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Friday, October 14th, 2011 Convective Threat


weatherwiz

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A fairly deep area of low pressure off to our west will remain rather stalled out across the upper mid-West through the day tomorrow. Out ahead of it a weak cold front will gradually shift eastward. A triple point will develop as a secondary area of low pressure develops just off the Carolina coast and traverses northward bringing a warm front northward with it. Some computer models indicate this warm front and associated triple point will cross into portions of southern New England tomorrow afternoon. If this does indeed occur temps could spike up into the lower or perhaps mid 70's if we can get some sun to break out and dewpoints could climb into the upper 60's to perhaps near 70F! We could end up seeing somewhere around 500-700 J/KG of SBcape with LI values around -2C or so.

Shear is forecasting to be quite strong as well which is usually the case anyways with the fall systems. The LLJ is forecasted to be around 20-25 knots with a MLJ of 50-60 knots with a LLJ max of 60-80 knots punching into the region later on in the afternoon! There will also be a strong 80-100 knot with a 100-125 knot ULJ max close to the region as well. Vertical shear values are expected to be anywhere from 40-50 knots then increasing to 50-60 knots as the afternoon goes on! While the shear aloft will mainly be unidirectional there may be a great deal of low-level helicity in place with the warm front in the vicinity of the region. sfc winds may be more from the ESE or SE while winds aloft will be from the due south.

500mb temps look fairly cold as well as they are forecasted to be around -12C or so, however, the wet-bulb heights just under 11,000ft or so but dropping slowly throughout the afternoon. This should yield to some decent lapse rates, probably just up around 6 C/KM or so.

PWAT values will be fairly juicy tomorrow, up around 1.50'' as well so heavy rain will certainly be a threat and this could lead to pockets of isolated flash flooding.

If we are to see convection tomorrow chances are we see some sort of fine, forced, low-topped squall line which may produce some gusty winds given strong shear aloft. If updrafts are able to mature or grow larger then the threat for some strong or even severe storms would be possible. Normally in setups like this we don't end up seeing much in the way of severe weather as instability is often very weak and the updrafts aren't strong enough to punch into the much stronger winds aloft and b/c they are weak as they reach the stronger winds the updrafts just topple over.

I guess we'll see if we can get any breaks of sun tomorrow to help increase instability a bit.

With this said some juicy probs by the SPC SREF...9z run

SREF_03HR_SVR_PROBS__f030.gif

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Quite interesting but forecast soundings do show at least some potential for a few breaks of sun tomorrow given how there is some dry air aloft which will be moving into the region. Often in these setups you usually see a highly moist atmospheric column with the dewpoint/temp line riding each other.

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I don't know if I am in good enough standing to give a few weanie symbols yet, but definitely deserve more than one.....but thanks for the write up. will be hoping for some sunshine to break through. I wouldn't mind a thunderstorm. just not looking forward to my next rumble of thunder being on the backside of a SWFE.

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Maybe a couple of rounds of tstms tomorrow?? Predawn one possible, then late day?

Certainly possible.

This is a pretty potent trough with a solid negative tilt and a very good ULJ max associated with it as well. Going to have lots of upward motion tomorrow and with 500mb temps <-10C and cooling as the day goes on this should yield to decent ML lapse rates and decent ML instability for this time of year.

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Seems like the best forcing tomorrow is going to slide around SNE and not right over us. May mitigate svr and heavy rain threat?

Still looks like a strong s/w rides through. It's not a clear warm sector, and they may be some damming across parts of the interior..but maybe one line predawn and another out in western SNE in the aftn moving east?

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Still looks like a strong s/w rides through. It's not a clear warm sector, and they may be some damming across parts of the interior..but maybe one line predawn and another out in western SNE in the aftn moving east?

Yeah potential is there.. timing just sort of challenging with the number of impulses interacting with one another rounding the base of the trough.

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Yeah potential is there.. timing just sort of challenging with the number of impulses interacting with one another rounding the base of the trough.

It's one of those things where it could be a line of hvy shwrs with embedded thunder, or a nasty squall line..lol. Eh, at least it's something to check out...even if nbd.

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5 Tornado reports down in northern VA already...impressive.

In this area, however, you have SBcapes of 1500-2500 J/KG, MLcapes of 1000 J/KG, MUcapes of about 2000 J/KG, Ncape of 0.15, LI of -4C to -6C, K-Index of about 35 with ML lapse rates of about 6.5 C/KM. This to go along with 40 knots of vertical shear, 200-250 m2s2 of 0-3km helicity, and 150-200 m2s2 of 0-1km helicity.

