Ellinwood Posted March 22, 2011 Share Posted March 22, 2011 Full discussion coming later today. For now, SPC: ...OHIO/TENNESSEE VALLEYS INTO THE MID ATLANTIC COAST... INITIAL STORM DEVELOPMENT MAY BE FOCUSED IN THE WARM SECTOR NEAR THE LOW...AND ALONG THE FRONTAL ZONE TO THE EAST SOUTHEAST OF THE LOW...PERHAPS AS EARLY AS MID DAY ACROSS PARTS OF SOUTHEASTERN INDIANA INTO OHIO. THIS MAY INCLUDE SUPERCELLS...BUT UPSCALE GROWTH INTO AN EVOLVING MESOSCALE CONVECTIVE SYSTEM APPEARS POSSIBLE...WHICH SHOULD DEVELOP SOUTHEASTWARD THROUGH THE CENTRAL APPALACHIANS BY LATE AFTERNOON. AS THIS OCCURS...AND AN AREA OF STRONG MID/UPPER FORCING FOR UPWARD VERTICAL MOTION BEGINS TO OVERSPREAD THE REGION WITH THE APPROACHING UPPER JET STREAK...ADDITIONAL STORM DEVELOPMENT IS EXPECTED SOUTHWESTWARD ALONG AN EFFECTIVE DRY LINE TYPE STRUCTURE NEAR AND TO THE SOUTHEAST OF THE OHIO RIVER. THIS ACTIVITY MAY TEND TO REMAIN DISCRETE IN THE PRESENCE OF FAVORABLE SHEAR FOR SUPERCELLS. TORNADIC POTENTIAL...PARTICULARLY WITH THE DISCRETE STORMS... REMAINS THE PRIMARY UNCERTAINTY FOR THIS FORECAST...AND APPEARS LIKELY TO HINGE ON THE CHARACTER OF THE BOUNDARY LAYER. WHILE LOW-LEVEL HODOGRAPHS IN GENERAL MAY NOT BECOME PARTICULARLY LARGE AND CLOCKWISE CURVED...THE SHEAR STILL APPEARS SUFFICIENT. HOWEVER...FORECAST SOUNDINGS AMONG THE MODELS DO EXHIBIT SOME VARIABILITY CONCERNING THE BOUNDARY LAYER MOISTURE CONTENT. IF SURFACE DEW POINTS APPROACH 60F...AND THE SURFACE DOES NOT HEAT TOO STRONGLY AND SUPPORT DEEPER MIXING...THE TORNADO POTENTIAL MAY BE HIGHER...AND THE SEVERE THREAT PERHAPS GREATER THAN REFLECTED BY THE CURRENT SLIGHT RISK. CURRENTLY...IT SEEMS MORE PROBABLE THAT SLIGHTLY DRIER BOUNDARY LAYER CONDITIONS WILL PREVAIL...PROMOTING PRIMARILY A LARGE HAIL AND DAMAGING WIND THREAT. MODEST DESTABILIZATION AND INCREASING LARGE-SCALE ASCENT COULD ALSO PROMOTE STRONG/SEVERE STORM DEVELOPMENT TO THE LEE OF THE CENTRAL APPALACHIANS BY LATE AFTERNOON. BUT IT ALSO SEEMS POSSIBLE THAT THE MESOSCALE CONVECTIVE SYSTEM MAY MAINTAIN STRENGTH ACROSS THE APPALACHIANS...WITH A CONTINUING SEVERE THREAT ACROSS PARTS OF VIRGINIA AND NORTH CAROLINA DURING THE EVENING HOURS. COOL/COLD AIR TO THE NORTH OF A STALLED FRONTAL ZONE MAY MITIGATE THE SEVERE STORM POTENTIAL NEAR CHESAPEAKE BAY AND ACROSS NORTHERN VIRGINIA. Link to comment Share on other sites More sharing options...
