343
FXUS02 KWBC 160659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST MON JAN 16 2023
VALID 12Z THU JAN 19 2023 - 12Z MON JAN 23 2023
...LATE WEEK SYSTEM LIKELY TO BRING MEANINGFUL SNOW TO NORTHERN
PARTS OF THE EAST, ESPECIALLY THURSDAY-THURSDAY NIGHT...
..OVERVIEW
MOST MODELS AND ENSEMBLES CONTINUE TO SHOW A LARGE SCALE MEAN
PATTERN THAT FEATURES A BUILDING EASTERN PACIFIC RIDGE AND
DOWNSTREAM POSITIVELY TILTED TROUGH. IN GENERAL THIS REGIME
SHOULD FAVOR EPISODES OF MOISTURE SPREADING THROUGH THE NORTHWEST
AND EAST/SOUTHEAST INTO THE ROCKIES (AND COOL TEMPERATURES OVER
MOST OF THE WEST) AS SHORTWAVES DROP INTO THE MEAN TROUGH, AS WELL
AS ABOVE AVERAGE RAINFALL CHANCES/TOTALS ACROSS THE SOUTHEAST.
INDIVIDUAL MODEL/ENSEMBLE SOLUTIONS VARY CONSIDERABLY FOR SOME
DETAILS WITHIN THIS PATTERN, SO CONFIDENCE IS MUCH LOWER FOR THE
SPECIFICS OF COVERAGE AND AMOUNTS OF PRECIPITATION WITHIN THE
FAVORED AREAS AS WELL AS FOR MOISTURE THAT COULD EXTEND INTO OTHER
AREAS AT TIMES. JUST AHEAD OF THE CHANGING MEAN PATTERN, A SYSTEM
WILL TRACK EAST-NORTHEAST FROM THE MIDWEST THURSDAY INTO FRIDAY
AND BRING SNOW TO NORTHERN AREAS ALONG WITH SOME RAIN FARTHER
SOUTH.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE SPREAD FOR THE LEADING NORTHEAST SYSTEM HAS BEEN FAIRLY
STABLE TO SLIGHTLY IMPROVING IN LATEST RUNS. RECENT GFS RUNS HAVE
HAD THE TENDENCY TO OPEN THE UPPER LOW A BIT EARLIER THAN THE
MODEL MAJORITY, LEADING TO A CORRESPONDING EARLIER SHIFT OF
EMPHASIS TO A LEADING LOW TRACKING OFF THE EAST COAST FROM THE
INITIAL PARENT LOW BY EARLY FRIDAY. THE NEW 00Z GFS HAS NUDGED A
BIT TOWARD HOLDING ONTO THE PARENT LOW A BIT LONGER BUT IS ON THE
FAST SIDE WITH THE OFFSHORE WAVE.
THE REMAINDER OF THE FORECAST PRIMARILY INVOLVES INITIAL SHORTWAVE
ENERGY DROPPING INTO THE WEST TO FORM A CLOSED LOW LIKELY TO TRACK
OVER THE FOUR CORNERS/SOUTHERN ROCKIES REGION AROUND
FRIDAY-SATURDAY, IF/HOW THIS FEATURE MAY INTERACT WITH NORTHERN
STREAM FLOW, AND THEN SIGNIFICANT DIFFERENCES IN THE CHARACTER OF
THE EASTERN PACIFIC RIDGE/SURROUNDING ENERGY THAT SHOULD DROP INTO
THE MEAN TROUGH--WITH INFLUENCE ON THE FIRST FEATURE. IN A BROAD
SENSE THE GUIDANCE CLUSTERS DECENTLY WITH THE LEADING WESTERN
FEATURE INTO SATURDAY, THOUGH NEW 00Z MODEL RUNS SUGGEST A
SOMEWHAT SHARPER DIGGING/SOUTHWESTERN UPPER LOW TRACK VERSUS THE
12Z ECMWF/ECMWF MEAN. WITH TIME, RECENT CMC RUNS HAVE STRAYED
SOMEWHAT TO THE SLOW SIDE WHILE BUILDING MORE DOWNSTREAM RIDGING
THAN OTHER GUIDANCE. SIGNIFICANT DETAIL DIFFERENCES FOR CENTRAL
PACIFIC EVOLUTION ARISING AS EARLY AS THE SHORT RANGE TIME FRAME
ULTIMATELY LEAD TO THE PRONOUNCED DIFFERENCES SEEN OVER THE
EASTERN PACIFIC/WESTERN U.S. FROM THE WEEKEND INTO NEXT MONDAY.
