091
FXUS02 KWBC 170700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST TUE JAN 17 2023
VALID 12Z FRI JAN 20 2023 - 12Z TUE JAN 24 2023
..OVERVIEW
IN GENERAL, LATEST GUIDANCE IS SHOWING LITTLE CHANGE IN BOTH THE
AGREEABLE LARGE SCALE PATTERN FORECAST BUT ALSO SIGNIFICANT
EMBEDDED UNCERTAINTIES WITH UPPER FLOW/SURFACE DETAILS THAT WILL
AFFECT SENSIBLE WEATHER OVER SOME AREAS. FROM THE MULTI-DAY MEAN
PERSPECTIVE THE ONGOING CONSENSUS SHOWS POSITIVELY TILTED
TROUGHING OVER THE LOWER 48, BETWEEN A STRONG RIDGE OVER THE
EASTERN PACIFIC AND ANOTHER RIDGE TO THE SOUTH OR SOUTHEAST OF
FLORIDA. THIS PATTERN SHOULD FAVOR HIGHEST PRECIPITATION TOTALS
OVER THE SOUTHEASTERN QUADRANT OF THE COUNTRY WITH SOME MOISTURE
SPREADING ELSEWHERE OVER THE EASTERN HALF OF THE COUNTRY.
MEANWHILE SHORTWAVE ENERGY DROPPING INTO THE MEAN TROUGH WILL
PERIODICALLY SPREAD RAIN/MOUNTAIN SNOW FROM THE NORTHWEST
EAST/SOUTHEAST INTO THE ROCKIES, AND KEEP THE MOST OF THE WEST ON
THE CHILLY SIDE FOR DAYTIME HIGHS. WITHIN THESE GENERAL THEMES,
THE ONGOING DETAIL DIFFERENCES FOR IMPORTANT UPPER FLOW SPECIFICS
KEEP CONFIDENCE WELL BELOW AVERAGE FOR RESOLVING THE EXACT
CHARACTER OF PRECIPITATION COVERAGE/INTENSITY/TYPE OVER MANY AREAS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AS WAS BEEN THE CASE LATELY, THE GUIDANCE AGREES DECENTLY FOR
IMPORTANT FEATURES UP TO ABOUT EARLY DAY 4 SATURDAY. THIS
INCLUDES THE SYSTEM DEPARTING FROM THE NORTHEAST AND THE UPPER LOW
EXPECTED TO TRACK ACROSS ARIZONA/NEW MEXICO FRIDAY-SATURDAY. THEN
MODELS AND ENSEMBLE MEMBERS RAPIDLY DIVERGE FOR THE ULTIMATE
EVOLUTION OF A SHORTWAVE ENTERING WESTERN NORTH AMERICA ON
SATURDAY (WITH DIFFERENCES IN SHARPNESS/AMPLITUDE ALREADY SHOWING
UP BY EARLY SATURDAY), ALONG WITH WHAT BECOMES OF THE ARIZONA/NEW
MEXICO UPPER LOW AS WELL AS WHETHER NORTHERN STREAM FLOW INTERACTS
WITH IT. THESE DIFFERENCES LEAD TO A WIDE ARRAY OF POSSIBILITIES
FOR THE TRACK AND TIMING OF SURFACE LOW PRESSURE OVER THE EASTERN
HALF OF THE COUNTRY, AS WELL AS FOR THE DEPTH/LOCATION OF UPPER
TROUGHING OVER THE WESTERN-CENTRAL U.S. FROM THE WEEKEND INTO
EARLY NEXT WEEK.
