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2014 Mid-Atlantic Severe Discussion Thread


Kmlwx

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The Euro is impressed, showing a 979mb low just NW of PHL at 00z Thursday. 

yeah even the weaker models are pretty impressive for around here.  usually when you get a 500mb vort aligned along the front like that you get a big squall line though, at least from what i recall.  soundings are close at times but never quite get full turning plus there is some kink in the hodos. hard to say though since there will probably be some more localized backing at the sfc and we do tend to get a fair amount of tornadoes out of overall linear modes around here.  

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LWX HWO as of 2:15pm mentions potential for damaging wind gusts tomorrow and the potential for isolated tornadoes also being possible

i.e., standard language.. pretty much everyone says the same thing every storm threat. 

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Tomorrow looks great for a line of storms through the CWA. The strong temp gradient from ahead of front to 50 miles behind front is beyond impressive. That should create sufficient lift out ahead of front to ignite some storms. Using the 12z 925mb Hi-Res NAM you can draw a triangle with a separation of the cold and warm front and extend out 2 isobars to predict possible area of storm development. Southern Pa down to VA looks like a prime location. Plus, the strong PVA at 500 entering the area is beyond beautiful

 

nam-hires_namer_033_925_temp_ht.gif

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The NAM meteogram is pretty wild with the frontal passage.   It goes from the low 60's to the mid 20's in 3 hours.    sfc-based cape (bottom panel) is limited, but the frontal forcing should be tremendous.

 

We do fronts very poorly around here.  If this one can live up to the forecasts, it will be noteworthy.  ~64 at 9pm to ~27 at midnight on the NAM.

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We do fronts very poorly around here. If this one can live up to the forecasts, it will be noteworthy. ~64 at 9pm to ~27 at midnight on the NAM.

That said, the arctic front in January was pretty awesome. We went from 35 degrees to 5 degrees in a matter of hours. The wind out-matched the UHI effect around these parts.

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That said, the arctic front in January was pretty awesome. We went from 35 degrees to 5 degrees in a matter of hours. The wind out-matched the UHI effect around these parts.

 

Yeah, but even then the actual frontal passage (pressure and wind field) was earlier in the day.  I lost 25 degrees in 7 hours.  If this front is as advertised, we could do that in 90 minutes.

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Afternoon LWX AFD

 

ON WED...THE CWA WILL BE SITUATED IN PRE-FRONTAL WARM SECTOR
WITH ANOMALOUSLY DEEP/STRONG SLY FLOW DEVELOPING OVER THE ERN
SEABOARD. NOSE OF LLVL THETA-E RIDGE REACHES THE CWA AND WILL BE
ACCOMPANIED BY AFTN TEMPS IN THE 60S AND 70S WITH DEWPOINTS IN THE
50S. DO NOT EXPECT WIDESPREAD COVERAGE OF SHOWERS WED MRNG WELL
IN ADVANCE OF THE FRONT. MODELS CONTINUE TO INDICATE THE
POTENTIAL FOR A LINE OF CONVECTION TO DEVELOP IN THIS MODESTLY
UNSTABLE AIRMASS DURING THE AFTN. SIGNIFICANT HEIGHT FALLS WILL
OCCUR AHEAD OF THE MAIN UPPER LOW. THE GREATEST HEIGHT FALLS WILL
TAKE PLACE OVER THE MID-ATLANTIC REGION BETWEEN 18Z WED THRU
03Z...WHICH IS THE PERIOD THAT OUTLINES THE BEST CHANCE FOR
SHOWERS AND STORMS. AFTER COORDINATION WITH SPC...ENTIRE CWA WAS
PLACED IN A SLIGHT RISK WED FOR SVR STORMS. THE PRIMARY THREAT
FROM THESE STORMS ARE STRAIGHT LINE WIND DAMAGE ALTHOUGH A FEW
EMBEDDED QLCS TORNADOES ARE POSSIBLE. THE THREAT OF TORNADOES WILL
BE DEPENDENT ON HOW CLOSE THE WARM FRONT BOUNDARY WILL BE TO OUR
CWA. LATEST GUIDANCE TRENDING TOWARD THE WARM FRONT LIFTING NORTH
OF THE MASON-DIXON LINE PRIOR TO THE ARRIVAL OF CONVECTION.

PRECIP ASSOCIATED WITH THE COLD FRONT WILL LIKELY MOVE EAST OF
THE CHSPK BAY BY LATE WED EVE. MODELS CONTINUE TO SHOW IMPRESSIVE
PRESSURE RISES AND COLD AIR ADVECTION IN WAKE OF COLD FROPA. WIND
ADVISORIES WILL LIKELY BE REQUIRED FOR THE ENTIRE CWA WED NGT WITH
NW WIND GUSTS NEAR 50 MPH MIXING DOWN.
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Hi-Res NAM is :o worthy. Big line of convection right along the front, 980mb in C-PA by 5pm. Verbatim, the CAA begins right along the squall line, so the winds will continue to howl after the squall line passes..

Impressive vort max stripe from New York to California. http://mag.ncep.noaa.gov/Image.php?fhr=030ℑ=data%2Fnam-hires%2F18%2Fnam-hires_namer_030_500_vort_ht.gif&model=nam-hires&area=namer&param=500_vort_ht&group=Model+Guidance&preselected_formatted_cycle_date=20140311+18+UTC&imageSize=&ps=area

nam-hires_namer_030_500_vort_ht.gif

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I assume it still works to highlight max zones tho prob better to stack other products for same idea

Sig tor only parameter on that same run gets a little pocket of 1 in here. We seem to be "ground zero" for the best activity on that run of the SREF. Little pocket of 500 cape gets in here and a little pocket of -2 LI too. 

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Sig tor only parameter on that same run gets a little pocket of 1 in here. We seem to be "ground zero" for the best activity on that run of the SREF. Little pocket of 500 cape gets in here and a little pocket of -2 LI too. 

Yeah, it looks like here and to the west/nw to around the blue ridge probably has the best risk.  Timing may matter a little. If it holds off till 0z maybe not top end of potential.  But, when chasing going for the tip of the moisture plume usually works well and that's about where we are tomorrow.  Dews are still a little iffy.. but maybe underdone. I'd like to get to 60+. 

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Yeah, it looks like here and to the west/nw to around the blue ridge probably has the best risk.  Timing may matter a little. If it holds off till 0z maybe not top end of potential.  But, when chasing going for the tip of the moisture plume usually works well and that's about where we are tomorrow.  Dews are still a little iffy.. but maybe underdone. I'd like to get to 60+. 

I feel like these lines like to clear the area early tho - so that might be a good sign for it not holding off too late

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