314
FXUS02 KWBC 121942
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EST WED NOV 12 2025
VALID 12Z SAT NOV 15 2025 - 12Z WED NOV 19 2025
...HEAVY RAIN LIKELY IN SOUTHERN CALIFORNIA SATURDAY, CAUSING
POSSIBLE FLOODING CONCERNS...
..OVERVIEW
A SOUTHERN STREAM UPPER LOW WILL MOVE INTO SOUTHERN CALIFORNIA AND
VICINITY OVER THE WEEKEND, BRINGING WIDESPREAD RAIN THAT MAY CAUSE
FLOODING ON SATURDAY. PRECIPITATION INCLUDING HIGHER ELEVATION
SNOW IS FORECAST TO SPREAD ACROSS MUCH OF THE INTERMOUNTAIN WEST ON
SUNDAY. UPPER RIDGING AHEAD OF THIS SYSTEM WILL LEAD TO MUCH
WARMER THAN AVERAGE TEMPERATURES ACROSS THE CENTRAL TO EASTERN U.S.
OVER THE WEEKEND. MEANWHILE IN THE NORTHERN STREAM, AN UPPER
TROUGH WILL PUSH A SURFACE LOW/FRONTAL SYSTEM ACROSS THE GREAT
LAKES AND NORTHEAST OVER THE WEEKEND, LEADING TO RAIN AND SOME
WINTRY PRECIPITATION. INTO THE WORKWEEK, RAIN IS FORECAST TO SPREAD
INTO THE CENTRAL AND EAST-CENTRAL U.S. AS THE INITIAL UPPER LOW
AND SURFACE FRONTAL SYSTEM LIFTS AND THEN STALLS. YET ANOTHER
TROUGH MAY MOVE INTO THE WEST EARLY NEXT WEEK AND BRING ADDITIONAL
PRECIPITATION CHANCES ACROSS THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE PERIOD STARTS WITH A UPPER-LEVEL LOW OVER THE NORTHEAST U.S.,
A SECOND UPPER-LEVEL WAVE DROPPING SOUTH-EASTWARD ACROSS THE
NORTHERN TIER FROM THE NORTH CENTRAL U.S. INTO THE GREAT LAKES AND
A CUTOFF UPPER LOW WITHIN THE VICINITY OF CALIFORNIA, WITH A UPPER-
LEVEL TROUGH BEHIND. FOR THE FIRST PORTION OF THE PERIOD, MOST
MODEL GUIDANCE SHOWED OVERALL GOOD AGREEMENT WITH THESE MAJOR
FEATURES, ESPECIALLY THE AGREEMENT OF AN UPPER-LEVEL WAVE
REINFORCING THE UPPER LOW OVER THE NORTHEAST U.S. AND THE UPPER LOW
MOVING INTO THE SOUTHWEST TO SOUTH-CENTRAL U.S. BY MID PERIOD.
TOWARDS THE LATER PORTION OF THE PERIOD, THE MODELS DIVERGE WITH
THE GFS SHOWING THE MOST DIFFERENCES. THE GFS SHOWS THE UPPER LOW
OVER THE SOUTHERN TIER TRANSITIONING TO AN OPEN WAVE AS IT REACHES
THE SOUTH CENTRAL U.S. AND BEGINS TO SHEAR OUT WITH ASSOCIATED
PRECIPITATION ACCELERATING EASTWARD TOWARDS THE EAST COAST. ON THE
OTHER HAND, THE ECMWF AND CMC MAINTAIN A MORE DEFINED UPPER WAVE
AND A SLOWER MOVING ASSOCIATED SURFACE SYSTEM. THE MODEL MEANS TEND
TO FAVOR THE TRENDS OF THEIR RESPECTIVE DETERMINISTIC
COUNTERPARTS. THIS WILL HAVE IMPACTS ON PRECIPITATION CHANCES OVER
THE CENTRAL TO EASTERN U.S., WITH THE CMC AND ECMWF FAVORING MORE
PRECIPITATION OVER THE PLAINS AND MISSISSIPPI VALLEY. THERE ARE
ALSO DIFFERENCES WITH RESPECT TO THE COMPLICATED EVOLUTION OF THE
UPPER TROUGH DROPPING DOWN FROM THE NORTHEAST PACIFIC ALONG THE
WEST COAST. GUIDANCE INDICATES THE STREAMS MAY SPLIT INTO A
NORTHERN AND SOUTHERN WAVE THAT WILL MOVE INLAND BY MID NEXT WEEK.
THIS SUGGESTS A LIKELIHOOD OF PRECIPITATION, POTENTIALLY HEAVY,
ALONG THE WEST COAST, WHILE THE SOUTHERN WAVE MAY EVENTUALLY ALSO
BRING ANOTHER ROUND OF PRECIP TO THE CENTRAL U.S. DUE TO MODEL
DIFFERENCE THERE WILL BE UNCERTAINTY WITH THE SPECIFICS.
