Tuesday Night Technical Discussion

Synopsis:

High pressure will continue to make its way east and sit over New England until Thursday night. A cold front will traverse the state Friday and produce scattered rain showers across the region. Artic air will move into the region behind this system, along with scattered lake effect snow showers, especially for northwestern portions of the state, during the weekend.

Short Term: (Tuesday night through Thursday night)

High pressure will dominate the weather pattern for the northeastern states Tuesday night through Thursday night. Low temperatures for Tuesday night will be in the low to mid 20's statewide, indicated by the 18Z 12km NAM. As the flow become more southerly and skies remain mostly clear, high temperatures will moderate, with the entire state at least reaching the low 40's and southwestern PA reaching low 50's by Thursday. Clouds will begin to move in Thursday afternoon and, along with a southerly flow, will keep low temperatures for Thursday from dropping.

Long Term: (Friday into the weekend)

A mean southerly flow will allow temperatures to rise Friday just ahead of the cold front. The 12z GFS has the pre frontal precipitation reaching northwestern PA by 18Z Friday, but the 12Z NAM is a bit quicker and has the precipitation reaching the state by 12Z on Friday. GFS is currently slow and the NAM is doing much better with the timing. Expect some precipitation in the northwestern counties on Friday between 10Z and 12Z. The low pressure associated with the frontal passage will move north over Canada and sit for the weekend. A northerly flow behind the front will allow for cold air advection, which will usher in a cold air mass for the weekend. The flow will shift northwesterly and lake effect snow showers are possible for the northern and western portions of PA for Saturday night through Monday. High pressure will begin to make its way towards the state for the beginning of the workweek and the northwesterly flow will subside, cutting off the lake effect activity.

~ A.J. Herbert

Tuesday Afternoon Discussion

Synopsis:

The remainder of the week looks to be standard fall weather across Pennsylvania. Mostly cloudy skies and cool temperatures are what you can expect for Wednesday and Thursday. Highs in the 40's and lows in the upper 20's should be the norm across the state. Things change on Friday when we warm up a bit ahead of an approaching front. Temperatures should get back into the 50's for at least some the area on Friday. A blast of arctic air will slam into the region on Saturday bringing the coldest temperatures of the fall so far and a few snow showers are likely as the front pushes through.

Outlook:

An area of steady, high pressure and associated subsidence will dominate PA weather today and tomorrow.  Northerly winds and mostly clear skies will lead to below-normal temps and large diurnal temp swings.  Our next system develops in the wake of the high and closes off ~18Z Friday afternoon over the Great Lakes.  Yesterday, the ECMWF had this storm moving up the east coast with Nor'easter potential, but the current solution brings it up into Canada to our NW.  Consequently, instead of feeling the direct effects of the low, we will experience an Arctic cold front Saturday morning.  The precipitation might clear out by gametime, but so will the warm air.  With the 510 line in southern PA, we will likely experience the coldest air of the season so far, with highs Sunday and Monday struggling to rise above freezing.

Tuesday Night Technical Discussion

Synopsis:

High pressure will continue to dominate over the Mid-Atlantic Region for the first half of the week. A low-pressure system to our west will track over the great lakes and eventually to the north of us, and it's associated cold front will bring scattered rain showers across PA Wednesday night into early Thursday morning. Behind the front a northwest flow will provide cold air advection and a chance for scattered lake effect showers for northwestern counties Thursday night through Friday. High pressure will return to the area and provide mostly clear skies and slightly warmer conditions for the weekend.

Short Term: (Tuesday night through Wednesday night)

Cloud cover tonight should moderate temperatures, with the 18Z 12km NAM indicating mid to upper 30's for the western half of the state and low to mid 40's for the eastern half of the state due to low-level clouds associated with the southeasterly flow off the ocean. The mean southerly flow will persist during the day Wednesday providing warmer temps ahead of the cold front associated with the low-pressure system to our west. This low pressure will slowly make its way toward the great lakes and begin to push the high pressure currently over the region off the coast. The system will pass north of the region and its associated cold front will cross the state. The 18Z GFS and NAM, as well as the 21Z SREFMEAN, agree with the timing of the cold front to reach western counties by Thursday around 06Z and the pre-frontal precipitation to reach northwestern counties by Thursday at 03Z.

Long Term: (Thursday into the weekend)

As the cold front crosses the region it will bring widespread scattered rain showers for the entire state. A northwesterly flow will follow behind the front and initiate cold air advection as the 540dm line dips just south of the state Thursday night into early Friday, indicated by the 18Z NAM and GFS. The northwesterly flow will also provide a chance for scattered lake effect rain/snow showers Thursday night through Friday morning, mainly for the higher elevations in the northwestern portion of the state. High pressure will return to the region Friday night, but quickly move off the coast by Saturday evening. Another low pressure will move well north of PA and an associated shortwave will traverse New England on Sunday. Precipitation is not likely anywhere in the state and high pressure will follow in the wake of the shortwave passage for the beginning of the workweek.

~ A.J. Herbert

Monday Afternoon Technical Discussion

Monday Afternoon Technical Discussion

Synopsis:

Clear skies and average temperatures will dominate out forecast for much of this week with the exception of Thursday when some precipitation will move into the area. Friday looks to be a nice day as well

Short Term: (Monday night through Tuesday night)

A high pressure system located off the Maine coast will dominate our forecast during this time period. Associated with this high pressure system is a ridge going down the spine of the Appalachian Mountains, so much of the eastern seaboard is experiencing tranquil weather during this time period. Our sjies will be mostly sunny during this time period. Temperatures are expected to be climatology average during this time period with highs in the 50s and lows in the 30s. 

Long Term: (Wednesday through Friday)

The same pattern dominated by the short term forecast will dominate the long term forecast too until Thursday when a cold ! front will approach the area. As of right now, the timing of t! his cold front looks to be that is will arrive in the area by Thursday morning. Once this cold front moves through, high pressure will approach from the southwest and skies will clear out for Friday.