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April 24 severe obs/discussion


Riptide

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SPC AC 241245

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0745 AM CDT SUN APR 24 2011

VALID 241300Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS THROUGH TONIGHT FROM CENTRAL/N

TX AND SE OK ENEWD TO THE MID ATLANTIC...

...SYNOPSIS...

NO MAJOR CHANGES TO PREVIOUS OUTLOOK. A QUASI-STATIONARY FRONT WILL

REMAIN THROUGH THE PERIOD FROM CENTRAL/N CENTRAL TX NEWD TO THE OH

VALLEY. ALOFT...A BELT OF MODERATE SWLY FLOW WILL BE MAINTAINED

OVER THE FRONT FROM THE SRN PLAINS TO THE OH VALLEY AND NE

STATES...DOWNSTREAM FROM A TROUGH THAT WILL MOVE EWD FROM UT/AZ THIS

MORNING TO THE SRN HIGH PLAINS BY EARLY MONDAY. THE FRONT HAS BEEN

AUGMENTED BY MULTIPLE CONVECTIVE CLUSTERS DURING THE PAST 24

HOURS...AND CONVECTIVE OUTFLOWS WILL KEEP THE EFFECTIVE FOCUS FOR

NEW SURFACE-BASED CONVECTION A LITTLE S OF THE FORECAST POSITION OF

THE SYNOPTIC FRONT ACROSS THE OH VALLEY REGION.

...AR/SE OK/N TX AREA THROUGH TONIGHT...

WIDESPREAD ELEVATED THUNDERSTORMS NE OK THIS MORNING WILL LIKELY

PERSIST THROUGH THE DAY AND SPREAD EWD/DEVELOP SWD AND REINFORCE THE

FRONT FROM NRN AR INTO N TX. ISOLATED LARGE HAIL WILL BE POSSIBLE

WITH THE STRONGEST ELEVATED CONVECTION. S OF THE FRONT...A FEED OF

MID 60S TO LOW 70S BOUNDARY LAYER DEWPOINTS WILL CONTINUE ACROSS TX

AND THE LOWER MS VALLEY. SIMILAR TO THE PAST COUPLE OF DAYS...THE

RELATIVELY SHALLOW NATURE OF THE MARINE BOUNDARY LAYER WILL ALLOW

SOME INLAND MIXING OF MOISTURE DURING THE AFTERNOON...BUT AT LEAST

MID 60S DEWPOINTS WILL HOLD IN THE ZONE OF LOW-LEVEL

CONVERGENCE/ASCENT ALONG THE STALLED FRONT. THIS MOISTURE WILL BE

OVERSPREAD BY AN EML WITH MIDLEVEL LAPSE RATES AOA 7.5

C/KM...ESPECIALLY OVER SW AR/SE OK/N TX PORTION OF THE OUTLOOK AREA.

THE NET RESULT WILL BE ANOTHER DAY OF MLCAPE IN THE 2500-3500 J/KG

RANGE ALONG AND IMMEDIATELY SE OF THE FRONT.

THE MODERATE-STRONG INSTABILITY AND EFFECTIVE BULK SHEAR OF 40-50 KT

WILL AGAIN SUPPORT SUPERCELLS IN BROKEN BANDS ALONG THE FRONT THIS

AFTERNOON/EVENING...WITH CONVECTION AGAIN LIKELY TO TRAIN ALONG THE

BOUNDARY. THE DRYLINE WILL BE SUPPRESSED SWD INTO EDWARDS PLATEAU

REGION OF TX. AT LEAST ISOLATED THUNDERSTORM DEVELOPMENT WILL BE

POSSIBLE ON THE DRYLINE...BUT THE MORE WIDESPREAD CONVECTION WILL

AGAIN DEVELOP NEAR AND NE OF THE TRIPLE POINT ALONG THE STATIONARY

FRONT. LARGE HAIL WILL BE THE PRIMARY SEVERE THREAT...SOME OF WHICH

COULD BE VERY LARGE...AND DAMAGING WINDS WILL ALSO BE POSSIBLE. THE

TORNADO THREAT APPEARS TO BE RELATIVELY GREATER ALONG THE AR/SE OK/N

TX PORTION OF THE FRONT WHERE LOW-LEVEL MOISTURE AND SHEAR ARE

EXPECTED TO BE MAXIMIZED /0-1 KM SRH OF 150-200 M2 PER S2/.

