025
FXUS02 KWBC 291900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST WED NOV 29 2023
VALID 12Z SAT DEC 02 2023 - 12Z WED DEC 06 2023
...MULTI-DAY WET PATTERN FOR THE NORTHWEST TO ALSO INCLUDE HEAVY
SNOW THREATS INLAND FROM THE CASCADES TO THE NORTH-CENTRAL
INTERMOUNTAIN WEST/ROCKIES...
..OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
A COMPLEX AND ACTIVE WEATHER PATTERN IS PROJECTED TO CONTINUE
THROUGH THE WEEKEND AND INTO NEXT WEEK. AN AMPLIFIED TROUGH WILL
BE REINFORCED BY A COUPLE OF SHORTWAVES AS IT MOVES AND
PERIODICALLY REINFORCED FROM THE INTERIOR WEST TO THE EAST COAST
SATURDAY-MONDAY. AMPLIFIED RIDGING BUILDS BEHIND THIS ACROSS THE
WEST AND EVENTUALLY THE PLAINS EARLY NEXT WEEK AS THE NEXT SYSTEM
MOVES IN TO THE WEST COAST FROM THE EAST PACIFIC NEXT WEDNESDAY.
THE GUIDANCE CONTINUES TO BE QUITE AGREEABLE ON THE LARGE
SCALE/SYNOPTIC PATTERN BUT STILL WITH UNCERTAINTY IN THE DETAILS.
RUN TO RUN VARIABILITY AND TIMING OF INDIVIDUAL SHORTWAVES THROUGH
THE MIDWEST AND EAST THIS WEEKEND/EARLY NEXT WEEK STILL TRANSLATES
TO EVEN SOME REGIONAL SENSIBLE WEATHER/PRECIPITATION UNCERTAINTIES
ESPECIALLY ACROSS THE EAST. HOWEVER, FORECAST SPREAD HAS IMPROVED
SOME SINCE YESTERDAY, BOLSTERING CONFIDENCE TO A DEGREE. OUT WEST,
MODELS AGREE THAT AN ATMOSPHERIC RIVER MAY IMPACT THE WEST COAST
THIS WEEKEND, BUT STILL SHOW CONSIDERABLE DIFFERENCES IN PLACEMENT
OF THE HEAVIEST QPF. THE LATEST NBM STILL SEEMS TOO WET IN SPOTS,
AND THE WPC FORECAST TEMPERED THAT DOWN SOMEWHAT GIVEN
UNCERTAINTIES. THAT SAID, THE DEPICTED PATTERN WILL BE QUITE WET
AND SNOWY AND OFFERS PERIODS OF ENHANCED WINDS WITH PROGRESSIVE
PASSAGE OF DYNAMIC SYSTEMS.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY
DERIVED FROM A COMPOSITE BLEND OF BEST CLUSTERED GUIDANCE FROM THE
00 UTC GFS/ECMWF/UKMET/CANADIAN AND ECMWF ENSEMBLE MEAN FOR THE
COMING WEEKEND INTO MONDAY. REPLACED THE UKMET IN THIS BLEND WITH
THE 00 UTC GEFS MEAN THROUGH EARLY-MID NEXT WEEK TO ADDRESS
GROWING FORECAST SPREAD. OVERALL, THE 06 UTC GFS/GEFS WERE A BIT
OF AN OUTLIER WITH SHORTWAVES, BUT THE 12 UTC GUIDANCE CYCLE IS
NOW BACK MORE IN LINE WITH EARLIER 00 UTC GUIDANCE. WPC PRODUCT
CONTINUITY WAS REASONABLY MAINTAINED.
