372  
FXUS02 KWBC 200711  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
309 AM EDT SUN MAR 20 2022  
 
VALID 12Z WED MAR 23 2022 - 12Z SUN MAR 27 2022  
 
...A STRONG LOW PRESSURE SYSTEM WILL CONTINUE TO CAUSE  
PRECIPITATION IN THE EASTERN U.S. MIDWEEK, WITH SEVERE STORMS IN  
THE SOUTHEAST, LOCALLY HEAVY RAIN, AND WINTRY WEATHER ACROSS THE  
NORTHERN TIER...  
 
   
..OVERVIEW
 
 
THE MOST ACTIVE WEATHER DURING THE MEDIUM RANGE PERIOD WILL BE  
AROUND MIDWEEK, AS A POTENT UPPER LOW AND A SURFACE LOW PRESSURE  
SYSTEM TRACK FROM THE MID-MISSISSIPPI VALLEY TO THE GREAT LAKES  
REGION. RAIN IS FORECAST TO SPREAD AHEAD OF THE ASSOCIATED COLD  
FRONT WITH SOME EMBEDDED HEAVY TOTALS, WHILE SEVERE THUNDERSTORMS  
ARE POSSIBLE IN THE SOUTHEAST. MEANWHILE ON THE COLD NORTHERN SIDE  
OF THE SYSTEM, SPRINGTIME SNOW AND MIXED PRECIPITATION ARE  
POSSIBLE FROM THE GREAT LAKES REGION TO THE INTERIOR NORTHEAST. AS  
A RIDGE BUILDS INTO THE WEST, WARM TEMPERATURES INCLUDING SOME  
POSSIBLE RECORD HIGHS PARTICULARLY FOR CALIFORNIA ARE FORECAST.  
THE UPPER LEVEL PATTERN LOOKS TO STAGNATE OVER THE WEEKEND WITH AN  
EAST PACIFIC TROUGH, INTERMOUNTAIN WEST RIDGE, AND EASTERN U.S.  
TROUGH, WHICH WILL LEAD TO OVERALL DRY CONDITIONS.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE FROM THE 12/18Z YESTERDAY CYCLE CONTINUES TO AGREE  
WITH A POTENT ROUNDED UPPER LOW IN THE CENTRAL U.S. SUPPORTING A  
SURFACE LOW OVER THE MIDDLE MISSISSIPPI VALLEY DAY 3/EARLY WED.  
THESE FEATURES SHOULD MOVE NORTHEASTWARD THU, BUT WITH SOME MODEL  
DIFFERENCES ON THE UPPER-LEVEL FEATURE STAYING CLOSED OR OPENING  
UP. THE WPC FORECAST LEANS TOWARD A SOLUTION WITH THE LOW  
REMAINING CLOSED, FAVORING THE ECMWF/CMC AND THEIR MEANS. THE  
GFS/GEFS GUIDANCE SHOWS A MORE OPEN PATTERN BY THAT TIME, BUT THE  
MAIN OUTLIER FOR THE 12Z CYCLE APPEARED TO BE THE UKMET, WITH A  
MORE STRUNG OUT TROUGH HOLDING BACK MORE ENERGY INTO NORTHERN  
MEXICO THAN CURRENT CONSENSUS, LOOKING LIKE SOME GUIDANCE FROM  
PREVIOUS CYCLES BUT IT IS NOW ONE OF THE MAIN HOLDOUTS. THEN BY  
FRIDAY IT SEPARATES NORTHERN AND SOUTHERN STREAM ENERGY WITH THE  
NORTHERN STREAM TRACKING LIKELY TOO QUICKLY. OTHER THAN THE UKMET,  
DESPITE THE DIFFERENCES IN TIMING OF PHASING, THE PROGRESSION OF  
THE TROUGH/LOW EASTWARD IS MOSTLY MORE AGREEABLE. MODELS HAVE  
STUCK WITH THE TREND FOR AN OCCLUDED SURFACE LOW SPREADING MORE  
PRECIPITATION ON THE NORTHWESTERN SIDE.  
 
BY AROUND DAY 5/FRI AND BEYOND, THE TROUGHING SHOULD SLOWLY LIFT,  
THOUGH ADDITIONAL ENERGY DIGS FROM THE NORTH TO REINFORCE  
TROUGHING ACROSS THE EAST THROUGH THE WEEKEND, WITH SOME TYPICAL  
DIFFERENCES IN SHORTWAVE ENERGIES AND THUS TIMING FOR COLD FRONTS  
AND LOW PRESSURE SYSTEMS. NAMELY, ENSEMBLE GUIDANCE GENERALLY  
SHOWED LOW PRESSURE NEAR MAINE OR THE CANADIAN MARITIMES AROUND  
SAT, BUT THE 12/18Z DETERMINISTIC GUIDANCE SHOWED A LOCAL HIGH  
AROUND THERE WITH LOWS NORTH AND SOUTH. THE 00Z GUIDANCE SEEMS TO  
BE MORE IN LINE WITH THE ENSEMBLE CONSENSUS. MEANWHILE THERE IS  
RATHER GOOD CONSENSUS FOR PERIODS OF RIDGING IN THE WEST WITH ITS  
AXIS SHIFTING SLOWLY EASTWARD LATE IN THE WEEK. SHORTWAVES MOVING  
ACROSS THE NORTHWEST COULD SUPPRESS THE NORTHERN SIDE AROUND  
THU-FRI, BUT MOST GUIDANCE OTHER THAN THE CMC HAS THE RIDGE  
REBUILDING FOR THE WEEKEND. THE INCOMING 00Z SUITE OF GUIDANCE  
SHOWS A SIMILAR PATTERN BUT WITH TYPICAL WIGGLES IN THE DETAILS.  
 
