Technical Discussion

Synopsis:

A low pressure system passing by the state will leave lingering snow and rain showers through tomorrow.  Otherwise, expect cloudy skies and high temperatures in the upper 30s to low 40s.  High pressure will briefly build into the region this weekend, before another disturbance approaches late Sunday into Monday, bringing the opportunity for rain. 

Short-Term: 

The 000 UTC runs of both the WRF and GFS show the center of the low pressure system passing off the coast of New Jersey by early morning.  The bulk of the nice precipitation swath wrapped around the low pressure system will remain well to the northeast of Pennsylvania.  The ensemble mean of the 1500 UTC SREF pressure and precipitation runs for the NE shows some lingering showers tapering off as today progresses (the majority of the precipitation, albeit not a significant precipitation event, will occur into the early morning hours) over much of the state.   It also shows some spotty showers passing through tomorrow, associated with a weak shortwave.  Else, all model runs show high pressure briefly settling into place through Sunday.

Long-Term:

As the weekend progresses, a low is projected to continue to evolve over the Midwest.  By Monday, the associated warm front should pass through the state, along with a nice swath of precipitation. It is too far out to forecast with certainty the amounts and timing, as there is some model spread between the GFS and WRF, but it could be an interesting weather situation early next week, especially with a slight possibility of thunderstorms on Tuesday not being ruled out.

Wednesday Evening Technical Discussion

Synopsis:

A strong low pressure with pass to the east of the area Thursday evening into Friday bringing the chance of snow and rain to eastern areas of the state. After the low moves away, behind this system winds will pick up out of the Northwest for Saturday and into Sunday. Skies will reamin mostly cloudy for the weekend with temperatures near normal to a tad below. The next system will approach the region on Sunday night bringing more rain to the state.

Short Term(Thursday through Friday morning)

For most of day on Thursday, precipitation in the form of mostly showers, will fall on the eastern half of state. Precipitation totals should range between .05 and .20 inches of liquid. Due to warm surface temperatures most of this precipitation will fall in the form of rain. As we approach Thursday evening into Friday morning, another batch of precipitation will move into the area. During the overnight hours Thursday night, a new surface low will deepen rapidly as it passed by the New Jersey coast. This will cause a northerly flow which will allow air to cause snow over the Lehigh Valley region in the Poconos. However, places closer to the east near the Philadelphia metro area will experience a wintry mix of rain and snow. Precipitation should taper by midday Friday with snowfall accumulation of 5 to 10 inches in northeast PA in area such Scranton, Allentown, and Bethlehem. Snowfall totals should decrease substantially further to the south.

 

Mid Term (Friday Morning through Saturday Evening)

As the deepening low pressure passes to the east on Friday, a strong northwest flow will remain throughout the day. Temperatures should range the upper 30's to lower 40's in the northern areas to near 50 in the southern regions of the state. As skies clear late Friday evening, temperatures will fall to upper 20's to lower 30's in most areas. Saturday will be very pleasant with partly sunny skies with temperature rebounding well into the 40's. Winds will remain strong out of the northwest.

 

Long Term (Sunday morning through Monday Evening)

Sunday will be a similar day to Saturday with a few less clouds, especially in the eastern half of the state. Temperatures look to around normal for this time of year. Another system will approach the area from the west on Monday bringing the chance for more rain.

-Matthew Mehallow

Wednesday Afternoon Technical Discussion

Synopsis:

I wish it was an April fool's joke but unfortunately there is nothing comical here. I large two pronged storm system will pummel the Northeast with an assortment of heavy rain and snow over the next few days. The first wave of precipitation is currently moving through the state and is expected to leave anywhere from a tenth to a quarter inch of precipitation by Thursday evening. Depending on elevation and location, this will yield varying ratios and snowfall accumulations. The second punch, which has yet to be fully decided upon by the models will swing up the coast on Friday and could land anywhere from a short jab of precipitation as hinted by the NAM all the way to a full knockout blow is the GFS wins out. We will have to wait and see exactly what happens so be sure to pay close attention to the small run to run discrepancies as well as the fact that warm lower levels could make snow very difficult to accumulate. Behind this system winds will pick up out of the Northwest for Saturday and into Sunday keeping the state mostly cloudy for the weekend. Our next system will approach the region on Sunday night, bringing more rain to the state for the beginning of the next work week!