Kmlwx Posted March 22, 2011 Share Posted March 22, 2011 00z NAM had a decent line or something coming through between 0z and 06z tomorrow night. Hires models (near the end of their run) looked not too shabby as well. Link to comment Share on other sites More sharing options...
mappy Posted March 22, 2011 Share Posted March 22, 2011 I hope it misses - I'll be at a conference all day tomorrow, so I won't be able to follow it or enjoy it Link to comment Share on other sites More sharing options...
Ellinwood Posted March 22, 2011 Author Share Posted March 22, 2011 I hope it misses - I'll be at a conference all day tomorrow, so I won't be able to follow it or enjoy it It wouldn't hit until the evening out at BWI (given the current forecast) Link to comment Share on other sites More sharing options...
mappy Posted March 22, 2011 Share Posted March 22, 2011 It wouldn't hit until the evening out at BWI (given the current forecast) If it can wait until 8pm or so, then that's fine with me. Id rather be home enjoying it, then driving home through it. Link to comment Share on other sites More sharing options...
Ellinwood Posted March 22, 2011 Author Share Posted March 22, 2011 If it can wait until 8pm or so, then that's fine with me. Id rather be home enjoying it, then driving home through it. It'll actually probably rain most of the day at BWI before the storms roll through, so.... yeah. Rain. Link to comment Share on other sites More sharing options...
Ellinwood Posted March 22, 2011 Author Share Posted March 22, 2011 DISCUSSION: A rather unusual severe weather setup as a low pressure system rides along a frontal boundary that is NW-SE oriented from central OH into central MD. Warm-sector instability on the order of 500-1000+ J/kg SBCAPE will develop over WV and western VA during the afternoon, which will help initiate a few areas of showers and storms. A convergence area over the Appalachians will help trigger storms early, with better instability upstream ahead of the southward-moving cold front that will move through OH and WV during the late afternoon and early evening. Things will look a little messy on radar at first, but eventually some strong/severe cells will form in the westernmost parts of the region. The main threat from these storms will be hail and wind damage, with an isolated threat for a few tornadoes. Speed shear is good with this system, but winds will be largely unidirectional, which will hinder tornadic development. Upper-levels are somewhat favorable as left-exit region divergence and some support from the 500mb vort. provide good synoptic lift. As these storms push east into the Apps. and coastal plain, they will likely lose some intensity as the surface instability wanes. However, elevated instability should be sufficient to maintain thunderstorms with hail (maybe severe) and gusty winds (likely not severe) as the storms reach the DC/BWI region in the early evening. Depending on the amount of the elevated CAPE, storms could maintain themselves rather well and provide the area with a good lightning show. Chase-wise, I’m considering taking I-68 to Morgantown, WV and then waiting to see where storms initiate. Should storms end up more favorable to the south, it will be a quick drive on I-79 towards Charleston, WV to get into better position. ----- And just for record-keeping here's the Day 2 update from the SPC: Link to comment Share on other sites More sharing options...
CranberryWX Posted March 23, 2011 Share Posted March 23, 2011 DISCUSSION: A rather unusual severe weather setup as a low pressure system rides along a frontal boundary that is NW-SE oriented from central OH into central MD. Warm-sector instability on the order of 500-1000+ J/kg SBCAPE will develop over WV and western VA during the afternoon, which will help initiate a few areas of showers and storms. A convergence area over the Appalachians will help trigger storms early, with better instability upstream ahead of the southward-moving cold front that will move through OH and WV during the late afternoon and early evening. Things will look a little messy on radar at first, but eventually some strong/severe cells will form in the westernmost parts of the region. The main threat from these storms will be hail and wind damage, with an isolated threat for a few tornadoes. Speed shear is good with this system, but winds will be largely unidirectional, which will hinder tornadic development. Upper-levels are somewhat favorable as left-exit region divergence and some support from the 500mb vort. provide good synoptic lift. As these storms push east into the Apps. and coastal plain, they will likely lose some intensity as the surface instability wanes. However, elevated instability should be sufficient to maintain thunderstorms with hail (maybe severe) and gusty winds (likely not severe) as the storms reach the DC/BWI region in the early evening. Depending on the amount of the elevated CAPE, storms could maintain themselves rather well and provide the area with a good lightning show. Chase-wise, I’m considering taking I-68 to Morgantown, WV and then waiting to see where storms initiate. Should storms end up more favorable to the south, it will be a quick drive on I-79 towards Charleston, WV to get into better position. ----- And just for record-keeping here's the Day 2 update from the SPC: Glad to have you over this way. Just some advice, I would stick to the interstate as long as possible in the central part of the state. Once you get off, the roads twist around so much you won't tell what direction you're looking at, you won't see much unless you're on top of a hill, and the cell coverage sucks. Link to comment Share on other sites More sharing options...
