Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 3:07 PM GMT on September 30, 2008
"Afternoon Thoughts" (Updated 9/30)
Good morning!!! What a beautiful evening it was Monday night. Skies cleared after some afternoon diurnal cumulus, and temperature dropped down to dew point levels to give way to some heavy dew and ground fog. This time of year is always some enjoyable as fall colors dot the landscape, and fresh Canadian cold fronts draw down some cool temperatures for the nights. Each morning is always followed by ground fog. This is ground fog season the months of September and October. Last year, especially was known for lots of foggy mornings. I have noticed another busy time for nature, with squirrels swinging from every tree known to man. Also I have not seen the giant ogre groundhog in almost two weeks. The birds are still scurrying about at the birdfeeders and birdbaths, but shortly it will be time to empty the birdbaths as frosts and freezes approach. I never made it up to Hawk Mountain on Sunday due to the heavy rain and mountain fog, so hopefully in the coming weeks I will be able to witness the annual hawk migration over the ridge tops of Pennsylvania. Deer have been running about during the evening and early morning hours as they become a little more active during this cool weather season. This blog covers some of the interesting seasonal topics such as Fall Foliage and my October Outlook. This week will sure bring a taste of fall as temperatures plummet into the 30s for lows late in the week, and snowflakes potentially fall in the Adirondacks of New York State for Friday night. See below for more information on this significant trough moving into the Midwest and Northeast. Already frost advisories and freeze warnings are out for parts of the Great Plains as the cold front has already moved through. Enjoy the Fall season. Have a great day!!!
(Courtesy of NOAA)
(Courtesy of Penn State Meteo.)
(Courtesy of NOAA)
"Forecast Discussion" (Updated 9/30)
An active start to the forecast period for this week, but that will quiet down by the end of the week. A very strong cold front is moving across the Ohio Valley Tuesday morning. Steep lapse rates will develop ahead of the front along with some weak thermodynamic levels. CAPE values rise to near 500 j/kg. Winds aloft are marginal for severe weather with them near 25-30knots. Freezing levels aloft are quite low near 10,000ft and wet bulb temperatures are near 55. PWATs are pretty low with the front near 1.2inches max in a very narrow corridor with the frontal passage. Based on animated future radar provided by NMM it appears a narrow squall of showers and thunderstorms will push across the state. Overall a few severe weather reports are possible with hail and wind damage the primary threats. Hail parameters are a little high so I am thinking hail will be the primary threat. A surge of cooler air will approach western Pennsylvania overnight Tuesday as the front slows across eastern Pennsylvania. Left over showers and thunderstorms will occur Wednesday morning as the front crosses into the Atlantic. Total QPF is near .5inches max for central and eastern Pennsylvania. For the mid to late week a very amplified jet stream moves into the region with a deep trough over the east and ridge to the west. The 850mb line moves as far south as the Pennsylvania turnpike with a weak cut-off low to the north in Canada that will spin creating a strong northwesterly flow. Lake effect rain showers will form for late Wednesday through Friday night across much of the state. As cold air advection flows southeast over the entire northeast some of the higher elevations will be near critical levels for snowflakes. Thickness levels support a few flakes mixed in, but surface temperatures are marginal. Therefore I expect only marginal accumulations in the Adirondacks. It appears that snowflakes will only be confined to the higher elevations of New York State and New England. But I cannot rule out a flake or two across the higher plateaus near Bradford. For Saturday dry conditions develop as high pressure moves over the state. A reinforcing shot of cold air may occur on Saturday as indicated by the EURO. Saturday night may be the coldest night of this season so far. Through the end of the weekend upper level heights will only be near 5C at the most. 2m levels will max out near 10C for highs. It appears the best chance of the flow aligning for lake effect rain will be on Thursday with will be around 300. Some warmth builds in for the beginning of next week, which should bring temperatures back to seasonal values. Another trough though may be in the works to come down towards the Midwest by Tuesday as indicated by the GFS.