Short Term (Tonight through Thursday evening):

The first batch of precipitation is associated with overrunning and has been very well modeled for the better part of two days.  Mountainous regions will see mainly snow tonight while the eastern third of the state will see either a mix of rain and snow or even all rain towards Philadelphia. The precipitation will linger throughout the day on Thursday with most of the state receiving between .1 and .25 inches of liquid equivalent. Due to the warm surface, little to no accumulation will occur from this precipitation and instead it will only set the table for the next batch to hit on Friday.

Midterm (Thursday night through Saturday morning):

The upper level trough will produce another batch of precipitation that will swing up the eastern seaboard on Friday. There is great model discrepancy however, the UKMET, CMC, and GFS all have been fairly consistent with a full fledge nor'easter that will bring heavy rain to Southeastern, PA and about 10 inches of snow to Northeastern and North central Pennsylvania. The only model not on board is the NAM which keeps taking this low too far off to sea. However, it is also colder than the other models. Also, when looking at run to run trends of the NAM, it is now trending more and more westward which leads me to believe that it will soon find the same solution as the other three models. Because of this, I am leaning toward the more devastating of the two solutions however; please check the newer model runs in order to finalize the forecast.

Long term (Saturday and Sunday):

Behind this system winds will strengthen out of the Northwest and with the recently thawed lakes, possibly cause some lake effect snow showers or at least keep the state cloudy. Temperatures will remain below average due to the fresh snowpack and Saturday night looks to be a MOS bust scenario. Sunday will be a similar day to Saturday but with a few less clouds, especially in the eastern half of the state. The next system should approach the region on Sunday night bringing a wet start to the next work week.

RJ Patrizio

March 30, 2010 Technical Discussion

Synopsis:

The area of high pressure that was centered over south central Canada the past few days and brought the region sunny but cold weather will slide to the east today and remain north of the commonwealth in southern Ontario the next few days. A couple of storm systems will move there way through the region over the next few days. The first system will track to the south of the commonwealth through the Carolinas but will still spread some light rain and snow across the southern and central zones. Another storm system will move up the eastern seaboard Thursday night and into Friday bringing a chance of snow and rain, primarily across the eastern two thirds of the state. Drier weather will return for the weekend, but the below-average temperatures will remain.

Short-term:

A storm system making its way through the southeast and Ohio River Valley today will bring a surge of moisture northward during the day as it moves into the Carolinas. This surge of moisture will bring increasing cloudiness along with areas of rain and snow to the southern and central zones of the state Wednesday morning and into the afternoon. Light snow is possible in the Laurels and higher elevations across the state. Wednesday night, the storm begins to race off the coast clearing out a few of the clouds. A few locations could see a few lingering rain/snow showers during the overnight period. Thursday will be the transition day between the two storm systems. Mostly cloudy skies will prevail across the commonwealth, but clouds will be on the increase and precipitation will begin to move into the southern zones as we head into the late afternoon and evening hours.

Long-term:

The long term forecast has the look of something that we would normally see in January or February and not the end of March.Unlike earlier this week, the models seem to be coming closer to an agreement with the track of the coastal low as we head into the end of the work week. Despite this fact, there is still a high level of uncertainty with the exact track of the storm. Therefore, without a clear cut solution to the forecast of the path, the type of precipitation and intensity is hard to determine. As of the current track showed by the 18z GFS, the greatest potential of wintry weather lies in the eastern third of the commonwealth. Snow showers are possible across the rest of the commonwealth but the heavier QPF will be in the east. Much of the precipitation will start out as snow but then will change over to a mix or rain entirely. The storm will move out late Friday afternoon into evening. Lingering snow showers will remain across the region on Saturday, but many locations will remain dry. Chilly conditions will once again return to the area for the weekend.

