591  
FXUS02 KWBC 061901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT FRI MAY 06 2022  
 
VALID 12Z MON MAY 09 2022 - 12Z FRI MAY 13 2022  
 
...BLOCKY PATTERN NEXT WEEK TO SUPPORT RECORD HEAT OVER THE  
SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY INTO THE MIDWEST ALONG  
WITH EPISODES OF NORTH-CENTRAL U.S. CONVECTION AND NORTHERN GREAT  
BASIN/ROCKIES SNOW...  
   
..OVERVIEW
 
 
THE FIRST PART OF THE WEEK WILL FEATURE A PATTERN CLOSE TO AN  
OMEGA-STYLE BLOCK, WITH AN AMPLIFIED WESTERN MEAN TROUGH, A STRONG  
RIDGE EXTENDING FROM MEXICO INTO SOUTHEASTERN CANADA, AND AN UPPER  
LOW JUST OFF THE EAST COAST. WITH TIME THE CENTRAL/SOUTHERN PART  
OF THE RIDGE SHOULD WEAKEN WHILE THE NORTHERN PART MAY ULTIMATELY  
CONNECT WITH A RETROGRADING ATLANTIC RIDGE THAT SHOULD PUSH THE  
UPPER LOW TOWARD THE SOUTHEAST COAST. WITHIN THE WESTERN TROUGH, A  
LEADING SHORTWAVE WILL EJECT FROM THE NORTHERN HIGH PLAINS AND  
THEN UPSTREAM ENERGY SHOULD SHARPEN INTO MIDWEEK BEFORE EJECTING  
NORTHEASTWARD (POSSIBLY LEADING TO STRONG LOW PRESSURE). ANOTHER  
SYSTEM MAY REACH THE NORTHWEST LATE IN THE WEEK. THIS PATTERN  
WILL LEAD TO VERY WARM TO HOT WEATHER OVER THE  
CENTRAL/EAST-CENTRAL U.S., CHILLY AND UNSETTLED WEATHER OVER THE  
WEST, AND PERIODS OF RAIN/THUNDERSTORMS BETWEEN THESE TWO REGIMES.  
THE RETROGRADING UPPER LOW MAY ALSO BRING SOME MOISTURE INTO THE  
EAST LATE IN THE WEEK.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
IN GENERAL, THE GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE  
LARGE SCALE PATTERN, BUT WITH SOME VARIANCE FOR THE DETAILS AND  
TIMING, ESPECIALLY THE SECOND HALF OF THE PERIOD. THE MOST  
SIGNIFICANT FORECAST UNCERTAINTY DURING THE PERIOD CONTINUES TO  
INVOLVE DETAILS OF THE WESTERN U.S. MEAN TROUGH SPECIFICALLY HOW  
ENERGY THAT SHARPENS INTO MIDWEEK EJECTS OUT OF THE WEST IN  
RESPONSE TO AN UPSTREAM NORTHEASTERN PACIFIC SYSTEM THAT MAY  
CONTAIN A FAIRLY DEEP CLOSED LOW. GUIDANCE IS TRENDING BETTER WITH  
THE DEEP CLOSED LOW, BUT CONTINUE TO VARY SIGNIFICANTLY WITH THE  
LEADING EJECTING SHORTWAVE OUT OF THE ROCKIES. THE LATEST RUNS OF  
THE GFS AND CMC (INCLUDING TODAYS NEW 12Z RUN) ARE MUCH FASTER  
THAN THE ECMWF WITH THAT SHORTWAVE/SURFACE LOW. LATEST ENSEMBLES  
SUPPORT SOMETHING MORE IN THE MIDDLE (SLOWER THAN THE GFS/FASTER  
THAN THE EC). IN THE EAST, GUIDANCE SHOWS SOME VARIANCE WITH  
PLACEMENT OF A RETROGRADING CLOSED LOW NEAR THE SOUTHEAST LATE IN  
THE WEEK, BUT DIFFERENCES ARE WELL WITHIN THE NORMAL REALM FOR  
UNCERTAINTIES GIVEN THE TIME FRAME AND SEEM TO BE HANDLED WELL  
WITH AN ENSEMBLE MEAN BLEND.  
 
THE WPC FORECAST FOR TODAY USED A GENERAL MODEL BLEND FOR DAYS 3-5  
AMIDST ABOVE AVERAGE AGREEMENT. FOR 6-7, THE FORECAST TRENDED  
QUICKLY TOWARDS THE ENSEMBLE MEANS (WITH SMALLER PARTS GFS/ECMWF)  
WHICH GAVE A DECENT STARTING POINT, WITH SOME ADDED MANUAL  
ADJUSTMENTS TO THE EJECTING WEST SHORTWAVE. THIS APPROACH FIT WELL  
WITH PREVIOUS WPC CONTINUITY AS WELL.  
   
