283
FXUS02 KWBC 011907
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
206 PM EST THU FEB 01 2024
VALID 12Z SUN FEB 04 2024 - 12Z THU FEB 08 2024
...SOUTHERN TIER SYSTEM LIKELY TO SPREAD HEAVY RAIN ACROSS PARTS
OF THE SOUTHEAST THROUGH AT LEAST SUNDAY...
...ANOTHER STRONG WEATHER SYSTEM INCREASINGLY LIKELY TO IMPACT
CALIFORNIA WITH HEAVY RAIN BY EARLY NEXT WEEK AND EVENTUALLY
SPREAD ACROSS MORE OF THE WEST...
..OVERVIEW
WITH SOME PERSISTENT DETAIL DIFFERENCES, GUIDANCE CONTINUES TO
SHOW AN ACTIVE WEATHER PATTERN FOR THE WEST AT LEAST THROUGH
MIDWEEK. EXPECT A LARGE SCALE POSITIVELY TILTED MEAN TROUGH TO
PROMOTE A STRONG SOUTHWESTERLY FLOW OF MOISTURE INTO THE WEST OVER
A MULTI-DAY TIME FRAME, WITH HEAVIEST RAIN/MOUNTAIN SNOW LIKELY TO
FOCUS OVER CALIFORNIA. WITH TIME SOME OF THIS MOISTURE SHOULD
EXTEND INTO PARTS OF THE INTERMOUNTAIN WEST AND ROCKIES AS THE
UPPER TROUGH DRIFTS EASTWARD AND BROADENS. MEANWHILE AN UPPER LOW
TRACKING FROM THE SOUTHERN PLAINS THROUGH THE SOUTHEAST DURING
SUNDAY-MONDAY WILL SUPPORT A STRONG SURFACE SYSTEM AND A HEAVY
RAINFALL THREAT ACROSS THE SOUTHERN TIER. ADDITIONALLY, A STRONG
UPPER RIDGE CENTERED OVER THE UPPER MIDWEST/GREAT LAKES FROM THE
WEEKEND INTO MONDAY SHOULD MERGE WITH ANOTHER RIDGE BUILDING IN
ACROSS THE SOUTHWEST TO YIELD A SOUTHERN PLAINS INTO GREAT LAKES
RIDGE BY MIDWEEK. THESE RIDGES WILL SUPPORT WELL ABOVE NORMAL
TEMPERATURES OVER MUCH OF THE CENTRAL U.S. HOWEVER THE FLOW ALOFT
OVER THE NORTHEAST HAS BECOME MORE UNCERTAIN IN LATEST MODEL RUNS,
WITH A WIDE POTENTIAL SPREAD BETWEEN THE UPPER RIDGE MOVING IN
FROM THE WEST OR REINFORCEMENT OF UPPER TROUGHING OVER OR JUST
EAST OF THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST RUNS OF GUIDANCE MAINTAIN A HIGH CONFIDENCE FOR AN
ACTIVE WET PERIOD FOR THE WEST COAST/PARTS OF THE SOUTHWEST WITH A
GRADUAL EASTWARD DRIFT WITH TIME AND EVENTUAL BROADENING LATER IN
THE PERIOD. MULTIPLE CYCLES HAVE STRUGGLED WITH RESOLVING
INDIVIDUAL UPPER FEATURES (INITIAL ENERGY THAT MAY CONSOLIDATE
AROUND SUNDAY-MONDAY PLUS ONE OR MORE NORTHERN STREAM FEATURES
THAT MAY DROP INTO THE UPPER TROUGH) THAT HAVE LEAD TO VARIABILITY
OF WHERE PRECIPITATION WILL OCCUR AND ITS MAGNITUDE. THE CMC HAS
BEEN PERSISTENTLY LAGGING AMONG THE SOLUTIONS WHILE THE UKMET
CONTINUES TO BE THE FURTHEST EAST/FASTEST SOLUTION. ALTHOUGH THERE
IS SOME TIMING AND QPF AXIS DIFFERENCES, THE BEST PICTURE FOR THE
MEDIUM RANGE EVOLUTION REMAINS TO BE A COMBO FOR THE ECWMF AND
GFS.
