After the weekend's deludge, we've turned a corner in our weather pattern.  Three beautiful, sunny days in a row are a treat any time of the year here in Central New York, especially in the warm season.  You can thank high pressure for the nice weather we've had lately, but it will be coming to a brief end tonight. 

Summary:  A cold front will sweep through the area tonight, bringing showers and storms this evening and overnight.  As of this morning's data, the most likely time for the storms to develop between 8pm-11pm across Central New York.  You'll want to check back with us later today in case that changes.  The chance of severe weather is low, but some thunderstorms could produce gusty winds.

Discussion:
Ahead of the cold front, winds will switch into the southwest.  This will draw in (advect) warm, somewhat humid air into Central New York.  The airmass being advected into the area is not as humid as it typically is this time of year.  So, dewpoints are expected to rise only into the mid 60s today.  We'll have to keep a close eye on this number, because we've seen a marine influence off of the Great Lakes over the past few days.  There are three things that are needed to cause strong thunderstorms: instability, wind shear, and a trigger.  Lets take a look at each of these in more detail...

Trigger

The timing of the front brings it through CNY close to midnight.  This is not an ideal time for severe weather, because by that point the heating of the day is long over.  Thunderstorms thrive on heat and humidity, and there is almost always less of that at night than during the day.

Instability

This is a look at the forecasted CAPE for 06z, close to the timing of the front.  CAPE values are between 500-750j/kg in CNY...which is enough to generate or maintain storms but not enough for widespread severe weather.  The lifted index shows an axis of instability along the front at 06z.  A look at the 00z CAPE shows high instability values west, with little here in CNY.  Going by this data alone, the storms would move in well after midnight, but the GFS suggests that things could move a bit faster.

Wind shear

Here's a look at the sounding during the frontal passage (midnight).  There is a decent signiture of speed shear (wind speed increasing with increasing height), but no directional shear.  This is called unidirectional wind shear.  Storms in this scenario have a low probability of rotation, thus supercell storms are unlikely.  Storms could produce straightlined winds in a sounding like this, with perhaps some bow lines forming on the radar at times.  Also of note, temperatures stay warm in the upper levels of the atmosphere, which significantly reduces the potential for large hail.

Putting it all together...

The strongest storms today are forecasted to develop west of Central New York.  The front will pass through earlier to the west, during the peak heating of the day (meaning higher instability).  Our chances of severe weather will come from the leftovers of these storms.  With the front approaching the area after dark, these storms will lose some strength before they get here.  Any storms that do make it into Central New York will be weaker, but still able to produce thunder, lightning, and some wind.  The chances for large hail are also low, as the upper level temperatures will be too warm.  We are not concerned about supercell thunderstorms or textbook tornadic activity, as the soundings show unidirectional wind shear.

As always, we'll keep you posted on the latest developments throughout the day.
 

First off, I posted a picture from our YouNews section of our website. This is a picture of the EF2 tornado in Chautauqua County that actually crossed the Chautauqua Lake. Its maximum speed was 125mph, width 150 yards and traveled 6.5 miles. Besides the numerous severe weather/tornadic activities this month, the main story has been the abnormally warm temperatures. If the month ended today, it would be the 8th warmest July ever, with the average temperature of 73.2 degrees. Here is the chart for the top 10 warmest July’s  

Some heavy flooding took place last night in Herkimer County.  Take a look at the doppler radar estimated rainfall.  That bright orange suggests more than 2" of rain fell between Middleville to Dolgeville.  The high levels of humidity in the air today will bring the potential for more heavy rains as we head into the night tonight.

For today, the weather looks to stay dreary through the morning hours.  The high levels of humidity are creating fog and drizzle this morning and the sunshine is going to have to work hard to clear that out.  In the warm sector, skies typically clear out during the afternoon this time of year.  We expect the same to happen today unless storms from the west scatter debris clouds over our area.  We won't know how that works until it's about to happen.

