735  
AWUS01 KWNH 282212  
FFGMPD  
NMZ000-AZZ000-290410-  
 
MESOSCALE PRECIPITATION DISCUSSION 0074  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
510 PM EST WED FEB 28 2024  
 
AREAS AFFECTED...SOUTH-CENTRAL TO SOUTHEAST AZ...SOUTHWEST NM  
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE  
 
VALID 282210Z - 290410Z  
 
SUMMARY...SCATTERED BANDS OF HEAVY SHOWERS AND THUNDERSTORMS WITH  
LOCALLY HEAVY RAINFALL RATES MAY FOSTER AN ISOLATED CONCERN FOR  
RUNOFF PROBLEMS AND FLASH FLOODING GOING INTO THE EVENING HOURS.  
 
DISCUSSION...THE LATEST GOES-W VISIBLE SATELLITE IMAGERY IN  
CONJUNCTION WITH DUAL-POL RADAR HAS BEEN SHOWING AN UPTICK IN THE  
COVERAGE OF CONVECTION ACROSS AREAS OF SOUTH-CENTRAL TO SOUTHEAST  
AZ. A RELATIVELY STRONG AND COMPACT MID-LEVEL LOW CENTER/TROUGH IS  
SEEN GRADUALLY EJECTING EAST-NORTHEAST OUT OF FAR NORTHWEST  
MEXICO, AND STRONG DYNAMICAL FORCING/DIVERGENT FLOW ALOFT COUPLED  
WITH THE DIURNAL HEATING CYCLE HAS BEEN FAVORING THE EXPANSION OF  
CONVECTION AND INCREASE IN RAINFALL RATES OVER THE LAST COUPLE OF  
HOURS.  
 
MLCAPE VALUES ACROSS SOUTHERN AZ HAVE RISEN TO AS MUCH AS 500  
J/KG, AND THERE ARE POCKETS OF LOCALLY STRONGER MOISTURE  
CONVERGENCE IN PLACE THAT ARE SEEN HELPING TO FACILITATE SOME  
LOOSELY ORGANIZED BANDS OF CONVECTION AROUND THE EASTERN FLANK OF  
THE MID-LEVEL LOW CENTER. THE VISIBLE SATELLITE IMAGERY DOWNSTREAM  
OF THE CURRENT ACTIVITY INVOLVING ESPECIALLY SOUTHEAST AZ HAS BEEN  
REFLECTING AN INCREASINGLY AGITATED CU/TCU FIELD, AND THIS IS  
REFLECTIVE OF THE INCREASE IN DIURNALLY ENHANCED BOUNDARY LAYER  
INSTABILITY.  
 
DESPITE THE DRY BOUNDARY LAYER PROFILES, THE 12Z/18Z HREF GUIDANCE  
SUPPORTS SOME LOCALIZED 20 TO 30 PERCENT PROBABILITIES OF SEEING  
1"+/HOUR RAINFALL RATES WITH SOME OF THE STRONGER CONVECTIVE CELLS  
GOING THROUGH THE 00Z TO 03Z TIMEFRAME. THE HEAVIEST RATES SHOULD  
TEND GRADUALLY SHIFT FROM SOUTH-CENTRAL AZ INTO SOUTHEAST AZ AND  
SOUTHWEST NM THROUGH EARLY THIS EVENING. GIVEN SOME OF THE UPTICK  
IN CONVECTIVE ORGANIZATION AND BANDED STRUCTURES, SOME SPOTTY  
STORM TOTAL AMOUNTS OF 1.5 TO 2.5 INCHES CANNOT BE RULED OUT IN AT  
LITTLE AS 2 TO 3 HOURS.  
 
THESE RAINFALL AMOUNTS MAY CAUSE SOME ISOLATED CONCERNS FOR RUNOFF  
PROBLEMS AND FLASH FLOODING, WITH THE NORMALLY DRY WASHES/ARROYOS  
IN THIS CASE BEING THE MORE SENSITIVE AREAS TO CLOSELY MONITOR.  
 
ORRISON  
   
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC...  
 
ATTN...RFC...CBRFC...WGRFC...NWC...  
 
LAT...LON 33760861 33240777 32530764 32010788 31530831  
31310899 31190960 31201079 31441192 31771256  
32461238 33021150 33690960  
 
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