GUIDANCE FOR THE SYSTEM THAT TRACKS ACROSS THE SOUTHEAST HAS
AVERAGE CONFIDENCE, WITH THE UKMET CONSISTENTLY ON THE SOUTHERN
SIDE OF THE SPREAD. OVER THE PAST DAY A NEW COMPLICATION HAS
DEVELOPED REGARDING THE ULTIMATE EVOLUTION/TRACK OF THIS SYSTEM
OVER THE WESTERN ATLANTIC, AS THE GFS/CMC NOW ARE MUCH MORE
AGGRESSIVE TO DIG TROUGH ENERGY SOUTH THROUGH NEW ENGLAND AND
BEYOND BY TUESDAY ONWARD. THOSE SOLUTIONS RESULT IN A FARTHER
NORTH TRACK AND GREATER WIND IMPACTS (IF NOT EVEN SOME
PRECIPITATION) ALONG THE NORTHERN EAST COAST. TELECONNECTIONS
RELATIVE TO POSITIVE HEIGHT ANOMALIES FORECAST OVER SOUTHERN
CANADA, AS WELL AS THE 12Z ECMWF-INITIALIZED ML MODELS, DO NOT
FAVOR UPPER TROUGHING AS CLOSE TO THE EAST COAST AS WHAT THE
GFS/GEFS SUGGEST--BUT ALSO UPPER RIDGING PERHAPS NOT REACHING
QUITE AS CLOSE TO NEW ENGLAND AS IN THE ECMWF/ECMWF MEAN. THUS A
COMPROMISE LOOKS REASONABLE AT THIS TIME.
THE WPC BLEND FOLLOWED CONTINUITY BY STARTING WITH THE 00Z/06Z
GFS/00Z ECWMF AND THEN INCLUDING/INCREASING THE EC ENSEMBLE
MEANS/GEFS MEANS FOR THE MIDDLE AND LATER PERIODS.
..WEATHER/HAZARDS HIGHLIGHTS
THERE IS A STRONG SIGNAL FOR ANOTHER PLUME OF HIGH MOISTURE TO
MOVE ONSHORE OVER A MULTI-DAY PERIOD SUPPORTING HEAVY RAIN TO
CENTRAL/SOUTHERN STRETCH OF THE GOLDEN COAST AND POINTS INLAND
ALONG WITH MODERATE TO HEAVY SNOW IN THE AREAS OF HIGHER TERRAIN.
SOILS ACROSS THIS PART OF THE COUNTRY WILL ALREADY BE
PRE-CONDITIONED THANKS TO AN ATMOSPHERIC RIVER. THIS SECOND AR
EVENT IS DEPICTED TO YIELD DAILY ACCUMULATIONS OF 3 TO 7+ INCHES
SUNDAY AND MONDAY ACROSS CENTRAL AND SOUTHERN PORTIONS OF
CALIFORNIA. THE SLOW MOVEMENT OF THE SUPPORTING UPPER TROUGH MAY
PRODUCE A CONTINUED SOUTHWESTERLY FLOW OF MOISTURE INTO THE REGION
THROUGH AT LEAST TUESDAY (WITH PRECIPITATION ENHANCEMENT POSSIBLY
GENERATED BY ONE OR MORE TRAILING FRONTAL WAVES) WHILE THE LEADING
EDGE OF THE MOISTURE BEGINS TO PUSH INTO THE SOUTHWEST/GREAT
BASIN. HEAVY SNOW FAVORING SOUTHWARD-FACING TERRAIN SHOULD ALSO
SPREAD INTO THE ROCKIES DURING THE EARLY-MID WEEK TIME FRAME.
GIVEN THE INCREASINGLY ANOMALOUSLY WET PERIOD AND DYNAMIC SUPPORT,
MODERATE RISKS WERE RAISED FOR THE TRANSVERSE RANGES AND ADJACENT
LOCATIONS. THE SLIGHT AND MARGINAL RISK AREAS THAT WERE ALREADY IN
EFFECT WERE EXPANDED FURTHER EAST/SOUTHEAST ACROSS SOUTHERN
CALIFORNIA, BUT OF COURSE NOT TO HIGHER ELEVATION AREAS OF THE
SIERRA NEVADA WHERE HEAVY SNOW IS LIKELY. PRECIPITATION SHOULD
PERSIST ESPECIALLY FOR SOUTHERN PORTIONS OF CALIFORNIA THROUGH AT
LEAST MIDWEEK BUT WITH GRADUALLY DECREASING TOTALS. THIS EVENT
STILL APPEARS LIKELY TO PRODUCE GREATER LOW ELEVATION
RAIN/MOUNTAIN SNOW TOTALS THAN THE PRECEDING EVENT DUE TO A LONGER
DURATION OF SOUTHWESTERLY FLOW ALOFT AND A MORE DIRECT CONNECTION
WITH LOWER LATITUDE MOISTURE. CONTINUE TO MONITOR FORECASTS FOR
THIS TIME FRAME AS SPECIFICS GRADUALLY BECOME BETTER RESOLVED. BY
NEXT WEDNESDAY-THURSDAY, LEADING HEIGHT FALLS ALOFT AND ASSOCIATED
LOW PRESSURE MAY DEVELOP PRECIPITATION OVER THE NORTHERN PLAINS.
