140  
FXUS01 KWBC 200756  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
355 AM EDT WED JUN 20 2018  
 
VALID 12Z WED JUN 20 2018 - 12Z FRI JUN 22 2018  
 
...FLASH FLOODING THREATS EXIST ALONG THE TEXAS COAST AS WELL AS  
OVER THE MIDDLE MISSISSIPPI VALLEY...  
 
...RECORD WARM MINIMUM TEMPERATURES POSSIBLE ACROSS THE  
SOUTHEASTERN U.S. AND PACIFIC NORTHWEST...  
   
..EXCESSIVE HEAT EXPECTED OVER THE DESERT SOUTHWEST
 
 
A SLOW MOVING, MEANDERING UPPER LOW WILL LOOM LARGE ALONG THE  
TEXAS COAST THROUGH ROUGHLY THURSDAY MORNING. MOST RECENTLY, THIS  
SYSTEM HAS A HISTORY OF PRODUCING FLASH FLOODING, INCLUDING SOME  
WATER RESCUES ACROSS CORPUS CHRISTI, TEXAS. WITH ABUNDANT TROPICAL  
MOISTURE IN PLACE AND NUMEROUS SLOW MOVING THUNDERSTORMS,  
ADDITIONAL FLASH FLOODING IS LIKELY TO OCCUR SOMEWHERE ALONG THE  
TEXAS COAST. A WIDESPREAD 3 TO 5 INCHES OF RAINFALL IS POSSIBLE  
OVER THIS REGION THROUGH THURSDAY MORNING WITH ISOLATED POCKETS OF  
HEAVIER AMOUNTS EXPECTED. GRADUALLY THE PARENT UPPER LOW IS  
FORECAST TO SINK SOUTHWARD AND POSITION ITSELF OVER CENTRAL MEXICO  
BY THE END OF THE WORK WEEK.  
 
ANOTHER REGION WHICH CAN EXPECT A DECENT THREAT FOR FLASH FLOODING  
IS THE MIDDLE MISSISSIPPI VALLEY. THE PROMINENT ISSUES WILL LIKELY  
EXTEND FROM EASTERN SECTIONS OF NEBRASKA/SOUTH DAKOTA OUT INTO  
IOWA AND ADJACENT LOCATIONS. A MYRIAD OF DISTURBANCES ALOFT WILL  
WORK IN CONJUNCTION WITH A SLOW MOVING SURFACE CYCLONE TO AFFORD  
MULTIPLE EPISODES OF ORGANIZED SHOWERS AND THUNDERSTORMS. THIS  
COMBINATION WILL SET A FOCUS FOR A BROAD AXIS OF HEAVY RAINFALL  
EXTENDING OVER THE MENTIONED STRETCH OF STATES. LIKE THE TEXAS  
GULF COAST, SECTIONS OF THE MIDDLE MISSISSIPPI VALLEY ARE ALSO  
WITHIN THE MODERATE RISK FOR EXCESSIVE RAINFALL AS SHOWN IN THE  
LATEST GRAPHICS. NOT WITHSTANDING, AREAS FARTHER DOWNSTREAM ARE  
NOT OUT OF THE WOODS AS A WAVY FRONTAL ZONE SPRAWLING EASTWARD  
INTO THE OHIO VALLEY AND MID-ATLANTIC WILL BE A SITE FOR ORGANIZED  
HEAVY PRECIPITATION. A SLIGHT RISK FOR EXCESSIVE RAINFALL IS BEING  
ADVERTISED, GENERALLY ALONG I-70.  
 
SOUTH OF THE MENTIONED WAVY FRONTAL ZONE, IT WILL BE QUITE WARM  
AND MUGGY WITH LOW TEMPERATURES NOT DROPPING APPRECIABLY. AS SUCH,  
EXPECT WIDESPREAD MID 70S WITH LOCALIZED UPPER 70S THE NEXT COUPLE  
OF NIGHTS ACROSS THE SOUTHEASTERN U.S. BASED ON DAILY RECORDS,  
SOME OBSERVED MINIMA MAY APPROACH OR LOCALLY EXCEED THESE EXTREMA.  
DURING THE DAYTIME, WHILE RECORDS ARE NOT LIKELY, HOT CONDITIONS  
SHOULD PREVAIL ACROSS THE CAROLINAS AS HIGHS SOAR INTO THE UPPER  
90S. MEANWHILE, NORTH OF THE BOUNDARY, HIGHS IN THE 70S WILL BE  
COMMONPLACE OVER NEW ENGLAND.  
 
LOOKING TO THE WESTERN U.S., THE PACIFIC NORTHWEST CAN ALSO EXPECT  
FAIRLY WARM OVERNIGHT TEMPERATURES FOR MID/LATE JUNE. CURRENT  
FORECAST LOWS ARE IN THE MID 60S ACROSS INTERIOR WASHINGTON/OREGON  
WHILE UPPER 50S ARE MORE LIKELY CLOSER TO THE I-5 CORRIDOR. IF  
SUCH TEMPERATURES ARE ACHIEVED, SOME DAILY RECORDS MAY BE BROKEN.  
FARTHER SOUTH, EXCESSIVE HEAT WARNINGS AND WATCHES ARE IN EFFECT  
ACROSS THE DESERT SOUTHWEST. THIS WELL ADVERTISED INCREASE IN THE  
TEMPERATURES IS IN RESPONSE TO A BUILDING UPPER RIDGE. BY  
THURSDAY, HIGHS WILL LIKELY PUSH INTO THE 110S ACROSS MANY SPOTS  
INCLUDING LAS VEGAS, NEEDLES, AND PHOENIX. AND THE CURRENT  
FORECAST HIGH AT DEATH VALLEY, CALIFORNIA IS 124 DEGREES ON  
THURSDAY.  
 
AS AN UPPER RIDGE ERODES ACROSS THE NORTHWESTERN U.S., A NUMBER OF  
DISTURBANCES ADVANCING FROM THE PACIFIC WILL ENHANCE CHANCES FOR  
PRECIPITATION ACROSS THE PACIFIC NORTHWEST, UPPER INTERMOUNTAIN  
WEST, AND NORTHERN ROCKIES. SOMEWHAT LIMITED MOISTURE SHOULD KEEP  
OVERALL RAINFALL AMOUNTS ON THE LOWER END WITH GENERAL MAXIMA  
FOCUSING OVER AREAS OF LOCAL UPSLOPE EFFECTS.  
 
RUBIN-OSTER  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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