797  
FXUS02 KWBC 060700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 AM EST TUE FEB 06 2024  
 
VALID 12Z FRI FEB 09 2024 - 12Z TUE FEB 13 2024  
   
..OVERVIEW
 
 
A BROAD RELOADING UPPER TROUGH SHOULD HOLD ON OVER THE WEST INTO  
SATURDAY, BEFORE BEGINNING TO SLOWLY SHIFT EASTWARD AS UPPER  
RIDGING TRIES TO BUILD IN NEAR THE WEST COAST AGAIN AND A COUPLE  
OF STRONG SYSTEMS PUSH THROUGH THE EAST PACIFIC. THE TROUGH WILL  
CONTINUE TO KEEP THIS REGION QUITE ACTIVE WITH ROUNDS OF LOWER  
ELEVATION RAINS AND MOUNTAIN SNOW, INCLUDING POSSIBLY A COUPLE OF  
WEAK ATMOSPHERIC RIVERS INTO THE WEST COAST. MEANWHILE, A STRONG  
UPPER RIDGE SHIFTING OUT OF THE CENTRAL U.S. WILL CONTINUE TO  
SUPPORT WELL ABOVE NORMAL TEMPERATURES THAT COULD BE  
RECORD-SETTING ACROSS THE PARTS OF THE UPPER GREAT LAKES-NORTHEAST  
ON FRIDAY-SATURDAY BEFORE IT BECOMES SUPPRESSED AND SHIFTS  
EASTWARD OFF THE COAST. A FAIRLY STRONG STORM SYSTEM TRACKING OUT  
OF THE GREAT LAKES ON FRIDAY WILL PRODUCE SOME COLD SECTOR SNOW  
AND BRISK WINDS. THEN ADDITIONAL SHORTWAVES/ENERGY FROM THE MEAN  
UPPER TROUGH OVER THE WEST WILL PERIODICALLY EJECT INTO THE  
CENTRAL U.S. THERE IS SIGNIFICANT UNCERTAINTY OVER HOW ASSOCIATED  
SYSTEMS WILL REFLECT AT THE SURFACE TO THE EAST OF THE ROCKIES,  
BUT THE GENERAL PATTERN APPEARS FAVORABLE FOR INCREASING RAINFALL  
ACROSS THE MID-SOUTH/SOUTHEAST BY LATE WEEK OR WEEKEND.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
SHORTWAVE DIFFERENCES WITHIN THE WESTER U.S. UPPER TROUGH AND HOW  
THE TROUGH EVOLVES AND EVENTUALLY PUSHES EASTWARD CONTINUES TO  
PRESENT THE MOST UNCERTAINTY DURING THE MEDIUM RANGE PERIOD. AS  
EARLY AS FRIDAY-SATURDAY, THERE ARE NOTABLE DIFFERENCES IN  
SHORTWAVE ENERGY THAT DIGS SOUTHWARD ALONG THE WEST COAST AND HOW  
THAT BECOMES ABSORBED INTO THE MEAN TROUGH. MODELS HAVE SHOWN  
BETTER AGREEMENT FOR A MUCH MORE AMPLIFIED (WITH A POSSIBLE BRIEF  
CLOSED LOW) OVER THE SOUTHWEST THIS COMING WEEKEND, BUT AS THAT  
SOUTHERN STREAM ENERGY MOVES INTO THE SOUTH-CENTRAL PLAINS AND  
POSSIBLY INTERACTS WITH NORTHERN STREAM ENERGY DROPPING OUT OF  
CENTRAL CANADA PRESENTS SIGNIFICANT UNCERTAINTY IN THE PATTERN  
EVOLUTION ACROSS THE MIDWEST/EAST EARLY NEXT WEEK. THROUGH THE NEW  
00Z RUN TONIGHT, THE GFS SHOWS DISTINCT SEPARATION BETWEEN THE TWO  
SYSTEMS, WITH THE NORTHERN STREAM SYSTEM OUT RUNNING THE SOUTHERN  
STREAM AND A STRONG LOW PRESSURE SYSTEM THAT TRACKS ACROSS THE  
SOUTHEAST AND EVENTUALLY OFF THE MID-ATLANTIC COAST. PRIOR RUNS OF  
THE ECMWF AND CMC ON THE OTHER HAND SHOWED MORE INTERACTION IN THE  
TWO STREAMS RESULTING IN A SHARP SHORTWAVE/AMPLFIED TROUGH AND  
STRONG SURFACE LOW THAT TRACKS NORTHWARD INTO THE MIDWEST AND OFF  
THE NORTHEAST COAST AT THE SAME TIME. HOWEVER, THE NEW 00Z RUNS  
(AVAILABLE AFTER WPC FORECAST GENERATION) TONIGHT CAME MORE IN  
LINE WITH THE GFS SCENARIO. STILL TOO EARLY TO SUGGEST THIS MAY BE  
A TREND, BUT IT WILL NEED TO BE WATCHED AS IT WOULD HAVE SENSIBLE  
WEATHER IMPACTS. BOTH THE GEFS AND ECENS ENSEMBLES SHOW A LOT OF  
UNCERTAINTY, WITH THE RESULTING MEAN FORECAST QUITE WEAK AND  
WASHED OUT. THE WPC LATE PERIOD FORECAST USED A BLEND OF THE  
ENSEMBLE MEANS, WITH SOME ATTEMPTS TO ADD A LITTLE SYSTEM  
DEFINITION FROM YESTERDAYS 12Z ECMWF. THIS DID RESULT IN  
NOTICEABLE CHANGES TO PREVIOUS WPC CONTINUITY, WITH THE DEPICTION  
OF A MORE DEFINED WAVE/SYSTEM GIVEN THE BETTER MODEL SUPPORT.  
EITHER WAY, A VERY LOW CONFIDENCE FORECAST ACROSS THE EASTERN  
THIRD OF THE COUNTRY EARLY NEXT WEEK WITH PLENTY OF TIME FOR MODEL  
SWINGS AND VARIABILITY.  
 