A FAIRLY DEEP SURFACE LOW PRESSURE SYSTEM WILL TRACK ACROSS THE
SOUTHERN PLAINS AND SOUTHEAST SUNDAY THROUGH MONDAY USHERING IN A
SWATH OF HEAVY RAINFALL ACROSS THE GULF STATES AND SOUTHEAST. A A
BROAD MARGINAL RISK FOR EXCESSIVE RAINFALL WAS MAINTAINED FOR THE
DAY 4 PERIOD. ONE REGION OF POTENTIALLY GREATER INTEREST CONTINUES
TO BE OVER PARTS OF GEORGIA/SOUTH CAROLINA WHICH WILL BE JUST TO
THE NORTH OF ONE OR MORE FRONTS THAT COULD HELP TO FOCUS HEAVIER
RAINFALL. GUIDANCE EXPECTATIONS FOR INSTABILITY OVER THIS AREA DO
NOT APPEAR PARTICULARLY IMPRESSIVE THOUGH. SOME HEAVY RAINFALL
COULD LINGER INTO MONDAY OVER OR NEAR THE COAST OF THE CAROLINAS.
CURRENT GUIDANCE IS NOT SHOWING A COHERENT ENOUGH OF A SIGNAL TO
RECOMMEND A MARGINAL RISK OVER THIS LOCALIZED AREA IN THE NEW DAY
5 ERO BUT WILL CONTINUE TO MONITOR FOR IMPROVED CLUSTERING IN
UPCOMING MODEL RUNS. ONCE THE SURFACE SYSTEM MOVES OFFSHORE,
EXPECT A PERIOD OF STRONG WINDS ALONG/OFFSHORE THE SOUTHEAST COAST
AND POSSIBLY FARTHER NORTH AS WELL.
THE UPPER RIDGE INITIALLY OVER AND NEAR THE UPPER MIDWEST AND THEN
BECOMING ALIGNED FROM THE SOUTHERN PLAINS THROUGH GREAT LAKES WILL
SUPPORT A BROAD AREA OF UNSEASONABLY WARM TEMPERATURES OVER THE
CENTRAL U.S. THROUGH THE PERIOD. CONTINUE TO EXPECT THE GREATEST
ANOMALIES TO BE OVER/NEAR THE UPPER MIDWEST WHERE MORNING LOWS MAY
BE AS WARM AS 25-35F ABOVE NORMAL AND EXCEED DAILY RECORDS FOR
MULTIPLE DAYS, WHILE DAYTIME HIGHS SHOULD BE A LITTLE LESS
EXTREME, UP TO 15-25F OR SO ABOVE NORMAL. IN CONTRAST, THE
SOUTHWEST U.S./CALIFORNIA SHOULD SEE COOL DAYTIME HIGHS THROUGH
THE PERIOD WITH A FEW LOCATIONS UP TO 10-15F BELOW NORMAL ON ONE
OR MORE DAYS. CLOUDS/PRECIPITATION OVER THE WEST SHOULD KEEP
MORNING LOWS NEAR TO ABOVE NORMAL. FLORIDA SHOULD SEE A COUPLE
COOL DAYS WITH HIGHS 5-10F BELOW NORMAL BY TUESDAY-WEDNESDAY AFTER
PASSAGE OF THE SOUTHEAST SYSTEM. TEMPERATURES OVER THE NORTHEAST
FROM TUESDAY ONWARD HAVE GREATER UNCERTAINTY THAN MOST OTHER
AREAS. THE MOST LIKELY SCENARIO WOULD YIELD NEAR TO ABOVE NORMAL
TEMPERATURES AS UPPER RIDGING APPROACHES, BUT THERE IS LESSER
POTENTIAL FOR A NEARBY UPPER TROUGH/LOW TO KEEP TEMPERATURES
COLDER.
CAMPBELL/RAUSCH/TATE
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
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