816  
FXUS02 KWBC 061903  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
201 PM EST SUN MAR 06 2022  
 
VALID 12Z WED MAR 09 2022 - 12Z SUN MAR 13 2022  
   
..OVERVIEW
 
 
BROAD TROUGHING OVER THE CONUS MIDWEEK SHOULD BE REINFORCED BY A  
COUPLE OF POTENT SHORTWAVES, THE FIRST DIVING INTO THE NORTHWEST  
WEDNESDAY AND ANOTHER REACHING THE NORTH-CENTRAL U.S. THURSDAY  
INTO FRIDAY. THESE FEATURES SHOULD PRESS THE TROUGH AXIS EASTWARD  
LATE WEEK INTO THE WEEKEND, ALONG WITH AN ARCTIC COLD FRONT THAT  
WILL SPREAD CHILLY TEMPERATURES ACROSS THE INTERIOR WEST AND  
CENTRAL U.S. AND INTO THE EAST BY THE WEEKEND. EXPECT SNOW TO THE  
NORTHWEST OF THE LOW FROM THE CENTRAL ROCKIES/PLAINS TO THE  
MIDWEST ON WEDNESDAY AND THURSDAY, WITH LESS CERTAIN POTENTIAL FOR  
WINTRY WEATHER OVER THE OHIO VALLEY AND INTERIOR NORTHEAST FRIDAY  
AND SATURDAY. MEANWHILE SHOWERS AND THUNDERSTORMS ARE LIKELY IN  
THE SOUTHEAST THROUGH LATE WEEK BEFORE THE COLD FRONT CLEARS OUT  
THE MOISTURE BY NEXT SUNDAY. FLOW SHOULD BECOME SOMEWHAT MORE  
ZONAL ACROSS THE CONUS EARLY NEXT WEEK AS THE TROUGH LIFTS OUT OF  
THE EAST, WITH WEAK SYSTEMS THROUGH THE NORTHERN TIER STATES.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE CONTINUES TO SHOW FAIRLY GOOD AGREEMENT FOR THE  
OVERALL PATTERN ESPECIALLY INITIALLY IN THE MEDIUM RANGE PERIOD  
GIVEN THE LARGE SCALE OF THE FEATURES--STRONG EAST PACIFIC  
RIDGING, TROUGHING ACROSS THE LOWER 48, AND A SUBTROPICAL HIGH  
OVER THE CARIBBEAN TO RIDGING IN THE ATLANTIC. HOWEVER, THERE ARE  
SOME DIFFERENCES IN THE SHORTWAVE DETAILS THAT BECOME IMPACTFUL BY  
THE LATTER PART OF THE WEEK ESPECIALLY WITH THE TIMING OF THE  
TROUGH'S MOVEMENT AND THUS THE COLD FRONTAL TIMING. BROADLY, THE  
GFS MODEL SUITE IS FASTER WITH THE TROUGH AXIS AND FRONT PRESSING  
EASTWARD COMPARED TO THE ECMWF SUITE AND THE CMC. THIS IS SHOWN BY  
MOST INDIVIDUAL ENSEMBLE MEMBERS AS WELL AS THE OPERATIONAL RUNS  
AND ENSEMBLE MEANS FROM THE 00/06Z CYCLE, AND REMAINED THE CASE IN  
THE 12Z GUIDANCE THAT HAS COME IN THUS FAR. GIVEN TYPICAL MODEL  
PERFORMANCE, THE WPC FORECAST ATTEMPTED TO TAKE AN APPROACH IN  
BETWEEN BUT SOMEWHAT FAVORING THE ECMWF SUITE, WHICH SLOWED THE  
FRONT AND TROUGH AXIS DOWN FROM CONTINUITY A BIT. THE 06Z GFS WAS  
SOMEWHAT SLOWER AND THUS BETTER CLUSTERED WITH OTHER GUIDANCE  
COMPARED TO THE 00Z RUN, SO PREFERRED THE 06Z RUN. DIFFERENCES IN  
THE TROUGH/FRONT ALSO LEAD TO VARIABILITY WITH THE STRENGTH AND  
PROGRESSION OF GREAT LAKES LOW PRESSURE FRIDAY AND ITS EVENTUAL  
TRACK NORTHEASTWARD--OVERALL SLOWER TO STRENGTHEN AND MOVE. AS  
NOTED IN THE PREVIOUS DISCUSSION, CMC RUNS INCLUDING YESTERDAY'S  
12Z AND TODAY'S 00Z END UP CLOSING OR ALMOST CLOSING OFF AN UPPER  
LOW IN THE MIDWEST BY SATURDAY, WHICH IS AN OUTLIER COMPARED TO  
OTHER GUIDANCE THAT KEEPS THE TROUGH PHASED WITH A NORTHERN CANADA  
UPPER LOW. THUS THE CMC WAS NOT PREFERRED, BUT ITS NEW 12Z RUN  
SEEMS COMPARATIVELY MORE IN LINE WITH CONSENSUS. THEN THERE IS  
FAIRLY GOOD MODEL CONSENSUS FOR THE RIDGING INITIALLY OVER THE  
EAST PACIFIC TO TRACK INLAND LATE WEEK, BUT THEN GET SUPPRESSED BY  
SHORTWAVE ENERGY APPROACHING OR ENTERING THE PACIFIC NORTHWEST BY  
NEXT SUNDAY, BUT THERE ARE STILL UNCERTAINTIES WITH THE TIMING OF  
SHORTWAVES AND SURFACE FEATURES THERE.  
 