Kmlwx Posted March 23, 2011 Share Posted March 23, 2011 21z SREF Supercell Composite Parameter for tomorrow at 00z. Link to comment Share on other sites More sharing options...
Ian Posted March 23, 2011 Share Posted March 23, 2011 Tomorrow looks like a day where high temp forecasts around here will bust. Link to comment Share on other sites More sharing options...
yoda Posted March 23, 2011 Share Posted March 23, 2011 Tomorrow looks like a day where high temp forecasts around here will bust. Sure does seem like it. I do hope the warm front comes through.. I would dislike being stuck in the 50s and rain Link to comment Share on other sites More sharing options...
yoda Posted March 23, 2011 Share Posted March 23, 2011 21z SREF Supercell Composite Parameter for tomorrow at 00z. Hmmm a 12 DC and east... interesting. Link to comment Share on other sites More sharing options...
Ellinwood Posted March 23, 2011 Author Share Posted March 23, 2011 Hmm.... looks like storms could fire a little earlier than expected locally, though they'd still be elevated. It would be nice to play the convergence zone in VA since we wouldn't have to worry about the mountains, but the overall instability will likely not be as good as the air just ahead of the cold front. EDIT: GFS parameters look better than the NAM for central+northern VA... will depend on strength of low-level WAA to bring the warm sector further north. Lots of disagreement still with this one... Nowcasting FTW. Link to comment Share on other sites More sharing options...
Hoosier Posted March 23, 2011 Share Posted March 23, 2011 hatched hail area extending into much of West Virginia The SPC discussion was about as bullish on hail as I've ever seen lol Link to comment Share on other sites More sharing options...
Ellinwood Posted March 23, 2011 Author Share Posted March 23, 2011 hatched hail area extending into much of West Virginia The SPC discussion was about as bullish on hail as I've ever seen lol Can't read it now (time for work!), but it's elating to see them upgrade it to a Moderate Risk with 5% TOR risk (with the 45% hatched hail and 30% wind). NoVA and most of MD now included in the Slight! Link to comment Share on other sites More sharing options...
BadgerWXman Posted March 23, 2011 Share Posted March 23, 2011 Should be a fun day.. hopefully we can get enough sunshine in between the 2 rounds of rain. Link to comment Share on other sites More sharing options...
mdwx Posted March 23, 2011 Share Posted March 23, 2011 Looks like Ill be right on edge with wedge... Nice setup for Supercells and large hail.. NVA, WV looks like jackpot.. Might not get snow Jay but a few dents in your car are possible. Link to comment Share on other sites More sharing options...
Ellinwood Posted March 23, 2011 Author Share Posted March 23, 2011 Morgantown seems to be a good bet, with a little N/S range on I-79. It will be just west of the mountains, so hopefully it could be a better chase. Link to comment Share on other sites More sharing options...
CranberryWX Posted March 23, 2011 Share Posted March 23, 2011 Morgantown seems to be a good bet, with a little N/S range on I-79. It will be just west of the mountains, so hopefully it could be a better chase. Just an fyi...the area around the Flatwoods exit 67 on I-79 opens up where you can see far off if you get down that way. Link to comment Share on other sites More sharing options...
