Thursday Evening Technical Discussion

Synopsis

As an upper level trough approaches from the west, it will replace the 500mb cutoff low that has moved off to the northeast today. Behind this low, there will be strong cold air advection on Friday through Sunday. After the trough departs, a ridge of high pressure will build into the area and promote sunny skies. This should make the pattern feel much more fall-like.

Short Term

Temperatures have begun falling this evening and should continue to fall with lows tonight in most areas in the low-mid 50's. On Friday, skies will be partly cloudy along gusty winds. High temperatures look to reach around 70 in eastern areas while north and west areas will struggle to highs only in the 50's. However, eastern areas will cool off later Friday afternoon as the strong cold front associated with the upper level trough over the great lakes moves through the area. Once this cold front passes through the area Friday afternoon, strong cold air advection will occur. This air will be the coldest of the fall season so far with some locations falling into the mid to low 30's in northwest areas overnight Friday.  The winds will also be strong and will make it feel much cooler. The 21z SREF mean has wind speeds of 15-20 mph with higher gusts over most of the commonwealth. There is also the chance for showers on Saturday as the 500 mb low associated with the upper level strengthens as it moves off to the northeast.

Long Term

Sunday will be brisk as the northwesterly flow over the area continues to dominate. There is the chance on Sunday for more showers as the low pressure system to the east strengthens and creates precipitation over the area.  The 21z SREF mean has an average of .5-1 inches with a maximum in northern PA of near 2 inches. However, once this low departs the area to the northeast, a ridge of high pressure will build in for the start of the week.  Temperatures should rebound in the upper 60's to lower 70's as a result. This air mass will feel much more seasonable and should remain through Wednesday.

-Matt Mehallow

Thursday Afternoon Technical Discussion

Synopsis:

The upper level low will finally be moving out of the region come tomorrow (Friday).  Another upper-level system will move into the region Friday night, giving much of the Commonwealth some spotty showers. A ridge will be building behind this low and will be moving into the area at the beginning of next week. This will signal the end of showers and clearing conditions for the time being.

Short-term:

As the upper level system that has plagued the state for much of the last week finally gets itself out of the way, a stronger upper level system will follow right behind creating a northwesterly flow. Showers will accompany this system along with much colder conditions throughout the weekend. Conditions will be much of the same for the next 72 hours, only it will be from a different system.

Long-term:

The ridge will began to build into place early next week accompanied by calm and clear conditions. This ridge will also allow temperatures to gradually warm up next week. Some areas might reach the lower 70s.

 

Wednesday September 28th, 2011 Evening

Synopsis:

 

The upper level low that has dominated our weather for the past week will continue to do so until Friday. Another upper-level system will move into the region Friday night creating a batch of showers and much cooler temperatures for the weekend. A ridge will then build into place for the beginning of week allowing for clear and calm conditions.

 

Short-term:

 

An axis of heavy precipitation has set up in eastern Pennsylvania prompting several flash flood warnings. This can be attributed to an upper level low in the Midwest that is controlling our current weather pattern. The system has created a southeasterly flow which will bring mild, humid, and rainy conditions tomorrow and tomorrow night. The upper level system will scoot eastward on Friday accompanied by showers. A stronger upper level system will follow right behind creating a northwesterly flow. Showers will accompany this system along with much colder conditions.

 

Long-term:

 

Cool conditions will stay in place through Sunday. A ridge will began to build into place early next week accompanied by calm and clear conditions. This ridge will also allow temperatures to gradually warm up next week.

 

Dakota Smith

Wednesday September 28th, 2011 Afternoon

Synopsis:

The cut off low to our west will finally make movement eastward as the Commonwealth continues to get rain for the rest of the work week. A strong high pressure system looks to make way into the region on Sunday.

Short-Term:

The cold stationary front will slowly begin to exit the commonwealth by the end of the week, causing showers and possibly thunderstorms ahead of this front. They will travel from Southwestern PA toward the Northeast direction. Flash flooding is a major concern as these showers can drop an inch of rain in about a 20 minute interval. The front will pass through Wednesday night, shifting the direction of precipitation from south to westward. The cutoff low to our East will finally re-enter the jet stream and exit. Scattered showers are still seen throughout Thursday but the threat of flooding should not be as worrisome.

Long-Term:

The cutoff low will finally be pushed back into the jet stream by a strong storm system associated with a cold front. A strong high pressure system will push through the area Friday, leaving us with a possibility of scattered showers as remnants of the cut off low. Showers could still linger on Saturday morning, but should clear up after noontime. The high pressure should dominate Sunday, leaving us with sunny conditions.

Forecaster: Meredith Nichols

On Wed, Sep 14, 2011 05:32 PM, "Meredith Nichols" <man5187@psu.edu> wrote:

Synopsis:

A cold front will push through the Commonwealth Wednesday bringing large chances of precipitation.  A strong high pressure moves in for the rest of the week bringing partly sunny skies and temperatures back up to the mid-60s by the weekend.  