"Current Surface Map and Weekly History of Jet Stream Position"
(Courtesy of Weather Underground)
"Weekly Forecasts" (Updated 9/30)
Tuesday- A cold front approaches from the west with some morning left over debris clouds over western Pennsylvania and a few rain showers. With some afternoon heating downwind of the Appalachians, a broken line a showers and thunderstorms may form that could be marginally severe. Highest threat for severe weather today is in all of east-central Pennsylvania and eastern Pennsylvania. Total precipitation will near .5inches in the strongest thunderstorm with the heavy rain core. Upper levels and even surface values are pretty dry for Tuesday. Highs will be highly dependent on how much sun an area sees so I would expect highs in the mid 60s for western Pennsylvania, highs in the upper 60s for central Pennsylvania, and highs in the lower 70s for eastern Pennsylvania. Tuesday night showers and thunderstorms will be around eastern Pennsylvania as the front begins to slow down its eastward progression. Meanwhile cooler air funnels in to the west. Lows will near seasonable values under partly to mostly cloudy skies statewide.
Wednesday- A northwesterly flow begins to develop with moisture coming off the lakes. A few morning showers and thunderstorms will also occur in far eastern areas thanks to the departing cold front. High temperatures will be a large range across the state because the core of the cooler air only moves into western Pennsylvania and the higher elevations. Diurnal cumulus clouds will dominate with some lake effect rain showers across many areas. Some instability thunderstorms cannot be ruled out with some pea sized hail, especially across the higher elevations. A cold pocket aloft will keep things highly unstable. Overall northwesterly winds do remain light for the most part. Elevations above 2000ft in northern Pennsylvania will see highs in the low to mid 50s with the cooler values to the west. Valley locations of western Pennsylvania will see highs in the low 60s. Central Pennsylvania will see highs in the low 60s for mountains and mid 60s for valley locales. And most of eastern Pennsylvania from Harrisburg eastward as far north as Allentown will see highs in the upper 60s. Precipitation numbers will be pretty low, but in the strongest of bands off of Lake Erie rainfall totals may near .25inches. Wednesday night downsloping winds eliminate clouds east of the mountains, but a slight northwest breeze will still be felt. Lows will not get too awfully cold with them in the mid 40s for eastern Pennsylvania, and low 40s elsewhere.
Thursday- Northwesterly flow aligns perfectly for lake effect rain showers and bands across the west and north. Precipitation totals will be near .1-.25inches in areas that see the bands. Eastern areas may escape the precipitation due to downsloping winds, but I am still expecting mostly cloudy skies across the state. Dew point levels will continue to drop into the low 40s. Highs will be nearly 10-15degrees below normal with highs near Bradford near 49degrees, especially in the surrounding mountains. Most areas will struggle to reach the 60degree mark, but in Philadelphia it appears highs will reach the mid to upper 60s. Thursday night temperatures aloft drop below freezing, but surface temperatures are going to be near lows of mid 30s across the far north with low 40s elsewhere. With the cold air advection clouds and light winds will prevent temperatures from really dropping off.
Friday- High pressure begins to move in from the west along with the core of the coldest weather with this deep trough. Highs will again struggle to reach the low 50s across elevations above 2500ft, and many areas will be in the mid to upper 50s even in the valley locations. Highs east of the mountains will near the 60degree mark. Friday night should be the coldest night of the week so far as winds will try to calm, but still may hold a light west-northwest breeze. Dewpoints will be in the 30s to low 40s. With clear skies all of Friday and into the night I would expect many readings in the mid to upper 30s with low to mid 40s in the city locations. Frosts may occur in the sheltered valleys in the eastern Laural Highlands and ridge and valley region. Also some frosts may occur in the valleys of the Poconos.
