365  
FXUS02 KWBC 080659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST SAT JAN 08 2022  
 
VALID 12Z TUE JAN 11 2022 - 12Z SAT JAN 15 2022  
   
..OVERVIEW
 
 
THE MEDIUM RANGE PERIOD WILL BEGIN ON TUESDAY WITH SPLIT FLOW  
ACROSS THE WESTERN U.S. AS A SOUTHERN STREAM CLOSED LOW DRIFTS  
NEAR BAJA CALIFORNIA THROUGH MIDWEEK WITH RIDGING ACROSS THE  
NORTHWEST IN A REX BLOCK PATTERN. THE SOUTHERN STREAM LOW IS  
CURRENTLY EXPECTED TO PUSH INTO THE FOUR CORNERS AROUND THURSDAY  
WHILE ADDITIONAL PACIFIC ENERGY MOVES TOWARD THE WEST COAST.  
MEANWHILE, SHORTWAVE IMPULSES WILL TRACK THROUGH BROAD TROUGHING  
IN THE EASTERN (ESPECIALLY NORTHEASTERN) U.S. ALONG WITH LOW  
PRESSURE/FRONTAL SYSTEMS.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
REASONABLY GOOD MODEL AGREEMENT AND PREDICTABILITY EXIST EARLY IN  
THE MEDIUM RANGE PERIOD WITH DEEP UPPER TROUGHING ACROSS THE EAST  
AND RIDGING ACROSS THE WEST UNDERCUT BY THE SOUTHERN STREAM UPPER  
LOW. MOST GUIDANCE FOR THE 12/18Z (YESTERDAY) CYCLE WAS ALIGNED  
AND CONSISTENT WITH PREVIOUS RUNS WITH THE POSITION AND CLOSING  
OFF THE INITIAL SOUTHERN STREAM LOW FEATURE AT LEAST FOR A PERIOD  
ON TUESDAY/WEDNESDAY. THE MAIN EXCEPTION IN TERMS OF POSITION WAS  
THE 12Z CMC, WHICH HAS A CENTER POSITION FARTHER TO THE SOUTHWEST  
COMPARED TO THE VAST MAJORITY OF OTHER GUIDANCE. THEN ENERGY  
TRACKING EASTWARD ACROSS THE PACIFIC AND APPROACHING THE WEST  
COAST THURSDAY SHOWS CONSIDERABLY MORE VARIABILITY WITH STRENGTH,  
POSITION, AND TRACK AS WELL AS WHETHER OR NOT THE ENERGY CLOSES  
OFF (WHICH GFS RUNS HAD BEEN PERSISTENT WITH UNTIL THE 18Z RUN).  
TRENDS IN RECENT GUIDANCE INDICATE THAT IMPULSE MAY DRIFT IN THE  
EASTERN PACIFIC THROUGH LATE WEEK OR AT LEAST STAY LIMITED TO THE  
NORTHWEST WITH LESS INTERACTION WITH THE INITIAL LOW, BUT WITH LOW  
CONFIDENCE. CMC RUNS ARE THE EXCEPTION TO THIS IN TERMS OF  
DETERMINISTIC GUIDANCE, AND SPAGHETTI PLOTS SHOW TREMENDOUS  
VARIABILITY IN THE DETAILS OF THE WESTERN U.S. FLOW BY FRIDAY AND  
SATURDAY.  
 
MEANWHILE IN THE EAST, INITIAL MODEL AGREEMENT IS QUITE GOOD WITH  
THE TROUGH AXIS OVER THE EASTERN SEABOARD EARLY TUESDAY, WHICH  
LIFTS AWAY AND RELAXES THE AMPLITUDE OF THE OVERALL FLOW BY  
MIDWEEK, THOUGH ADDITIONAL SHORTWAVES APPROACH. ONE UPSTREAM  
SHORTWAVE DEVELOPS SOME CONSIDERABLE DIFFERENCES AMONG MODELS BY  
WEDNESDAY AND THURSDAY. IN TERMS OF THE 12Z MODEL CYCLE, THE UKMET  
AND CMC APPEARED TO BE OUTLIERS IN HOW DEEP THE ENERGY FROM THE  
SHORTWAVE CAUSES THE TROUGH AXIS TO DIG IN THE EAST-CENTRAL U.S.,  
AS CONFIRMED BY THE 12Z CMC THE DEEPEST AND THE UKMET COMPARED TO  
INDIVIDUAL ENSEMBLE MEMBERS' 500MB HEIGHTS. HOWEVER, INCOMING 00Z  
GUIDANCE INCLUDING THE GFS AND ECMWF SHOW DEEPER TROUGHING THAN  
THEIR PREVIOUS RUNS, EVEN CLOSING OFF A LOW ACROSS THE ATLANTIC BY  
FRIDAY, SO THE TREND APPEARS TO BE IN A DEEPER DIRECTION.  
 
