944
FXUS02 KWBC 220659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST THU DEC 22 2022
VALID 12Z SUN DEC 25 2022 - 12Z THU DEC 29 2022
***UNSETTLED CONDITIONS FOR THE WEST COAST WITH HEAVY RAIN AND
HEAVY MOUNTAIN SNOW WITH AN ATMOSPHERIC RIVER EVENT EARLY NEXT
WEEK***
..SYNOPTIC OVERVIEW
THE OVERALL WEATHER PATTERN IMPROVES GOING INTO CHRISTMAS WEEKEND
ACROSS THE EASTERN HALF OF THE NATION AS THE CORE OF THE INTENSE
LOW LIFTS FARTHER NORTHWARD ACROSS CENTRAL CANADA AND WEAKENS WITH
TIME. HOWEVER, THERE WILL STILL BE SOME LINGERING LAKE EFFECT
SNOW, MAINLY DOWNWIND OF LAKES ERIE AND ONTARIO. THE IMPRESSIVELY
COLD AIRMASS WILL BEGIN MODIFYING AS THE SURFACE HIGH SETTLES
ACROSS THE SOUTHERN TIER STATES. LOOKING AHEAD TO EARLY NEXT
WEEK, AN ALBERTA CLIPPER SYSTEM TRACKS ACROSS THE CENTRAL/NORTHERN
PLAINS, AND A SOUTHERN STREAM DISTURBANCE TRACKS EASTWARD NEAR THE
GULF COAST. MULTIPLE SHORTWAVE PASSAGES NEAR THE PACIFIC
NORTHWEST WILL KEEP THINGS UNSETTLED FROM NORTHERN CALIFORNIA TO
WASHINGTON STATE WITH AN ATMOSPHERIC RIVER EVENT LIKELY DURING THE
MONDAY-TUESDAY NIGHT TIME PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST 00Z MODEL GUIDANCE SUITE INDICATES VERY GOOD SYNOPTIC
SCALE AGREEMENT ON SUNDAY ON THE OVERALL UPPER LEVEL PATTERN THAT
FEATURES A WEST COAST RIDGE AND A GRADUALLY WEAKENING EASTERN U.S.
TROUGH, WITH PACIFIC SHORTWAVES ROUNDING THE RIDGE AND FEEDING
INTO THE MEAN TROUGH. ATTENTION TURNS TO THE PLAINS AND THEN THE
GULF COAST REGION AS TWO DISTINCT SHORTWAVES TRACK DOWN THE EAST
SIDE OF THAT RIDGE, BUT RIGHT NOW THE GUIDANCE DOES NOT INDICATE
ANY APPRECIABLE PHASING OF THESE DISTURBANCES THROUGH TUESDAY, SO
THIS WOULD LIMIT THE POTENTIAL FOR ANY COASTAL SURFACE LOW TRYING
TO DEVELOP NEAR THE SOUTHEAST U.S., BUT STILL WORTH MONITORING.
EASTERN PACIFIC INTO WESTERN NORTH AMERICA SHORTWAVES AND
ASSOCIATED SURFACE SYSTEMS DURING THE WEEKEND GENERALLY APPEAR TO
EXHIBIT TYPICAL DETAIL AND TIMING SPREAD. THE LARGER SCALE TROUGH
EXPECTED TO MOVE INTO THE WEST BY DAY 6 WEDNESDAY, ALONG WITH THE
FAIRLY STRONG PACIFIC SURFACE LOW THE PRIOR DAY, HAVE SOME
DETAIL/TIMING SPREAD BUT WITH A REASONABLY CONSISTENT MULTI-DAY
SIGNAL OVERALL.
..WEATHER/HAZARD HIGHLIGHTS
SATURDAY WILL FEATURE WIDESPREAD TEMPERATURE ANOMALIES OF 20-30
DEGREES BELOW AVERAGE FOR MORNING LOWS AND DAYTIME HIGHS ACROSS
MUCH OF THE CENTRAL AND EASTERN U.S. SUNDAY WILL STILL BE QUITE
COLD OVER THE EASTERN HALF OF THE COUNTRY WITH A BROAD AREA OF
READINGS 15-25 DEGREES BELOW NORMAL. THE THEME FOR NEXT WEEK WILL
BE A STEADY WARMING TREND AS THE UPPER PATTERN BECOMES LESS
AMPLIFIED. MODERATELY ABOVE NORMAL TEMPERATURES WILL BECOME
ESTABLISHED OVER THE WEST (LOWS TENDING TO BE A LITTLE MORE ABOVE
NORMAL THAN DAYTIME HIGHS) AND THEN SPREAD INTO THE HIGH PLAINS BY
NEXT TUESDAY-WEDNESDAY WITH SOME AREAS REACHING 10-20F ABOVE
NORMAL. THE EASTERN HALF OF THE COUNTRY WILL CONTINUE TO
MODERATE, LEADING TO MOSTLY SINGLE-DIGIT NEGATIVE ANOMALIES BY
NEXT WEDNESDAY.
A SERIES OF NORTHEASTERN PACIFIC SYSTEMS SHOULD BRING A MULTI-DAY
PERIOD OF ATMOSPHERIC RIVER EVENTS TO THE WEST COAST, LEADING TO
SIGNIFICANT TOTALS OF RAIN AND HIGHER ELEVATION SNOW. SOME OF
THIS MOISTURE WILL LIKELY EXTEND EASTWARD TO THE ROCKIES. THE
PRIMARY FOCUS DURING THE WEEKEND IS FORECAST TO BE OVER THE
PACIFIC NORTHWEST AND FAR NORTHERN ROCKIES. THERE IS STILL SOME
UNCERTAINTY OVER THE PRECISE INTENSITY AND SOUTHWARD EXTENT OF
PRECIPITATION AT ANY PARTICULAR TIME, THOUGH AT THE MOMENT THE
BEST SIGNAL FOR HIGHEST AMOUNTS IS OVER THE OLYMPICS AND
WASHINGTON CASCADES. THEN THE PRECIPITATION SHIELD WILL LIKELY
PUSH SOUTHEASTWARD DURING THE FIRST HALF OF THE WEEK AS A MORE
AMPLIFIED UPPER TROUGH AND LEADING SURFACE FRONT MOVE IN. AS THIS
OCCURS, THE HEAVIEST RAIN/MOUNTAIN SNOW SHOULD FOCUS ALONG THE
CENTRAL WEST COAST INTO THE SIERRA NEVADA WHILE SOME MOISTURE
EXTENDS FARTHER SOUTH OVER CALIFORNIA AND EAST INTO THE GREAT
BASIN/ROCKIES, AND NOTEWORTHY PRECIPITATION PERSISTS OVER THE
NORTHWEST. THESE SYSTEMS MAY BRING PERIODS OF HIGH WINDS TO SOME
AREAS NEAR THE WEST COAST. ELSEWHERE, A WEAK ALBERTA CLIPPER MAY
BRING AN AREA OF LIGHT SNOW FROM THE NORTHERN PLAINS INTO THE
MIDWEST DURING SUNDAY-MONDAY. GULF COAST SHORTWAVE ENERGY AND
ASSOCIATED STATIONARY FRONT SHOULD SPREAD SOME MOISTURE ACROSS THE
GULF OF MEXICO AND WESTERN ATLANTIC EARLY-MID WEEK, WITH FLORIDA
POSSIBLY SEEING SOME RAINFALL DURING THAT TIME. IT REMAINS
UNCERTAIN ABOUT HOW MUCH, IF ANY, OF THIS MOISTURE REACHES THE
GULF/SOUTHEAST COAST AREAS THOUGH.
HAMRICK
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, 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/#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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page