ELSEWHERE, THERE IS A LOT OF UNCERTAINTY AS WELL WITH POTENTIAL  
FOR A COUPLE OF WEAKER SHORTWAVES TO IMPACT THE WEST COAST  
SUNDAY-TUESDAY, BUT QUESTIONS ARISE WITH HOW MUCH THESE ARE ABLE  
TO DISRUPT/GET THROUGH THE OVERALL MEAN RIDGE THAT TRIES TO BUILD  
BACK IN OVER THE WEST. A BLEND OF THE ENSEMBLE MEANS HELPED TO  
SMOOTH OUT THESE DIFFERENCES AND WAS A GOOD STARTING POINT FOR THE  
FORECAST OUT WEST LATE PERIOD.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
GENERAL BROAD TROUGHING OVER THE SOUTHWEST SHOULD KEEP THE WESTERN  
U.S. PERIODICALLY ACTIVE WITH WIDESPREAD LOWER ELEVATION  
RAIN/MOUNTAIN SNOWS INTO NEXT WEEKEND. BEST SNOW POTENTIAL SHOULD  
BE OVER THE FAVORED TERRAIN OF THE FOUR CORNERS STATES. ADDITIONAL  
ROUNDS OF RAIN AND MOUNTAIN SNOWS COULD COME INTO CALIFORNIA  
THROUGH FRIDAY, THOUGH WITH VERY LOW CONFIDENCE ON EXACT AMOUNTS  
AND LOCATIONS OF HEAVIEST PRECIPITATION. GIVEN EXTREME RAINFALL  
ACROSS MUCH OF CALIFORNIA RECENTLY, THE AREA IS MORE SENSITIVE  
THAN USUAL TO ADDITIONAL RAINFALL, BUT THE FACT THAT ANY DIGGING  
DYNAMICS ALOFT SHOULD TAKE AN ALONG-COAST OR INLAND PATH SHOULD  
REDUCE THE HEAVY PRECIPITATION THREAT. GUIDANCE SPREAD FOR  
SHORTWAVE DETAILS ALOFT AND RESULTING QPF KEEPS CONFIDENCE TOO LOW  
TO DEPICT ANY RISK AREAS ON THE DAY 4 EXCESSIVE RAINFALL OUTLOOK  
VALID ON FRIDAY. PRECIPITATION MAY CLEAR OUT OF MUCH OF THE  
INTERMOUNTAIN WEST BY SATURDAY, BUT ONE OR MORE PROGRESSIVE  
SYSTEMS COULD BRING EPISODES OF LIGHT TO MODERATE TOTALS TO THE  
PACIFIC NORTHWEST.  
 
