yoda Posted June 21, 2016 Share Posted June 21, 2016 Area Forecast DiscussionNational Weather Service Baltimore MD/Washington DC947 AM EDT TUE JUN 21 2016.SYNOPSIS...A cold front over the eastern Great Lakes will move through theMid Atlantic states this afternoon and evening. High pressure willpass to the north Wednesday. Low pressure will track to the northof the region Thursday. High pressure will return for the weekend.&&.NEAR TERM /UNTIL 6 PM THIS EVENING/...12Z surface analysis showed low pressure over Quebec with anattendant cold front extending from New England southeast acrossfar southern Pennsyvlania into southern Ohio. This will descendinto the northern part of our forecast area later thisafternoon/this evening. Temperatures will warm to around90...hence there will be plenty of low level energy/CAPE. Thewesterly flow which was thought could temper convectivedevelopment does not look as significant today...with more of asoutherly component than expected. This is happening due to a veryweak surface wave which is developing along the front...causing itto slow its approach just to our north. Thus...our convectiveexpectations have increased. The slowly approaching boundary willprovide a focus for afternoon convection...with DC/Balt areasbeing the most likely target. Helicity is marginal but winds aloftare strong. SPC has placed DC...MD south of Baltimore...much ofeastern WV and almost all of the LWX part of VA in slight risk.Strong winds and large hail are the most prominent concerns. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted June 21, 2016 Share Posted June 21, 2016 ^posted just as winds shift to the west on the latest rounds of obs Link to comment Share on other sites More sharing options...
mappy Posted June 21, 2016 Share Posted June 21, 2016 Ian Link to comment Share on other sites More sharing options...
Kmlwx Posted June 21, 2016 Share Posted June 21, 2016 12z NAM 4km is tasty with supercell composite parameter this afternoon. It kind of has a DC split, though... Link to comment Share on other sites More sharing options...
Eskimo Joe Posted June 21, 2016 Share Posted June 21, 2016 Looks like the front has settled somewhere between I-70 and the Mason-Dixon Line. Link to comment Share on other sites More sharing options...
osfan24 Posted June 21, 2016 Share Posted June 21, 2016 Firing up in a big way already in SW PA. Looks like game on. Link to comment Share on other sites More sharing options...
Kmlwx Posted June 21, 2016 Share Posted June 21, 2016 Mesoanalysis already has 1500-2500 SBCAPE depending on your location. MLCAPE of about 1500 for most of us. Pocket of 1000 DCAPE also showing up. Link to comment Share on other sites More sharing options...
yoda Posted June 21, 2016 Share Posted June 21, 2016 12z NAM 4km is tasty with supercell composite parameter this afternoon. It kind of has a DC split, though... at the soundings just east of DC at 21z on the 12z 4km NAM Link to comment Share on other sites More sharing options...
Kmlwx Posted June 21, 2016 Share Posted June 21, 2016 at the soundings just east of DC at 21z on the 12z 4km NAM You using pivotal? Link to comment Share on other sites More sharing options...
yoda Posted June 21, 2016 Share Posted June 21, 2016 You using pivotal? Yes, thats the only place I can find that has soundings on the 4km NAM Link to comment Share on other sites More sharing options...
high risk Posted June 21, 2016 Share Posted June 21, 2016 given that storms have fired in southern PA, sufficient cape and instability are already in place across our area, and the hi-res guidance shows an early show, I expect a mesoscale discussion before noon and a blue box soon thereafter Link to comment Share on other sites More sharing options...
Eskimo Joe Posted June 21, 2016 Share Posted June 21, 2016 given that storms have fired in southern PA, sufficient cape and instability are already in place across our area, and the hi-res guidance shows an early show, I expect a mesoscale discussion before noon and a blue box soon thereafter Would like to see te clouds thin a bit more in MD/VA and the southerly component return to the winds. Link to comment Share on other sites More sharing options...
mappy Posted June 21, 2016 Share Posted June 21, 2016 given that storms have fired in southern PA, sufficient cape and instability are already in place across our area, and the hi-res guidance shows an early show, I expect a mesoscale discussion before noon and a blue box soon thereafter Wouldn't a watch at noon be kind of late? The stuff coming out of PA is the main line, right? Link to comment Share on other sites More sharing options...
yoda Posted June 21, 2016 Share Posted June 21, 2016 12z 4km NAM though has SBCAPE nearing 5000 at 21z today at KDCA Link to comment Share on other sites More sharing options...
high risk Posted June 21, 2016 Share Posted June 21, 2016 There could be a couple of rounds, but you are right that this line is likely the primary show. Given that it's not yet severe, and the parameters are still ramping up, I would expect gradual intensification instead of explosive intensification, so that's why I'm assuming that there isn't a need to issue right this second. I'm going with the idea of SPC first issuing the "watch likely" MD soon with the box coming out 30 minutes or so later. Wouldn't a watch at noon be kind of late? The stuff coming out of PA is the main line, right? Link to comment Share on other sites More sharing options...
mappy Posted June 21, 2016 Share Posted June 21, 2016 There could be a couple of rounds, but you are right that this line is likely the primary show. Given that it's not yet severe, and the parameters are still ramping up, I would expect gradual intensification instead of explosive intensification, so that's why I'm assuming that there isn't a need to issue right this second. I'm going with the idea of SPC first issuing the "watch likely" MD soon with the box coming out 30 minutes or so later. Ahh, okay... that makes sense. I probably shouldn't expect severe stuff up this way. Better chance for you southerners as the storms move over the better parameters. Thanks for the explanation! Link to comment Share on other sites More sharing options...
