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Severe T-Storm Threat for Mon, Jul 18th


tornadojay

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day1probotlk_1300_wind.gif

...NERN U.S...

THE ESEWD PROGRESSION OF MULTIPLE MIDLEVEL IMPULSES WILL

COLLECTIVELY LOWER HEIGHTS ACROSS THE REGION THROUGH THE D1

PERIOD...DOWNSTREAM FROM EXPANSIVE CNTRL U.S. ANTICYCLONE. COLD

FRONT CURRENTLY FROM THE ST. LAWRENCE VALLEY WWD INTO THE UPPER

GREAT LAKES WILL PROGRESS SEWD TO OFF THE NEW ENGLAND AND MID

ATLANTIC COASTS BY 19/12Z. PERSISTENT WLY LOW-LEVEL FLOW AHEAD OF

FRONT WILL SERVE TO ENHANCE THE FLUX OF AN INCREASINGLY WARM AND

HUMID AIR MASS INTO THE AREA FROM THE OH VALLEY.

LOOSELY ORGANIZED MCS OVER UPSTATE NY WILL LIKELY CONTINUE SEWD THIS

MORNING...THOUGH UNCERTAINTY EXISTS WHETHER THIS COMPLEX WILL

INTENSIFY BY LATE MORNING/EARLY AFTERNOON...OR UNDERGO DIURNAL

DECAY. IN ADVANCE OF THIS ACTIVITY...DAYTIME HEATING COUPLED WITH

LOW-LEVEL MOIST ADVECTION FROM THE W WILL YIELD AFTERNOON MLCAPE

APPROACHING 1000-2000 J/KG. AS SUCH...EXPECT THE INTENSIFICATION OF

ANY STORMS THAT CAN PERSIST THROUGH THE MORNING...AS WELL AS SUPPORT

THE DEVELOPMENT OF ADDITIONAL STORMS ALONG PRE-EXISTING OUTFLOW

BOUNDARIES AND COLD FRONT ITSELF.

EXIT REGION OF 100+ KT UPPER-LEVEL JET STREAK WILL GRADUALLY DEVELOP

SEWD FROM ONTARIO...ENHANCING DEEP-LAYER SHEAR FOR BOWING LINE

SEGMENTS AND SUPERCELLS CAPABLE OF MAINLY DAMAGING WINDS AND PERHAPS

SOME HAIL.

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Tomorrow's severe potential has been looking less impressive over the past few runs as the guidance has backed the better shear parameters farther to the north. Check out the loop of the past few SREF runs showing the better probability of severe weather staying north of our area.

http://www.spc.noaa.gov/exper/sref/sref_matrix_hover.php?fhr=f030&startdate=2011071715&field=SREF_03HR_SVR_PROBS__

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I think patience is the key with today's threat. Lots of CIN out there right now but that line is many hours away and we should get maximum heating. I would think SBCAPE should be in excess of 2000/JKG right up to the coast with an offshore flow, dew points in the 60's and full sun. The limiting factor could be shear but with this type of setup 30kts should be sufficant. We seem to do our best in these types of marginal setups and with a healthy looking squall line already ongoing I like our chances of at least some strong storms this afternoon.

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SPC in their 13z outlook uncertain where the storms will fall apart or intensifty on the next few hours:

LOOSELY ORGANIZED MCS OVER UPSTATE NY WILL LIKELY CONTINUE SEWD THIS MORNING...THOUGH UNCERTAINTY EXISTS WHETHER THIS COMPLEX WILL INTENSIFY BY LATE MORNING/EARLY AFTERNOON...OR UNDERGO DIURNAL DECAY. IN ADVANCE OF THIS ACTIVITY...DAYTIME HEATING COUPLED WITH LOW-LEVEL MOIST ADVECTION FROM THE W WILL YIELD AFTERNOON MLCAPE APPROACHING 1000-2000 J/KG. AS SUCH...EXPECT THE INTENSIFICATION OF ANY STORMS THAT CAN PERSIST THROUGH THE MORNING...AS WELL AS SUPPORT THE DEVELOPMENT OF ADDITIONAL STORMS ALONG PRE-EXISTING OUTFLOW BOUNDARIES AND COLD FRONT ITSELF.

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6z NAM brings line into our area by 5pm. It breaks it down though, as it approaches.

6z GFS keeps the line intact and hits the whole area pretty hard. It however, is a few hours behind the NAM and doesnt bring the line in until the overnight hours.

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NAM is still looking pretty juicy for tonight. Maybe it's not going to be severe but hopefully we can get some good nighttime soaking thunderstorms.

Yeah. 12z NAM is definitely better then 6z for our area. Focuses the really heavy stuff in NW Jersey, but brings the NYC area a decent line of rain as well.

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Comparing the latest NAM to current radar depiction, shows that the line of storms is a few hours faster the the models are forecasting.

The line is flying right now on radar.

wow, no kidding. swings through by early afternoon?

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Comparing the latest NAM to current radar depiction, shows that the line of storms is a few hours faster the the models are forecasting.

The line is flying right now on radar.

No surprise the SPC WRF caught that as well on its run last night, it was well ahead of most models then.

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No surprise the SPC WRF caught that as well on its run last night, it was well ahead of most models then.

NAM has the line on us around 6-8pm.

GFS is even later, after 10pm.

What time do you think the line swings thru? Just looking at radar, I cant see how its later then 2pmish.

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The newest HRRR has this initial line, that the radar has, swinging thru in the next 3-4 hours, mostly missing to our NE.

And then develops another line coming out of the lakes area and swings it thru NYC in the evening and night hours.

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The newest HRRR has this initial line, that the radar has, swinging thru in the next 3-4 hours, mostly missing to our NE.

And then develops another line coming out of the lakes area and swings it thru NYC in the evening and night hours.

It better, cuz that first line is very meh. Probably why the models seem so fast, it won't hold up.

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Interestingly today is July 18th and recently I brought up 7/18/97 in the top 5 severe weather days...the setup at 500mb and even the surface is similar across the country....we saw an initial pre-frontal unexpected early line of storms followed by 4-5 hours of heating and then more storms thereafter...the first line of storms was totally unforecast and missed by most models....something similar could occur today though I don't know if we can get enough heating following the initial line.

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It still has precip after 6z though, maybe not that impressive but rarely do I look at the GFS QPF amounts when talking about short term

New GFS picks up on the current situation and has this line thru us now by 9pm.

Weak and disorganized too.

6z GFS and 0z GFS had the line coming thru in the overnight hours tonight.

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Wouldn't be surprised to see SPC remove the 30%...the mid level temps are a real problem despite the shear. It's going to be difficult to get these storms churning south without a well developed cold pool. The shear is still strong though--so who knows. That decayed MCS can still cause wind shift problems even though it's weakened, too.

The 30% contour should really be back over Western and Central NY for later this afternoon if you ask me.

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