Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 19:23 GMT le 26 octobre 2008
"Afternoon Thoughts" (Updated 10/25)
So yes here it is… my format for the winter each week. Now when significant winter storms or lake effect snows head our way, then there will be a special format for those storms. While some may consider it a bit premature to have my blogs in a winter format, some areas have already seen their first snowflakes as far south as State College and other areas may see their first accumulations during the coming week. Also some areas will see highs in the 30s and other areas in the 40s. In any case we are entering November very shortly and typically in November most areas see their first measurable snow. So all in all I thought it was prudent to issue this format awhile. If anyone has any suggestions on other sections that could be necessary for the winter, just drop a comment below.
Anyways I want to quickly recap Saturday’s rainfall. A dying cold front was moving across the state along with several disturbances along the front. A weak low pressure was also found in the Southeast helping to pump up moisture ahead of the front. Strong southeasterly winds developed ahead of the front in eastern Pennsylvania with gusts to near 40mph in extreme eastern areas. Rain moved into western Pennsylvania overnight Friday dumping up to nearly 2.5inches in some locations. This batch of rain reorganized itself after much of it moved into New York State. Meanwhile the southeasterly flow brought in warmer temperatures at the surface and aloft for slightly more unstable air. PWATs several deviations above normal moved into east central and eastern Pennsylvania where rainfall organized into very heavy stratiform rain over the Susquehanna Valley. Rainfall amounts in this region were 1.5inches-2inches. Then some unstable air 3k ft aloft developed in eastern Pennsylvania creating an embedded squall line of thunderstorms that developed in the Delaware Valley and Southeast Piedmont region. Then the squall developed into areas farther north in the Lehigh Valley. In this squall line were rain rates to up to 2.5inches per hour and gusty winds upwards of 45mph. This squall line continued to strengthen and turned severe as it moved into New Jersey. There were several reports of wind damage in far eastern Pennsylvania. Rainfall amounts in this region were from .75inches-1inch. Overall the entire region saw a nice significant rain greatly boosting monthly totals closer to normal, but still below normal. I am very pleased with my forecast for this event. Enjoy the recent rains, because any significant signs of precipitation do not appear to be on the horizon anytime soon. Have a great day!!!
"Current Surface Plot"
(Courtesy of HPC)
(Courtesy of Wunderground)
(Courtesy of NOAA)
"Forecast Discussion" (Updated 10/25)
So who is ready for our favorite computer model games? Lol. Yes they are up to their normal antics, but in any case here is my forecast discussion for this coming week. A strong cold front primarily dry with QPF less than .1inch will cross over Pennsylvania by early afternoon Monday. Temperatures will slowly drop after the frontal passage along with drier air. Winds will shift to the 300degree trajectory. Lake effect rain showers will develop occasional mixing with graupel. H85 will only be in the (-3C)-(-4C) range, which is not that unusual for October. Clouds will be over the region with a thick cumulus deck. But then a second pocket of cold air moves in for Monday night with heights lowering to near –6C with lake effect snow bands developing off the Great Lakes. With steep lapse rates and CAPE values in the 50-100 j/kg range I would not rule out some thundersnows. Accumulations will only be in the nuisance range for the most part, but I am starting to think there could be a decent accumulation of snow in the southern portions of Erie County in the higher elevations. A band looks to want to setup in that region. 2m temperatures from the GFS show them near 32degrees for most areas north and west of the Gettysburg-Harrisburg-Reading-Easton line. South of that temperatures should stay in the mid to upper 30s as winds will be pretty gusty during Monday night along with varying cloud cover. The third and final cold pocket of air kicks in during the day Tuesday turning the flow more west northwesterly. H85 lower to near –9C across extreme northern Pennsylvania. 2m temperatures indicate temperatures in the 30s for much of western and northern Pennsylvania during the days Tuesday and Wednesday. Even the latest 12z GFS shows temperatures below 40degrees during the day Wednesday for KMDT. Best Omega growth looks to be Tuesday night with the third pocket of cold air. Snow accumulations will occur in favored snow belts up to several inches. Some flurries may even make it just east of the mountains. Latest computer models also complicate forecasts for Wednesday with developing a coastal low. As the trough moves into the region it becomes negatively tilted along with a negative NAO. The PNA also becomes positive making for a pretty amplified flow. 0z EURO really developed a monster coastal low with light snows in northeastern Pennsylvania but near record breaking snows up in New England. GFS up until the 12z run had not really developed anything. NAM has recently swayed towards latest 0z EURO. But just recently the 12z EURO came out and is similar to the GFS with keeping the low out to sea. Last 12z JMA and 12z UKMET though do develop a coastal low with heavy wet snow in New England. At this point placement of the low is questionable. Even if the scenario sways back to the 0z EURO the only affects Pennsylvania would have would be some very light synoptic snows across eastern Pennsylvania mainly from the Lehigh Valley on north, but it would not amount to anything. But the low could draw down some cooler air and inhibit the drier air eventually causing more lake effect snows across northwest Pennsylvania. So we will see. Trough eventually moves out towards the end of the week with 1028mb high pressure over the Southern Middle Atlantic keeping clear skies and temperatures near normal values.