Ellinwood Posted March 23, 2011 Author Share Posted March 23, 2011 Just an fyi...the area around the Flatwoods exit 67 on I-79 opens up where you can see far off if you get down that way. Not sure if we'll make it that far south... multiple hi-res models showing a nice area of convection between Clarksburg up to around Washington, PA going into the early evening. That's kind of what I was hoping to catch. Thanks for the information regardless... always helps to get terrain info. out in that area. Link to comment Share on other sites More sharing options...
North Balti Zen Posted March 23, 2011 Share Posted March 23, 2011 Sure does seem like it. I do hope the warm front comes through.. I would dislike being stuck in the 50s and rain How do 40s and rain strike you? This morning is pretty yuck in downtown Baltimore anyway. Link to comment Share on other sites More sharing options...
Ellinwood Posted March 23, 2011 Author Share Posted March 23, 2011 Not much change with the 13z update... here's some interesting discussion: ...OH/TN VALLEYS EWD TO THE ATLANTIC COAST THROUGH TONIGHT... A SWATH OF 55-60 F BOUNDARY LAYER DEWPOINTS IS SPREADING NEWD FROM MS/AL/TN/AR TOWARD THE OH VALLEY ON A 40-50 KT WSWLY LLJ. THIS MOISTURE WILL COMBINE WITH DAYTIME HEATING AND 8 C/KM MIDLEVEL LAPSE RATES N OF THE JET CORE TO SUPPORT MODERATE INSTABILITY /MLCAPE VALUES AROUND 1500 J PER KG/ IN THE WARM SECTOR THIS AFTERNOON. CONVECTIVE INHIBITION WILL WEAKEN BY MIDDAY OVER A RATHER BROAD AREA...AND MULTIPLE BANDS OF THUNDERSTORMS ARE EXPECTED TO DEVELOP BY EARLY AFTERNOON. THOUGH LOW-LEVEL FLOW IS EXPECTED TO WEAKEN SOME AND VEER TO MORE WLY DURING THE DAY...DEEP-LAYER VERTICAL SHEAR AND STRAIGHT HODOGRAPHS WILL BE FAVORABLE FOR BOTH SPLITTING SUPERCELLS AND FAST-MOVING LINE SEGMENTS. THE COLD MIDLEVEL TEMPERATURES /NEAR -20 C AT 500 MB/...STEEP LAPSE RATES...AND SUPERCELL WIND PROFILES APPEAR SUPPORTIVE OF A RELATIVELY WIDESPREAD THREAT FOR LARGE HAIL...SOME OF WHICH COULD BE SIGNIFICANT. DAMAGING WINDS CAN ALSO BE EXPECTED AS A RESULT OF HIGH MOMENTUM /35-50 KT/ FLOW IN THE LOWEST FEW KM AGL...IN COMBINATION WITH STEEP LOW-LEVEL LAPSE RATES. THE TORNADO THREAT IS LESS CERTAIN GIVEN THE LIMITED LOW-LEVEL HODOGRAPH CURVATURE...BUT A FEW TORNADOES WILL STILL BE POSSIBLE GIVEN THE LIKELIHOOD OF MULTIPLE SUPERCELLS OVER A BROAD AREA THIS AFTERNOON/EVENING. THUNDERSTORMS WILL ALSO SPREAD E OF THE APPALACHIANS LATE THIS AFTERNOON INTO TONIGHT AS THE SYNOPTIC SYSTEM PROGRESSES EWD/ESEWD. STRONG WIND PROFILES WILL CONTINUE...BUT LESSER INSTABILITY COMPARED TO AREAS W OF THE MOUNTAINS SHOULD RESULT IN A GRADUAL LESSENING OF THE DAMAGING WIND/HAIL THREAT OVERNIGHT TOWARD THE ATLANTIC COAST. THE SRN EXTENT OF THE SEVERE STORM THREAT IS SOMEWHAT UNCERTAIN. DEEP-LAYER VERTICAL SHEAR WILL BE VERY STRONG BENEATH THE JET CORE AS FAR S AS NRN AL...WHERE BOUNDARY LAYER DEWPOINTS SHOULD REMAIN NEAR 60 F. MIDLEVEL LAPSE RATES WILL BE MUCH LESS FAVORABLE COMPARED TO AREAS FARTHER N...ON THE CYCLONIC SIDE OF THE JET...AND THIS WILL LIMIT CAPE. STILL...THE STRONG WIND PROFILES AND SUBSTANTIAL LOW-MIDLEVEL BUOYANCY COULD SUPPORT STORMS WITH DAMAGING WINDS. Link to comment Share on other sites More sharing options...