THE WPC FORECAST WAS BASED ON A COMPOSITE BLEND OF ECMWF, GFS, AND
CMC FOR THE FIRST PART OF THE PERIOD, GIVEN GOOD OVERALL
AGREEMENT. USED AN INCREASED CONTRIBUTION FROM THE ECENS AND CMC
MEANS AND REMOVED THE GFS TOWARDS THE LATTER PART OF THE PERIOD
GIVEN HOW THE GFS AND GEFS MEAN SOLUTIONS DIFFERED.
..WEATHER/HAZARDS HIGHLIGHTS
THE SOUTHERN STREAM CUTOFF LOW MOVING INTO SOUTHERN CALIFORNIA
WILL PROVIDE DYNAMICAL SUPPORT FOR AMPLE PRECIPITATION, MOSTLY
RAIN, ACROSS SOUTHERN CALIFORNIA AND INTO THE SOUTHWEST ON
SATURDAY. PRECIPITABLE WATER VALUES WILL LIKELY BE OVER THE 95TH
PERCENTILE FOR THIS TIME OF YEAR, AND SOME MODEST INSTABILITY
EXISTS AHEAD OF AND UNDERNEATH THE DEEP UPPER LOW. A SLIGHT RISK OF
EXCESSIVE RAINFALL WILL CONTINUE FOR MUCH OF SOUTHERN CALIFORNIA
IN SATURDAY'S ERO WITH THIS SLOW-MOVING SETUP CAUSING SCATTERED
FLOODING CONCERNS, ESPECIALLY FOR SENSITIVE AREAS LIKE BURN SCARS
AND URBAN AREAS. 2 TO 5 YEAR ARI EXCEEDANCES MAY BECOME COMMON IN
DESERT AREAS THAT DO NOT OFTEN SEE THIS MUCH RAIN. BY SUNDAY THE
UPPER LOW LOOKS TO LIFT NORTHEAST AND LOSE THE DEEPER MOISTURE
CONNECTION, BUT WIDESPREAD LIGHT TO MODERATE PRECIPITATION IS
LIKELY ACROSS THE INTERMOUNTAIN WEST. PRECIPITATION SHOULD BE
MOSTLY RAIN EVEN INTO PARTS OF THE MOGOLLON RIM, BUT FARTHER NORTH
INTO THE HIGHER ELEVATIONS OF THE CENTRAL ROCKIES SNOW IS LIKELY.
WILL HOLD OFF ON ANY EXCESSIVE RAINFALL AREAS ON DAY 5/SUNDAY DUE
TO THE LESSENING MOISTURE LEVELS AND THE UNCERTAINTY IN PLACEMENT.
RAIN AND POSSIBLY THUNDERSTORMS MAY SPREAD EAST LATER SUNDAY AND
ESPECIALLY INTO MONDAY ACROSS THE PLAINS AND MISSISSIPPI VALLEY,
AND PERHAPS STALLING IN THE SOUTH-CENTRAL U.S. STRETCHING INTO THE
OHIO/TENNESSEE VALLEYS ON TUESDAY BUT WITH GREATER UNCERTAINTY.
BROAD PRECIPITATION CHANCES ARE LIKELY ACROSS THE NORTHEASTERN
QUADRANT OF THE CONUS OVER THE WEEKEND AS A LOW PRESSURE SYSTEM
MOVES THROUGH. ACCUMULATING SNOW IS LIKELY IN THE INTERIOR
NORTHEAST, ESPECIALLY IN HIGHER ELEVATIONS, AND SOME FAVORED AREAS
COULD SEE FREEZING RAIN.
PERIODIC PRECIPITATION IS LIKELY ACROSS THE PACIFIC NORTHWEST AND
INTERMOUNTAIN WEST INTO THE WEEKEND, WITH HIGHER ELEVATION SNOW. BY
SUNDAY, PRECIPITATION CHANCES SHOULD RAMP UP INTO NORTHERN
CALIFORNIA AND FARTHER INLAND AS WELL, AS BROAD UPPER TROUGHING
APPROACHES. TROUGHING LOOKS TO MOVE THROUGH THE WEST EARLY NEXT
WEEK AND COULD SPREAD PRECIPITATION ACROSS THE INTERMOUNTAIN WEST
ONCE AGAIN, THOUGH THE DETAILS REMAIN UNCERTAIN. PRECIPITATION
COULD BE MODERATE OR HEAVY AT TIMES.
TEMPERATURES ARE FORECAST TO BE WARMER THAN AVERAGE FOR MUCH OF
THE CENTRAL AND EAST-CENTRAL U.S. ON SATURDAY. 80S WILL BE
WIDESPREAD ACROSS TEXAS, AND HIGHS REACHING THE UPPER 70S WELL INTO
THE MID-MISSISSIPPI VALLEY AND OHIO VALLEY WILL BE 15 TO 25
DEGREES ABOVE NORMAL. TEMPERATURES IN THE NORTHERN TIER SHOULD COOL
IN THE NORTHERN U.S. SUNDAY AND MONDAY, BUT THE SOUTH-CENTRAL TO
SOUTHEAST U.S. LOOKS TO STAY ABOVE AVERAGE. MEANWHILE THE ROUNDS OF
TROUGHING IN CALIFORNIA TO THE SOUTHWEST WILL LEAD TO BELOW
AVERAGE HIGHS THERE MOST DAYS.
OUDIT/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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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