IWXwx Posted August 21, 2014 Share Posted August 21, 2014 I figured I'd start this thread to cover the severe and heavy rain threat over the next few days along the boundary. I maybe should have left the end date open, but used an arbitrary date, as the models keep pushing back the ridge breaking down. The first area of possible heavy rain is outlined below: MESOSCALE PRECIPITATION DISCUSSION 0305NWS WEATHER PREDICTION CENTER COLLEGE PARK MD544 AM EDT THU AUG 21 2014 AREAS AFFECTED...CENTRAL AND SOUTHERN MN...WESTERN AND SOUTHERNWI...NORTHEAST IA...NORTHERN IL...NORTHWEST IN CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE VALID 210940Z - 211400Z SUMMARY...TRAINING CONVECTION AND A FEW CELL-MERGERS WILL FOSTER AFLASH FLOOD THREAT THROUGH THE MID-MORNING HOURS.DISCUSSION...THE LATEST IR SAT IMAGERY SHOWS A COLD-TOPPED MCSIMPACTING CNTRL/SRN MN ATTM...WITH THE MCS BEGINNING TO ADVANCEESEWD TWD SERN MN. MEANWHILE...A NW/SE ORIENTED BAND OF ELEVATEDCONVECTION IS SEEN IMPACTING SWRN WI...WHICH IS CONNECTED TO AGRADUAL INCREASE IN WARM ADVECTION VIA A MOIST/UNSTABLE SWLY LOWLVL JET INVOF A FRONTAL ZONE. THIS DOWNSTREAM CONVECTION MAY WELLBE GETTING INFLUENCED TO A DEGREE BY A DEVELOPING MCV ASSOCD WITHTHE MN CONVECTIVE SYSTEM.OVER THE NEXT FEW HOURS...THE MCS OVER MN WILL ADVANCE ESEWD ALONGAND JUST NORTHEAST OF A WARM FRONT...WITH ADDITIONAL BANDS ORCLUSTERS OF CONVECTION EXPECTED TO ORGANIZE DOWNWIND OF THE MCSINVOLVING ESP SRN WI...NERN IL AND POSSIBLY FAR NWRN IN. THELATEST VAD WIND PROFILER DATA INDICATES 30 TO 40 KTS OF SWLY LOWLEVEL JET AND THIS WILL CONTINUE AT LEAST THROUGH ABOUT 12Z. THELARGER SCALE ENVIRONMENT WILL REMAIN CONDUCIVE FOR CELL MERGERSAND TRAINING GIVEN THE ORIENTATION OF THE ONGOING CONVECTION ANDEXPECTED PROPAGATION.THIS COUPLED WITH RAINFALL RATES OF UP TO 2 INCHES/HR WILL FAVORTHE POTENTIAL FOR FLASH FLOODING AT LEAST THROUGH THE MID-MORNINGHOURS. HOWEVER...THE LATEST HI-RES GUIDANCE INCLUDING THE 00ZNAM-CONEST AND 00Z NSSL-WRF WHICH BOTH HAVE A SOMEWHAT REASONABLEHANDLE ON THE MN MCS...SUGGEST THAT THE CONVECTION WILL TEND TOWEAKEN BEYOND 12Z. SO THE FLASH FLOOD THREAT SHOULD TEND TOCONTINUE FOR A FEW MORE HOURS AND THEN SUBSIDE. And today's slight risk. I'm thinking probs may be increased in later forecasts. I love summertime nocturnal MCS's. DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1233 AM CDT THU AUG 21 2014 VALID 211200Z - 221200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY TO THE OH VALLEY... ...SUMMARY... SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM PORTIONS OF THE UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY. DAMAGING WINDS AND LARGE HAIL ARE THE PRIMARY THREATS WITH THIS ACTIVITY. ...UPPER MS VALLEY/OH VALLEY... EARLY MORNING WV IMAGERY DEPICTS A TRANSITORY SHORT-WAVE TROUGH EJECTING EWD ACROSS THE CNTRL DAKOTAS. THIS FEATURE IS EXPECTED TO TOP THE RIDGE OVER THE UPPER MS VALLEY EARLY IN THE PERIOD BEFORE TURNING SEWD INTO THE UPPER GREAT LAKES REGION. CONSIDERABLE AMOUNT OF CONVECTION IS NOTED AHEAD OF THIS FEATURE AT MIDNIGHT FROM SERN ND INTO NCNTRL SD. THIS ACTIVITY SHOULD PROGRESS INTO SRN MN BY 12Z. LATEST MODEL GUIDANCE SUPPORTS THE PROGRESSION OF SHORT WAVE INTO MN BY DAYBREAK AND SFC WARM FRONT DRAPED ACROSS MN/SRN WI IS EXPECTED TO MOVE LITTLE THROUGH THE PERIOD. FOR THIS REASON EARLY MORNING THUNDERSTORMS