145  
FXUS01 KWBC 180758  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
357 AM EDT TUE SEP 18 2018  
 
VALID 12Z TUE SEP 18 2018 - 12Z THU SEP 20 2018  
   
..POST-TROPICAL REMAINS OF FLORENCE TO AFFECT NEW ENGLAND TODAY
 
 
...FLASH FLOOD THREAT SHIFTING UP TO THE MIDDLE MISSISSIPPI VALLEY  
AND UPPER MIDWEST...  
 
...RETURN OF MONSOONAL MOISTURE TO ENHANCE THUNDERSTORM CHANCES  
OVER SOUTHERN ARIZONA/NEW MEXICO...  
 
...RECORD OVERNIGHT WARMTH IN PLACE THIS MORNING ALONG THE EASTERN  
SEABOARD...  
 
WHILE WHAT WAS HURRICANE FLORENCE HAS WEAKENED TO A POST-TROPICAL  
CYCLONE, IT STILL MAINTAINS A THREAT FOR LOCALIZED HEAVY RAINFALL  
AS IT SHIFTS INTO NEW ENGLAND TODAY. ADDITIONALLY, ABUNDANT  
TROPICAL MOISTURE SURGING UP THE EASTERN SEABOARD WILL MAINTAIN A  
RATHER MILD START TO THE DAY. PERHAPS UP TO A COUPLE OF DOZEN  
DAILY RECORDS MAY BE BROKEN GIVEN LITTLE ABILITY TO NOCTURNALLY  
RADIATE. WIDESPREAD 70S CURRENTLY BLANKET THE REGION ALTHOUGH SOME  
RELIEF WILL BE IN SIGHT BY MID-WEEK AS THE EXTRATROPICAL REMAINS  
OF FLORENCE EXIT INTO THE WESTERN ATLANTIC.  
 
DURING THE PERIOD, AN UPPER TROUGH WILL BEGIN TO DIG ACROSS THE  
WESTERN U.S. WHILE MAINTAINING QUASI-ZONAL FLOW OVER THE  
NORTH-CENTRAL STATES. A MULTITUDE OF DISTURBANCES WITHIN THIS  
REGIME SHOULD PROVIDE AN IMPETUS FOR MULTIPLE ROUNDS OF CONVECTION  
THE NEXT COUPLE OF DAYS. THIS IS EXPECTED TO FOCUS JUST NORTH OF A  
WEST-EAST ORIENTED FRONTAL ZONE WHICH SHOULD NOT MOVE APPRECIABLY  
THROUGH WEDNESDAY. BASED ON THE LATEST FORECAST, THE HEAVIEST  
RAINFALL WILL LIKELY CONGREGATE FROM SOUTHEASTERN SOUTH DAKOTA  
EASTWARD ACROSS SOUTHERN MINNESOTA/NORTHERN IOWA AND INTO WESTERN  
WISCONSIN. A LARGE PORTION OF THIS AREA HAS BEEN PARTICULARLY WET  
THE PAST COUPLE OF WEEKS WHICH ENHANCES THE THREAT FOR FUTURE  
FLASH FLOODING CONCERNS. AS SUCH, THE WEATHER PREDICTION CENTER  
HAS HIGHLIGHTED SECTIONS OF THIS REGION IN A SLIGHT RISK ON  
WEDNESDAY INTO THE FOLLOWING MORNING.  
 
AN AREA OF DISTURBED WEATHER CURRENTLY WELL SOUTH OF CABO SAN  
LUCAS HAS THE POTENTIAL FOR TROPICAL CYCLONE DEVELOPMENT THE NEXT  
COUPLE OF DAYS. CURRENTLY THE NATIONAL HURRICANE CENTER HAS A 40  
PERCENT CHANCE FOR SUCH DEVELOPMENT AS THE ASSOCIATED SHORTWAVE  
ENERGY AND MOISTURE PLUME SHIFTS NORTHWARD IN TIME. REGARDLESS OF  
WHETHER THIS SYSTEM DEVELOPS, ITS ANOMALOUS MOISTURE WILL BE FELT  
ACROSS THE FOUR CORNERS REGION. AS AN UPPER TROUGH SWEEPS THROUGH  
THE SOUTHWESTERN U.S., IT WILL ENCOUNTER THIS MOIST AIR MASS WITH  
WIDESPREAD PRECIPITATION BREAKING OUT OVER SOUTHERN ARIZONA/NEW  
MEXICO. WHILE A BULK OF THE HEAVIEST AMOUNTS SHOULD SHIFT SOUTH OF  
THE INTERNATIONAL BORDER WITH MEXICO, IT WOULD NOT TAKE MUCH TO  
MOVE THE FOCUS INTO THE U.S.  
 
GIVEN THE PRESENCE OF A QUASI-STATIONARY WEST-EAST ORIENTED  
BOUNDARY ACROSS THE CENTER OF THE COUNTRY, A FAIRLY POTENT  
TEMPERATURE CONTRAST WILL BE NOTED IN SURFACE OBSERVATIONS. ON  
WEDNESDAY, HIGHS ACROSS THE CENTRAL U.S. SHOULD PUNCH INTO THE LOW  
90S WHILE ACROSS THE NORTHERN TIER READINGS STRUGGLE TO ESCAPE THE  
UPPER 50S/LOW 60S. DEPARTURES FROM CLIMATOLOGY ON EITHER SIDE OF  
THE FRONT TEND TO BE IN THE 10 TO 15 DEGREE RANGE.  
 
RUBIN-OSTER  
 
FOR ALL INFORMATION ON THE RAINFALL ASSOCIATED WITH FLORENCE AND  
THE EXCESSIVE RAINFALL OUTLOOKS, VISIT WWW.WPC.NCEP.NOAA.GOV  
 
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