...OH VALLEY INTO THE MID ATLANTIC THROUGH TONIGHT...

THE SYNOPTIC FRONT IS LOCATED N OF THE OH RIVER...WHILE A COUPLE OF

WEAKENING/DISSIPATING CONVECTIVE CLUSTERS ARE LOCATED S OF THE FRONT

FROM WV TO CENTRAL KY. OUTFLOW WITH THIS CONVECTION...ALONG WITH

REMNANT MCV/S AND DAYTIME HEATING IN CLOUD BREAKS...WILL SUPPORT

ADDITIONAL THUNDERSTORM DEVELOPMENT TODAY ALONG THE SAME CORRIDOR AS

THE PAST TWO DAYS. ASIDE FROM LOCALLY HEAVY RAINFALL...ISOLATED

DAMAGING WINDS WILL BE THE PRIMARY CONCERN WITH STORM CLUSTERS

MOVING ALONG THE FRONT/OUTFLOWS...WITHIN A BELT OF 500-1500 J/KG

MLCAPE AND THE SRN FRINGE OF THE STRONGER MIDLEVEL FLOW.

day1otlk_1300.gif

Looks promising? Don't remember the last time there was such a potent stationary front in the area.

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.NEAR TERM /THROUGH TONIGHT/...

-- Changed Discussion --IN TERMS OF THE SYNOPTIC SCALE IT IS ABOUT THE SAME SITUATION AS

YESTERDAY. ACROSS THE MID-ATLANTIC HOWEVER...MUCH LESS CLOUD

COVER...WE GOT A HEAD START ON TEMPS THAT ONLY DROPPED INTO THE

60S AND THERE IS A BETTER CHANCE OF CONVECTIVE ACTIVITY LATER

TODAY. AT THIS HR...TEMPS ARE ALREADY CLIMBING INTO THE 70S /WHICH

WERE YESTERDAYS HIGHS/ A WILL KEEP RISING UNTIL REACHING THE

L-M80S THIS AFTN.

ONE OF THE MANY MCS IMPULSES THAT HAVE TRUDGED ACROSS THE OHIO RVR

VLY IN THE PAST COUPLE OF DAYS IS NOW ALMOST COMPLETELY

DISSIPATING AS IT REACHES THE POTOMAC HIGHLANDS. SEVERAL MORE ARE

ON THEIR WAY TAKING NEARLY THE SAME PATH. ONE BACK IN CNTRL KY IS

DYING-OFF WELL BEFORE IT EVEN REACHES THE CNTRL APLCNS. THE COLD

FRONT HAS NOW BECOME ALMOST STATIONARY ACROSS THE I-70 CORRIDOR

FROM INDIANA TO CNTRL PA. UPPER LEVEL STEERING CURRENTS ARE AGAIN

WSWLY AS A LONGWAVE UPPER TROUGH TRIES TO EXIT THE ROCKIES AND

JOIN UP W/ AN UPPER WAVE OVER S CNTRL CANADA /BY EARLY THIS COMING

WEEK/.