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Yeah potential is there.. timing just sort of challenging with the number of impulses interacting with one another rounding the base of the trough.

It's one of those things where it could be a line of hvy shwrs with embedded thunder, or a nasty squall line..lol. Eh, at least it's something to check out...even if nbd.

Looks a bit more impressive (to me) for some of us tomorrow than earlier today. Decent LCHS cool season set-up in my opinion. Catskills east to Litchfield Hills/S'rn Berkshires could see some MESO's with brief spin-ups within a QLCS. Has some similarities to 11/17/2010 and 11/20/1989. While these two cited dates were much more impressive from a kinematic perspective tomorrow's event should feature some moderate range wind speeds and divergence. I would expect the best chance for any spinups tomorrow to be to the left of the 850 hPa jet and in the RRQ of the 300 hPa jet.

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Looks a bit more impressive (to me) for some of us tomorrow than earlier today. Decent LCHS cool season set-up in my opinion. Catskills east to Litchfield Hills/S'rn Berkshires could see some MESO's with brief spin-ups within a QLCS. Has some similarities to 11/17/2010 and 11/20/1989. While these two cited dates were much more impressive from a kinematic perspective tomorrow's event should feature some moderate range wind speeds and divergence. I would expect the best chance for any spinups tomorrow to be to the left of the 850 hPa jet and in the RRQ of the 300 hPa jet.

Will be interesting to see how everything aligns tomorrow in the AM and whether or not we can get any breaks of sun. Models still show some drying through the column which could help.

Nice area of showers/storms forming too south of us.

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0600 DAY 1 SPC OTLK... 5 wind/0 hail/0 tor Sorry Wiz :(

..NORTHEAST INTO WRN NEW ENGLAND

SEVERAL ROUNDS OF NUMEROUS SHOWERS WITH EMBEDDED TSTMS ARE EXPECTED

THIS MORNING INTO EARLY EVENING AS MID-LEVEL DCVA INTENSIFIES AND A

FAVORABLE LARGE-SCALE ASCENT REGIME PERSISTS. THE ABUNDANT

CONVECTION/CLOUD COVERAGE WILL LIKELY RETARD THE NWD RETREAT OF A

WARM FRONT ACROSS THE NORTHEAST INTO SRN NEW ENGLAND...AND LIMIT

DAYTIME DESTABILIZATION ACROSS THE REGION. DESPITE MIDDLE 60S

SURFACE DEW POINTS IN THE MOIST AXIS S OF THE WARM FRONT...WEAK

MID-LEVEL LAPSE RATES SHOULD HOLD MLCAPE AOB 500 J/KG...AND SERVE TO

LARGELY MITIGATE SEVERE POTENTIAL. NEVERTHELESS...IT REMAINS

CONCEIVABLE THAT A CORRIDOR OF GREATER HEATING COULD OCCUR ALONG THE

COLD/OCCLUDED FRONT PUSHING EWD. IF THIS OCCURS...DEEP/NEARLY

UNIDIRECTIONAL SLY SHEAR PROFILES WOULD BE FAVORABLE FOR FAST-MOVING

CLUSTERS/SHORT-LINE SEGMENTS CAPABLE OF SPORADIC/LOCALIZED DAMAGING

WINDS.

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Looks interesting for some sct stronger tstms today. Could be a couple of lines with one pushing into the area this aftn..maybe a continued development of the stuff in CT now, and another line along the actual front late this aftn accompanied by a strong s/w swing into western areas. Very dynamic system with strong height falls and entrance region of jet pushing into the area. CAPE might be meh with all the cloud cover however, but a few good cells certainly possible.

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Looks interesting for some sct stronger tstms today. Could be a couple of lines with one pushing into the area this aftn..maybe a continued development of the stuff in CT now, and another line along the actual front late this aftn accompanied by a strong s/w swing into western areas. Very dynamic system with strong height falls and entrance region of jet pushing into the area. CAPE might be meh with all the cloud cover however, but a few good cells certainly possible.

Couple tor's certainly possible

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Looks interesting for some sct stronger tstms today. Could be a couple of lines with one pushing into the area this aftn..maybe a continued development of the stuff in CT now, and another line along the actual front late this aftn accompanied by a strong s/w swing into western areas. Very dynamic system with strong height falls and entrance region of jet pushing into the area. CAPE might be meh with all the cloud cover however, but a few good cells certainly possible.

Ill probably see my best SVR today on 10/14

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