CranberryWX Posted March 23, 2011 Share Posted March 23, 2011 Warming up nicely here...currently partly cloudy, 70/55 with light SW wind. Band getting it's act together from Cleveland to Cincy...If that holds together it should be in WV in about 3 hours. Link to comment Share on other sites More sharing options...
yoda Posted March 23, 2011 Share Posted March 23, 2011 In regards to elevated instability, is there usually a hail limit as to how large the hail is that the storms can produce? For example, if a storm in WV in the unstable airmass is producing ping pong sized hail and it moves into an elevated instability airmass... will it keep that sized hail or will it slowly weaken? I hope my question makes sense Link to comment Share on other sites More sharing options...
Kmlwx Posted March 23, 2011 Share Posted March 23, 2011 In regards to elevated instability, is there usually a hail limit as to how large the hail is that the storms can produce? For example, if a storm in WV in the unstable airmass is producing ping pong sized hail and it moves into an elevated instability airmass... will it keep that sized hail or will it slowly weaken? I hoe my question makes sense I would think it would weaken but pea to nickel sized hail would remain possible. This is obviously not a scientific answer. Link to comment Share on other sites More sharing options...
eyewall Posted March 23, 2011 Share Posted March 23, 2011 I am rather frustrated that it has trended out of NC which makes sense with the horribly dry dewpoints here. Hopefully we get lucky but my prospects for a chase are not good. Link to comment Share on other sites More sharing options...
Kmlwx Posted March 23, 2011 Share Posted March 23, 2011 11z HRRR has a nice line before it gets into the LWX area. It weakens down to showers by the time it gets to us. Link to comment Share on other sites More sharing options...
CranberryWX Posted March 23, 2011 Share Posted March 23, 2011 CRW's Disco... Severe to occur later this afternoon after this first batch moves through late morning. NAM/GFS/HRRR MODELS INDICATE AN AREA OF SHOWERS/STORMS WILL DEVELOP TO OUR WEST LATER THIS MORNING...AND THEN MOVE EAST THRU THE LATE MORNING HOURS. IN ITS WAKE...THE AIRMASS IS EXPECTED TO RECOVER INTO THE AFTERNOON HOURS. WHILE THE AIRMASS WILL BECOME UNSTABLE...MODELS SOUNDINGS SUGGEST THERE WILL BE A MID-LEVEL CAP. THE COMBINATION OF DAYTIME HEATING AND UPPER LEVEL FORCING ASSOCIATED WITH FEATURE APPROACHING FROM THE WEST SHOULD RESULT IN THE CAP BREAKING AND THUNDERSTORMS DEVELOPING. SPC HAS A MODERATE RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING. APPEARS LARGE HAIL AND DAMAGING WINDS WILL BE THE MAIN THREAT. THEY EVEN INDICATE THAT SOME OF THE STORMS COULD BE PARTICULARLY DAMAGING WITH LARGE AMOUNTS OF HAIL. Link to comment Share on other sites More sharing options...
Kmlwx Posted March 23, 2011 Share Posted March 23, 2011 The 09z SREF run off of SPC website for 00z tonight. Still highlighting that high supercell parameter area. Link to comment Share on other sites More sharing options...
Avdave Posted March 23, 2011 Share Posted March 23, 2011 11z HRRR has a nice line before it gets into the LWX area. It weakens down to showers by the time it gets to us. what a suprise that is for us, LOL Link to comment Share on other sites More sharing options...
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