As for the thunderstorms, the cold front drving in from the west isn't going to cross Central New York until tomorrow morning.  On paper, that diminishes our threat for thunderstorms today.  I can't rule anything out based on all the weird boundaries that we usually have in Central New York on a day like today.  Still, the thought this morning is that not everyone gets wet this afternoon with thunderstorms.  Any thunderstorms that do develop today could produce some heavy rain.  Severe weather will be dependent on how much sunshine we get this afternoon.

Tonight's weather looks interesting.  An approaching cold front with high levels of humidity could spark some rare night time severe weather.  An upper level jet approaches the area along with a trigger (cold front).  Even though the storms move in during the overnight, there will still be enough energy in the atmosphere to sustain stronger storms.  High winds, heavy rain, and frequent lightning are possible. 

A shower or storm may linger around on Sunday as the front crosses the area early.  There will be gradual improvements in our weather through Sunday afternoon.

Our spell of fair weather with relatively less humidity has been short-lived.  This evening on the weather map, a warm front is situated along the southern borders of Minnesota, Wisconsin and Michigan and is lifting northeastward.  North of this boundary, heavy rain has been falling with some Flash Flood Watches posted for the northern half of the state of Michigan.  Along and south of the front, the air mass is considerably more unstable and there have been severe thunderstorms and even some tornado warnings.

Here in CNY, we'll be on the northern, more stable side of this warm front through the first half of Friday.  This means that we'll likely see a good deal of cloud cover and some periods of rain.  Some of the rain may be briefly heavy.  Right now widespread flooding is not expected as we've had a rather dry July so far.  As the warm front lifts north of the area by late Friday, we'll notice an increase in the humidity.  By the end of the day CAPE values climb to ~ 1000 J/kg and Lifted Index reaches -2.  This suggests that here could be a thunderstorm or two by evening, but the intensity of the storms may be limited by extensive cloud cover.  If we see a little sunshine, a couple of severe thunderstorms cannot be ruled out.

The warm front lifts to our north on Friday Night and we'll be back into a very warm and muggy air mass.  Temperatures will struggle to fall much below 70 through the night and there may be a few leftover showers or thunderstorms.

On Saturday, CNY will find itself in a very warm and muggy regime.  Some sunshine is likely, but this sunshine will be self-destructive in an unstable air mass.  A cold front will approach from the west during the day and serve as a trigger for thunderstorm development.  CAPE values will climb to 1500-2000 J/kg (sufficient for severe weather) and Lifted Index will be around -4.  On paper it looks like a better opportunity for scattered severe thunderstorms will be Saturday afternoon.  Check with us here on the blog and on NewsChannel 2.  We'll keep you up to speed as thunderstorms develop.

A break from the heat and humidity (and any thunderstorms) will arrive Sunday as another (and this time, longer lasting) dry air mass arrives from Canada.

After a slow start, thunderstorms developed across CNY in the humid unstable air mass earlier this evening.  Thunderstorms were intense for a time.  Preliminary damage reports include some thunderstorm wind damage in McKeever, Ohio and Herkimer, as well as Oppenheim.  There were also reports of 1 1/4" hail near Newport and 1" hail near Clinton.  The wind was quite intense at our television studios as the storms crossed the area.  Officially at Griffiss Park, a 44 mph wind gust was recorded at 8:01 PM.  Thanks to Becky for sending in this picture as the storms rolled through Lewis County earlier this evening.

The cold front which helped to trigger these storms is now situated to our east.  Slightly cooler and drier air is now working in from Canada and the Upper Midwest. Dew point temperatures have fallen back to near 60 degrees and should stay there through much of the day Thursday.  With high pressure in control, a nice sunny to partly sunny day is expected.  With 850 mb temperatures falling to the 12/13 range we expect high temperatures to be near 80 degrees.

Our next weather maker arrives on Friday and Saturday in the form of a complex system with a couple of frontal boundaries.  Some thunderstorms will return to the forecast in this time frame.  We'll pinpoint the coverage and intensity likely with these storms over the next couple of days.