3/29 technical discussion

Synopsis

 

Over Mid-Atlantic region there currently is an area of high pressure sitting over the general region, bringing in cooler temperatures and some scattered clouds. As the week progresses a shortwave  will  bring scattered rain and snow showers.  Through the later part the week, a low pressure system moving along the coast could intensify into a Nor'easter which could possibly bring large amounts of snow and rain to the Mid-Atlantic and Northeastern regions.  As the weekend approaches some colder temperatures could move in with a trough digging into Virginia.

 

Short-term ( Wednesday into Thursday Night)

 

As the middle of the week approaches, a shortwave associated with a weak trough will move through the Mid-Atlantic bringing increasing cloud cover and chances of rain, snow and mixed precipitation due to Positive Vorticity Advection.  Wednesday night the shortwave will move out and some clearing of clouds could take place with few lingering snow/rain showers possible.  As Thursday approaches, clouds will start to increase with an approaching coastal cold front. The track for this storm is not quite certain yet, but current models are suggesting tracks for the storm that would allow for up to 18 inches of snow to be dropped at various locations depending if the storm takes more of a coastal track or seaward track.

 

Long-term ( Thursday Night to Monday)

 

 

The approaching coastal low pressure system will likely move through the area sometime Thursday evening into Friday morning, causing problems for the Friday morning rush hour.  This storm will likely lay down a layer of snow showers through some areas and then change over to rain showers closer to the coastal regions.  The coastal low pressure system will move into the Northeast sometime late Friday afternoon into Friday evening. Behind this coastal low, 1000-500 mb thicknesses will start to decrease greatly bringing in much colder temperatures to the Mid-Atlantic. Some leftover snow showers could hang around on Saturday as a 500 mb trough moves over the eastern seaboard. There could be a brief clearing in skies over the later part of the weekend before the next storm moves through.

Technical Discussion

Synopses

Today, the northerly flow keeps the entire northeast below normal for temperatures today. Clouds and snow showers push in on Wednesday when the first piece of energy comes up from the south.  The remainder of the energy gathers itself Friday and could ride up the coast as a nor'easter.  It is looking more likely that there will be a storm, but exact track is still very uncertain.

Short term

Our entire state should be sunny but cold today since we are under the influence of the eastern side of a large high pressure system and its accompanying northerly flow. Wednesday, energy starts to build along the gulf coast and an initial piece looks to break of and head north. This initial storm doesn't appear very strong and the ridge of high pressure should remain strong enough to keep it mostly to our south. Southern regions of our state should see some snow or perhaps even rain showers.

 

Long term

On Thursday, clouds remain prevalent across the state. The remainder of the energy along the gulf coast starts to organize and move up the eastern seaboard.  Friday could be interesting day weather wise across Pennsylvania and the entire northeast. This is beginning to look like it could be a classic Nor'easter. Models vary on track and strength with the GFS taken the most aggressive stance, showing a very potent low right along the coast. If the low stays farther off shore, eastern regions will see the bulk of the precipitation; rain to snow and rain along the immediate coast. If the low tracks further west, the axis of heavy snow shifts westward into central and western pa. Eastern Pa would probably see mostly rain in this instance. In any case, the storm system deserves close attention over the coming days. By Saturday, all precipitation should have wrapped up leaving us with lingering clouds and a fresh shot of cold air.

Steven Fuhrman      

 

3-29-2011 Technical Forecast Discussion

Technical Forecast Discussion

Synopsis:

The temperatures will remain cool despite the sunny conditions on Tuesday. Some clouds will start to move in late Tuesday night as a storm system approaches from the Midwest. Wednesday features a possibly for some rain/snow showers due to the aforementioned storm system passes to our south. The showers may continue into Wednesday night and gradually taper off. However, the clouds shall linger throughout much of Thursday with some wintry precipitation finding their way back into the Commonwealth again as another storm system develops along the southeast coast on Friday.

