471  
FXUS02 KWBC 180706  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
305 AM EDT FRI MAR 18 2022  
 
VALID 12Z MON MAR 21 2022 - 12Z FRI MAR 25 2022  
 
...STRONG LOW PRESSURE SYSTEM WILL LIKELY PRODUCE HEAVY  
RAIN/SEVERE STORMS ACROSS PORTIONS OF THE SOUTHERN U.S. AND HEAVY  
CENTRAL ROCKIES SNOW BY EARLY NEXT WEEK...  
   
..OVERVIEW
 
 
THE MAIN UPPER LEVEL FEATURE OF NOTE DURING THE MEDIUM RANGE  
PERIOD WILL BE AN INITIALLY CLOSED LOW/TROUGH TRACKING FROM THE  
FOUR CORNERS STATES MONDAY NORTHEASTWARD THROUGH THE WORKWEEK WITH  
AN ASSOCIATED SURFACE LOW PRESSURE SYSTEM. THIS WILL SPREAD A  
MYRIAD OF SIGNIFICANT AND HAZARDOUS WEATHER TO THE U.S., INCLUDING  
POTENTIALLY HEAVY SNOW OVER THE CENTRAL ROCKIES AND VICINITY,  
HEAVY RAIN FROM THE SOUTH-CENTRAL U.S. TO THE OHIO/TENNESSEE  
VALLEYS AND SOUTHEAST, AND SEVERE THUNDERSTORMS FROM TEXAS THROUGH  
THE DEEP SOUTH. SOME PRECIPITATION IN THE NORTHERN FRINGE OF THE  
MOISTURE SHIELD COULD BE IN THE FORM OF SNOW FOR THE  
CENTRAL/EASTERN U.S. AS WELL. BEHIND THIS SYSTEM A STRONG UPPER  
RIDGE WILL BUILD INTO THE WEST, BRINGING MOSTLY DRY AND WARM  
WEATHER TO THE REGION.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE AGREES THAT A WELL-DEFINED UPPER LOW SHOULD BE  
CLOSED WITH ITS CENTROID LIKELY OVER NEW MEXICO BY MONDAY MORNING,  
LIFTING INTO THE SOUTHERN HALF OF THE PLAINS BY TUESDAY. THE  
INITIAL POSITION OF THIS UPPER LOW ALONG WITH THE ASSOCIATED  
SURFACE LOW ON DAY 3/MON DID HAVE A BIT OF WEST-EAST SPREAD IN THE  
12/18Z (YESTERDAY) MODEL CYCLE, WITH THE ECMWF THE FARTHEST WEST  
AND GFS RUNS A BIT ON THE EASTERN SIDE, BUT A COMPROMISE POSITION  
OF DETERMINISTIC GUIDANCE WORKED WELL EARLY IN THE MEDIUM RANGE  
PERIOD AND WAS CONSISTENT WITH ENSEMBLE MEAN GUIDANCE AND  
CONTINUITY. GUIDANCE ALSO AGREES THAT STRONG RIDGING COMING INTO  
THE WEST WILL SERVE TO AMPLIFY THE TROUGH.  
 
BY DAY 5/WED AND BEYOND, THERE IS MORE NOTABLE SPREAD IN THE  
12/18Z CYCLE (AND RUN TO RUN OF GUIDANCE CYCLES) WITH THE  
EVOLUTION OF THE UPPER LOW/TROUGH, WITH QUESTIONS ABOUT STREAM  
SEPARATION, WIDTH OF THE TROUGH, AND TROUGH AXIS/HOW MUCH ENERGY  
IS HELD BACK TO THE WEST. THE 12Z ECMWF WAS PARTICULARLY NEUTRALLY  
TILTED AND NARROW WITH ITS TROUGH PATTERN WITH MORE PHASING IN  
NORTHERN AND SOUTHERN STREAMS FOR DAY 6/THU. GFS RUNS WERE  
POSITIVELY TILTED AND WITH MORE STREAM SEPARATION, WITH SOME  
SOUTHERN STREAM ENERGY HELD BACK ACROSS THE SOUTH-CENTRAL  
U.S./MEXICO FOR LATE WEEK. THE 12Z CMC APPEARED TO BE A BROAD,  
ROUNDED OUTLIER WITH ITS 500MB HEIGHT PATTERN COMPARED TO OTHER  
DETERMINISTIC GUIDANCE AND ENSEMBLE MEMBERS BY WEDNESDAY THROUGH  
FRIDAY, MORE SEPARATED FROM THE POLAR JET AND THE SLOWEST SOLUTION  
FOR ITS TRACK EASTWARD. HOWEVER, THE NEWER 00Z MODEL CYCLE APPEARS  
TO BE MORE AGREEABLE, AND ACTUALLY TRENDING OVERALL TOWARD THE CMC  
WITH A MORE ROUNDED UPPER LOW ESPECIALLY WED WITH MORE SEPARATION  
FROM THE POLAR JET, AND A SLOWER OVERALL TROUGH MOVEMENT.  
 