THE WPC FORECAST WAS BASED ON AN INITIAL BLEND OF THE 12Z ECMWF,  
12/18Z GFS, AND 12Z CMC, JUST EXCLUDING THE UKMET IN TERMS OF THE  
DETERMINISTIC MODELS. ENSEMBLE MEAN GUIDANCE WAS PHASED IN AROUND  
DAY 5 AND INCREASED SOMEWHAT THROUGH DAYS 6-7, BUT ONLY TO ABOUT  
40 PERCENT GIVEN FAIRLY GOOD AGREEMENT FOR THE LARGE SCALE PATTERN  
EVEN IN THE ECMWF/GFS IN PARTICULAR.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
ANOTHER RAINY DAY IS EXPECTED AS THE MEDIUM RANGE PERIOD BEGINS  
WEDNESDAY AS AMPLE GULF OF MEXICO MOISTURE FLOWS INTO THE LOW  
PRESSURE SYSTEM TRACKING ACROSS THE CENTRAL U.S. STORMS COULD BE  
SEVERE ACROSS THE DEEP SOUTH DOWN TO THE CENTRAL/EASTERN GULF  
COAST PER THE STORM PREDICTION CENTER. FURTHERMORE, WIDESPREAD  
RAIN IS LIKELY ACROSS THE EAST, WHICH COULD POTENTIALLY CAUSE SOME  
ISOLATED FLASH FLOODING IN SOME AREAS FROM THE SOUTHERN/CENTRAL  
APPALACHIANS EASTWARD. NORTH AND WEST OF THE LOW TRACK, SNOW AND  
WINTRY PRECIPITATION ARE POSSIBLE, WITH THE HIGHEST PROBABILITIES  
FOR NOTABLE SNOW IN THE UPPER GREAT LAKES REGION. WINTRY MIX OR  
SNOW COULD ALSO OCCUR PARTICULARLY IN HIGHER ELEVATIONS OF THE  
INTERIOR NORTHEAST NORTH OF A WARM FRONT ON WEDNESDAY-THURSDAY AND  
AS A WESTERN ATLANTIC LOW DEVELOPS BY EARLY FRIDAY. SHOWERS COULD  
LINGER INTO LATE WEEK ACROSS THE EAST WITH GENERALLY LIGHT AMOUNTS  
EXPECTED, BUT PERHAPS WITH MORE MODERATE AMOUNTS AS A FRONT  
LINGERS IN FLORIDA, WHICH COULD CAUSE LOCALIZED FLOODING ISSUES IF  
RAIN FALLS ATOP SATURATED SOILS. A MAINLY DRY PATTERN IS EXPECTED  
FOR THE WESTERN AND CENTRAL U.S. FOR THE LATTER PART OF THE WEEK,  
THOUGH WITH SOME PACIFIC NORTHWEST AND NORTHERN ROCKIES LIGHT  
PRECIPITATION POSSIBLE BEFORE A MORE WIDESPREAD MOISTURE SURGE  
NEXT WEEKEND.  
 
THE STRONG UPPER RIDGE BUILDING INTO THE WEST WILL LEAD TO A BROAD  
AREA OF HIGHS 10-20F ABOVE NORMAL WEDNESDAY-SUNDAY WITH SLIGHTLY  
HIGHER LOCALIZED ANOMALIES POSSIBLE. THERE IS POTENTIAL TO REACH  
DAILY RECORD HIGHS ACROSS CALIFORNIA WEDNESDAY TO FRIDAY AND  
SPREADING EASTWARD INTO THE INTERMOUNTAIN WEST AND SOUTHWEST AS  
THE RIDGE AXIS SHIFTS EAST. LEADING UPPER LEVEL TROUGHING SHOULD  
SUPPORT TEMPERATURES 10-20F BELOW AVERAGE ACROSS THE  
CENTRAL/SOUTHERN HIGH PLAINS WEDNESDAY. THE COOLER AIR SHOULD  
MODERATE CLOSER TO NORMAL BY THE LATTER PART OF NEXT WEEK AS IT  
PROGRESSES EASTWARD. AHEAD OF THE TROUGH AND COLD FRONTS,  
GENERALLY WARMER THAN NORMAL CONDITIONS ARE LIKELY ACROSS MUCH OF  
THE EASTERN THIRD OF THE U.S. FOR MUCH OF THE WEEK, TRANSITIONING  
TO NEAR NORMAL TEMPERATURES BY FRIDAY AND SATURDAY AND A COOLDOWN  
ASSOCIATED WITH A SECONDARY COLD FRONT IN THE GREAT LAKES BY  
SUNDAY. ISOLATED RECORD HIGHS ARE POSSIBLE OVER PARTS OF FLORIDA  
TUESDAY-WEDNESDAY.  
 
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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