Short Term:

A high will continue to move out of the area as we head into Wednesday night. A low pressure system will come up the east coast, bringing slightly cooler temperatures for the rest of the week. This will bring in cloud cover and a chance for precipitation for most of Thursday. Temperatures will drop significantly Thursday night, reaching the high 30s in some areas.  Winds around 10-15kts will be felt going into Thursday night as the front passes through. Cloud cover will slightly dissipate as a high hovers above the commonwealth which will stick around for the weekend. 

Long Term:

Temperatures should stay in the high 50s/ low 60s as we head into the weekend. Saturday and Sunday bring warmer temperatures as well as mostly sunny skies across the commonwealth, as cloud coverage dissipates Saturday morning. Temperatures will stay in the mid-60s throughout the weekend, leaving us with a few remnants of summer. 

Forecaster: Meredith Nichols

Meredith Nichols
Undergraduate of Meteorology
Pennsylvania State University '14

Wednesday Midday

Synopsis:  A Cutoff low will be slowly moving east, as it does so, the Commonwealth will deal with rain for the rest of the work week.  First rain will be from the south, and then Thursday onward it will be from the west.  Strong high pressure looks to come into the region for Sunday.

Short-term:    With the cold front/stationary front slowly moving eastward, showers/thunderstorms are likely to occur, ahead of the front.  They will be traveling from the South/Southwest and moving to the North/Northeast.  Flash flooding could occur, as some of these showers can put down a quick inch in about a 20 min span.  Already the GFS/NAM is off on where it should be precipitating for the day.  The current radar shows a line of shower that will affect the Central and Eastern parts of the state, while Western part looks partly to mostly cloudy.  Relied more on the current weather, then on guidance.  The front will pass through sometime over Wednesday night, shifting the precipitation travel from the south to from the west.  The GFS has the cutoff low finally getting caught back up into the jet stream, while the NAM is just beginning this at around 15z Thursday.  We will still see scattered showers, throughout the day on Thursday.  The threat of flooding on Thursday does not look as bad as it does for Wednesday.

Long-term:  The system that is causing the jet stream to finally pick up the cutoff low is a strong storm system that pushing through the Northern Great Lakes and has an associated powerful cold front with it.  Behind it, a strong high pressure will move into the Ohio River Valley for the end of the weekend.  But before that, the cold front will push through on Friday with scattered showers that will linger into the night. The difference between the models for the timing of the front looks to be a 50 mile difference, and at 18z Friday, the front should be through Central PA according to both GFS & NAM.  Showers might linger on Saturday morning, but clearing conditions will occur after noontime.  High pressure looks to dominate Sunday, hence mostly sunny conditions for Sunday.

Kept temperatures near previous shift.

Tuesday Night Technical Discussion 9/27/11

Synopsis: The low pressure system that moved into the great lakes region late last week has stalled, and continues to sit over the great lakes. As the week progresses, the cut off low will begin slowly making its way across the state bringing showers and cooler temperatures throughout the week and into the weekend.

 Short-Term: The stalled low pressure system will continue to wobble back and forth over the Ohio Valley before slowly making its way across the state, providing a chance for showers throughout the week as the trough moves through. The passing of this system will bring cooler temperatures for the end of the week Both the 00Z NAM and the 18Z GFS show the low exiting late Friday to the northeast.

 Long-Term: As the cut off low moves out of the state, the showers will begin to taper off and another system will dive southeast and move into the state bringing cooler temperatures for Saturday. The temperatures will remain cool for the rest of the weekend while a ridge builds into the region at the beginning of next week bringing temperatures back to normal.

-Aaron Herbert

Tuesday afternoon technical discussion

Synopsis: A stalled front associated with the occluded low is currently bringing rain showers to parts of Pennsylvania. As center of low pressure makes its way east, this will continue to bring the chance of rain across the state.

Short-Term: A dry slot is currently providing few and scattered clouds across the western half of the state. Heavy rain is being generated to the east. Upper level low will continue to spin over the next few days and slowly propagate eastward until the trough builds its way in. The cut off low will continue to bring the opportunity of rain to parts of PA especially as the core moves into the area. Both the 12Z WRF and 12Z NAM move the low into the keystone state late Thursday into Friday before exiting. The SREF shows fairly high 3 hour POPS likely over the upcoming days.

Long-Term: The upper level low will linger across our area until a long wave trough makes its way into the state around Friday. This will continue to produce rain showers which move in from the northwest. Expect winds to shift to a northwest and bring cooler than average temperatures. A ridge will develop the west and advance to the east bring dry and warmer temperatures early next week.