AT THE TIME OF FORECAST CREATION, THE LATTER PART OF THE MEDIUM  
RANGE PERIOD WENT TO AN ENSEMBLE MEAN-HEAVY BLEND PERHAPS EARLIER  
THAN AVERAGE GIVEN THESE DIFFERENCES, WITH MANUAL ADJUSTMENTS TO  
DEEPEN SURFACE LOWS. THE 12Z EC ENSEMBLE MEAN WAS A GOOD PROXY FOR  
THE PREFERRED CONSENSUS AT LEAST IN TERMS OF MASS FIELDS, AND THE  
WPC FORECAST HAD GOOD CONTINUITY WITH PREVIOUS FORECASTS FROM THIS  
APPROACH. FUTURE CHANGES TO THE FORECAST REMAIN LIKELY GIVEN RUN  
TO RUN MODEL DIFFERENCES, PERHAPS WITH A SLOWER FRONT TRACK  
ESPECIALLY BY DAY 7/FRI IN THE EAST.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
AMPLE GULF OF MEXICO MOISTURE FLOWING INTO THE SURFACE/UPPER-LEVEL  
LOWS TRACKING ACROSS THE COUNTRY WILL LEAD TO WIDESPREAD RAIN AND  
THUNDERSTORMS FOR THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY  
EARLY IN THE WEEK, SPREADING EASTWARD INTO THE OHIO AND TENNESSEE  
VALLEYS AND SOUTHEAST BY AROUND MIDWEEK. PER THE STORM PREDICTION  
CENTER, STORMS COULD BE SEVERE IN EASTERN TEXAS MONDAY AND ACROSS  
THE GULF COAST STATES AS THE WEEK PROGRESSES. FURTHERMORE, HEAVY  
RAIN IS LIKELY TO CAUSE AREAS OF FLASH FLOODING PARTICULARLY DUE  
TO HEAVY RAIN RATES MONDAY INTO WEDNESDAY, AND SLIGHT RISK AREAS  
ARE INDICATED NEAR THE ARK-LA-TEX/EASTERN OKLAHOMA AND FOR THE  
LOWER MISSISSIPPI VALLEY/MID-SOUTH REGION FOR DAYS 4 AND 5 IN THE  
EXPERIMENTAL WPC MEDIUM RANGE EXCESSIVE RAINFALL OUTLOOK. RAIN  
SHOULD SPREAD INTO THE EASTERN SEABOARD AROUND THURSDAY.  
ADDITIONALLY, HEAVY SNOW IS INCREASINGLY LIKELY FOR THE CENTRAL  
ROCKIES MONDAY, WITH SOME POTENTIAL FOR SNOW TO SPREAD INTO THE  
HIGH PLAINS AS WELL, ALONG WITH AN AREA OF ENHANCED RAINFALL  
TOTALS LIKELY NEAR THE CENTRAL PLAINS/MIDDLE MISSISSIPPI VALLEY  
(THOUGH WITH LESSER RAINFALL AMOUNTS THAN FARTHER SOUTHEAST).  
PRECIPITATION COVERAGE FROM THE NORTHERN HALF OF THE PLAINS INTO  
THE MIDWEST AND NORTHEAST HAS MUCH LOWER CONFIDENCE, BUT IF  
MOISTURE REACHES THAT FAR NORTH SOME PRECIPITATION COULD BE IN THE  
FORM OF SNOW. IN THE WEST, MAINLY DRY CONDITIONS ARE LIKELY AFTER  
A PERIOD OF PRECIPITATION IN THE PACIFIC NORTHWEST ON MONDAY.  
 
SOMEWHAT BELOW NORMAL TEMPERATURES ARE EXPECTED UNDERNEATH THE  
UPPER LEVEL TROUGHING, WITH PARTICULARLY HIGH TEMPERATURES 10-20F  
BELOW AVERAGE ACROSS THE INTERMOUNTAIN WEST MONDAY AND  
CENTRAL/SOUTHERN HIGH PLAINS TUESDAY AND WEDNESDAY. THE COOLER AIR  
SHOULD MODERATE CLOSER TO NORMAL BY THE LATTER PART OF NEXT WEEK.  
MEANWHILE, THE MIDWEST WILL SEE WARMER THAN AVERAGE TEMPERATURES  
BY AROUND 20F ON MONDAY, AND GENERALLY WARMER THAN NORMAL  
CONDITIONS ARE FORECAST FOR THE EASTERN THIRD OF THE U.S. THROUGH  
MUCH OF THE WEEK AHEAD OF THE MAIN SYSTEM. THE WEST SHOULD ALSO  
SEE WARMTH BUILD WITH THE RIDGING, WITH TEMPERATURES 10-20F ABOVE  
NORMAL EXPANDING FROM THE WEST COAST INLAND THROUGH THE WORKWEEK.  
DAILY RECORD HIGHS ARE POSSIBLE PARTICULARLY IN CALIFORNIA.  
 
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  
 
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/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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