273  
FXUS02 KWBC 170704  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
203 AM EST THU FEB 17 2022  
 
VALID 12Z SUN FEB 20 2022 - 12Z THU FEB 24 2022  
 
...DEVELOPING HEAVY RAINFALL THREAT ACROSS PORTIONS OF THE SOUTH  
NEXT WEEK...  
 
   
..OVERVIEW
 
 
AS NEXT WEEK BEGINS, QUASI-ZONAL FLOW ACROSS MUCH OF THE U.S. WILL  
BE TRANSITIONING TO A MORE AMPLIFIED PATTERN AS UPPER-LEVEL ENERGY  
SPILLS INTO THE WEST TO CREATE DEEP TROUGHING, WHILE RIDGING  
BUILDS IN THE EAST. THE TROUGH WILL SLOWLY TRACK EASTWARD ALONG  
WITH A STRONG FRONTAL SYSTEM, BEHIND WHICH ARCTIC HIGH PRESSURE  
SHOULD PRODUCE WELL BELOW NORMAL TEMPERATURES IN THE CENTRAL U.S.,  
WITH WARMER THAN AVERAGE TEMPERATURES IN THE EAST. LIGHT TO  
MODERATE PRECIPITATION IS LIKELY IN THE WEST UNDERNEATH THE TROUGH  
AND SPREADING INTO THE CENTRAL AND EASTERN U.S., WITH THE  
POSSIBILITY OF NORTHERN TIER SNOW AND SOUTHERN U.S. RAIN AND  
THUNDERSTORMS. A MULTI-DAY RAINY PERIOD FOR PARTS OF THE LOWER  
MISSISSIPPI AND TENNESSEE VALLEYS COULD LEAD TO FLOODING AND FLASH  
FLOODING THERE.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT MODEL GUIDANCE SHOWS FAIRLY GOOD AGREEMENT WITH THE LARGE  
SCALE PATTERN THROUGH THE MIDDLE OF NEXT WEEK, THOUGH WITH PLENTY  
OF UNCERTAINTY IN THE SMALLER SCALE DETAILS, LIKE INDIVIDUAL  
SHORTWAVES AS WELL AS THE MAIN TROUGH'S TRACK AND TIMING. THERE  
REMAINS GOOD AGREEMENT FOR A COMPACT UPPER LOW LIKELY WEST OF BAJA  
CALIFORNIA TO BEGIN THE PERIOD SUNDAY AND WEAKENING AS IT MOVES  
EASTWARD, AS WELL AS GOOD CONSENSUS ON THE LARGE SCALE FOR ENERGY  
TO SPILL INTO THE WEST EAST OF AN AMPLIFIED EASTERN PACIFIC RIDGE  
BY NEXT SUNDAY-MONDAY, GRADUALLY DEEPENING AND SHIFTING SLOWLY  
EASTWARD. FOR THE 12/18Z MODEL CYCLE, EACH MODEL SUITE MAINLY  
STAYED WITHIN THEIR OWN CAMPS, AS SHOWN BY THE SPAGHETTI PLOTS OF  
INDIVIDUAL ENSEMBLE MEMBERS AND CLUSTER ANALYSIS. FOR THE MOST  
PART, THE ECMWF SUITE INCLUDING THE DETERMINISTIC, THE ENSEMBLE  
MEAN, AND THE BULK OF ENSEMBLE MEMBERS SHOWED A SLOWER AND DEEPER  
SOLUTION FIRST WITH THE SMALL BAJA UPPER LOW AND MORE PROMINENTLY  
WITH THE LARGER SCALE TROUGH FORMING AND BROADENING IN THE WEST.  
THE CMC AND GFS SUITES WERE MORE PROGRESSIVE WITH THESE FEATURES.  
THESE DIFFERENCES ARE MOST EVIDENT BY WEDNESDAY-THURSDAY, WITH ONE  
REASON FOR THE DIFFERENCES IN THE TROUGH TRACK BEING ADDITIONAL  
ENERGY SPILLING SOUTHWARD NEAR THE WEST COAST--STRONGER IN THE GFS  
RUNS WITH LESS PHASING WITH THE INITIAL TROUGH. THE EVOLUTION OF  
UPSTREAM ENERGY IS RATHER UNCERTAIN STEMMING FROM HIGH LATITUDES  
AND ROUNDING THE PACIFIC RIDGE, LEADING TO LOW CONFIDENCE IN THE  
SPECIFICS OF THE EMBEDDED ENERGIES WITHIN THE MAIN TROUGH AND ITS  
EVENTUAL MOVEMENT. GIVEN THESE DIFFERENCES, AND CONSIDERING COMMON  
MODEL BIASES, THE WPC FORECAST STROVE FOR A MIDDLE GROUND SOLUTION  
WITH THE PATTERN, NOT DISCOUNTING THE SLOWER EC OR THE FASTER  
CMC/GFS SOLUTIONS BUT LEANING IN BETWEEN. THE INCOMING 00Z  
DETERMINISTIC ECMWF APPEARS TO HAVE SPED UP SOMEWHAT COMPARED TO  
THE 12Z RUN AND IS FORTUNATELY SOMEWHAT IN LINE WITH THE WPC  
FORECAST TROUGH AXIS. THE FORECAST BLEND WAS BASED ON THE 12/18Z  
(NEWEST AVAILABLE AT THE TIME) DETERMINISTIC MODEL SUITE THROUGH  
DAYS 3-5, PHASING IN AND INCREASING THE PROPORTION OF THE GEFS AND  
EC ENSEMBLE MEANS BY THE LATER DAYS RATHER THAN KEYING ON ANY  
PARTICULAR MODEL.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PRECIPITATION WILL BE INCREASING IN THE PACIFIC NORTHWEST AND  
NORTHERN ROCKIES OVER THE WEEKEND WITH THE UPPER TROUGH COMING IN.  
COASTAL AND VALLEY RAIN AND MOUNTAIN SNOW ARE LIKELY OVER THE  
PACIFIC NORTHWEST SPREADING INTO CALIFORNIA, THE GREAT BASIN, AND  
THE ROCKIES AND PERSISTING THERE INTO THE MIDDLE OF NEXT WEEK.  
SNOW COULD ALSO SPREAD FARTHER EAST INTO THE NORTHERN HIGH PLAINS  
SUNDAY AND INTO THE REST OF THE NORTHERN TIER STATES AS THE FIRST  
HALF OF THE WEEK PROGRESSES. THE CONFIDENCE IN THE AXIS OF  
HEAVIEST SNOW AND SNOWFALL AMOUNTS REMAINS SOMEWHAT LOW. FARTHER  
SOUTH, MOIST INFLOW IS FORECAST TO RETURN TO THE SOUTH-CENTRAL AND  
SOUTHEASTERN U.S., WITH INCREASING CHANCES FOR HEAVY TO POSSIBLY  
EXCESSIVE RAINFALL. MODELS SEEM TO BE CONVERGING ON PORTIONS OF  
THE LOWER MISSISSIPPI/TENNESSEE VALLEY STATES AS THE GREATEST  
THREAT FOR HEAVY RAINFALL NEXT MONDAY-WEDNESDAY. MULTIPLE ROUNDS  
OF RAIN AND STORMS OVER THE SAME AREA COULD INCREASE THE POTENTIAL  
FOR FLOODING AND FLASH FLOODING. THERE REMAIN PLENTY OF  
UNCERTAINTY IN THE DETAILS WHICH LIKELY ARE GOING TO TAKE ANOTHER  
FEW DAYS TO RESOLVE, BUT REGARDLESS, THE PATTERN ITSELF WOULD  
SUPPORT SOME SORT OF HEAVY RAINFALL AND POSSIBLY SEVERE WEATHER  
WITH THUNDERSTORMS FOR THE FIRST HALF OF THE WEEK.  
 