..WEATHER/HAZARDS HIGHLIGHTS
OUT WEST, PRECIPITATION WILL BE ONGOING AS THIS FORECAST PERIOD
BEGINS SATURDAY, WITH A PROTRACTED WET EVENT INTO THE NORTHWEST
CONTINUING WELL INTO NEXT WEEK, WITH GROWING TOTALS AND IMPACTS
POSSIBLE. SOME MODEST RAINFALL TOTALS ARE LIKELY ALONG THE COAST,
WITH POTENTIALLY HEAVY SNOWS WITH GUSTY WINDS ALSO FARTHER INLAND
ACROSS THE HIGHER ELEVATIONS OF THE CASCADES AND NORTHERN SIERRAS
THROUGH THE NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES BUT PERHAPS
ESPECIALLY THIS WEEKEND FROM AROUND THE GRAND TETONS TO THE
NORTHERN WASATCH. A SMALL MARGINAL RISK FOR EXCESSIVE RAINFALL WAS
MAINTAINED FOR THE DAY 4/SATURDAY ERO ACROSS FAR NORTHWEST
CA/SOUTHWEST OR GIVEN GUIDANCE QPF TRENDS IN A WET PATTERN. THE
STRONGER SYSTEM/POTENTIAL AR MOVES IN SUNDAY AND WITH SNOW LEVELS
RISING, COULD BRING A MORE WIDESPREAD HEAVY RAINFALL THREAT ALONG
THE OREGON COAST AND WESTERN SLOPES OF THE CASCADES. A MARGINAL
RISK IS INCLUDED FOR THIS AREA ON THE DAY 5/SUNDAY ERO. THE NEXT
SYSTEM IN THE EAST PACIFIC EARLY NEXT WEEK BRINGS ANOTHER
RAIN/MOUNTAIN SNOW THREAT, THOUGH AT THIS POINT LOOKS TO FOCUS
FARTHER NORTH ACROSS MAINLY WASHINGTON STATE.
DOWNSTREAM, EJECTING SHORTWAVE ENERGY AND A LEADING/WAVY FRONTAL
SYSTEM WITH AN ENHANCED GULF MOISTURE SURGE ARE EXPECTED TO
SUPPORT A MODERATE TO HEAVY RAINFALL THREAT FOR THE GULF COAST AND
SOUTHEAST INTO SATURDAY, WHERE THERE IS A MARGINAL RISK FOR
EXCESSIVE RAINFALL WITHIN AN AREA OF ANOMALOUS MOISTURE AND
INSTABILITY. RAINFALL MAY CONTINUE INTO SUNDAY AND MONDAY AS WELL
ACROSS THE SOUTHEAST, BUT GUIDANCE IS QUITE MIXED AND OVERALL
TRENDING LESS SIGNIFICANT. MUCH OF THE EASTERN U.S. LOOKS
UNSETTLED THROUGH NEXT WEEK, ALBEIT WITH HIGHER UNCERTAINTY ON
RAINFALL AMOUNTS GIVEN SHORTWAVE DIFFERENCES. HOWEVER, THE
APPROACH AND PASSAGE OF SEVERAL SHORTWAVES AND ADVANCE OF AN
AMPLIFIED MAIN UPPER TROUGH SHOULD SPAWN SEVERAL WAVY FRONTS. SOME
OF THE PRECIPITATION SHOULD BE IN THE FORM OF SNOW ACROSS PARTS OF
THE GREAT LAKES AND NORTHEAST. NORTHERN NEW ENGLAND TERRAIN WILL
FOCUS SNOWFALL THREAT GIVEN LONGEVITY OF PATTERN AND COLD AIR
AVAILABILITY LATER WEEKEND/EARLY NEXT WEEK.
TEMPERATURES ACROSS THE EAST THIS WEEKEND MAY BE MODERATELY ABOVE
NORMAL, WITH SLIGHTLY BELOW NORMAL TEMPERATURES ACROSS THE
INTERIOR SOUTHWEST. THE WESTERN U.S. SHOULD TREND WARMER WITH TIME
AND ESPECIALLY BY NEXT TUESDAY-WEDNESDAY IN THE NORTHERN HIGH
PLAINS/PLAINS WHERE DAYTIME HIGHS COULD BE 10 TO 20 DEGREES ABOVE
NORMAL. MEANWHILE, THE EASTERN U.S. SHOULD TREND BACK TOWARDS
NORMAL/SLIGHTLY COOLER THAN NORMAL NEXT WEEK AS REINFORCED
TROUGHING AFFECTS THE AREA.
SCHICHTEL/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page