914  
FXUS02 KWBC 300710  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
308 AM EDT MON MAY 30 2022  
 
VALID 12Z THU JUN 02 2022 - 12Z MON JUN 06 2022  
 
...LATE WEEK HEAVY RAIN THREAT INCREASING OVER SOUTHERN FLORIDA  
AHEAD OF A TROPICAL SYSTEM...  
   
..OVERVIEW
 
 
THE MEDIUM RANGE PERIOD WILL SEE A FAIRLY STAGNANT MID-UPPER  
PATTERN AS A CLOSED LOW SPINS ACROSS SOUTH-CENTRAL CANADA, SENDING  
PERIODS OF LOW AMPLITUDE TROUGHING ACROSS THE CENTRAL AND EASTERN  
U.S. ALONG WITH SURFACE FRONTS THAT COULD PROVIDE FOCI FOR  
CONVECTION. MEANWHILE, TROPICAL MOISTURE IS EXPECTED TO INCREASE  
THROUGH THE PERIOD ACROSS SOUTHERN FLORIDA STREAMING NORTHWARD  
FROM TROPICAL CYCLONE AGATHA CURRENTLY LOCATED IN THE EASTERN  
PACIFIC. ENERGY FROM AGATHA MAY COMBINE WITH ADDITIONAL CARIBBEAN  
ENERGY IN A LARGE AND COMPLEX AREA OF LOW PRESSURE NEAR THE  
YUCATAN TO FORM A TROPICAL SYSTEM IN THE NORTHWESTERN CARIBBEAN OR  
GULF OF MEXICO LATE WEEK, BUT WITH HIGH LEVELS OF UNCERTAINTY AT  
THIS TIME. ELSEWHERE, UPPER-LEVEL RIDGING IS FORECAST TO BUILD  
ACROSS THE INTERIOR WEST WHILE A NORTHEASTERN PACIFIC UPPER LOW  
PRODUCES TROUGHING AND UNSETTLED WEATHER INTO THE NORTHWEST.  
 
   
..MODEL GUIDANCE EVALUATION/PREFERENCES
 
 
RECENT MODEL GUIDANCE IS IN REASONABLY GOOD AGREEMENT FOR THE  
OVERALL SYNOPTIC PATTERN AT LEAST IN THE NORTHERN STREAM LATE WEEK  
INTO EARLY NEXT WEEK. THE CENTROID OF THE CENTRAL CANADA UPPER LOW  
SHOWS FAIRLY GOOD CONSENSUS BETWEEN THE 12Z/18Z GFS AND 12Z ECMWF  
AND UKMET, WHILE THE 12Z CMC SUNK THE LOW A BIT FARTHER SOUTH. THE  
00Z CMC HAS COME IN WITH SOMEWHAT BETTER ALIGNMENT. THE DETAILS OF  
TROUGHING STEMMING FROM THE LOW AND THUS PLACEMENT OF THE SURFACE  
FRONTS AND AXES FOR RAIN/CONVECTION ARE MORE UNCERTAIN. A  
MULTI-MODEL BLEND OF MAINLY THE DETERMINISTIC GUIDANCE, THOUGH  
WITH LESS INFLUENCE FROM THE CMC AND INCREASING INFLUENCE FROM THE  
GEFS/EC ENSEMBLE MEANS LATER IN THE PERIOD, SEEMS THE BEST WAY TO  
HANDLE THE SMALLER-SCALE DIFFERENCES FOR NOW. THIS ALSO WORKED  
WELL FOR THE UPPER LOW SPINNING OFFSHORE BRITISH COLUMBIA AND ITS  
TROUGHING INFLUENCE INTO THE WEST COAST. GFS RUNS HAVE BEEN MORE  
AGGRESSIVE THAN THE ECMWF/CMC AT A SHORTWAVE EJECTING INTO THE  
NORTHERN ROCKIES BY NEXT MONDAY, WHICH MAY BE TOO FAST.  
 