UNTIL THEN...THIS NEARLY ZONAL UPPER FLOW WILL DIRECT THESE SMALL-

SCALE IMPULSES AND KINKS IN THE FLOW ACROSS THE OHIO VLY. MANY OF

THESE DISSIPATING UPON ENTRY TO THE MID ATLC BUT TODAY...WE WILL

SEE A BETTER CHANCE FOR PIECES OF THIS ACTIVITY TO AFFECT OUR

REGION IN THE FORM MORE DISCRETE CELLS...POSSIBLY BECOMING BETTER

ORGANIZED INTO THE MCS/BOWING SEGMENTS AS THE DAY PROGRESSES.-- End Changed Discussion --

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Not terribly impressed.. we'll see. We currently have some cin in the mixed layer, on days like this we need a good trigger. Though some stuff did roll through y-day. I think in this case we might need to get into evening to try to erode some capping.

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Not terribly impressed.. we'll see. We currently have some cin in the mixed layer, on days like this we need a good trigger. Though some stuff did roll through y-day. I think in this case we might need to get into evening to try to erode some capping.

SPC mesoanalysis shows little... but agree with you on the trigger. MLCAPE is 500, SBCAPE 1000-1500... LI's are actually ok this time around -3 to -5 and ML Lapse Rates are 6-7C/KM... we shall see

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SPC mesoanalysis shows little... but agree with you on the trigger. MLCAPE is 500, SBCAPE 1000-1500... LI's are actually ok this time around -3 to -5 and ML Lapse Rates are 6-7C/KM... we shall see

There's a little vort max moving toward wva now, so it could be enough. Usually these fresh warm days are harder as it's also still warming aloft. Tomorrow's prob one of those days that has great CAPE etc but a strongish cap. Hopefully we'll get a little action today... last night over-performed locally by at least .5%. ;)

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Md out... watch possible

http://www.spc.noaa..../md/md0549.html

MESOSCALE DISCUSSION 0549

NWS STORM PREDICTION CENTER NORMAN OK

0112 PM CDT SUN APR 24 2011

AREAS AFFECTED...SERN PA...NJ...DE...MD...NRN VA...WASHINGTON DC

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 241812Z - 241945Z

PORTIONS OF SERN PA...NJ...DE...MD...NRN VA...AND WASHINGTON DC ARE BEING MONITORED FOR THUNDERSTORM INITIATION AND SUBSEQUENT INCREASE IN SVR WEATHER POTENTIAL/POSSIBLE WW ISSUANCE THIS AFTERNOON.

MESOANALYSIS INDICATES A COLD FRONT WAS LOCATED FROM SERN NY WSW ACROSS CNTRL/SRN PA AND INTO THE OH VALLEY REGION AT 18Z. TEMPERATURES S OF THE FRONT ARE WARMING INTO THE 70S AND 80S...WHICH IS AIDING IN STEEPENING LOW-LEVEL LAPSE RATES AND BOUNDARY LAYER DESTABILIZATION. IN ADDITION...AXIS OF LOW 60S DEWPOINTS EXTENDS NWD INTO THE MID ATLANTIC REGION...WHICH IS AIDING IN WEAK TO MODERATE INSTABILITY...WITH MLCAPE VALUES EXPECTED TO PEAK AROUND 500-1500 J/KG DURING THE AFTERNOON. THOUGH UPPER-LEVEL SUPPORT FOR ADDITIONAL AIRMASS DESTABILIZATION IS GENERALLY LACKING...COMBINATION OF CONTINUED SURFACE HEATING...CONVERGENCE/ASCENT ALONG THE COLD FRONT...AND VERTICAL MOTION FIELDS ASSOCIATED WITH APPROACHING MCV OVER SERN OH/NRN WV MAY AID IN THUNDERSTORM INITIATION DURING THE NEXT FEW HOURS. VWP WIND PROFILES AND RUC FORECAST SOUNDINGS INDICATE THAT VERTICAL WIND SHEAR IS FAVORABLE FOR BOTH SUPERCELLS AND FAST MOVING LINE SEGMENTS. THE PRIMARY THREAT ASSOCIATED WITH ANY SVR STORM ACTIVITY WILL LIKELY BE DAMAGING WINDS...THOUGH ISOLATED LARGE HAIL AND A TORNADO CANNOT BE RULED OUT. ..GARNER.. 04/24/2011

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0-6km shear and effective bulk shear are both 40-50 kts... so we are good there. Per the 1800z SPC meso, looks like the CIN is gone west of I95 and MLCAPE is up to 1000 in N VA and SBCAPE between 1000-1500. LI's -4 to -5, ML Lapse rates ~6.5 C/KM and LL lapse rates are ~ 8 C/KM.

