Sharp Temperature Gradient Over Area

October 1st, 2014 at 4:01 pm by under Chad's WLFI Weather Blog

Today reminds me so much of spring.  We have this significant temperature gradient across the area from 84 to 66 with front slowly working northeastward.  In these situations in spring, you can have 75 at Crawfordsville with severe weather threat, while Camden or Delphi may be 47 with rain. 

In spring, you see these big contrasts & you see that in October, too. 

It is 62 at Wabash, 64 at Columbia City & 62 at Fort Wayne-Beacon, but 87 at Mount Vernon, Indiana (west of Evansville). 

With front oriented highly north-northwest to south-southeast, Kentland is warmer than Indianapolis.

Even in Greater Lafayette, there is variability with the front.  I have 75 at the station, but the northeast side is 73, while the south side is 77.

This shows that we are shifting gears out of the late summer-early fall mode to true fall mode with the rapid changes & occasional storminess of this seasonal change.

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T’Storms, Windy & Big Cool-Down

October 1st, 2014 at 1:20 pm by under Chad's WLFI Weather Blog

TONIGHT-THURSDAY AFTERNOON………….

Clouds will increase tonight with lows only near 60.

A wave of showers & t’storms will pass Thursday morning-midday.  This will be followed by a break with sun & breezy, warm & humid conditions as temperatures surge to around 80.

THURSDAY EVENING-NIGHT…………..

Squall line is possible Thursday evening with rain & a few t’storms into Thursday night.  The rain/storms Thursday evening-night will be accompanied by good south wind to 30 mph.

Higher surface instability, in tandem with dynamics/shear supports a few scattered severe gusts, perhaps isolated hail &/or an isolated tornado.

Evening surface CAPE could be as high as 1500-2000 J/kg with +55 mph low-level jet & 120 mph upper jet stream nosing in, causing surface low to our northwest to deepen rapidly.

Looks like the best potential of several tornadoes is Missouri to Arkansas with this system.

Locally-heavy rainfall is likely in our area.  Much of the area will see 1″ with some places seeing up to 3″ total.

FRIDAY MORNING-SUNDAY……………

After morning rainfall potential & clouds (low around 63), Friday’s high will occur near noon with dry slot (period of sun) with 66.  Temperatures will fall into the 60s in the afternoon as stratocumulus deck pivots in.  With some clearing, 30s are likely Friday night.  Wind on Friday may gust from the west/northwest to 40 mph.

Saturday looks partly to mostly cloudy, windy & chilly with highs only in the 50s with 30s & frost Saturday night.  Winds Saturday may gust to 31 mph from the west/northwest.

After frost Sunday morning, highs will rebound to the 60s Sunday afternoon with skies becoming partly cloudy.


Outlook to October 25

September 30th, 2014 at 10:28 pm by under Chad's WLFI Weather Blog

NOW-TOMORROW……………

It was a cooler, but pleasant day with highs of 63-73.  We are cooling off rapidly tonight as front (which was starting to work back northward), is pushed southward once again by surface high moving into central Michigan.

Temperatures are already largely 48-53 as of 11 p.m. (57 Covington near front).  The temperature profile is indicative of the seasonal change that you see in spring, as well.  Cold/warmth migration of the seasons tends to follow the 4 Indiana climate zones.  For example, it is 47 at Grissom Air Reserve Base, but 71 at Evansville right now!  The afternoon HIGH today at Fort Wayne was a mere 56, but 86 at Evansville.  This tight gradient is a factor in severe weather, but also the fall color gradient over the state & the gradient you see in spring with the budding/blossoming trees.  I have seen redbuds & flowering dogwoods in blossom in Evansville & Peru look brown like February at the same time in spring.

We will drop into the lower to middle 40s with upper 40s in the far southwest tonight with patchy fog potential.

After cool, damp 40s Wednesday morning, we will rise to 74-81 across the area Wednesday as front lifts back northward.  Despite the front moving through, skies look mostly sunny.

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THURSDAY-THURSDAY NIGHT…………..

Scattered showers & t’storms are likely the early half of Thursday, followed by a break.  Then, widespread rain/t’storms are likely Thursday night-Friday morning.