WILL LIKELY NOT DISSIPATE PRIOR TO DIURNALLY-ENHANCED DESTABILIZATION. MODEST NWLY FLOW...ON THE ORDER OF 30KT AT 500MB...APPEARS ADEQUATE FOR UPWARD GROWTH OF TSTMS AS THEY TRACK ESEWD ALONG WARM FRONT. FORECAST SOUNDINGS SUGGEST MODERATE BUOYANCY WILL DEVELOP ACROSS MUCH OF THE WARM SECTOR FROM SERN SD INTO THE OH VALLEY WHERE SBCAPE SHOULD EASILY EXCEED 3000 J/KG. THERE IS SOME CONCERN THAT WARM FRONTAL CONVECTION COULD ORGANIZE INTO MORE EXPANSIVE THUNDERSTORM CLUSTERS THAT COULD SURGE SEWD INTO THE OH VALLEY DUE TO CONTRIBUTIONS OF FORWARD PROPAGATION. AT THIS TIME WILL ONLY INTRODUCE 15 PERCENT SEVERE PROBS FOR WIND AND HAIL AS IT/S NOT REAL CLEAR HOW THIS CONVECTION WILL ULTIMATELY EVOLVE. FARTHER WEST ACROSS THE CNTRL PLAINS...POST SHORT WAVE AIRMASS IS FORECAST TO DESTABILIZE SIGNIFICANTLY FROM SERN SD INTO ERN NEB WHERE SBCAPE COULD APPROACH 4000 J/KG. WV IMAGERY AND MODEL GUIDANCE DO NOT SUGGEST ANY MEANINGFUL DISTURBANCE INTO THIS REGION DURING THE AFTERNOON/EVENING HOURS. FOR THIS REASON IT APPEARS WEAK LOW LEVEL CONVERGENCE AND DIURNAL HEATING WILL BE THE PRIMARY MECHANISMS FOR POTENTIAL ISOLATED THUNDERSTORM DEVELOPMENT. WEAK WARM ADVECTION ATOP THE BOUNDARY LAYER MAY ALSO CONTRIBUTE TO ELEVATED CONVECTION AFTER DARK...MAINLY ACROSS IA. LARGE HAIL/GUSTY WINDS ARE THE MAIN THREATS WITH THIS ACTIVITY.[attachment=132938:day1otlk_1200.gif] Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 21, 2014 Share Posted August 21, 2014 Killer light show morning. Real classic summer feel. Gonna get rolled tonight. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 21, 2014 Share Posted August 21, 2014 areas in NE IL will easily see 4"+ from both events Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 21, 2014 Share Posted August 21, 2014 At roughly 1.25 inches so far....this next batch looks like it could dump another inch or so Link to comment Share on other sites More sharing options...
wisconsinwx Posted August 21, 2014 Share Posted August 21, 2014 Killer light show morning. Real classic summer feel. Gonna get rolled tonight. Tonight's action may well be too far north for you, but this first one sounds like a good deal. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 21, 2014 Share Posted August 21, 2014 Tonight's action may well be too far north for you, but this first one sounds like a good deal. you know i'm going to hedge south in this setup every time Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 21, 2014 Share Posted August 21, 2014 Too much festering convection back through iowa for the boundary to make major headway imo....i'm satisfied for the month storm-wise with what i got this morning...but i just don't see it budging much without a dominant mcs clearing the boundary for movement...we'll see how it shakes out Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 21, 2014 Share Posted August 21, 2014 Too much festering convection back through iowa for the boundary to make major headway imo....i'm satisfied for the month storm-wise with what i got this morning...but i just don't see it budging much without a dominant mcs clearing the boundary for movement...we'll see how it shakes out it will shoot up and convection will initiate north of us this evening but i think it sinks south with ease overnight Link to comment Share on other sites More sharing options...