(Courtesy of Penn State Meteo.)
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Weekly Forecasts" (Updated 10/25)
Monday- A strong cold front will be moving across Pennsylvania during the morning hours. Ahead of the front temperatures will be near seasonal values along with a gusty southwest wind. Winds may gust to near 35mph. As the front approaches a weak band of rain showers will move across Pennsylvania, but dry up in central Pennsylvania over the Appalachians. No precipitation will be expected for eastern or east central Pennsylvania. Some areas across the Laurel Highlands may see some morning snow showers after the frontal passage before changing to rain showers by later in the day. By early afternoon the front will be across the state with falling temperatures for the most part statewide. Winds will be out of the northwest gusting upwards of 40mph at times, especially on the ridge tops. A widespread cumulus deck will develop across western and northern areas with occasional rain showers. Areas in the east will see downsloping winds. Highs will be mainly during the morning hours for western areas and during the early afternoon for eastern areas. Highs will range from the upper 40s in the west to low 50s in the east. Monday night cooler air continues to funnel in. The lake effect machine kicks in with a northwest trajectory. A strong band looks to develop in Erie and Crawford County up through Warren and McKean Counties also. At first it will be rain, but then dynamic cooling should set in for changing over to snow. A dusting to one inch of snow is possible in snow belts. Elsewhere across the state flurries will be widespread for western and northern Pennsylvania.
Tuesday- Colder air continues to funnel in over the region Tuesday with lake effect precipitation dominating the radars. The lake effect flow will shift more towards the west-northwest, which is a favorable flow for widespread lake effect activity for western and even sometimes central areas. Snow showers should be widespread during the morning hours, but change to a mix in the afternoon hours. Snow showers should stay confined to areas west of the Altoona-State College-Lock Haven line, but some areas in the northeastern mountains will also see snow showers. Highs will be well below normal with highs not getting out of the 30s for elevations above 1700ft in western areas. Cloud cover will be pretty widespread statewide. For eastern areas and valley locations highs will be in the mid 40s. For the Philadelphia metro region highs will be in the low 50s. Tuesday night looks to be the most widespread for lake effect activity as the coldest air settles in over the region. Some models want to develop a coastal low enhancing lake effect and orographic snows, but this scenario remains to be seen. Under a continued west-northwest flow snow showers may make it east of the mountains, but only to areas in the Lower Susquehanna Valley up through the Lehigh Valley. Snow accumulations for northwestern areas in the higher elevations may be several inches with dusting to one inch in the valleys even out near Pittsburgh. Some areas in the northwest ridge and valley region may also see a dusting. Out in the northeastern mountains of Tioga, Bradford, Susquehanna, and Wayne Counties may also see a dusting to an inch or two of snow. Lows will be in the 30s for most areas and in the 20s for northern areas.
Wednesday- Lake effect machine should still be kicking during the morning hours with an additional dusting to one inch of snow for the favored snow belts. Again there remains more uncertainty with the prospects of a coastal low. Some morning flurries will occur for the ridge and valley region also. Clouds will be widespread though for most of the day making Wednesday the coldest day of the week. Lake effect snow will be ending by the end of the day as high pressure moves in. Still though some models want to develop some strong lake effect bands during the day with a northwest trajectory. But those bands will only develop with the enhancing of the coastal low. Downsloping winds east of the mountains will keep their conditions partly cloudy most of the day with temperatures in the mid 40s even low 40s at elevations above 1000ft. In the mountains highs will only be in the 30s. By Wednesday night only flurries remain confined to far northwestern areas and lows drop below freezing in all locales. Winds could be a bit gusty if the coastal low develops.