-Matthew Ray

Models are agreeing on an upper level low continuing to sit over Indiana for the next few days. This will keep the clouds and southwesterly flow over the area.  This will keep temperatures in the 70s and the humidity high. The skew-t 12z runs show a lower cloud layer which conforms the instability of the upper-level low. Also it seems the chance for clouds will be around as well as the chance for early morning fog.  Another upper-level disturbance will move down from Canada later on Wednesday, which will help kick out the cutoff low there now.  The models consistently show the next trough sitting over the area through the weekend. The 18z gfs shows the highest qpf on Tuesday and Thursday. The GFS also is hinting at a trough building over the east next week as a trough enters the west and ends there hot streak. 

Technical Discussion

Synopsis:

A low pressure system will approach the state through the first half of the week, bringing an opportunity for scattered showers.

Short-Term:

An upper level low is currently hovering over the Midwest region, as evidenced by the nice vorticity maximum and height patterns. It will proceed quite slowly towards the Mid-Atlantic region.  The 1200 UTC run of WRF is projecting reasonable amounts of moisture in both upper and lower levels in the atmosphere, as displayed by the relative humidity plots, so cloudy skies (but no significant precipitation) are expected tomorrow across the state, except for a few spotty showers in the southeastern portions (as the 900 UTC run of SREF is showing).

Long-Term:

The 1200 UTC runs of both WRF and GFS show the low pressure system approaching the state and bringing an associated swath of moisture by Tuesday.  The 1200 UTC run of the GEFS plumes project the precipitation to begin as Tuesday progresses.  The individual ensemble members diverge quite a bit into Wednesday and Thursday, but the general consensus is that this will not be a significant precipitation event, with 6-hour precipitation totals not really exceeding 1 inch by Wednesday.  The 900 UTC SREF ensemble's precipitation projections show the precipitation arriving late Monday evening into Tuesday, western and south-central portions of the state first.  Spotty showers appear to linger around the state through the end of our forecasting period.

Thursday Evening Technical Discussion

Synopsis

As the deep upper level trough over the Midwest moves slowly east, it will slowly become separated from the upper level flow and will cutoff.  This cutoff low will stall out over the Ohio River valley and leave us in a wet and stormy pattern.  An area of low pressure from the south will move into area Friday and promote periods of rain. Once this low exits off to the northeast, the cutoff to the west will provide clouds and a chance of showers through mid-week.

Short Term

Through the morning hours on Friday, the possibility of some clearing tonight will allow for radiational cooling and the formation of fog exists near dawn. However, as shortwave approaches from the south during the day on Friday, there is the strong possibility for moderate rainfall. The 12z European and 12z GFS both are in decent agreement of rain beginning around 18z Friday. Rain will overspread the area and increase in intensity as we approach the evening hours Friday. The rain will become more convective over the eastern portions of PA as we head into Saturday morning.  In central to western areas, the rain will gradually subside overnight into Saturday morning. Conversely, in eastern areas, particularly Southeast PA, the rain will continue throughout the day Saturday into Sunday morning.

Long Term

By the midday Sunday, the rain should begin to end in western counties while the rain will gradually subside in eastern areas by Sunday evening. The 21z SREF mean indicates potential total rainfall of 1 to 3 inches of rainfall with closer to 1 inch in western and central areas of the commonwealth. In eastern PA, mainly in extreme southern eastern regions of PA, there could be totals upwards of 3 inches. As the low pressure associated with this shortwave moves off to the northeast, the 500 mb cutoff low will persist to the west and bring more unsettled weather. The cutoff low eventually lifts to northeast mid-week and is replaced by a ridge of high pressure later in the week.

-Matt Mehallow

Thursday Afternoon Technical Discussion

Synopsis

 

The low pressure system over the Ohio Valley has become cut off and will continue to deepen over the weekend. It will be anchored over this region for the weekend and the beginning of next week. Precipitation and thundershowers remain a distinct possibility during this time.

 

Looking ahead to the weekend and early next week:

 

A strong upper level low has detached itself form the jet stream. Broad ridging will allow for the system to nearly stall over the Ohio valley sometime on Friday. The low will become closed off and will continue to deepen and spin up moisture from the Atlantic. Unsettled weather is expected for Friday and Saturday due this system. Temperatures on Friday will be slightly below average in western zones of the state due to the passage of a cold front and cooler air being brought in by the upper level low.

  

As the upper level system continues to spin into Friday night and Saturday, swaths of heavy rain will move north across the region. Model guidance does not seem to have a good handle on exactly where and when these heavy bands will hit however. Latest WRF (0Z) has heavy bands moving through central zones early Saturday and then separate bands moving through extreme eastern and western zones later in the day. GFS guidance likes move the rain through earlier, ie. late in the day Friday. Regardless, there will be bands of heavy rain moving through Friday night as the system deepens and becomes stagnant. This will keep a chance of rain through at least Tuesday, with conditions becoming better for the second half of next week as the cutoff slowly moves out.