Short-term (Tuesday – Wednesday night)

A high pressure ridge situated over the Great Lakes will continue to usher in cold air from Canada on Tuesday. Despite the emergence of a vorticity maxima near the 500-mb level and spotty low-level moisture, the skies shall remain sunny to mostly sunny for much of the day on Tuesday. Some clouds may start to move in later Tuesday night as a 500-mb shortwave races across the Midwest toward the east coast. Its associated surface low pressure system will throw some moisture into the region, but the models do not show any substantial precipitation to enter the region until Wednesday. Wednesday will feature mostly cloudy skies with a slight chance of rain/snow showers. Any precipitation shall end Wednesday night but clouds will linger over the region.

Mid-term (Thursday – Thursday night)

Thursday will be the break in between two storm systems. The 500-mb shortwave will slide offshore on Thursday, but it will leave some low level moisture behind. Another upper level energy will quickly follow the existing storm system, which will give us another chance of wintry precipitation starting Thursday night.

Long-term (Friday – Saturday)

The models diverge quiet a bit at this point concerning the timing and the formation of the second storm. It seems like the models are still having trouble handling this second piece of upper energy swinging across the central states. First, let's talk about the GFS. The 12Z GFS depicts an area of PVA crashing into the Central Plains on late Thursday night. However, it breaks off another shortwave energy ahead of the amplifying trough, which will spun a weak coast low just offshore South Carolina. The main piece of energy lags behind, but will eventually merge with the first coastal low after crossing the Tennessee Valley on Friday. The two lows will combine into a bigger system but still not too strong in terms of intensity. Expect the main bulk of precipitation confined along the coastal regions if this scenario is true. The WRF also a weak shortwave forming ahead of the much stronger shortwave, but it keeps the shortwave on the weaker side, thus a weaker initial coastal low. This may benefit main storm to intensify stronger once it hits the coastal waters, but the true outcome remains to be seem. The UKMET model is on the extreme side of the solution with a very sharp 500-mb trough to start with. The trough becomes more negatively tilted as it approaches the east coast, eventually close off into a closed 500-mb low once it reaches the Northeast coast. This scenario would spin up a very robust coastal storm, possibly a late-season nor'easter, which will dump large quantities of precipitation to parts of the Northeast. The precipitation type is still uncertain as of now, but we cannot rule out the possibly of some places seeing blizzard conditions this upcoming weekend. However, the main point is that the models do not have a general agreement at this time.

David Wang

TECHNICAL DISCUSSION

...SYNOPSIS...

 

The beginning of the week seems to be relatively normal with temperatures in the 40s for most of the state. A high pressure system lies to the north from Canada, which will bring good weather until it leaves on Tuesday.  After the high dissipates, a low pressure system will be forming in the gulf on Wednesday according to the 12z GFS model. This low will be riding up the coast for the remainder of the week producing precipitation for the later end of the week.

…short term...

A few high pressure systems from Canada will be lingering around for the beginning to the middle of the week. The 12Z GFS shows the highs staying around until Wednesday when positive vorticity advection from the mid-West will be making their way in. The relatively zonal flow into Tuesday will also account for the rather good but chilly weather.  The positive vorticity advection with the low pressure system coming up the coast will contribute to some possible extreme precipitation events later this week. A rather chilly evening will be seen tonight with clear skies, and tomorrow looks to be mostly sunny until the high leaves PA.

…long term…

Later in the week seems to be pretty disastrous but still needs to be watched closely. Positive vorticity gaining a negative tilt towards the end of the week according to the 12Z GFS model could account for extreme precipitation amounts over PA. This could bring snow or a mixed precipitation to most areas starting mostly Thursday into Saturday. Wednesday could see some precipitation, but the SREFS only show the southern parts of PA experiencing most of this precipitation. Sunday appears to be dry, sunny, and decent weather, but the 12Z GFS shows another wave of positive vorticity coming in for Monday of next week, which could make for an even wetter Sunday if the system moves fast enough.

Technical Discussion 3-28-11

Synopsis...

 

Cold wintry weather will hang around all week with a quiet start and nasty end to the week as a potential snow storm could impact Pennsylvania and the northeast.