Chitown Storm Posted August 21, 2014 Share Posted August 21, 2014 Moved from chitown up to beautiful St Paul,MN last week. Picked up a little under an inch of rain this morning. Blue skies taking shape now. If the sun stays out it's gonna get into the lower 90s here. There's talk of redeveloping storms this afternoon but quite dependent on where that boundary lies. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 21, 2014 Share Posted August 21, 2014 4km NAM with a classic urban flood event for NE IL Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 21, 2014 Share Posted August 21, 2014 hair under 3 inches this morning from roughly 3am to 8am ... bringing the boy to school revealed all retention ponds are pretty high locally, but the ground looks like it could still possibly soak up a little more rain. Anything moderate locally would prolly create some bigger problems than the minor nuisance problems this morning. a decent outflow boundary headed south and east just SW of QC...I'm sure it will mix out and be overcome throughout the day....but convection still festering through iowa and even into western northern IL Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 21, 2014 Share Posted August 21, 2014 Tonight's action may well be too far north for you you know i'm going to hedge south in this setup every time LOT: THE WESTERN WAVE OVER IA IS ONE OF A LITTLE MORE INTEREST AS THAT COMES EASTWARD. HIGH RESOLUTION MODELS HAVE A SURPRISINGLY LARGE SPREAD IN SOLUTIONS WITH THIS...WITH THE RAP BEING A FURTHER SOUTH ONE. RADAR AND SATELLITE TRENDS ARE SUPPORTING THIS HOWEVER. MKX: I AM THINKING I WILL BE SIGNIFICANTLY TAKING DOWN POPS ACROSS SOUTHERN WI FOR TONIGHT. Link to comment Share on other sites More sharing options...
wisconsinwx Posted August 21, 2014 Share Posted August 21, 2014 Well it turns out N Illinois' morning convection will screw everyone over since a cold pool has developed and even clearer areas have taken awhile to destabilize. Link to comment Share on other sites More sharing options...
daddylonglegs Posted August 21, 2014 Share Posted August 21, 2014 Some rain here..not as impressive as i thought it would be. Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 21, 2014 Share Posted August 21, 2014 84/75 filtered sunshine for about 45 minutes now... PWATS at or above 2 inches for a solid chunk of LOT disturbance in E Iowa looks to be moving into an area with minimal cap over N IL...at least per meso analysis Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 21, 2014 Share Posted August 21, 2014 Getting monsooned....just as school let out too lol and this from the WP regarding heavy rain this evening.... NWS WEATHER PREDICTION CENTER COLLEGE PARK MD259 PM EDT THU AUG 21 2014 AN ACTIVE CONVECTIVE PATTERN EXPECTED IN THE VICINITY OF A FRONTALBOUNDARY AND ASSOCIATED AXIS OF ABOVE AVERAGE PW VALUES---1 TO 2STANDARD DEVIATIONS ABOVE THE MEAN---STRETCHING FROM THE MID MSVALLEY/LOWER LAKES TOWARD THE UPPER MS VALLEY THIS PERIOD.CONFIDENCE HAS DECREASED WITH RESPECT TO THE DETAILS OF THE TIMINGOF AREAS OF CONVECTION AS THERE IS LARGE MODEL TO MODELDIFFERENCES AND LARGE RUN TO RUN DIFFERENCES---ESPECIALLY IN THEHI RES GUIDANCE WHICH OFTEN WILL DEPICT THESE ORGANIZED CONVECTIVEREGIONS BETTER. MOIST WEST SOUTHWESTERLY FLOW INTO THIS BOUNDARYAND ENHANCED UVVS ASSOCIATED WITH SHORTWAVES MOVING ALONG THESOUTHERN EDGE OF THE WESTERLIES WILL SUPPORT ADDITIONAL CONVECTIVEDEVELOPMENT ALONG THIS FRONT. THERE IS POTENTIAL FOR TRAINING OFCELLS IN A GENERAL WEST NORTHWEST TO EAST SOUTHEAST DIRECTION THISPERIOD---SUPPORTING HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS.ALONG WITH THE DIFFERENCES IN TIMING AMONG THE MODELS---THERE ISDIFFERENCES LATITUDE WISE WITH THE MAX QPF AXES. THE FARTHERSOUTHWARD OVERALL AXIS OF THE NAM WAS FAVORED -ALTHOUGH AMOUNTSWERE INCREASED GIVEN TRAINING POTENTIAL. WHILE THERE IS A LOT OFDIFFERENCES IN QPF AXES---THERE IS A SIGNAL FOR POTENTIAL OF VERYHEAVY RAINFALL TOTALS IN THE HI RES GUIDANCE. IN AREAS OFTRAINING---ISOLATED TOTALS OF 1-2"+ IN AN HOUR AND TOTALS OF 3-5"+POSSIBLE. also... Rick regarding next week potential... TUESDAY NIGHT THROUGH THURSDAY...SPREAD INCREASES ON THE ENSEMBLES AND OPERATIONAL MODELS WITHRESPECT TO SPEED AT WHICH DEEP UPPER TROUGH AND ASSOCIATED SURFACELOW DIG INTO GREAT LAKES REGION. HAVE CONCERN IN THIS PERIOD EVENTHIS FAR OUT FOR HEAVY RAIN/FLOODING POTENTIAL...AS POSITION OF CWABETWEEN DEEP UPSTREAM TROUGH AND STRONG DOWNSTREAM RIDGE IS ASYNOPTICALLY FAVORABLE SET-UP FOR STRONG LLJ/MOISTURE TRANSPORT.PWAT VALUES COULD NEAR 2 INCHES. INCREASED FLOW ALOFT WILL ALSORESULT IN INCREASED DEEP LAYER SHEAR SUPPORTIVE OF STRONG/SEVERESTORMS PENDING MESOSCALE COMING TOGETHER. 