THE WPC FRONTS/PRESSURES FORECAST WAS BASED MAINLY ON A BLEND OF  
THE 12Z/18Z GFS AND 12Z ECMWF EARLY ON, PHASING IN THE GEFS AND EC  
ENSEMBLE MEANS AS THE PERIOD PROGRESSED TO DOWNPLAY THE SPECIFICS  
OF A PARTICULAR MODEL RUNS. AT THE TIME, DID NOT FAVOR THE  
CMC/UKMET FOR THE REASONS ABOVE, BUT GIVEN THE WAY 00Z MODELS ARE  
TRENDING, PERHAPS THEIR INFLUENCE WITH A DEEPER TROUGH IN THE EAST  
WOULD HAVE BEEN HELPFUL.  
   
..WEATHER HIGHLIGHTS
 
 
DRIER CONDITIONS ARE LIKELY OVER MUCH OF THE CONTIGUOUS U.S. ON  
TUESDAY AS LARGE SURFACE HIGHS INFLUENCE THE INTERMOUNTAIN WEST TO  
THE CENTRAL U.S. BEHIND A COLD FRONT, AND HIGH PRESSURE WILL PUSH  
INTO THE EAST ON WEDNESDAY. SHOWERS COULD LINGER OVER FLORIDA ON  
TUESDAY AFTER THE FRONT PASSES THROUGH, WHILE GENERALLY WESTERLY  
FLOW COULD CAUSE LAKE EFFECT SNOW DOWNWIND OF THE GREAT LAKES AT  
TIMES THROUGH THE WEEK, THOUGH IN LESSER AMOUNTS THAN DURING THE  
SHORT RANGE PERIOD MONDAY. THE PACIFIC NORTHWEST SHOULD SEE  
PERIODS OF PRECIPITATION AS FRONTS APPROACH THE AREA, WITH HIGHER  
TOTALS OVER TYPICAL UPSLOPE AREAS OF THE OLYMPICS AND CASCADES.  
LOCALLY MODERATE TO HEAVY ACTIVITY MAY BE POSSIBLE OVER THE  
OLYMPICS AND VICINITY AROUND MIDWEEK WHEN THE AREA COULD BE ON THE  
SOUTHEAST FRINGE OF AN ATMOSPHERIC RIVER EVENT AIMED AT VANCOUVER  
ISLAND. THE UPPER LOW INITIALLY DROPPING SOUTHWARD NEAR THE  
CALIFORNIA COAST MAY SPREAD MOISTURE INTO THE SOUTHWEST BY  
TUESDAY-WEDNESDAY. THIS PRECIPITATION SHOULD BE FAIRLY LIGHT BUT  
HEAVIER RAINFALL MAY DEVELOP OVER THE SOUTHERN PLAINS AND LOWER  
MISSISSIPPI VALLEY BY MID-LATE WEEK AS THE UPPER LOW TRACKS/SHEARS  
NORTHEASTWARD AND THE SURFACE PATTERN BECOMES MORE FAVORABLE FOR  
DRAWING MOISTURE NORTHWARD FROM THE GULF OF MEXICO. IT WILL TAKE  
ADDITIONAL TIME TO REFINE THE DETAILS OF RAINFALL COVERAGE AND  
MAGNITUDE THOUGH.  
 
COLD AIR WILL BE IN PLACE OVER THE UPPER MIDWEST AND SPREADING  
INTO THE NORTHEAST ON TUESDAY, WITH HIGH TEMPERATURES 10-30F BELOW  
AVERAGE FOR ONE OF THE COLDEST DAYS OF THE SEASON THUS FAR. THEN  
THE CENTRAL U.S. WILL SEE A PRONOUNCED WARMING TREND NEXT WEEK  
WITH EXPANDING COVERAGE OF MAX/MIN TEMPERATURES 10-20F ABOVE  
NORMAL TUESDAY ONWARD. SOME LOCATIONS IN THE NORTHERN TWO-THIRDS  
OF THE PLAINS MAY SEE EVEN WARMER READINGS MID-LATE WEEK. ACROSS  
THE WEST EXPECT TO SEE DAYTIME HIGHS WITHIN 10F ON EITHER SIDE OF  
NORMAL THROUGH THE PERIOD, WHILE ABOVE NORMAL LOWS SHOULD BECOME  
MORE PREVALENT WITH TIME. BY THE END OF THE WEEK TEMPERATURES ARE  
CURRENTLY FORECAST TO MODERATE CLOSE TO NORMAL.  
 
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, 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/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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