Ian Posted June 21, 2016 Author Share Posted June 21, 2016 Decent chance we jakcpot around here today. Partly time!!! Link to comment Share on other sites More sharing options...
mappy Posted June 21, 2016 Share Posted June 21, 2016 Link to comment Share on other sites More sharing options...
Ian Posted June 21, 2016 Author Share Posted June 21, 2016 Jakcpot. I can't spell for ish. Link to comment Share on other sites More sharing options...
H2O Posted June 21, 2016 Share Posted June 21, 2016 Ian storm :Wes snow storm when one speaks, i listen Link to comment Share on other sites More sharing options...
Kmlwx Posted June 21, 2016 Share Posted June 21, 2016 Ian is just trying to get as many of us on the bus so he can drive it off a cliff with us all on board. Link to comment Share on other sites More sharing options...
eurojosh Posted June 21, 2016 Share Posted June 21, 2016 Decent chance we jakcpot around here today. Partly time!!! Are we buying in to the 17z round or the 22z round? Link to comment Share on other sites More sharing options...
Ian Posted June 21, 2016 Author Share Posted June 21, 2016 Are we buying in to the 17z round or the 22z round? HRRR seems to be a bit fast with the 'first round' but I think you have to probably favor that to be the most intense. Link to comment Share on other sites More sharing options...
Kmlwx Posted June 21, 2016 Share Posted June 21, 2016 SARS hail parameter decent on mesoanalysys just to the NW Link to comment Share on other sites More sharing options...
NinjaWarrior2 Posted June 21, 2016 Share Posted June 21, 2016 Storm near Mercersburg PA looks like it could turn severe. Meanwhile 89 at DCA and BWI, fuel this afternoon. Link to comment Share on other sites More sharing options...
high risk Posted June 21, 2016 Share Posted June 21, 2016 damn! missed by one minute. given that storms have fired in southern PA, sufficient cape and instability are already in place across our area, and the hi-res guidance shows an early show, I expect a mesoscale discussion before noon and a blue box soon thereafter Link to comment Share on other sites More sharing options...
salseneca Posted June 21, 2016 Share Posted June 21, 2016 Severe box around Hagerstown just popped up. Link to comment Share on other sites More sharing options...
eurojosh Posted June 21, 2016 Share Posted June 21, 2016 MESOSCALE DISCUSSION 1002NWS STORM PREDICTION CENTER NORMAN OK1100 AM CDT TUE JUN 21 2016AREAS AFFECTED...PARTS OF SRN PENNSYLVANIA/NEWJERSEY...MARYLAND/DELAWARE AND NRN VIRGINIACONCERNING...SEVERE POTENTIAL...WATCH LIKELYVALID 211600Z - 211730ZPROBABILITY OF WATCH ISSUANCE...80 PERCENTSUMMARY...INCREASING AND INTENSIFYING THUNDERSTORM ACTIVITY ISEXPECTED ACROSS THE REGION...INCLUDING THE WASHINGTON D.C./BALTIMOREMETRO AREAS...BY MID AFTERNOON. A SEVERE WEATHER WATCH IS LIKELYWITHIN THE NEXT HOUR OR TWO.DISCUSSION...THUNDERSTORMS HAVE INITIATED ALONG THE EASTERN SLOPESOF THE ALLEGHENY MOUNTAINS...NEAR A SURFACE FRONT ACROSS SOUTHERNPENNSYLVANIA...SOUTHWARD INTO PARTS OF NORTHWESTERN VIRGINIA. ADIVERGENT UPPER FLOW FIELD ON THE SOUTHERN PERIPHERY OF A BROADCLOSED LOW CENTERED NEAR HUDSON BAY APPEARS TO BE SUPPORTINGACTIVITY...WHICH IS EXPECTED TO GRADUALLY INCREASE WHILE PROPAGATINGOFF THE HIGHER TERRAIN BETWEEN NOW AND 17-19Z.A MOIST BOUNDARY LAYER /CHARACTERIZED BY SURFACE DEW POINTS OF 70F+/ACROSS MUCH OF NORTHERN VIRGINIA INTO NORTHERN MID ATLANTIC COASTALAREAS IS DESTABILIZING WITH INSOLATION...WITH MIXED LAYER CAPEALREADY ESTIMATED ON THE ORDER OF 1500-2000 J/KG AND LOCALLY HIGHER.ALTHOUGH LOW/MID-LEVEL THERMAL LAPSE RATES ARE NOT PARTICULARLYSTEEP...SEASONABLY HIGH MOISTURE CONTENT PROBABLY WILL BECOMEINCREASING CONDUCIVE TO POTENTIAL FOR WET DOWNBURSTS WITH FURTHERBOUNDARY LAYER HEATING THIS AFTERNOON.BENEATH 40-50 KT WEST NORTHWESTERLY 500 MB FLOW...VERTICAL SHEARAPPEARS MORE THAN SUFFICIENT FOR ORGANIZED CONVECTION. THIS MAYINCLUDE ISOLATED SUPERCELLS...WITH AT LEAST SOME POTENTIAL FORSEVERE HAIL. THE EVOLUTION OF AN UPSCALE GROWING MESOSCALECONVECTIVE SYSTEM SEEMS POSSIBLE...WHICH COULD BE ACCOMPANIED BYBROADER-SCALE DAMAGING WIND GUST POTENTIAL ACROSS THECHESAPEAKE/DELMARVA PENINSULA AREA BY LATE AFTERNOON. Link to comment Share on other sites More sharing options...
mappy Posted June 21, 2016 Share Posted June 21, 2016 Jakcpot. I can't spell for ish. it happens. you guys should do well. not sure i'll see anything severe. enjoy! Link to comment Share on other sites More sharing options...
AmericanWxFreak Posted June 21, 2016 Share Posted June 21, 2016 may SPC go ENH? Link to comment Share on other sites More sharing options...
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