953
FXUS02 KWBC 172026
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
325 PM EST TUE JAN 17 2023
VALID 12Z FRI JAN 20 2023 - 12Z TUE JAN 24 2023
..OVERVIEW
GUIDANCE OFFERS AN AGREEABLE LARGE SCALE PATTERN FORECAST OVERALL,
ALBEIT WITH 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
GUIDANCE SOLUTIONS STILL AGREE DECENTLY FOR MOST 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, RECENT GFS RUNS REMAIN THE SHARPEST WITH THE ARRIVING
FEATURE, CLOSING OFF AN UPPER LOW OVER THE GREAT BASIN WHILE
CONSENSUS SHOWS AN AMPLIFIED TROUGH. GFS RUNS AND TRENDS FROM THE
00 UTC TO THE 12 UTC CANADIAN 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/ECMWF RUNS AND RECENT ECMWF RUNS
AGREE UPON A LESS EXTREME TROUGH/IMPLIED UPPER LOW OVER A SIMILAR
AREA.
FARTHER EAST, 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. RECENT GEFS MEAN RUNS ARE SHOWING SOME
PHASING AS WELL, BUT ULTIMATELY SHIFTS LOW PRESSURE EMPHASIS TO
THE NEW ENGLAND COAST BY EARLY MONDAY. THE 00 UTC ECMWF AND
CANADIAN OFFERED MORE MODEST PHASING, LEADING TO A SOUTHEAST
U.S./EAST COAST TRACK. HOWEVER, THERE IS AN EMERGING GUIDANCE
SIGNAL IN THE 12 UTC ECMWF/CANADIAN TOWARD MORE PHASING. ENSEMBLE
MEMBERS STILL DIVERGE CONSIDERABLY LATE IN THE PERIOD FOR THE
UPPER PATTERN AND SURFACE LOWS. AT THE SURFACE THE GEFS/ECENS HAVE
BEEN TENDING TO FAVOR A PROGRESSIVE SURFACE SYSTEM REACHING NEAR
NEW ENGLAND BY EARLY MONDAY. PREFERENCE WAS TO CONTINUE TO
INCORPORATE ENSEMBLE THEMES WHICH ALSO YIELDS THE BEST CONTINUITY
WHILE AWAITING MORE CONFIDENCE ADJUSTMENTS. HOWEVER, THE TREND OF
THE 12 UTC ECMWF/CANADIAN TOWARD PHASING MAY YIELD A PRODUCT
CONTINUITY SHIFT WITH FUTURE FORECAST PACKAGES THAT AWAIT FURTHER
CONFIDENCE BUILDING WITH FAVORABLE SUPPORT FROM UPCOMING RUNS.
THE WPC MEDIUM RANGE FORECAST WAS PRIMARILY DERIVED FROM A
COMPOSITE OF 00/06 UTC OPERATIONAL MODELS FRIDAY INTO SATURDAY.
THEN AS CENTRAL U.S. PHASING BECAME AN ISSUE IN THE GFS BY SUNDAY
AND WITH QUICKLY GROWING FORECAST SPREAD INTO/FROM THE WEST
CONTINUING INTO NEXT WEEK, THE WPC FORECAST QUICKLY INCORPORATED
SIGNIFICANTLY MORE 06 UTC GEFS/00 UTC ECENS MEAN INPUT.
..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, INCLUDING WINTRY WEATHER THREATS. 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 MOST RECENT MANUAL/GRIDDED FORECASTS. HOWEVER, THE
LATEST TRENDS FROM THE 12 UTC GUIDANCE SUITE SUGGEST A POTENTIALLY
MORE WESTWARD SHIFTED AND STRONGER LOW TRACK TO CERTAINLY MONITOR
FOR FORECAST UPDATES.
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/SCHICHTEL
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
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, THE LOWER
MISSISSIPPI VALLEY, THE SOUTHERN
APPALACHIANS, AND THE TENNESSEE VALLEY, SAT, JAN 21.
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, THE MID-ATLANTIC,
THE SOUTHERN APPALACHIANS, AND THE
TENNESSEE VALLEY, SAT-SUN, JAN 21-JAN 22.
- HEAVY SNOW ACROSS PORTIONS OF THE PACIFIC NORTHWEST, THE
NORTHERN ROCKIES, AND THE NORTHERN GREAT
BASIN, SAT, JAN 21.
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL ROCKIES, SUN, JAN 22.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE PACIFIC
NORTHWEST.
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