. Probability of precipitation 30%. Precipitation totals less than 0.05 inches. Skies will clear during the afternoon, becoming mostly sunny by mid afternoon. It will be very breezy and cooler.

High temperatures in the low 50s in Pittsfield and North Adams, mid 50s in Great Barrington and upper 40s over elevated terrain and the hilltowns.

Northwest winds at 15-25 mph with gusts to 30 mph.

Tuesday Night

Clear. Winds will become calm and allow for good radiational cooling. It will be seasonably cold.

Low temperatures generally in the low 30s.

Northwest winds becoming light in the evening and then calm after midnight.

Wednesday

Partly cloudy. It will be much milder than Tuesday despite a cold start.

High temperatures near 60 over elevated terrain but in the low to mid 60s in Pittsfield and North Adams and mid 60s in Great Barrington.

West to southwest winds at 5-10.

Summary: After a warm front moved through this morning with about 0.60 inches of rain, we broke into the warm sector of its associated mid-latitude cyclone (surface low pressure system), which is moving through the Great Lakes, this afternoon. As the sun came out, temperatures shot into the 60s countywide and even approached 70 in South County (68 in Great Barrington). Seemed strange after our hard freeze on Saturday morning (21.6 deg. F. at BCC and 24 deg. at PSF [Pittsfield airport], which was a record low for the date) but such is the roller-coaster ride that we frequently experience in New England this time of year as the sun progresses south of the equator and the meridional (north-south) temperature gradient steepens across the Northern Hemisphere. Just a note about our first killing frost/freeze. Even though the long-term average killing frost/freeze for Berkshire County is mid to late September (exact date depending on location), anyone with a garden knows that the average for the past ten years has been mid to late October. More evidence, albeit anecdotal, of global climate change’s local impact on Berkshire County.

As the mid-latitude cyclone continues its trek to the northeast over the next 24 hours, it will finally drag its associated cold front through Berkshire County late Monday afternoon and evening. The front will lift the very moist air for this time of year causing a band of rain or showers to develop and move through the region. This precipitation will be enhanced by a secondary surface low pressure system developing along the front as it moves slowly to our east. This low will move northeast from the Del Marva Peninsula to the Gulf of Maine tomorrow night. However, most of the heavier rain associated with this low should stay to our south and east. This will allow a high pressure system to build in from the west with a cooler but drier day on Tuesday. As the source region of the approaching air mass (high pressure system) is the Midwest instead of Canada, it will not get nearly as cold as with our last cold front passage on Friday night. As the high moves over the region and then to our east, the return flow around the high (south/southwest winds) will result in fair and progressively milder weather on Wednesday and Thursday until the next cold front passage sometime on Friday. Temperatures are likely to reach well into the 60s again by Thursday.

Sunday Night

Clear early. Increasing cloudiness after midnight.

Despite the clear skies early, a persistent southerly wind and high dewpoints in the 50s will prevent much radiational cooling. The increasing cloud cover will prevent any further cooling. Low temperatures will only fall into the upper 50s.

South-southwesterly winds at 8-12 mph.

Monday

As the cold front approaches from the west it will become increasingly cloudy, becoming mostly cloudy during the morning (75-90% cloud cover) and then overcast during the afternoon. There is a good chance of scattered light rain showers from late morning through most of the afternoon. Probability of precipitation before 3 pm is 50%. Any precipitation during this period should be less than 0.05 inches. A more solid band of rain or showers will likely move through from late afternoon through the evening hours. Probability of precipitation is 80%. There is a slight chance of some imbedded thunder within the band of rain. Rainfall amounts should average about 0.25 inches but up to 0.50 inches in a few isolated heavier showers.

High temperatures will climb into the mid 60s in most of the county.

South-southwest winds at 10-15 mph.

Monday Night

Any rain or showers should end well before midnight but it will remain mostly cloudy.

It will feel much cooler as dewpoints and temperatures drop through the night. Temperatures will fall into the low to mid 40s countywide by daybreak.

Southwest winds early shifting to northwest at 8-12 mph.

Tuesday

Decreasing clouds throughout the day. Mostly cloudy at daybreak but becoming mostly sunny during the afternoon. Becoming very breezy and much cooler than Monday.

High temperatures in the low 50s in Pittsfield and North Adams, mid 50s in Great Barrington and upper 40s over elevated terrain and the hilltowns.

Northwest winds increasing to 15-20 mph during the afternoon with gusts to 30 mph.

Summary: It now appears that a good solid freeze is likely on Friday night. Drizzle and light showers will continue off and on through the afternoon due to the moist flow off the ocean (easterly wind). The departing high pressure system over the Canadian maritime has been slow to move, accounting for winds off the moist ocean instead of south-southwesterly in advance of the cold front as had been expected today. Therefore, it is wetter and cooler than had been forecast. However, winds will shift to the south-southwest later this afternoon as the cold front approaches. A band of scattered showers will move through the county late this afternoon into early this evening, as had been expected. Skies will clear overnight behind the front as a surface high pressure system builds into the region. This will result in mostly sunny but cool and breezy conditions for Thursday. It will cloud up again Thursday night as another, even stronger cold front approaches. Very widely scattered showers will accompany this cold front passage on Friday morning. It will begin to clear up Friday afternoon but it will be quite cool as a strong, cool, autumnal, high pressure system from Canada finally makes it into New England. Temperatures will remain in the 40s on Friday and a widespread freeze is likely Friday night as clear and calm and dry (dewpoints 20 or below!) conditions lead to ideal radiational cooling conditions as the high pressure system becomes centered right over the Northeast.