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Dynamics/shear/height falls/strong surface cold front/forcing all point to an organized severe squall line.  HOWEVER, hindrance is just a bit of lacking in the instability forecast.  If there was just a bit more buoyancy/surface instability expected, severe threat would be no-brainer as surface low deepens to an impressive 984 mb over far northern Wisconsin.

A windy fall system, it is strong, but unless it can become a hair more unstable, then this will be a gusty system with wind-driven rain/t’storms embedded in a large northeastward-moving band/mass Thursday night-Friday morning (after that scattered rainfall Thursday).

This will need to be monitored.  Just perhaps a bit more instability into our area would make us cross a threshold & support severe threat that is definite west & southwest of here.  Looking at these impressive wind parameters at all levels, IT IS CONCEIVABLE that severe threat could be expanded by tomorrow into our area.

Locally-heavy rainfall of 1-2″ still looks likely in the area.

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FRIDAY-MONDAY……………

After morning rainfall, Friday looks like a windy day with gusts perhaps to 37 mph.  There may be a dry slot for a while during the day with sun, but stratocumulus/cumulus will likely pivot in after this, turning skies mostly cloudy.

After 63 in the morning, we may get to 66, but then fall in the afternoon into the 50s, it appears.

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After 30s Friday night (models have freezing line into north-central Illinois…….wind may prevent frost here…….will watch), Saturday looks gusty & cool with strong northwest winds cranking up to gusts of 30 mph with highs in the 50s.

After 30s Saturday night with frost (lows 32-37), flow turns to southwest Sunday with a rebound to the 60s.  An Alberta Clipper Monday may bring a few showers, perhaps even an isolated t’storm or two, with highs in the 60s.

NEXT TUESDAY-FRIDAY……………

Looks like a push of cooler air Tuesday with highs at 55-60 with 30s (& frost) Tuesday night & 60s Wednesday.

Right now, it appears as if storm system will pass over area with periodic showers/t’storms next Thursday-Friday.

Looks like we may be on warm side of system with 70 or 70s with southerly flow.  Exact storm track will dictate the temperatures & whether there is severe potential.  We these dynamic fall systems & battle of the seasons, we are getting into that severe mode that sees uptick in fall after lulling for a good 1.5-2 months.

SATURDAY, OCTOBER 11-THURSDAY OCTOBER 16………..

After potential 70s Friday with storms, the coldest air of the season will blast in on strong northwest winds around October 11.  The highs may only run 47-54 with freeze possible on multiple occasions October 12-16.

Only issue with better timing of freezes will be that little shortwaves will be pivoting around upper low to our north that will be slow to exit.

This pattern may keep sky filled with a lot of stratocumulus/cumulus during the days with spotty diurnal showers & 40s & 50s.  At night, with variable clearing & some fog, it is again likely that reaching 32 or less may occur multiple times.

This looks like a pretty chilly period of weather for us with temperatures below normal & considerable cloudiness, especially at peak heating.  With looks northwesterly & quite brisk each day.

 FRIDAY, OCTOBER 17-MONDAY, OCTOBER 20……………..

There are signs of warmer, sunny weather during this time period.  With the chilly weather & frost/freezing prior, trees should really be changing color & peak color will be within reach.

Widespread 60s to perhaps 70 are possible at this time.

OCTOBER 21-25…………..

At the moment, there are subtle trends of storminess in this period (showers/storms).  Temperatures are a bit nebulous, but warmth with lots of wind, followed by rain/storms & cool-down with freezing temperatures at night seems reasonable.


Climatology of the Last 80° Temperature In the Viewing Area

September 30th, 2014 at 6:05 pm by under Chad's WLFI Weather Blog

The normal last occurrence of 80 or more is October 9 in West Lafayette (1954-2013).

The latest last occurrence was in November 2, 1950 & a closer examination revealed the earliest last occurrence September 14, 1896.

The longest stretch of 80 or more so late in the season was October 23-27, 1963, while the longest stretch of 70 or more so late in the season was October 24-31, 1989 (after the historic snowfall!).