 

Short Term...

Today and through tuesday looks to be pleasant as far as sunshine goes, but definitely quite chilly for spring. The large area of high pressure stretching from western Canada into the northeastern US coupled with a low pressure system over the the Canadian maritimes is allowing cold air to funnel into the northeast to bring chilly days and cold nights. The flow over the eastern US is generally zonal, so we shouldn't see any large storms brewing through tuesday.

 

Long Term...

Things get a little tricky as we head into wednesday through friday as a meridional flow starts to build and amplify. A southern-tracking weak low pressure system will give the chance for some rain/snow showers for very southern parts of PA on wednesday. This area of disturbed weather will move off the coast thursday morning, but it will be followed quickly by another, more potent storm possibly, thursday afternoon and overnight. The GFS model shows the 500mb trough continuing to amplify as it moves towards the east causing greater cyclonic vorticity values, thus the potential for a low to strengthen more significantly. Whether we will see significant accumulating snow or just slush will have to be determined later in the week as the stronger March sun and warmer boundary layer will cause melting. Definitely a storm to keep an eye on.

 

Josh Aikins

Technical Discusion

Synopsis...

Quiet beginning to the week. Snow and rain likely on Wednesday with a reprieve on Thursday before much uncertainty about a storm Friday or Saturday.

Details...

Large done of high pressure NW of Great Lakes will promote sunny skies through Tuesday.  Temps will remain below average but moderate each day as air mass modifies.  Went close or slightly below MOS for the week due to abnormal chilliness of airmass for late March.  Should be a tranquil/non eventful beginning to the week with chilly nights and brisk days, more reminiscent of late October or November.  Expect a bit of a breeze as well for the beginning of the week making it feel cooler despite the strong late March sun.

Storm system on Wed bears watching.  Most guidance has primary low sliding south of the region with precip breaking out on Wed across entire state.  Definitely a mix of precip types due to warm boundary layer at this time of year.  Also, any snow that does fall will struggle to accumulate due to the high sun angle.  Biggest difference noted in the model guidance was how WRF handled the 500mb shortwave vs. every other model.  The WRF keeps it much more compact while other models shear out all the energy.  This is a known bias of the GFS but the WRF is not as great >60 hrs out.  Something to keep watching early this week.  Scattered rain and snow showers will occur on Thursday.

ddpdtdt

Sunday Morning Technical Discussion

Synopsis: Clouds along the Turnpike associated with a Southern Mid-Atlantic Storm.  This storm will not affect the state in any shape except for some clouds.  The rest of the Commonwealth is being dominated by strong high pressure in Central Canada.  This high pressure will dominate into the work week before moving off the coast of Nova Scotia.  In the wake of the departing high pressure, a storm system will try to affect us on Wednesday with snow shower in the AM, and showers in the PM, but for the most part will remain south of us.  Another storm system will try to take aim at us for Friday, but we will be spared in terms of a "direct hit".

Short term: Both the NAM and GFS both show mostly sunny/partly cloudy conditions for Sunday and into Monday.  They have their solution of where the clouds will be, but went on a compromise that the whole Commonwealth will see partly cloudy skies during this period.

Long term: Continuing from the short term, Tuesday looks to be another day of partly cloudy skies.  Only exception is that a storm system is taking aim at us for Wednesday.  The NAM looks to be faster than the GFS in terms of progression and precipitation.  The NAM has precipitation on the door steps of the state by 8am Wednesday, while the GFS lags behind for a 6-12hours.  For some odd reason, the GFS wants to stall the storm for 6 hours.  The SREF shows that we will mostly snow in the morning of Wednesday, and the GFS hints at AM snow becoming PM rain showers.  So went with the NAM progression over the GFS, but a combo in terms of what will fall from the sky.  The GFS as we progress into Thursday shows clearing conditions before our next system makes a run at us for Friday.  Hint for Friday the 0z shows the majority of the storm should be on the rainy side except at the very end and that a shot of cooler air will be with us for that weekend.