Saturday- There is some computer model confliction to whether cold air reinforces itself. But in any case currently I am expecting dry conditions with high pressure of the region with plentiful sunshine. Dewpoints will be very low in the 30s across much of the state with light northwesterly winds. Highs will be chilly once again in the mid to upper 50s across western half of Pennsylvania and across all of the north, but in the low 60s for the eastern areas. For Saturday night it should be the coldest night of the season with possibly widespread frost as radiational cooling is near max. With already cool highs temperatures will really drop to wet bulb levels which are in the 30s. I am expecting frosts to occur possibly as far south as the Pennsylvania turnpike. Freezes may occur across the north. The question that remains with all of this, is will the winds decouple. Further details will become clearer in the days to come.
"Current Water Vapor Loop"
(Courtesy of Penn State Meteo.)
"Fall Foliage Outlooks" (Updated 9/30)
After some pretty cool nights before the rains this weekend, leaves have begun to turn colors in some of the species of trees that are often prone to early color change. Across northern Pennsylvania latest fall foliage reports are at about 15-25% color change with the majority of the trees being maple. Some species of maple such as the Silver Maple has only a rust type color at this point, but on the other maples the red is beginning to shine. Across central areas of Pennsylvania around the I-80 corridor to about as far south as a little north of the turnpike, color change is about 5-10% with the majority once again being young and mature maples turning the bright reds. Some of the ornamental trees are also beginning to turn colors and loose leaves. Across southern Pennsylvania from the turnpike area on south conditions remain spotty and depend on locations. Areas in western Pennsylvania near the Laural Highlands are having some nice fall foliage reports coming in, but yet areas in the Dutch country area are seeing little if any change. Across the coal regions of Pennsylvania reports of beautiful yellow color are coming in from the local birch trees, which are known to change color early. I have not heard many reports from the Lake Erie region, but I am sure leaves are starting to change there too. With the upcoming cool and clear skies for late this week leaves will continue to change, with some areas peaking the end of next week in the higher elevations of Potter, Tioga, Wayne, Bradford, Warren, McKean, and Susquehanna Counties. Across the nation the Rocky Mountain region will be reaching its peak as the Aspens continue to shed their beautiful yellow color. In Alaska, based on some tower cameras it appears like the peak has passed. In fact in Fairbanks, Alaska they recorded a measurable snowfall a few days ago, which is in fact even early for them to see snowfall. Average temperature for highs this time of year is 50degrees up that way. Across Michigan color is pretty brilliant in some areas with again maples and ornamental trees. Parts of New England are seeing some beautiful color in the Green and White Mountains. Adirondacks are also reporting nice color. To see some of these colors, just take a glance in the Wunderground photo gallery, lots of pictures of fall color. So again it continues to look like fall. O and a friendly reminder, only 2 months to the start of the meteorological winter and about 1 month until I start looking at snow chances for the mountains of northwestern Pennsylvania.
"Wildfire Outlook" (Updated 9/30)
September has come to a close quite wet across much of the state. Early in September Hanna delivered a few inches of rain to eastern Pennsylvania and central Pennsylvania. Then heavy thunderstorms moved through a few days later with more rain. After that there was a period of dry weather for a week or two. Then a coastal storm moved inland towards the end of the month and acted as a cut-off low once inland creating heavy rain across much of the state, excluding extreme northwestern Pennsylvania. To end the month a dry cold front is going to move through with widespread rain showers and thunderstorms. So overall across the state ground levels are quite moist for most areas. It is still a little early for fall leaves to cover the forest floor, so really there is no natural fuel for the forest fires to form in the mountains. Temperatures for the coming week will be going below normal along with dry dew points in the 30s and 40s. But each night will feature heavy dew and ground fog adding some residual morning moisture. I do not expect any concerns with forest fires this week. Across the nation there is a heightened risk of forest fires out in the west with dry thunderstorms. Those conditions will persist through the next couple of days. Once again here is the criteria according to the State College NWS for fire development...Link.
Criteria for rapid initiation and spread of wildfires in PA:
1. Winds must be sustained at 15 mph (13 knots) for two hours or more, and
2. Minimum Relative Humidities (which usually occur in the afternoon) must be 30 percent or less, and
3. 10-hour Fuel Moistures must be 15 percent or less (and expected to remain there for two or more days).