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Last occurrences of 80 or greater 1879-present:

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High Evaporation Rates Over Past Two Weeks Big Benefit to Farmers

September 30th, 2014 at 1:40 pm by under Chad's WLFI Weather Blog

At the Purdue ACRES site (this is NOT the Ag Farm, it is actually near the White County line off I-65 on 900 W), evaporation & rainfall are measured with automated equipment.

Nearly 10″ of rain fell at this site August 1-September 15.  During that time frame, 4.29″ of water evaporated.  Since September 15, NO rain has fallen & around 1.60″ of water has evaporated.

In fact, the evaporation rate on Sunday was 0.15″ in a 24-hour period at this site.  This was the highest evaporation rate since September 6.  Prior to September 6 back to July 1, only three days have had evaporation rates of 0.15″ or greater in the 24-hour period.  Those dates include August 5, July 10 & July 5.

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At the Ag Farm site near Romney, it has been drier than the ACRES site (in terms of amount of rain that has fallen since August 1).  August 1-September 15, 8.26″ was measured.  During that time, 4.09″ of water evaporated.  Since September 15, that site has seen NO rainfall & upwards of 1.50″ evaporate.

Interestingly, there has been greater variation in evaporation rates at the Romney site.  Evaporation has equaled or exceeded 0.15″ seven times since July 1.  It has only been three in the wetter area in northern Tippecanoe.  However, slightly more water evaporated, overall, in northern Tippecanoe.

Regardless, the higher evaporation, on average (0.09″ August 1-September 15 & 0.16″ September 15-30), lack of rainfall & sun have all contributed to grain drying & drying of soils over the past 2-3 weeks, which has greatly benefited farmers in the viewing area.

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Remembering the ’99 Supercells……..Outlook Based On Latest Data

September 29th, 2014 at 8:49 pm by under Chad's WLFI Weather Blog

If you experienced these storms, I would love to hear your memories of them!  Thank you for sharing, in advance!  -Chad

September 28, 1999 – The Autumn HP Supercells


Three high-precipitation supercell t’storms popped on the outflow boundary from morning/afternoon rain/storms to the north & west amidst a hot, humid airmass on September 28, 1999.  Ahead of a strong fall cold front that was to usher in the first light frost of the season & under strong jet stream winds amidst substantial wind shear, the cells very rapidly pulsed up & became severe.  The first report of severe weather was a 58 mph wind gust at Pine Village.  This was the beginning of a long track of destruction across the heart of the WLFI viewing area from as the three supercells evolved into a cluster, then bowing line segment.  Flash flooding was an issue with these high-precipitation supercells & 3 corridors of substantial flash flooding developed as extreme rainfall rates occurred.  You can certainly understand why this event is one of the top autumn severe events.  Imagine +100 mph downbursts, 2-3″ per-hour rainfall rates & golfball sized hail.  In fact, up to 6″ of hail accumulated on the ground 1 mile north of Buck Creek & old State Road 25 was close northeast of Lafayette by up to 4″ of hail on the roadway.

Interestingly, after the storms, very dense fog formed over these areas that had so much hail, making travel difficult.

The rain was very welcome, however, as the area was in the midst of a significant drought.

Supercell #1:  Pine Village to South of Yeoman

Reports of extremely high winds began in northeastern Warren County, then continued east-northeastward, blasting Montmorenci, West Lafayette & Klondyke.  The highest measured non-tornadic wind gust on record in our viewing area occurred from this storm with a 103 mph gust near Montmorenci.  Hundreds of acres of corn & soybeans that were about to be harvested were totally flattened by the apparent macroburst (damage diameter greater than 2.5 miles).  A 5th-wheel camper was overturned, injuring the occupant & 2 dozen homes received damage.

Numerous trees were blown down in Pine Village & several roads were reportedly blocked by fallen trees in Lafayette. As I said formerly, an amazing hail depth of up to 6″ was reported 1 mile north of Buck Creek.