FAIRLY STRONG LOW PRESSURE WILL BE TRACKING OUT OF THE GREAT LAKES  
ON FRIDAY, THOUGH WITH STILL SOME LINGERING SNOW AND GUSTY WIND  
THREAT ON THE BACKSIDE OF THE SYSTEM. THE TRAILING COLD FRONT  
SHOULD FOCUS MOISTURE AND SOME WEAK INSTABILITY TO PRODUCE RAIN  
ACROSS THE MID-SOUTH, ESPECIALLY INTO THE WEEKEND AIDED BY  
SHORTWAVE ENERGY OUT OF THE SOUTHWEST. THIS MAY INCREASE POTENTIAL  
FOR TRAINING/REPEAT SHOWERS AND THUNDERSTORMS OVER SOME AREAS, BUT  
WITH STILL A LOT OF SPREAD IN THE DETAILS AND CORRESPONDING  
LOCATION/MAGNITUDE/TIMING OF THE HEAVIEST RAINFALL. ENSEMBLES  
SUGGEST THE PRIMARY REGION THAT REQUIRES MONITORING EXTENDS FROM  
THE TENNESSEE VALLEY INTO LOWER MISSISSIPPI VALLEY AND SOUTHEAST.  
THIS OVERALL AREA HAS A MIX OF ANTECEDENT SOIL MOISTURE  
CONDITIONS. DESPITE THE PRESENCE OF ANAMOLOUS MOISTURE AND SOME  
INSTABILITY, CONFIDENCE REMAINS TOO LOW THOUGH TO INTRODUCE ANY  
RISK AREAS IN THE DAYS 4-5 EROS AT THIS TIME, BUT AGAIN THE  
GENERAL PATTERN MAY ULTIMATELY SUPPORT A HEAVY RAINFALL EVENT  
SOMETIME IN THE WEEKEND TIME FRAME. MEANWHILE, THE FAR NORTHERN  
FRINGE OF THE SOUTHERN TIER MOISTURE SHIELD COULD PRODUCE SOME  
SNOW FROM THE WEEKEND INTO EARLY NEXT WEEK, BUT HIGHLY UNCERTAIN  
AND DEPENDENT ON THE EXACT TRACK OF THE VERY UNCERTAIN LOW  
PRESSURE SYSTEM OUT OF THE SOUTH-CENTRAL STATES.  
 
THE UPPER RIDGE PROGRESSING FROM THE EASTERN U.S. INTO THE WESTERN  
ATLANTIC LATE THIS WEEK WILL SUPPORT A BROAD AREA OF UNSEASONABLY  
WARM TEMPERATURES WHICH WILL GRADUALLY SHIFT FROM THE GREAT  
LAKES/MIDWEST TOWARD THE EAST COAST. DEPARTURES FROM NORMAL SHOULD  
EVENTUALLY BECOME SOMEWHAT LESS EXTREME WITH TIME. THE UPPER  
MIDWEST/GREAT LAKES SHOULD BE WARMEST VERSUS NORMAL ON FRIDAY WITH  
ANOMALIES UP TO PLUS 30-35F FOR MORNING LOWS AND PLUS 20-30F FOR  
DAYTIME HIGHS, LEADING TO WIDESPREAD DAILY TEMPERATURE RECORDS. BY  
THE WEEKEND EXPECT THE EAST TO SEE LOWS OF 15-30F ABOVE NORMAL AND  
HIGHS 10-20F ABOVE NORMAL WHILE THE CENTRAL U.S. TRENDS CLOSER TO  
NORMAL. IN CONTRAST, THE SOUTHWEST U.S./CALIFORNIA SHOULD BE  
PERSISTENTLY COOL, ESPECIALLY FOR DAYTIME HIGHS THAT MAY BE UP TO  
10-15F BELOW NORMAL INTO THE WEEKEND. THIS REGION SHOULD BEGIN TO  
SEE A MODERATING TREND BY SUNDAY OR MONDAY. CLOUDS/PRECIPITATION  
OVER THE WEST SHOULD KEEP MOST MORNING LOWS WITHIN A FEW DEGREES  
ON EITHER SIDE OF NORMAL BUT A FEW LOCALIZED COOLER SPOTS ARE  
POSSIBLE.  
 
SANTORELLI  
 
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 FORECAST, EXCESSIVE RAINFALL OUTLOOK,  
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY  
MESSAGES 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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 

 
 
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