At this point it appears that a nice stretch of weather will return for the second half of the weekend and early next week.  Pleasant temperatures and low humidity are expected.  That would be quite a turnaround from what is shaping up to be a very warm and rather humid summer

A weak area of low pressure will drag a warm front through the area this morning.  A cold front moves in this afternoon.  The cold front has the potential of producing severe weather today. 

Summary:  The cold front swings through later this afternoon (5-8pm).  The threat for thunderstorms as of this morning looks to be between 3-8pm.  Some storms could grow to severe standards, producing winds in excess of 58mph along with hail over 1" in diameter.  For more details on how we came up with our forecast, see the discussion below...

Instability

There will be a decent amount of instability in the atmosphere this afternoon ahead of that cold front.  CAPE values exceed 2000j/kg on the NAM, with the lifted index falling below -6 near the Capital District.  These numbers are relatively high for Central New York standards (on a scale of 1-10 here, this would be like a 7 or 8).  Sunshine is the key here.  Our forecast models are assuming that temperatures will climb into the low to mid 80s today...something that will only happen if we get enough sunshine.  So, sky conditions will be important this morning and afternoon.  We need the sun in order to charge the atmosphere.

Wind shear

Wind shear, which aids in helping thunderstorms maintain their updrafts, will be sufficient today for sustained storms.  We have a decent amount of speed shear and directional shear on BUFKIT.  In other words there won't be many 'pulsers' here today as there would without wind shear.  It's possible, though not likely, that a few of these storms could rotate.  Rotating storms primarily produce strong winds and hail.  Rotating storms also have the ability to produce a tornado. The odds of this happening today are quite low, but not zero.

Trigger

The trigger will be that cold front, which will cross the area between 5-8pm today.  The timing of the front is favorable for strong weather because it arrives close to the peak heating of the day.  Even if storms fire up ahead of the front, they will still be with us during 'prime time'.  So, from a forecasting standpoint, there's reason for us to be concerned and on watch for stronger storms later today.

We will keep you up to speed on the situation as we head throughout the afternoon, so check the comments section for the latest.  If you have any questions or comments, feel free to post below and we'll get back to you as soon as we can (we may be a bit busy this afternoon though so be patient).  You can find the latest weather conditions from our weather bloggers in the comments section as well.

Wet weather returns for parts of the area today and tomorrow...

Good morning Central New York and TGIF!  It's been a hot stretch of weather, but the next two weawther systems will help bring down the high levels of humidity.  Thunderstorms will arrive today late this morning and early this afternoon, with most of them leaving by 5-6PM.  There's a small chance for severe weather today, with our main concern being gusty winds.  Heavy rain is possible in some of these thunderstorms due to the high amounts of humidity in the air.

There are many different types of thunderstorms: air mass storms, pulsers, supercells, and squall lines just to name a few.  Each type of thunderstorm produces different types of weather.  In order to figure out what kind of storm will develop today we have to look at the forecast sounding.

There are two types of wind shear: directional shear and speed shear.  Directional shear is when winds that change direction with height.  Speed shear is when winds change speed with height.  Directional shear aids in the rotation of thunderstorms.  Speed shear helps separate the updraft from the downdraft.  You need both in order to produce rotating thunderstorms.

Take a look at this map.  This is called a hodograph.  It is a diagram that represents wind speeds in the atmosphere.  The yellow lines represent winds from the surface to 3km.  The lines go in the same direction (they look straight), which means the winds aren't changing direction with height.  The lines branching away from the center means that winds are getting stronger with height (speed shear).

Today's sounding show little directional shear, with ample amounts of speed shear.  We call this 'unidirectional shear'.  In this kind of situation, we look for multi-celled thunderstorms.  Multi-celled storms mainly produce wind and sometimes small hail.  The temperature profile looks too warm for any significant hail to form today, so winds look to be the main concern. 

It's possible, if the right ingredients coming together (jet stream influence, etc), that a squall line could develop along the front this afternoon.  If this does happen, it will likely develop either over or to the east of Central New York....meaning we'll have very little lead time on the situation.  It's difficult to pinpoint exactly where and when this will happen.