The storm continued east-northeastward & dropped an F1, 105 mph tornado on the southwest corner of the supercell, which tracked 4 miles to east-southeast to near Buck Creek.  Up to a half-mile wide, it produced over $300,000 in damage.  3 farm tool sheds were totally destroyed with the structural debri found in the tops of trees as far as 1-2 miles away.  With the tornado touchdown, golfball-sized hail began to fall from the storm.  A second downburst (in this case a microburst) belched from the storm with a measured wind gust of 64 mph at Buck Creek.  There is evidence of wind gusts to 80 mph east of Buck Creek.  This combined with golfball hail caused siding & roof damage to several homes & destroyed fields of unharvested crops all the way to western Carroll County.  Gaping holes were ripped in roofs by the wind-driven large hail.  Route 225 was impassable due to fallen trees.

Supercell #2:  South of Attica to Flora

Golfball-sized hail began to fall with this supercell southwest of Lafayette.  In Lafayette proper, $100,000 in damage was done (largely to cars).  Large hail continued with the storm with northeastward progression.  Golfball hail was reported at Radnor & Flora.  The first downburst (microburst) with this storm occurred near Radnor with a 64 mph wind gust measured & an 80 mph gust causing substantial tree damage.  A barn was destroyed by this microburst.

In White County, southwest of Brookston, the large hail core accumulated a snow-like covering several inches deep.  Radnor, in Carroll County also reported golfball-sized hail with substantial hail accumulation with a wind gust to 64 mph, as a third microburst was belched from the storm.  A barn was destroyed east of Radnor with estimated microburst gusts around 80 mph.  Golfball-sized hail was reported at Flora.

Supercell #3:  South of Otterbein to Brookston to Fulton (Storm Continued Northeastward with Sporadic, But Impressive Damage to Near Fort Wayne)

The third severe supercell popped just south of Otterbein, tracked into White County & began to produce a prolific golfball hailstorm.  Hail accumulated several inches near Brookston.  Entire fields of crops were destroyed & trees were totally stripped of leaves.  The storm continued northeastward with several inches of golfball hail in northwest Carroll County.  The first downburst (in this case microburst) was belched out northwest of Logansport with a 75 mph wind gust that caused tree & power line damage with crops fields damaged.  The storm then belched out the second extreme macroburst of the evening with 100 mph wind gust doing heavy damage southwest of Fulton to  Nyond Lake & South Mud Lake.  This macroburst alone produced over $125,000 in structural damage.  This storms second gust, a microburst, produced tens of thousands of dollars in structural damage north of Macy in Miami County. This same storm produced winds up to 80 mph in Whitley, DeKalby & Allen counties.  Significant damage to trees & powerlines occurred in Columbia City with many homes receiving minor structural damage.  Much of the city had no power for at least 24 hours.

The damage costs to these supercells were phenomenal.  In Tippecanoe County alone, just the hail caused over $100,000 in damage to structures.  Damage to automobiles was upwards of an additional $100,000 (Tippecanoe County, alone).  +$100,000 was done to structures via damaging winds.  $300,000 in damage was incurred by the tornado.  Crop damage in Warren, Tippecanoe, White, Carroll, Cass, Fulton & Miami counties mounted into the tens of millions of dollars as thousands of acres of crops were flattened or completely destroyed.

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What a stretch we have had recently!

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Front will slide through late tonight-Tuesday morning, turning skies cloudy to mostly cloudy with an isolated shower possible.

Data shows clearing trend in the afternoon with 66-76 for highs.

Front will move right back northward tomorrow night in response to approaching storm system.

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Two waves of showers & t’storms will pass Thursday afternoon-evening & another night-Friday morning.  The heaviest one looks to be Thursday night-Friday morning.

Right now, the severe weather threat zone is South Dakota to Arkansas to as far northeast as southwestern Illinois Thursday-Friday.

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7:37 P.M. Update

September 29th, 2014 at 7:37 pm by under Chad's WLFI Weather Blog

Today was another warm one with 79-85 after patchy dense fog & upper 40s to mid 50s this morning.

DMA Map II

Cold front will approach tonight & pass tomorrow morning.  We will drop to 50-56 tonight, then rise as front approaches to 55-60.