..WEATHER/THREAT HIGHLIGHTS
 
 
STRONG UPPER RIDGING WILL LEAD TO PERSISTENT MUCH ABOVE NORMAL  
TEMPERATURES OVER THE CENTRAL-SOUTHERN PLAINS AND MOST OF THE  
MISSISSIPPI VALLEY THROUGH THE WEEK, WITH SOME OF THIS WARMTH  
GRADUALLY EXPANDING THROUGH THE GREAT LAKES AND NORTHEAST AS WELL.  
EXPECT A BROAD AREA OF HIGHS/MORNING LOWS 10-20F ABOVE NORMAL WITH  
SOME LOCALIZED AREAS REACHING HIGHER THAN THAT. NUMEROUS DAILY  
RECORDS ARE LIKELY THROUGH THE WEEK OVER THE SOUTHERN PLAINS AND  
LOWER MISSISSIPPI VALLEY, AND MAY ALSO EXTEND INTO THE CENTRAL  
PLAINS/MIDWEST AROUND TUESDAY/WEDNESDAY. HIGHEST HEAT INDEX VALUES  
WILL BE OVER SOUTHERN TEXAS EARLY IN THE WEEK BUT THE COMBINATION  
OF HEAT AND HUMIDITY MAY STILL PRODUCE MAXIMUM HEAT INDEX VALUES  
OVER 100F AT SOME SOUTHERN LOCATIONS INTO LATE WEEK. EXCESSIVE  
HEAT, GUSTY WINDS, AND DRY CONDITIONS SHOULD LEAD TO AN ELEVATED  
FIRE WEATHER THREAT ACROSS PARTS OF THE SOUTHERN HIGH PLAINS  
THROUGH AT LEAST MID-WEEK.  
 
IN CONTRAST, THE WEST WILL SEE UNSEASONABLY COOL AND UNSETTLED  
CONDITIONS NEXT WEEK. COLDEST ANOMALIES SHOULD BE EARLY IN THE  
WEEK WHEN HIGHS WILL LIKELY BE 10-20F OR SO BELOW NORMAL. BEST  
POTENTIAL FOR SOME DAILY RECORDS FOR COLD HIGHS WILL BE ON MONDAY.  
TEMPERATURES MAY APPROACH NORMAL OVER SOUTHERN AREAS BY NEXT  
FRIDAY BUT LOCATIONS FARTHER NORTH SHOULD REMAIN AT LEAST  
MODERATELY BELOW NORMAL. PERIODS OF RAIN AND HIGHER ELEVATION SNOW  
WILL TEND TO BE LIGHT TO MODERATE, BUT THERE COULD BE A PERIOD OF  
ENHANCED ACTIVITY ALONG AND INLAND FROM THE WEST COAST LATE IN THE  
WEEK DEPENDING ON DETAILS OF AN ARRIVING NORTHEASTERN PACIFIC  
SYSTEM.  
 
BETWEEN THESE TWO REGIMES, THE CENTRAL U.S. WILL SEE PERIODS OF  
RAIN AND THUNDERSTORMS AS EJECTING WESTERN SHORTWAVES PRODUCE  
MULTIPLE LOWS, ALONG WITH A ROCKIES TO UPPER MIDWEST FRONT THAT  
ULTIMATELY STALLS AND THEN LIFTS NORTHWARD AHEAD OF ANOTHER SYSTEM  
THAT BRINGS A COLD FRONT INTO THE PLAINS LATE IN THE WEEK.  
DECELERATION OF THE LEADING FRONT AND THEN THE LATE WEEK SYSTEM  
MAY PRODUCE AREAS OF SIGNIFICANT RAINFALL THAT WOULD BE A RUNOFF  
THREAT OVER NORTHERN TIER AREAS THAT ALREADY HAVE VERY WET SOIL.  
THE STORM PREDICTION CENTER HIGHLIGHTS A CONCERN FOR SEVERE  
WEATHER OVER PARTS OF THE NORTHEASTERN PLAINS/UPPER MIDWEST EARLY  
IN THE WEEK, WHILE THE LATE-WEEK SYSTEM COULD MERIT WATCHING FOR  
STRONG CONVECTION AS WELL.  
 
MOST RAINFALL WITH THE SYSTEM OFF THE EAST COAST SHOULD STAY JUST  
OFFSHORE EARLY IN THE WEEK, BUT IS LIKELY TO EXPAND BACK TO THE  
WEST LATE IN THE WEEK AS THE VERTICALLY STACKED LOW RETROGRADES  
BACK TOWARD THE SOUTHEAST COAST.  
 
SANTORELLI/RAUSCH  
 
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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