There's the chance for more storms tomorrow, as another disturbance passes through the area.  We'll keep you updated with all the latest developments for today and tomorrow's storms as we head throughout the afternoon.

As a forecaster for this area since '06, I have a good feel for how temperatures typically behave across the area, but I wanted to find a way to quantify this information.  The purpose of this project is to compare the average high and low temperatures of local weather stations to Rome, NY. 

Methodology

Weather data from 23 weather stations was collected during the period of July 5th through July 8th (the heat wave).  This time period was used due to the persisent, dry, uniform weather conditions across all of Central New York.  Sky conditions were 90-100% clear through this time period, with no rainfall in any of the locations studied.  The average of the high and low temperatures of each station was compared to Rome.

Results:

Average temperatures (high + low divided by 2) vs Rome during the heat wave:

	Avg
Albany	4.5
Downtown Syr	4.0
Syracuse	2.5
Milford	2.0
North Utica	1.6
Cooperstown	1.3
Oneonta	0.7
Binghamton	0.5
Rome	0
Westmoreland	-0.5
Lakeport	-0.8
Roseboom	-1.0
Hurricane	-1.3
Hamilton	-1.5
Sherburne	-1.6
Holland Patent	-1.7
Fairfield	-2.3
Inlet	-2.7
Saranac Lake	-2.8
Schenevus	-3.7
Cold Brook	-4.2
West Leyden	-5.2
Old Forge	-5.5

High temperatures vs Rome

	High
Oneonta	4.7
Albany	3.7
Cooperstown	3.7
Downtown Syr	3.3
Milford	3
Syracuse	2.3
Westmoreland	2
North Utica	1.7
Hurricane	0.5
Sherburne	0.5
Holland Patent	0.3
Rome	0
Hamilton	-0.3
Binghamton	-1
Saranac Lake	-1.3
Inlet	-2
Lakeport	-2.7
Fairfield	-3.5
Roseboom	-3.7
Schenevus	-3.7
Cold Brook	-4.7
Old Forge	-4.7
West Leyden	-5.3

Low Temperatures vs Rome

	Low
Albany	5.3
Downtown Syr	4.7
Syracuse	2.7
Binghamton	2
Roseboom	1.7
North Utica	1.5
Lakeport	1
Milford	1
Rome	0
Fairfield	-1
Cooperstown	-1
Hamilton	-2.7
Hurricane	-3
Westmoreland	-3
Oneonta	-3.3
Inlet	-3.3
Cold Brook	-3.7
Sherburne	-3.7
Holland Patent	-3.7
Schenevus	-3.7
Saranac Lake	-4.3
West Leyden	-5
Old Forge	-6.3

Results:

The average temperature of most (14 of our 22) local weather stations run colder than Rome.  The biggest cold bias occurs at night, with 11 stations running an average 3 degrees or more colder than Rome.  Many area weather stations run warmer during the day, with an even split (11 warmer, 11 cooler) of high temperatures vs Rome. 

Conclusion:

In the next blog about this topic, I'll explain how climate factors such as elevation, aspect, bodies of water, and surface type explain the different tendencies in temperature.  Look for that early next week.

If you want to see how your weather station ranks on this list, send me the high and low temperatures from July 5th-8th along with your elevation.

It's been a very impressive run here in Central New York with the hot weather, but it will eventually come to an end as we head into the weekend.  Today will be the last 90+ day of our heat wave.  Heat waves, as defined as 3 consecutive days of 90 degrees or higher, are very rare in Central New York.  The last one occured in August 2002.  There has only been 9 heat waves over the past 30 years!  Here's a look at them, along with the highest temperature of the heat wave in ()'s:

July 15-18, 1982 (94)
June 13-18, 1983 (91)
July 18-20, 1983 (90)
July 8-11, 1988 (93)
Aug 2-4, 1988 (94)
July 18-20, 1991 (93)
June 16-18, 1994 (92)
August 11-14, 2002 (97)
July 5-8, 2010 (92 so far)

As you can see, 1988 and 1983 hold four of the past 8 heat waves, so these things may tend to occur in the same year.  This current heat wave ties as the longest (4 days) going back to 1980.