Thursday- Thursday looks to generally be a nice weather day across the state as high pressure kicks the coldest core of the air out of the Northeast. Skies will generally be clear with a light westerly breeze. Any snow accumulations in the northwest will melt during Thursday. Highs will make it up into the low 50s for many areas, but still in the 40s for elevations above 1700ft. Thursday night will generally be clear with light winds making for a very cold night. Lows may be in the mid 20s for many areas and I cannot rule out teens for the northwest if winds decouple. Dry air will be prevalent over much of the region.
Friday- To finish out the workweek a ridge of high pressure develops ahead of a potential weekend frontal system with more cold air. Highs will get back to near seasonal values with highs in the 50s for most areas, but in the low 60s for metro locations. Skies will be clear with widespread sunshine. Friday night looks to be another radiational cooling night with dry dewpoints and clear skies with light winds. Lows will be below freezing most likely statewide including most metro locations. Some ground fog may form late.
"Current River Ice Reports and Ski Conditions" (Updated 10/25)
Well obviously there are no river ice concerns nor ski reports. But during the winter this section will contain valuable information on local river ice reports. Also there will be local lake ice report levels found here. Many times people find themselves in dangerous situations because the ice is not as thick as it may look. So this section will be an outlook for ice levels for the coming week. Also here will be local ski resort reports across Pennsylvania for the week in terms of snow conditions. Many people really do enjoy the winter sports season here in Pennsylvania and are looking for local ski conditions. Below are a few links you may also find valuable during the height of ski season and ice levels.
-Link to official reports page from NWS...Link.
-Link to local ski resort snow conditions...Link.
"Current Northeast Snow Depth and Northeast Windchills"
(Courtesy of Wunderground)
"Lake Effect Snow Conditions" (Updated 10/25)
During a majority of the cold season, lake effect snows occur with almost every post frontal passage. These frontal passages are typically once or twice a week during the winter. Many people have concerns with the Great Lakes to prepare sometimes for unanticipated squall lines. I am hoping this section will provide some education on lake effect snows, and forecasts for lake effect snows each week. Below are some interesting maps I found concerning Lake Erie wind speeds/direction and sea surface temperature. I also will provide in this section information about how much ice can be found throughout the lake. On severe winters Lake Erie sometimes does freeze over completely due to its smaller size and shallower waters than the other great lakes.
Alright the first lake effect snow outbreak is heading our way with quite a winter-like pattern setting up for the next couple of days. Cold front will be marching eastward throughout Sunday and into Monday morning across Pennsylvania. This will provide a wind shift to the northwest and a temperature drop. Heights aloft will be dropping down to near –3C for Monday. Surface temperatures will be in the low 40s for snow belt regions, so it does not appear that any accumulations will occur Monday. It appears that the majority of the precipitation Monday will be of the graupel variety. Flow looks to setup near the 300degree trajectory keeping much of the lake effect snows in the northern part of the state. By nightfall another cold pocket of air will drop down with heights dropping to near –6C. With water temperatures of Lake Erie nearly in the 60s, strong instability will develop. Surface and 1-3k ft CAPE near 50-100 j/kg looks to develop along with surface temperatures overnight Monday in the low 30s for northern areas. Best banding looks to be setting up just south of Erie in Erie County and Crawford County. The 12z NAM from Sunday has a great hold on forecasting this band. Occasional this band may waffle south into Mercer, McKean, and Warren Counties. With some dynamic and evaporational cooling rain will change to snow for many areas with elevations above 1000ft. Snow accumulations may occur several inches if the band does in fact become strong like it is progged to. This band looks to stretch all the way up to the city of Buffalo. The winds then seem to shift more west-northwesterly near the 280degree trajectory keeping lake effect snows widespread during the day for all of western Pennsylvania. Temperatures will be marginal, which is common during early season outbreaks and ground temperatures are warm. No daytime accumulations are anticipated at this time. Snow flurries may stretch all the way into the Ridge and Valley Region of central Pennsylvania into State College and Huntingdon/Franklin Counties. Tuesday night the flow stays west-northwest putting the Laurel Highlands at risk for some snow accumulations. The third cold pocket aloft moves in over night with heights lowering to nearly –9C. Surface temperatures should drop below freezing for many areas. Snow accumulations of several inches may occur Tuesday night over typical snow belts and especially with elevations above 1700ft. With ground temperatures still very warm, it will be a bit before the initial development of accumulations. There also has been some indication of a slight more northerly component that night developing a band over the northeastern mountains in Susquehanna and Wayne Counties. If this develops an inch or two of snow cannot be ruled out. Also with the very unstable lakes I would not be surprised for some flurries east of the mountains towards Wednesday morning. Keep an eye out for that. The last time I believe many areas saw snowflakes in October was in 2002. That also was our last very severe winter, so I guess we will see. Look for a snow map to be issued by me tomorrow afternoon. Lake effect snow situation sort of reminds of the 2007 November 7 event. Here is a link from the Buffalo NWS for more information... Link.