"Fire Outlooks from Storm Prediction Center Days 1, 2, and 3"
(Courtesy of NOAA)
"Fall Gardening Outlook" (Updated 9/30)
Well this is one of probably the last gardening forecasts, maybe next week a forecast too. But we are starting to enter the heart of the fall season with only cool weather crops persevering through the cold, long nights and shortened days. Frosts and freezes will be coming late this week to many areas across Pennsylvania. But some areas may not decouple, especially across the north, so stay tuned for more updates throughout the week on the frost and freeze situation. I guess this weekend I will be headed out to buy some of my favorite plants such as the Mums and Ornamental Cabbage plants. I love this season of planting even though it is quite short. Looking ahead at this week it looks to be several periods of rainfall possible, which will make watering not very necessary this week. Towards the weekend though, conditions may start to get dry. Temperatures will generally be below normal. Here is an update on my vegetable garden. My cucumber plant is still hanging in there and I just picked a beautiful cucumber just yesterday after the rain. My lettuce plants are doing wonderfully and growing it seems inches every day. I guess tomorrow evening I will do one of my first harvests for the lettuce with these plants. My spring onions (scallions) I am not sure what happened to them. It seemed a lot of them disappeared with only a few large ones still growing. I am a little disappointed, but I guess they are mainly for planting during the spring. My cabbage plants ended up dying after the groundhog destroyed them. My broccoli and cauliflower plants are still trying to grow, but I doubt I will get any crop. My pepper plants are still producing and I picked a pepper just a few days ago with another ripening hopefully in the next couple of days before the cold hits. The tomato plants are still alive and have a decent amount of green tomatoes on them, but I doubt they will ripen. My radish plants are doing pretty well and I am guessing I will be able to pick some by the end of the coming weekend. And lastly my herbs, basil, parsley, and chives, are still growing nicely and shortly I will begin the challenge of cutting all the herbs off to store in the freezer for the winter. So overall a nice end to a successful season of my first largely expanded vegetable garden. Thanks to everyone for all of the helpful advice with a special thanks to TheRasberryPatch, JDinWPA, Sullivanweather, and others. Happy gardening!!!
"Soil Moisture Anomalies and 5-day Precipitation Amounts from Hydro Prediction Center"
(Courtesy of NOAA)
"Average Date of First Freeze"
(Courtesy of NOAA)
"Long Term Outlook" (Updated 9/30)
Looking at teleconnection patterns for the first half of October it appears the weather pattern will be made up of several different types of patterns, which is pretty typical of this time of year. Weather patterns are transitioning from summer to winter patterns, which can cause some unusual weather. But those extremes are nothing like what occurs during the transition period in the Spring. Anyways NAO favors negative for first half of month with PNA favoring positive. This is indicating troughing over east and ridging over west. AO is also remaining negative, which indicates some cool weather funneling down from the Arctic. Long term EURO model favors near normal temperatures with only some slight troughing over the east. Long term GFS is pretty similar to EURO with periods of warmer and cooler weather. There are already appearing some GFS fantasy storms, which do not even need to be bothered to look at currently. So for next week I am looking at near seasonal values with a few periods of precipitation. Also there appears to be some decent Greenland blocking as some very cold anomalies move over that region. Hopefully that will help add some snow cover and recovering of sea ice. Snow has already started falling in northern Canada. Looking in comparison to last year, snow cover and the sea level ice levels are higher and more widespread than what they were last year at this time. For us winter lovers this proves optimistic to show that cold air has the possibility to begin to develop early and build, soon to become let loose come winter hopefully.
"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 to 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)
"Here north of Harrisburg 2008 statistics"
(Severe Weather Stats...)
Severe Thunderstorm Watches- 8
Severe Thunderstorm Warnings- 4
Tornado Watches- 1
Tornado Warnings- 0
Total Thunderstorms- 32
Flood Watches- 6
Flood Warnings- 5
Monthly Precipitation- 4.36inches
Yearly Precipitation- 33.59inches
Heat Advisories- 4
Excessive Heat Warnings- 0
90degree days- 17
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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