Going forward, we'll being to see changes at the price of showers and thunderstorms.  Today, the ridge overhead begins to fall apart.  This will allow for a backdoor weak marine front to move in from the east.  The major cities along the coast will see the largest cooldown from this front today.  It won't make it here in Central New York today, so it is still expected to be hot.  However, that front will attempt to kick off a shower or thunderstorm late this afternoon.  The activity will likely being in Eastern NY early this afternoon, with storms slowly moving from east to west. 

Severe weather is unlikely with this kind of setup.  The winds are going to be very weak, and that will be counter productive to thunderstorm development.  Remember, we need instability AND shear to maintain strong storms.  Without wind shear, the downdraft in thunderstorms competes against and overpowers the updraft.  The updraft is the lifeline of a storm.  Given the amount of instability in the atmosphere, I think the types of storms we will see today will be 'pulsers'.  These storms fire up quickly, looking quite strong at times, but also fall apart quickly.  These kinds of storms happen in Florida all the time because of the ocean breeze, and most of them don't produce severe weather.  Heavy rain will be the bigger deal with these storms, as we have a ton of humidity in the air.  In addition, the weak winds will make most of these storms very slow movers.  This is something we'll be watching closely today and especially tomorrow.

The cold front arrives tomorrow night.  It stays warm and humid on Friday, with thunderstorms developing in the afternoon and evening.  Heavy rain is going to be the big concern with these storms, with just an outside threat of some gusty winds.  The front may get hung up for Saturday, and that's why we're being more pessimistic about the first half of the weekend.  Worse case scenario is that Saturday becomes a washout.  The wet weather will push east by Sunday, but we could see a lot of residual clouds early Sunday morning.  Not a bad thing if you're running in the Boilermaker.

I'm working on a project that compares all of the weather stations across Central New York during the heat wave we've had since Monday.  It's a good weather pattern to compare the highs and lows of the area to each other.  If you haven't already sent in your data, I'm looking for highs and lows on Monday-Wednesday.  So far, I have 20 locations.  If you know your elevation let me know that as well.  I'll have a report on this when the weather quiets down (probably next week).

We're in the middle of a likely heat wave here in Central New York.  That term 'heat wave' gets tosses around quite a bit, but it does have a meteorological definition.  A heat wave is three consecutive days or more with highs at or above 90 degrees.  It's tough to do here in this part of the state, so the term is often overused.  The last heat wave we had here was August 11th-14th of 2002.  Four days in a row were 90+, with the peak of the heat climbing to 97 on the 14th (Syracuse hit 100 that day). We're on track for seeing a heat wave, as we hit 91 yesterday, and will likely be in the low 90s today and tomorrow.

As for heat safety tips...the bottom line is just to think ahead and be smart.  Keep drinking water throughout the day, even if you aren't thirsty.  Your body will run through water a lot faster than you may be aware of on days like today.  Avoid strenous work during the hottest parts of the day.  If you have to do work outside, plan on taking breaks, indoors if possible.  Keep your pets hydrated through the day too (add ice cubes to the water...they'll love you for it).  Again, the weather over the next few days isn't dangerous unless you allow it to be.

A large area of high pressure continues to pump heat and humidity into the Northeast.  This high pressure system is also causing subsidence, or sinking air.  This sinking air hinders any thunderstorm development.  Many often automatically equate thunderstorms with humidity and heat.  In addition to heat and humidity, we also need a trigger to cause storms...something we won't have today or tomorrow. 

On Thursday, the ridge begins to break down.  This will slow down all that subsidence, which may allow for a few thunderstorms to pop up in the afternoon.  A slow moving cold front will bring and end to the hot spell on Friday with tropical downpours and thunderstorms.

Cooler, more comfortable weather for the weekend.  The long range patterns suggest another warmup here for the middle of July.  Unlike most years, the hot weather may be here for a while.