Wednesday Afternoon

Overcast and cool with intermittent drizzle and light showers early this afternoon. Mostly cloudy, with some peeks of sunshine late this afternoon. A band of scattered light showers will pass through the region around dinner time. Probability of precipitation with that band of showers is 40%. Any rainfall should be less than 0.10 inches.

Temperatures holding fairly steady in the low to mid 50s in most locations, with the cooler temperatures in the hills. Temperatures could reach the upper 50s in any locations that see sun later this afternoon.

Northeast winds shifting to south-southwest at 5-10 mph.

Wednesday Night

The relatively narrow band of scattered light rain showers accompanying the cold front passage will come through between 8 and 9 pm. Probability of precipitation is 40%. Any rainfall totals will be less than 0.05 inches. Skies will begin to clear after the cold front passage and it will become partly cloudy, breezy and cooler after midnight.

Low temperatures are expected to be in the upper 30s countywide with a some mid 30s in the elevated terrain and hilltowns.

Winds out of the west-northwest at 8-15 mph.

Thursday

Partly cloudy (25-50% cloud cover) in the morning, becoming mostly sunny (<25% cloud cover) in the afternoon. Breezy and cool.

High temperatures in the low 50s for most of the county including Pittsfield and North Adams, with upper 40s over elevated terrain and in the hilltowns. Highs will likely reach the mid 50s in parts of south county, such as in Great Barrington and Sheffield.

West- northwest winds at 10-20 mph.

Thursday Night

Clear early. Clouding up after midnight. Slight chance of a shower near daybreak. Probability of precipitation 20%.

Low temperature near 40.

Light southwest winds.

Friday

The next cold frontal passage will occur during the morning. Once again, the accompanying band of showers will be broken and light. Probability of precipitation 50%. Any rainfall should be less than 0.10 inches. It will be mostly cloudy in the morning. Skies will clear during the afternoon. It will become breezy and unseasonably cool during the afternoon post-frontal passage.

High temperatures will be in the upper 40s in most of the county, including Pittsfield and North Adams. Highs over the elevated terrain and hilltowns will be in the mid 40s and in the low 50s in lower elevations of South County.

Winds shifting from southwest to northwest and increasing to 10-20 mph with gusts near 30 mph.

Friday Night

Clear and unseasonably cold.

A widespread freeze is likely with temperatures dropping below freezing by midnight and low temperatures should be in the low to mid 20s by daybreak.

Winds becoming calm.

Summary: The jet stream (associated with the full thickness tropospheric front) and its associated surface front continues to meander over the region as it has for the past week. The meridional (north-south) temperature contrast is still relatively weak so the jet stream, as well as any surface lows and associated fronts associated with the jet also remain relatively weak. In addition, the jet stream is oriented in a predominantly zonal (east-west) configuration. Therefore, there has not been enough “waviness” in the jet stream or its associated front to allow for the passage of any strong cold fronts with subsequent strong surface high pressure. As such we have remained under relatively persistent cloud cover with intermittent rain showers since last week. This pattern will continue for the next few days. However, the next two cold fronts will be slightly stronger, with slight amplification in the wave pattern, which should permit the sun to return on Thursday after the passage of the first front and then again on Saturday after the second front passes on Friday. There will be the chance of scattered showers with the passage of the first front near dinner time tomorrow. However, this front is still relatively weak so the showers will not be widespread and any rain that does fall should be quite light. A surface high pressure system will then build in behind the front, clearing skies overnight and through the day Thursday. Despite the sunshine, temperatures will struggle past 50 as cooler and drier air moves in behind the front. In fact, it will feel quite “autumnal”. The second front will move through on Friday. This front will probably only be associated with clouds and not any rainfall as the air in advance of the front will be quite dry. One important note: It appears that as high pressure moves in behind the front Friday night, the sky will clear and winds will be light or calm and the air will be quite dry as dew points drop into the 20s for the first time this fall. This will set up ideal radiational cooling conditions overnight that could result in our first widespread frost and, possibly, even a light freeze as temperatures fall into the upper 20s countywide. I will provide more information on this developing situation in tomorrow’s forecast.

Tuesday Night

Remaining mostly cloudy and cool.

Temperatures will not drop much with the cloud cover. Low temperatures should fall to the mid 40s countywide.

Calm winds.

Wednesday

Mostly cloudy. There is the chance of scattered light rain showers late afternoon to early evening with the passage of the cold front. There will be a band of light showers moving through Berkshire County with this frontal passage but it should be broken, not a solid band, so that only some portions of the county will receive any rain. The probability that any one location will receive rainfall is approximately 50%. Any rain that does fall should total less than 0.10 inches.

Despite the cloud cover, it should be slightly milder than on Tuesday as winds shift to the southwest in advance of the front during the afternoon. High temperatures are expected to be in the mid to upper 50s for most of the county with some readings around 60 in portions of South County. If any sun breaks through the temperatures could approach 60 everywhere.

Southeast winds shifting to southwest at 8-12 mph in the afternoon.

Wednesday Night

Mostly cloudy early with the chance of an early evening shower (see daytime forecast). Clearing skies after midnight, becoming breezy and cooler.

Low temperature in the upper 30s.

West-northwesterly winds at 10-15 mph.

Thursday

Partly cloudy (25-50% cloud cover) for most of the day, becoming mostly sunny (<25% cloud cover) later in the afternoon. Breezy and cool.

High temperatures in the low 50s for most of the county including Pittsfield and North Adams, with upper 40s over elevated terrain and in the hilltowns. Highs will likely reach the mid 50s in parts of south county, such as in Great Barrington and Sheffield.

West- northwest winds at 10-20 mph.