IN SUMMARY THE WPC FORECAST BEGAN WITH A MULTI-MODEL DETERMINISTIC  
BLEND, AND GRADUALLY TRANSITIONED TO A BLEND FAVORING THE ECMWF IN  
TERMS OF DETERMINISTIC GUIDANCE WITH SOME 06Z GFS INPUT, AND  
ADDING AND INCREASING THE PROPORTION OF THE ENSEMBLE MEANS,  
PARTICULARLY THE ECENS MEAN, TO REDUCE INDIVIDUAL MODEL  
DIFFERENCES.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A STATIONARY BOUNDARY SETTLING ACROSS THE SOUTHEAST AND AMPLE  
MOISTURE AND INSTABILITY FROM THE GULF OF MEXICO SHOULD KEEP  
SHOWERS AND STORMS IN THE FORECAST WEDNESDAY TO EARLY SATURDAY.  
LOCALIZED HEAVY RAINFALL RATES ARE LIKELY IN THIS ENVIRONMENT, AND  
FLOODING/FLASH FLOODING MAY BE A THREAT WITH HEAVY DOWNPOURS,  
ESPECIALLY WHERE MULTIPLE ROUNDS OF CONVECTION TRACK OVER THE SAME  
AREAS DURING THE PERIOD, DESPITE THE ANTECEDENT DRY CONDITIONS.  
MEANWHILE, A SHORTWAVE MOVING THROUGH THE WEST ON WEDNESDAY WILL  
CONTINUE A THREAT FOR HEAVY MOUNTAIN SNOWS FOR PARTS OF THE  
INTERIOR WEST AND CENTRAL ROCKIES. A LOW PRESSURE SYSTEM SPINNING  
UP IN THE LEE OF THE ROCKIES AND LIFTING INTO THE UPPER MIDWEST  
THURSDAY-FRIDAY BRINGS A WINTER STORM THREAT FROM THE CENTRAL  
PLAINS TO THE UPPER MIDWEST. THE ELONGATED UPPER TROUGH SHOULD TAP  
GULF OF MEXICO MOISTURE WITH WIDESPREAD RAIN INTO THE EAST AHEAD  
OF THE COLD FRONT ON FRIDAY, WITH SOME POTENTIAL FOR WINTRY  
WEATHER ON THE NORTHERN/WESTERN SIDE OF THE PRECIPITATION SHIELD,  
BUT WITH LOW CONFIDENCE FOR AMOUNTS AND PLACEMENT AT THIS POINT.  
THE NEXT SYSTEM COMING INTO THE NORTHWEST NEXT WEEKEND IS LIKELY  
TO INCREASE RAIN AND MOUNTAIN SNOW CHANCES ACROSS THE PACIFIC  
NORTHWEST AND NORTHERN ROCKIES.  
 
ARCTIC SOURCED AIR WILL SPILL INTO THE PLAINS, WITH DAYTIME HIGHS  
20-30+ DEGREES BELOW NORMAL AS FAR SOUTH AS TEXAS THROUGH FRIDAY.  
OVERNIGHT LOWS ACROSS THE NORTHERN PLAINS AND IN HIGHER ELEVATIONS  
OF THE ROCKIES ARE LIKELY TO BE NEAR OR BELOW ZERO FOR MANY  
LOCATIONS. AHEAD OF THE COLD FRONT, ABOVE NORMAL TEMPERATURES  
SHOULD SPREAD ACROSS THE EASTERN THIRD OF THE COUNTRY THURSDAY AND  
FRIDAY BEFORE BEING REPLACED BY BELOW NORMAL TEMPERATURES BY  
SATURDAY FOLLOWING THE PASSAGE OF THE COLD FRONT. BY NEXT SUNDAY,  
MOST OF THE COUNTRY SHOULD MODIFY CLOSER TO NORMAL AS UPPER FLOW  
BECOME LESS AMPLIFIED, THOUGH WITH LINGERING COOL TEMPERATURES IN  
THE EAST AND ALONG THE GULF COAST.  
 
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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