TEMPERATURES AS NEXT WEEK BEGINS ARE EXPECTED TO BE ABOVE NORMAL  
FOR PARTS OF THE WEST INTO THE PLAINS, WITH THE LARGEST ANOMALIES  
OF HIGHS 20+ DEGREES ABOVE AVERAGE OVER NEBRASKA. AS THE PATTERN  
AMPLIFIES, THE SOUTH-CENTRAL U.S. TO THE EAST COAST WILL FURTHER  
WARM THROUGH THE FIRST HALF OF NEXT WEEK, WITH WIDESPREAD HIGHS  
10-20F AND LOWS 20-30F ABOVE NORMAL. MEANWHILE, A COLD ARCTIC HIGH  
IS FORECAST TO EXPAND ACROSS THE NORTH-CENTRAL U.S., LEADING TO  
WELL BELOW AVERAGE TEMPERATURES INITIALLY ACROSS THE NORTHERN HIGH  
PLAINS AND SPREADING SOUTHWARD (AS FAR SOUTH AS TEXAS) THROUGH  
MIDWEEK. TEMPERATURES IN SOME PLACES COULD BE 30 OR MORE DEGREES  
BELOW NORMAL, AND HIGHS IN THE SINGLE DIGITS TO EVEN BELOW 0F ARE  
EXPECTED FOR MONTANA, THE DAKOTAS, AND NORTHERN MINNESOTA MONDAY  
AND TUESDAY WITH COLD TEMPERATURES LINGERING THROUGH WEDNESDAY AND  
THURSDAY AS WELL.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page