12Z ECMWF IS ACTUALLY ONFASTER END OF SPECTRUM COMPARED TO GFS AND ENSEMBLE MEAN WITHPROGRESSION OF SYSTEM...SO GENERALLY MAINTAINED CHANCE POPS FROMBLENDED GUIDANCE DUE TO UNCERTAINTY. TEMPERATURES WEDNESDAY WILL BEDICTATED BY TIMING...AS UPSTREAM AIR MASS IS MUCHCOOLER...ESPECIALLY ON LATEST ECMWF. THURSDAY TEMPS COULD RANGE FROMNEAR TO SLIGHTLY BELOW SEASONABLE TO WELL BELOW NORMAL...BUT DID NOTSTRAY AWAY FROM SMART BLEND. Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 21, 2014 Share Posted August 21, 2014 sun is back out again.... decent 850 feed right into the region where those storms are in southeast LOT Link to comment Share on other sites More sharing options...
IWXwx Posted August 21, 2014 Author Share Posted August 21, 2014 Still looking to get waylaid later. Link to comment Share on other sites More sharing options...
Chicago WX Posted August 21, 2014 Share Posted August 21, 2014 Still looking to get waylaid later. Good luck. You and Jim may have a bit of fun this evening. Dark dark skies to the north, from my vantage point right now. No action locally, but you know... Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 22, 2014 Share Posted August 22, 2014 Good luck. You and Jim may have a bit of fun this evening. Dark dark skies to the north, from my vantage point right now. No action locally, but you know... was wonder when one of you two would drop in Link to comment Share on other sites More sharing options...
Powerball Posted August 22, 2014 Share Posted August 22, 2014 Impressive amount of lightning with those storms... Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 22, 2014 Share Posted August 22, 2014 so close for LAF, either way it's probably a great light show Link to comment Share on other sites More sharing options...
Chicago WX Posted August 22, 2014 Share Posted August 22, 2014 so close for LAF, either way it's probably a great light show Yeah, nice lightning show. And kind of a strange yellowish sky. Shame it'll just miss here, by the slimmest of margins. Nice reflectivity on this cell. Link to comment Share on other sites More sharing options...
Gilbertfly Posted August 22, 2014 Share Posted August 22, 2014 850 transport starting to get cooking into northern mizzu...pwats hitting 2.2 there Link to comment Share on other sites More sharing options...
cyclone77 Posted August 22, 2014 Share Posted August 22, 2014 Some broad rotation on the cell right over LAF. I'd be watching that a bit in case it decides to tighten up. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 22, 2014 Share Posted August 22, 2014 talk about a graze job Link to comment Share on other sites More sharing options...
Powerball Posted August 22, 2014 Share Posted August 22, 2014 talk about a graze job More like a split job for the south/west side of LAF. Another cell is going to merge with the line just to the SW of town. Link to comment Share on other sites More sharing options...
Chicago WX Posted August 22, 2014 Share Posted August 22, 2014 Car alarms going off...quality thunder. Best of the year here, easily. I tried to take some video of the light show, but it turned out to be lame. The tail end of the video, where one hit pretty close, made me jump a bit though. Link to comment Share on other sites More sharing options...
cyclone77 Posted August 22, 2014 Share Posted August 22, 2014 Meanwhile upstream over Iowa...crickets. SPC dropped much of the slight risk west of the Indiana action. Link to comment Share on other sites More sharing options...
Chicago WX Posted August 22, 2014 Share Posted August 22, 2014 More like a split job for the south/west side of LAF. Another cell is going to merge with the line just to the SW of town. Yeah, I'm gonna get in on the SW merging cell. And it's pouring buckets. Awesome. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.