"Lake Effect Snow Map"
***Update as of 4:15pm Monday...
Well I do not really have any different thoughts for the lake effect snow situation. Warm ground temperatures should keep a hold on heavy accumulations, but I do feel worried about a few stronger bands setting up. I am even thinking there could be a enlongated Erie-Huron Streamer that brings some heavier snow to Cambria County. Areas in typically lake effect snow areas will definitely see flurries and some dustings to perhaps one inch, such as Pittsburgh and maybe State College if they are lucky. Anyways looks like my discussion above should suit for the most part.
"Current Lake Erie Wind Direction and Speed"
(Courtesy of NOAA)
"Current Lake Erie Water Temperature"
(Courtesy of NOAA)
"Long Term Outlook"
The long term period is highly questionable at this point in time. But by the end of this week after returning to near normal temperatures, another cold front approaches, which actually has a deeper core of cold air with even temperatures aloft in Southern Canada near –20C. This trough does not become nearly as amplified and only really affects areas north of the Mason-Dixon Line. But it does look quite chilly for this weekend with 850s below –10C as far south as New York State. But high pressure remains parked over region so lake effect snows do not look likely. With high pressure parked in southern Ontario and Quebec it appears that very dry air will be over the region making for some very cold nights with ideal radiational cooling. 2m dewpoints showed them as far south as Harrisburg in the teens, which would probably translate to low temperature in the low 20s. That seems a bit extreme though. Pattern though remains highly progressive and trough lifts out by Monday for a zonal flow keeping temperatures near normal with no signs of significant precipitation. It appears dips in the trough will occur every now and then before a major trough develops late in the month. Many long term meteorologists indicate a very amplified trough moving in by mid November. And in fact the latest 12z GFS shows a very large trough moving in with heights as low as –10C as far south as the Pennsylvania/Maryland border. That could be the unofficial start to winter. AO is showing signs of heading negative during that period, which translates to a shift in the arctic air to areas farther south. Latest ice analysis shows that very cold air has been building up in that region. This cold air will eventually poor into the northern US. So all in all a very winter like pattern looking to setup by mid November. Until then enjoy a nice zonal flow during the early part of November. My first guess at widespread accumulating snows would be sometimes in mid to late November. I do not think we will have to wait till December like some years.
"Current NAO and PNA Predictions"
(Courtesy of NOAA)
"Monthly Outlook" (October)
So September has now just about come to a close. Precipitation was above normal for most of the state of Pennsylvania, except for parts of western and extreme northwestern Pennsylvania. Temperature wise it was about 1-2degrees above normal for much of the state. My forecast called for normal temperatures along with above normal precipitation, so overall I am pleased with my forecast for September. The first half of the month was much warmer than normal followed by a cooler than normal second half of the month. So now we are in October, the height of the fall season, and many are wondering if we will have another scorcher like last year. Temperatures were into the 80s for much of the month along with an extremely late fall foliage season. As many bloggers have mentioned, they were swimming in pools during the first half of the month. By the end of the month finally many areas received a very late frost and freeze followed by a relatively cold November with an early snow around mid month. So for October here is what I am thinking...
Temperature- There does not seem to be quite an evident trend for temperatures for October. There does not seem to be one distinctive pattern setting up other than a consistent eastern United States trough. The NAO seems to be staying negative for next two weeks along with PNA mostly positive. AO index is also staying the majority of the time in the negative range. Also EURO long-range model supports Greenland blocking with a slight eastern trough. GFS has shows a similar pattern with cold and mild periods throughout much of the month. So overall I expect temperature values to be near normal with slightly below normal temperatures in some areas. I do not think we will be seeing any extreme warmth this month like last year.