REGARDING THE SATURDAY SHORTWAVE DROPPING INTO THE WEST
THEREAFTER, LATEST GFS RUNS HAVE GENERALLY BEEN THE SHARPEST WITH
THE ARRIVING FEATURE. THE NEW 00Z RUN HAS BECOME MORE EXTREME BY
SUNDAY, CLOSING OFF AN UPPER LOW OVER THE GREAT BASIN WHILE
CONSENSUS HAS A MERE TROUGH. PRIOR GFS RUNS CLOSED OFF THE LOW
OVER THE NORTHERN ROCKIES AT THAT TIME. EITHER WAY, THESE GFS
RUNS EVENTUALLY BRING A DEEP UPPER LOW OVER THE SOUTHWEST EARLY
NEXT WEEK. TELECONNECTIONS RELATIVE TO THE EAST PACIFIC RIDGE'S
CORE OF POSITIVE HEIGHT ANOMALIES STILL SUGGEST THAT BRINGING SUCH
LOW HEIGHTS INTO THE SOUTHWEST COULD BE A LITTLE OVERDONE, BUT
LATEST GEFS RUNS AND THE 12Z ECMWF BOTH AGREE UPON A LESS EXTREME
TROUGH/IMPLIED UPPER LOW OVER A SIMILAR AREA. LATEST CMC RUNS AND
THE 12Z ECMWF DIVERT THE TROUGH SOMEWHAT EASTWARD WHILE THE OLD
00Z/16 ECMWF WAS MORE LIKE LATEST GFS RUNS.
FARTHER EAST, THE GFS HANDLING OF INCOMING WESTERN ENERGY RESULTS
IN SHARP DIGGING OF SOUTHERN CANADA/PLAINS FLOW AND PHASING WITH
THE EJECTING SOUTHWEST UPPER LOW. THIS RESULTS IN A SOUTH-CENTRAL
PLAINS THROUGH GREAT LAKES SURFACE SYSTEM THAT BECOMES FAIRLY
STRONG BY LATE SUNDAY. GEFS MEAN RUNS ARE SHOWING SOME PHASING AS
WELL BUT ULTIMATELY SHIFTS LOW PRESSURE EMPHASIS TO THE NEW
ENGLAND COAST BY EARLY MONDAY. THE 00Z/16 ECMWF HAD MORE MODEST
PHASING, LEADING TO A SOUTHEAST U.S./EAST COAST TRACK. NON-PHASED
SOLUTIONS WITH A FASTER-MOVING NORTHERN STREAM SHORTWAVE
(CMC/UKMET RUNS AND 12Z ECMWF) TEND TO YIELD MORE UPPER RIDGING
NEAR THE EAST COAST BY EARLY MONDAY AND A SLOWER AND/OR WESTWARD
SURFACE LOW. NOT SURPRISINGLY GIVEN THE MODEL SPREAD, INDIVIDUAL
ENSEMBLE MEMBERS DIVERGE CONSIDERABLY LATE IN THE PERIOD FOR THE
UPPER PATTERN AND SURFACE LOWS. GEFS MEMBERS TENDED TO CLUSTER
SOMEWHAT CLOSER TO THE AMPLIFIED SOUTHWEST TROUGH WHILE THE
ECENS/CMCENS MEMBERS HAD GREATER SPREAD ALOFT. AT THE SURFACE THE
GEFS/ECENS HAVE BEEN TENDING TO FAVOR A PROGRESSIVE SURFACE SYSTEM
REACHING NEAR NEW ENGLAND BY EARLY MONDAY. PREFERENCE IS TO
INCORPORATE THESE ENSEMBLE THEMES WHICH ALSO YIELDS THE BEST
CONTINUITY WHILE AWAITING MORE CONFIDENCE ADJUSTMENTS.
THE UPDATED FORECAST BLEND STARTED WITH A COMPOSITE OF 12Z/18Z
OPERATIONAL MODELS FRIDAY INTO SATURDAY (THOUGH WITH THE ECMWF
SPLIT BETWEEN THE LAST TWO RUNS). THEN AS CENTRAL U.S. PHASING
BECAME AN ISSUE IN THE GFS BY SUNDAY, THE FORECAST STARTED TO
INCORPORATE MORE 18Z GEFS/12Z ECENS MEAN INPUT AND THEN PHASE OUT
THE CMC DUE TO ITS PATTERN STRAYING FROM THE GEFS/ECENS. BY DAYS
6-7 MONDAY-TUESDAY, THE BLEND COULD STILL INCORPORATE THE 18Z GFS
IN TEMPERED FORM WHILE USING ONLY THE 00Z/16 ECMWF FOR THAT
MODEL'S CONTRIBUTION SINCE ITS PATTERN COMPARED A LOT BETTER TO
THE MEANS WHOSE TOTAL WEIGHT REACHED 50-60 PERCENT.