MORE NOTABLE DIFFERENCES CONTINUE TO BE SEEN FARTHER SOUTH WITH  
TROPICAL MOISTURE AND ENERGY THAT COULD AFFECT FLORIDA IN  
PARTICULAR. MODELS CONTINUE TO SHOW THE POTENTIAL FOR ENERGY IN  
THE BAY OF CAMPECHE/YUCATAN/WESTERN CARIBBEAN TO CONSOLIDATE INTO  
A FORMING TROPICAL SYSTEM WITH A GENERAL TRACK NORTHEASTWARD.  
HOWEVER, THERE ARE AMPLE DIFFERENCES IN DETERMINISTIC MODELS AND  
ENSEMBLE MEMBERS WITH PARTICULARLY THE TIMING OF THIS EJECTION  
NORTHEASTWARD (ON THE ORDER OF DAYS), BUT ALSO WITH ITS STRENGTH  
AND TRACK. GFS AND CMC RUNS HAVE BOTH TENDED TO BE ON THE FAST  
SIDE OF THE ENVELOPE, AND WITH THE GFS ON THE SOUTHERN SIDE ALONG  
THE FLORIDA STRAITS AND THE CMC MORE NORTH CROSSING FLORIDA AND  
MAKING ITS WAY INTO THE WESTERN ATLANTIC. THE ECMWF ON THE OTHER  
HAND HAS BEEN ON THE SLOWER SIDE AND MORE FAVORED, INCLUDING THE  
12Z RUN, THOUGH NOTABLY ITS NEW 00Z RUN HAS SPED UP CONSIDERABLY  
WITH ITS LOW TRACK, THOUGH NOT TO THE SPEED OF THE GFS/CMC RUNS.  
THE WPC FORECAST HAS CONTINUED TO TAKE A CONSERVATIVE (IN  
STRENGTH) AND SLOWER APPROACH WITH THE LOW AT THIS POINT AND WILL  
CONTINUE TO COORDINATE WITH THE NATIONAL HURRICANE CENTER FOR  
UPDATES.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
A COLD FRONT IS FORECAST TO PRESS ACROSS THE EAST LATE THIS WEEK,  
WITH RAIN AND THUNDERSTORMS EXPECTED ALONG IT. WHILE THERE IS SOME  
UNCERTAINTY WITH THE PLACEMENT OF HEAVIEST RAINFALL, IT APPEARS  
THAT AREAS OF THE EASTERN MID-ATLANTIC COULD SEE LOCALLY HEAVY  
RAINFALL AND AN ISOLATED FLASH FLOOD THREAT THURSDAY. HOWEVER, THE  
TRAILING PORTION OF THE FRONT IS FORECAST TO MOVE MUCH MORE SLOWLY  
THROUGH SOUTHERN PARTS OF THE PLAINS AND CAUSE MULTIPLE DAYS OF  
CONVECTION FROM THE SHORT RANGE PERIOD LASTING INTO THURSDAY AND  
POSSIBLY FRIDAY. FLASH FLOODING IS POSSIBLE ESPECIALLY WHERE  
STORMS REPEAT OVER THE SAME AREA, AND WITH LIKELY WET SOILS BY THE  
TIME THE MEDIUM RANGE PERIOD BEGINS THURSDAY, THIS WILL LESSEN THE  
AMOUNT OF RAIN NEEDED TO GET FLASH FLOODING. THE BEST CHANCE FOR  
FLASH FLOODING ISSUES LOOKS TO BE ACROSS OKLAHOMA AND NORTHERN  
PARTS OF TEXAS. BY THE WEEKEND, THE FRONT IS FORECAST TO LIFT  
NORTHWARD AS A WARM FRONT WHILE COOLER AIR FROM CANADA IS FORECAST  
TO EDGE SOUTHWARD INTO THE NORTHERN PLAINS. THESE FRONTS WILL  
CONTINUE TO SPARK ADDITIONAL ROUNDS OF ENHANCED RAINFALL ACROSS  
THE CENTRAL U.S. THIS WEEKEND, BUT WITH LOW CONFIDENCE IN THE  
DETAILS.  
 
THERE IS INCREASING FORECAST AGREEMENT FOR TROPICAL CYCLONE AGATHA  
OVER THE EASTERN PACIFIC TO MOVE NORTHEASTWARD ACROSS MEXICO OVER  
THE NEXT COUPLE OF DAYS. SCATTERED SHOWERS AND THUNDERSTORMS ARE  
EXPECTED TO BECOME MORE FREQUENT AND WIDESPREAD ACROSS SOUTHERN  
FLORIDA LATER THIS WEEK, FIRST WITH THE MOISTURE FROM AGATHA  
STREAMING NORTHEAST AND THEN WITH THE POTENTIAL FOR ENERGY  
CONSOLIDATING INTO A POSSIBLE TROPICAL SYSTEM TRACKING  
NORTHEASTWARD. THE TIMING AND AMOUNTS OF RAINFALL WILL BE  
DEPENDENT ON THE INTERACTION OF A SUBTROPICAL JET WITH TROPICAL  
MOISTURE COMING FROM AGATHA, THEN ANY REMAINING ENERGY STEMMING  
FROM AGATHA AFTER CROSSING MEXICO AND THE POSSIBILITY IT COULD  
COMBINE WITH TROPICAL WAVE ENERGY OVER THE WESTERN CARIBBEAN TO  
PRODUCE A TROPICAL CYCLONE.  
 
ADDITIONALLY, RAIN CHANCES ARE EXPECTED TO INCREASE IN THE  
NORTHWEST DURING THE LATTER HALF OF THE WEEK GIVEN THE TROUGH AXIS  
NEAR THE WEST COAST AND A COUPLE OF FRONTAL SYSTEMS. THE SOUTHWEST  
SHOULD REMAIN DRY AND HOT THOUGH.  
 
A RELATIVELY FLAT PATTERN ALOFT COMPARED TO THE MORE AMPLIFIED  
SHORT RANGE PERIOD SHOULD PRODUCE LESSER TEMPERATURE ANOMALIES  
LATE THIS WEEK INTO EARLY NEXT WEEK. COOLER THAN AVERAGE SPOTS  
WILL BE ACROSS THE CENTRAL/SOUTHERN PLAINS THURSDAY INTO FRIDAY  
WITH RAIN COOLED AIR, BUT SHOULD SWITCH TO ABOVE NORMAL IN TEXAS  
BY ABOUT 10F BY EARLY NEXT WEEK. PERIODIC TROUGHING IN THE  
NORTHERN TIER SHOULD LEAD TO SLIGHTLY BELOW AVERAGE TEMPERATURES  
BY 5-10F THERE. THE WESTERN U.S. COULD BE WARMER THAN NORMAL BY  
5-10F LATE IN THE WORKWEEK BUT COOLER TEMPERATURES ARE FORECAST BY  
THE WEEKEND UNDER THE TROUGHING INFLUENCE. WARM TEMPERATURES  
ACROSS THE SOUTHEAST THURSDAY WILL MODERATE CLOSER TO NORMAL LATE  
WEEK BEHIND A COLD FRONTAL PASSAGE.  
 
TATE  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE  
AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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