Precipitation- Precipitation wise again there does not quite seem to be an evident storm track. I am thinking a typical October like setup occurs with a few dry cold fronts along with some wetter low-pressure systems. Around midmonth the long range GFS has consistently showed a large coastal storm so we will have to see what happens with that. Tropics are beginning to calm down, so I do not feel too confident on the east coast experiences another tropical system. So my forecast for precipitation is normal to slightly below normal. Overall I think October should be pretty consistent with 30-year historical means.
"Temperature and Precipitation Outlooks from Climate Prediction Center for next 30 days"
(Courtesy of NOAA)
-Winter 2008-2009 forecast... Link.
-Winter 2008-2009 forecast update... Link.
"Here northeast of Harrisburg 2008-2009 winter statistics"
Current Snow Cover- 0.00inches
Monthly Total- Trace
Seasonal Total- Trace
Winter Storm Warnings- 0
Heavy Snow Warnings- 0
Blizzard Warnings- 0
Lowest Temperature- 26
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First Snow - October 29 - Trace
***Update as of 8:30pm Monday on Nor'easter...
Wow, it is hard for me to believe we are looking at the situation that is unfolding. It is a bit early, and if this were 40 days later we would be talking about a blockbuster snowstorm. And when I start looking at some of the outlandish prospects of the bufkit data from the models, I have to stop myself and say it is only October. The crazy 18z NAM showed beautiful banding effects on the southwest side of the center of the low delivering an unbelievable 1.7inches of liquid equivalent snowfall. Yep that is 17inches of snow. But never going to happen. Interestingly enough some times all winter we never see bufkit data look that great. GFS also delivers impressive snowfall totals to nearly a foot of snow in the northeastern mountains near Scranton. Again that looks overdone. The deep and amplified trough is moving across the northeast with the second batch of cold polar air. The trough is already beginning its transition to a negative orientation as visible on the water vapor loop and infrared satellite images. Radar loops indicate a strengthening band of mostly rain across the upper Middle Atlantic. Much of that rain had been virga as dewpoints were in the upper 20s, but now the rain is reaching the ground and should cause some nice evaporational cooling conditions across much of the eastern part of the state. Recent pressure drops indicate a 1006mb low forming off of Hatteris and heading north-northeast along the perifual of the trough. As the low moves near the Gulf Stream a rapid intensification should form putting a 988mb low south of Long Island. Precipitation bands may get as far west as State College and recent models put nearly 1inch or more of QPF over much of eastern Pennsylvania. But surface temperatures are key, and they will be a struggle between an excellent forecast or a bust. I also think a lot of people will be taken surprise by the snows. Wet snows can cause plenty of damage especially in some of the valleys where leaves remain on trees. Then the GFS predicts winds aloft to nearly the surface being near 60knots with some of that reaching the surface. Winds will gust to nearly 55mph during parts of the storm plastering the wet snow all over the mountains. Elevations above 1600ft in the northeastern mountains will see the worst of the conditions with snowfall possibly over 6inches. I would not rule out even a 10inch snow report. This is quite a storm. The low will then head up through the CT Valley and up through the Berkshires continuing to further strengthen and cause high winds and heavy snow in some areas. The Adirondacks are going to get slammed possibly over a foot of heavy, wet snow. Some problems this early in the season arise for accumulations and that is mainly surface temperatures and ground temperatures. Temperatures aloft are no worry and have dropped below freezing in the H85 range for most of Pennsylvania. Surface temperatures may get pretty close to current dewpoint levels. If the precipitation becomes heavy enough dynamic cooling may take place, especially as the low rapidly intensifies. Highs will be in the 30s on Tuesday with heavy snow across the northeast. I would not be surprised for some reports of snow across the northern Lehigh Valley and coal regions. Ridge tops especially could get in on the action. I do not have much time to write about a fully detailed report tonight, so I hope this covers the basics.
Snow map for Coastal Storm...
I feel pretty good about my snow map. Most of the snow accumulations higher than 6inches will be confined to elevations above 2000ft. The shading does some a bit odd at first glance, but this storm is highly elevation specific so I looked at a topographic map while creating the snow amounts.
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