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Party has started:

BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

314 PM EDT SUN APR 24 2011

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

NORTHEASTERN PAGE COUNTY IN NORTHWEST VIRGINIA...

NORTH CENTRAL RAPPAHANNOCK COUNTY IN NORTHWEST VIRGINIA...

NORTHWESTERN FAUQUIER COUNTY IN NORTHERN VIRGINIA...

WARREN COUNTY IN NORTHWEST VIRGINIA...

EAST CENTRAL SHENANDOAH COUNTY IN NORTHWEST VIRGINIA...

CITY OF WINCHESTER IN NORTHWEST VIRGINIA...

CLARKE COUNTY IN NORTHWEST VIRGINIA...

WESTERN LOUDOUN COUNTY IN NORTHERN VIRGINIA...

SOUTHERN JEFFERSON COUNTY IN THE PANHANDLE OF WEST VIRGINIA...

SOUTHEASTERN FREDERICK COUNTY IN NORTHWEST VIRGINIA...

* UNTIL 400 PM EDT

* AT 312 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN

EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING

FROM GREENWOOD TO 7 MILES SOUTHWEST OF STEPHENS CITY TO 12 MILES

SOUTHWEST OF FRONT ROYAL...AND MOVING EAST AT 35 MPH.

* LOCATIONS IMPACTED INCLUDE...

FRONT ROYAL...

BERRYVILLE...

NEERSVILLE...

ROUND HILL...

BLUEMONT...

PURCELLVILLE...

DELAPLANE...

ST. LOUIS...

THE PLAINS...

LAT...LON 3929 7757 3885 7777 3881 7845 3921 7821

TIME...MOT...LOC 1914Z 268DEG 31KT 3919 7808 3901 7825

3883 7836

$$

BAJ

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BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

336 PM EDT SUN APR 24 2011

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

SOUTHERN FREDERICK COUNTY IN NORTH CENTRAL MARYLAND...

WESTERN MONTGOMERY COUNTY IN CENTRAL MARYLAND...

NORTH CENTRAL FAUQUIER COUNTY IN NORTHERN VIRGINIA...

EAST CENTRAL CLARKE COUNTY IN NORTHWEST VIRGINIA...

LOUDOUN COUNTY IN NORTHERN VIRGINIA...

SOUTHEASTERN JEFFERSON COUNTY IN THE PANHANDLE OF WEST VIRGINIA...

NORTH CENTRAL FAIRFAX COUNTY IN NORTHERN VIRGINIA...

* UNTIL 415 PM EDT

* AT 333 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DESTRUCTIVE WINDS

IN EXCESS OF 70 MPH. THESE STORMS WERE LOCATED ALONG A LINE

EXTENDING FROM 7 MILES WEST OF NEERSVILLE TO BLUEMONT TO 11 MILES

WEST OF ST. LOUIS...AND MOVING EAST AT 45 MPH.

* LOCATIONS IMPACTED INCLUDE...

ST. LOUIS...

PURCELLVILLE...

BRUNSWICK...

POINT OF ROCKS...

OATLANDS...

LEESBURG...

LANSDOWNE...

BROADLANDS...

BRAMBLETON...

POOLESVILLE...

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Damn, wild storm just rolled in to the burg. Saw that mini line on the wV-Va border and was heading this way. Awesome clouds as I was cutting the front yard and finishing up, felt the outflow boundary and then nailed us with some heavy rains and thunder and lightning.

Nice bow on the radar before it came into Leesburg

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