..WEATHER/HAZARD HIGHLIGHTS
THE NORTHEAST WILL LIKELY SEE SNOW LINGERING THROUGH FRIDAY AS A
BAND OF MOISTURE LINGERS OVER THE REGION BEHIND LOW PRESSURE
TRACKING OFFSHORE FROM NEW ENGLAND. THE FOUR CORNERS STATES
SHOULD SEE SOME SNOW AND VERY LOW ELEVATION RAIN LATE THIS WEEK
WITH THE UPPER LOW TRACKING THROUGH THE REGION. THE TRAILING
UPPER TROUGH DROPPING INTO THE WEST, AND THE LEADING COLD FRONT,
WILL BRING SOME RAIN/MOUNTAIN SNOW INTO THE NORTHWEST BY SATURDAY
AND THEN SPREADING EAST/SOUTH INTO THE GREAT BASIN/ROCKIES,
POSSIBLY REACHING INTO THE SOUTHWEST AS WELL. PRECISE COVERAGE
AND AMOUNTS ARE STILL UNCERTAIN THOUGH. CONFIDENCE IS ALSO BELOW
AVERAGE FOR THE DISTRIBUTION, AMOUNTS, AND TYPE OF PRECIPITATION
OVER THE EASTERN HALF OF THE COUNTRY FROM THE WEEKEND INTO EARLY
NEXT WEEK. THE BEST SIGNAL AT THE MOMENT IS FOR SOME ENHANCED
RAINFALL ACROSS THE SOUTH/SOUTHEAST BASED ON TELECONNECTIONS
RELATIVE TO THE EXPECTED LARGE SCALE MEAN PATTERN, AND
SPECIFICALLY THE INTERACTION OF THE GULF MOISTURE WITH A WAVY WARM
FRONT THAT MAY REACH/PASS THROUGH THE GULF COAST. THERE IS STILL
A FAIR DEGREE OF GUIDANCE SPREAD JUST FOR THE TIMING OF THIS FRONT
THOUGH. OTHERWISE, THERE IS A VERY WIDE ENVELOPE FOR WHERE A
SIGNIFICANT SURFACE WAVE MAY TRACK WITH OBVIOUS PRECIPITATION/TYPE
IMPLICATIONS. POTENTIAL LOW TRACKS EXTEND AS FAR WEST AS THE
MIDWEST OR COULD BE CONFINED MORE TO THE EAST COAST, THE LATTER
BEING THE SCENARIO CURRENTLY FOLLOWED BY THE MANUAL/GRIDDED
FORECASTS.
MUCH OF THE WEST AND INTO PARTS OF THE HIGH PLAINS SHOULD SEE
BELOW NORMAL TEMPERATURES THROUGH THE PERIOD, EXPECT PERHAPS FOR
FAR NORTHERN AREAS. HIGHS WILL BE PARTICULARLY COOL WITH EACH DAY
LIKELY TO FEATURE MAX TEMPERATURES 5-20F BELOW NORMAL. AN
ISOLATED LOCATION OR TWO COULD SEE A RECORD COLD HIGH. ON THE
OTHER HAND, THE EASTERN U.S. SHOULD SEE NEAR TO ABOVE NORMAL HIGHS
THROUGH THE PERIOD WITH WARMER ANOMALIES FOR MORNING LOWS. THE
NORTHERN PLAINS WILL ALSO SEE ABOVE NORMAL TEMPERATURES LATE THIS
WEEK INTO THE WEEKEND BUT THEN DECLINE TO NEAR OR SLIGHTLY BELOW
NORMAL.
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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