There will be a considerable amount of cloudiness with it as it passes & followed the passage.  I cannot rule out an isolated shower or two/sprinkle (mainly in our northern/northeastern counties) as it passes.  Models tend to clear the clouds in the afternoon or at least just have scattered fair weather cumulus.  Went “mostly cloudy in the morning, then decreasing clouds in the afternoon” for forecast wording as a result.

It will keep highs at upper 60s to upper 70s tomorrow with 47-56 tomorrow night.

However, front will move right back north tomorrow night & Wednesday & Thursday will warm up again.

Looks like one wave of scattered showers & t’storms Thursday late, then break, then main wave of rain/t’storms Friday.  Right now, looks like best estimate of timing is Friday morning.

Locally-heavy rainfall of 1-2″ in places is still possible.  Despite good dynamics, instability will be an issue.  With lack of it, severe weather does not look like an issue right now, but we do need to watch it for any changes.  It is possible that greater instability may develop & lack of severe threat need be re-evaluated.  Severe weather is still likely in the Plains to western & southern Illinois.

Cooler weather will come in Friday-Sunday with highs only in the 50s Saturday.  A couple/three nights over the weekend, even early next week will see widespread 30s with some frost.


Latest Outlook

September 28th, 2014 at 10:38 pm by under Chad's WLFI Weather Blog

Highs Sunday ranged from 79-85 with lots of sun with only some wispy cirrus & a few fair weather cumulus in the area.  After 50s & some patchy fog tonight, we will be back to 79-84 tomorrow with plenty of sunshine.

DMA Map II

I think we will fail to reach 80 in the area Tuesday as a weak, dry front comes through in the morning.  We will still see 70s, though.  There may be some clouds with the frontal passage in the morning, followed by  lots of sun & a north-northeast wind at 10-15 mph.

This front is in response to strong upper trough & surface cold front swinging through Manitoba, Minnesota to Ontario & Quebec just skimming area.

The front will tend to work right back north by Wednesday with highs back at 79-84 after 47-56 in the morning.  The wind should go back south as front lifts northward through area after 3 a.m. early Wednesday morning.

Scattered showers & t’storms are likely Thursday late with peak in coverage Thursday night, followed by another wave of widespread rainfall & t’storms Friday.  Dynamics/shear are great, but instability is lacking due to widespread rainfall, which appears to diminish any severe potential at the moment.  We will watch.  Severe weather is likely Kansas to Missouri to western & southern Illinois to Arkansas.

Here, locally heavy rainfall of 1-2″ is possible in parts of the area.

Cooler air will follow.  Highs by Saturday will only run in the 50s with lows in the 30s.  With 50s to around 60 Sunday, lows will be in the 30s.

A rapid warm-up back to 70s is possible after this with overall pretty dry conditions.


Latest Outlook Out Later This Evening

September 28th, 2014 at 8:34 pm by under Chad's WLFI Weather Blog

The latest outlook will be out later this evening.


11:45 P.M. Update

September 27th, 2014 at 11:03 pm by under Chad's WLFI Weather Blog

Highs today varied from 79-84.

Tonight, patchy high/mid clouds will exit & patchy, locally-dense fog will develop with lows of 51-56.

Sunday & Monday look great with brilliant sun & highs from around 80 to as high as 84, with lows in the 50s with some patchy fog.

Again, Tuesday looks a hair cooler at 77-81 with 79-84 Wednesday & 78-83 Thursday.

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It looks like scattered showers & t’storms will come in Thursday & increase Thursday night, followed by a main round Friday.  It is still a bit questionable when exactly the heaviest showers/storms pass (with cold front) Friday & if any rainfall will linger into Saturday morning.

Regardless, storm system looks pretty strong with strong wind fields at all levels & good forcing.  For us, question is instability.  If it can get unstable enough, then severe threat would need to be put in place.  The latest data still suggests an issue of getting unstable enough for severe threat, but it looks plenty unstable enough from Kansas to Iowa to western Illinois to Missouri & Arkansas for severe event late week.

It also still appears that locally-heavy rainfall may occur with widespread 1-2″ amounts.

Much cooler weather still looks to follow with a couple nights in the 30s before the warmth rapidly returns.

We will continue to monitor & tweak forecast as needed as additional data arrives.