BASED ON TELECONNECTIONS RELATIVE TO THE STRONG CORE OF POSITIVE
HEIGHT ANOMALIES ASSOCIATED WITH THE EAST PACIFIC RIDGE, LATEST
GFS RUNS MAY BE OVERDONE WITH THE OVERALL DEPTH OF THE WESTERN
TROUGH/UPPER LOW WHILE THE 12Z ECMWF/ECMWF MEAN COULD BE A
UNDERDONE--AS ALSO SUGGESTED BY THE CMC/CMC MEAN. THUS PREFER AN
INTERMEDIATE REFLECTION OF THIS SECOND BUNDLE OF AMPLIFYING
ENERGY. THE NEW 00Z ECMWF HAS MADE A DRAMATIC CHANGE TOWARD MORE
TROUGHING. INFLUENCE OF THIS EVOLUTION ON THE FEATURE EMERGING
FROM THE ROCKIES, AS WELL AS ANY POSSIBLE STREAM INTERACTION, LEAD
TO VERY LOW CONFIDENCE ON WHAT THE SURFACE EVOLUTION MAY BE OVER
THE EASTERN U.S. AFTER EARLY SATURDAY. LATEST GFS/GEFS MEAN RUNS
AND THE 12Z ECMWF SEEMED TO OFFER THE CLOSEST CLUSTERING FOR A
COHERENT SYSTEM WHILE THE 12Z ECMWF MEAN WAS ON THE FAST SIDE DUE
TO MORE NORTHERN STREAM DOMINANCE.
THE UPDATED FORECAST STARTED WITH AN OPERATIONAL MODEL COMPOSITE
FOR THE FIRST HALF OF THE PERIOD, FOLLOWED BY A TRANSITION TO 60
PERCENT TOTAL 18Z GEFS/12Z ECMWF MEANS AND 40 PERCENT 18Z GFS/12Z
ECMWF BY DAY 7 MONDAY. THIS APPROACH YIELDED THE DESIRED
COMPROMISE EVOLUTION OVER THE WEST LATE IN THE PERIOD WHILE
KEEPING THE ECMWF MEAN SUFFICIENTLY IN THE MINORITY OVER THE EAST.
..WEATHER/HAZARD HIGHLIGHTS
THE SYSTEM TRACKING FROM THE MIDWEST THROUGH THE NORTHEAST
THURSDAY INTO FRIDAY SHOULD BRING SNOW TO AREAS FROM THE
CENTRAL/NORTHERN GREAT LAKES THROUGH NEW ENGLAND. EXPECT RAINFALL
TO THE SOUTH, WITH SOME LOCALLY MODERATE TO HEAVY POCKETS OF
RAINFALL POSSIBLE BUT LIKELY NOT REACHING THE POINT OF BEING
EXCESSIVE. WITH THE PATTERN CHANGE DEVELOPING FARTHER WEST, THE
NEXT AREA OF RAIN/MOUNTAIN SNOW CROSSING THE WEST LATE THIS WEEK
SHOULD BE ON THE MODERATE SIDE AND PROGRESS THROUGH THE INTERIOR
WEST/ROCKIES. AS THE SUPPORTING DYNAMICS EXTEND BEYOND THE
ROCKIES, EXPECT THE SOUTH TO SEE A REBOUND IN RAINFALL BY SATURDAY
AS A FRONT LINGERING OVER THE GULF LIFTS BACK NORTHWARD AHEAD OF
POSSIBLE DEVELOPING LOW PRESSURE. THIS POTENTIAL SYSTEM AND ITS
MOISTURE MAY SPREAD FARTHER NORTH OVER THE EASTERN U.S. THROUGH
THE WEEKEND AND THE START OF NEXT WEEK, WITH SOME WINTRY WEATHER
POSSIBLE OVER NORTHERN AREAS. CONFIDENCE REMAINS LOW FOR THE
DETAILS OF SURFACE EVOLUTION AND PRECIPITATION COVERAGE/AMOUNTS
OVER THE EAST IN THIS TIME FRAME. EXPECT ANOTHER FRONT TO SPREAD
SOME RAIN/MOUNTAIN SNOW INTO THE NORTHWEST AND THEN FARTHER
EAST/SOUTHEAST SATURDAY-MONDAY, BUT AGAIN WITH DECREASING
CONFIDENCE IN SPECIFICS.
THE PATTERN FROM LATE THIS WEEK INTO EARLY NEXT WEEK WILL FAVOR
PERSISTENTLY COOL DAYTIME HIGHS OVER MUCH OF THE WEST, ASIDE FROM
FAR NORTHERN AREAS AND THE PACIFIC NORTHWEST COAST, AND INTO PARTS
OF THE HIGH PLAINS. MOST LOCATIONS SHOULD SEE HIGHS OF 5-15F
BELOW NORMAL WITH SOME DAY-TO-DAY VARIABILITY WITH THE PROGRESSION
OF INDIVIDUAL FEATURES. ON THE OTHER HAND, THE EASTERN U.S. AND
NORTHERN TIER SHOULD BE ABOVE NORMAL ON MOST DAYS WITH SOMEWHAT
HIGHER ANOMALIES FOR MORNING LOWS RELATIVE TO DAYTIME HIGHS.
THURSDAY INTO EARLY FRIDAY WILL BE PARTICULARLY WARM OVER THE EAST
WITH SOME ANOMALIES EXCEEDING PLUS 20F AHEAD OF THE
MIDWEST/NORTHEAST SYSTEM. MOST OF ANY DAILY RECORDS SHOULD BE FOR
WARM LOWS, AT LEAST IF SUCH READINGS CAN HOLD ON THROUGH THE END
OF THE CALENDAR DAY.
RAUSCH
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
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