478  
FXUS01 KWBC 202001  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
400 PM EDT WED JUN 20 2018  
 
VALID 00Z THU JUN 21 2018 - 00Z SAT JUN 23 2018  
 
...ADDITIONAL FLASH FLOODING EXPECTED FOR PORTIONS OF THE TEXAS  
COAST BEFORE IMPROVING CONDITIONS BY THE END OF THE WEEK...  
 
...A THREAT FOR FLASH FLOODING WILL CONTINUE FROM THE MIDWEST TO  
THE MID-ATLANTIC THROUGH THE END OF THE WEEK...  
 
...INCREASING TEMPERATURES EXPECTED THROUGH THE END OF THE WEEK  
FROM CALIFORNIA INTO THE SOUTHWEST AND TEXAS...  
 
A SLOW MOVING FRONT STRETCHING FROM THE MID-ATLANTIC COAST TO THE  
SOUTHERN PLAINS WILL CONTINUE TO POSE A THREAT FOR THUNDERSTORMS  
AND FLASH FLOODING OVER THE NEXT COUPLE OF DAYS, BUT WITH WANING  
COVERAGE ACROSS THE LOWER 48 EACH DAY. CONDITIONS NEAR AND SOUTH  
OF THE FRONTAL BOUNDARY WILL SEE HIGH HUMIDITY WITH ANOMALOUSLY  
HIGH MOISTURE VALUES WHICH WILL SUPPORT DIURNALLY DRIVEN  
THUNDERSTORMS DURING THE AFTERNOON AND EVENING HOURS. SOME OF  
THESE THUNDERSTORMS WILL HAVE THE ABILITY TO PRODUCE STRONG TO  
LOCALLY SEVERE WEATHER IN ADDITION TO HEAVY DOWNPOURS WITH FLASH  
FLOODING.  
 
ONE OF TWO SIGNIFICANT THREATS FOR FLASH FLOODING THROUGH THURSDAY  
MORNING EXISTS IN THE VICINITY OF NORTHWESTERN IOWA INTO PORTIONS  
OF EASTERN SOUTH DAKOTA/NEBRASKA NEAR A SURFACE LOW AND OUT HEAD  
OF AN UPPER LEVEL DISTURBANCE CROSSING THE PLAINS. AN EQUALLY  
CONCERNING THREAT IS IN PLACE FROM SOUTH TEXAS, UP THE COASTAL  
PLAIN INTO THE SABINE RIVER VALLEY WHERE SOME LOCATIONS HAVE  
RECEIVED 5 TO 15 INCHES OVER THE PAST 72 HOURS. A SLOW MOVING  
UPPER LEVEL LOW OVER SOUTH TEXAS WILL GRADUALLY BEGIN TO SHIFT  
SOUTH AND WEST OVER THE NEXT 12 TO 36 HOURS, ALLOWING FOR A  
REDUCTION IN AVAILABLE MOISTURE AND LIFT WHICH SHOULD END THE  
FLASH FLOOD THREAT WITH FRIDAY LIKELY A DRY DAY FOR THE REGION AS  
WELL AS SATURDAY.  
 
THURSDAY'S THREAT FOR FLASH FLOODING WILL AGAIN BE FOCUSED IN THE  
VICINITY OF THE FRONT, WITH A FOCUS OVER ILLINOIS, INDIANA INTO  
EASTERN KENTUCKY, BUT WITH REDUCED COVERAGE FOR MUCH OF THE  
PLAINS. WIDESPREAD COVERAGE OF THUNDERSTORMS WILL STILL BE  
EXPECTED NEAR AND SOUTH OF THE FRONT HOWEVER.  
 
OUT WEST, AHEAD OF AN UPPER LEVEL DISTURBANCE APPROACHING THROUGH  
THE EASTERN PACIFIC, HIGH TEMPERATURES ARE EXPECTED TO INCREASE  
ACROSS CALIFORNIA, THE SOUTHWEST AND TEXAS WITH TRIPLE DIGIT HEAT  
FORECAST FOR ALL THREE LOCATIONS ON FRIDAY. EXCESSIVE HEAT WATCHES  
HAVE ALREADY BEEN POSTED FOR PORTIONS OF THE SACRAMENTO VALLEY  
INTO SOUTHERN ARIZONA IN ANTICIPATION OF TEMPERATURES RISING TO  
AND ABOVE 105 DEGREES.  
 
OTTO  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page