916
FXUS02 KWBC 151900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST THU FEB 15 2024
VALID 12Z SUN FEB 18 2024 - 12Z THU FEB 22 2024
...ATMOSPHERIC RIVER TO BRING HEAVY RAIN AND MOUNTAIN SNOW TO
CALIFORNIA EARLY NEXT WEEK...
..GENERAL OVERVIEW
AN UPPER-LEVEL TROUGH INITIALLY OVER THE THE NORTHEASTERN U.S. IS
FORECAST TO PULL AWAY TO THE NORTHEAST AND ALLOW A MORE ZONAL FLOW
PATTERN TO SET UP EAST OF THE ROCKIES SUNDAY INTO MONDAY. IN
FLORIDA, A SURFACE LOW WILL TRACK ACROSS THE PENINSULA ALONG A
SLOW-MOVING COLD FRONT, WHICH WILL TRIGGER A ROUND OF RAINFALL
OVER THE WEEKEND. MEANWHILE, A DEEP UPPER LOW WILL APPROACH THE
WEST COAST, STEERING A STREAM OF PACIFIC MOISTURE INTO CALIFORNIA
THAT WILL RESULT IN HEAVY RAIN AND MOUNTAIN SNOW ON SUNDAY AND
MONDAY. THIS LOW IS FORECAST TO QUICKLY WEAKEN MID-WEEK AS THE
ASSOCIATED SURFACE CYCLONE PUSHES ONSHORE. BY THURSDAY, THIS
SYSTEM WILL PUSH PAST THE ROCKIES AND DEVELOP A LOW PRESSURE
SYSTEM IN THE SOUTHERN PLAINS AND MIDWEST. LATE NEXT WEEK, ANOTHER
UPPER LOW WILL APPROACH THE WEST COAST THAT COULD BRING ANOTHER
ROUND OF HEAVY RAINFALL, AND A COLD FRONT WILL DROP SOUTH INTO THE
NORTH-CENTRAL AND NORTHEASTERN U.S. THAT WILL BRING THE NEXT
CHANCE OF RAIN TO THE EAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE EVOLUTION OF THE
UPPER LEVEL PATTERN THROUGH THE PERIOD. A GENERAL DETERMINISTIC
MODEL BLEND COMPRISED OF THE GFS/ECMWF/CMC/UKMET WAS USED FOR
SUNDAY AND MONDAY. DIFFERENCES BETWEEN THE MODELS BECOME MORE
NOTICEABLE BY TUESDAY INTO WEDNESDAY WITH SLIGHT DIFFERENCES IN
THE PLACEMENT OF THE UPPER LOW NEAR THE WEST COAST. THE
DETERMINISTIC GFS PULLS THE LOW MORE SOUTH THAN THE EUROPEAN,
CANADIAN, AND ENSEMBLE MEANS WHICH COULD AFFECT THE PLACEMENT OF
THE EVENTUAL LOW PRESSURE SYSTEM DEVELOPING DOWNSTREAM OVER THE
PLAINS. FOR THIS REASON, THE WPC MODEL BLEND PUT LESS WEIGHT ON
THE GFS THAN THE ECMWF TUESDAY THROUGH THURSDAY AND INTRODUCED
ENSEMBLE MEANS TO THE BLEND TO SMOOTH OUT SMALL DIFFERENCES
BETWEEN THE DETERMINISTIC MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
MOST OF THE SIGNIFICANT RAINFALL ASSOCIATED WITH THE GULF/FLORIDA
LOW ON SUNDAY SHOULD BE CONFINED TO CENTRAL AND SOUTH FLORIDA, AND
BY MONDAY, THE LOW WILL BE OFFSHORE AND THE FRONT WILL PUSH SOUTH
OF THE STATE. A LACK OF INSTABILITY WILL LIMIT RAIN RATES, BUT
TRAINING CONVECTION COULD CAUSE ISOLATED FLASH FLOODING IF THE
MOVE OVER URBAN AND/OR POOR DRAINAGE AREAS. IN THE DAY 4 EXCESSIVE
RAINFALL OUTLOOK (12Z SUNDAY TO 12Z MONDAY), A MARGINAL RISK AREA
IS IN PLACE ALONG THE CENTRAL AND SOUTH FLORIDA ATLANTIC COASTS
FROM TITUSVILLE TO THE GREATER MIAMI METRO AREA.
THE PROSPECTS FOR HEAVY RAINFALL AND POTENTIAL FLOODING ARE EVEN
GREATER ACROSS MUCH OF CALIFORNIA GOING INTO SUNDAY AND EVEN MORE
SO ON MONDAY. A SLIGHT RISK OF EXCESSIVE RAINFALL IS IN PLACE FROM
SAN FRANCISCO TO LOS ALAMOS ON SUNDAY WHERE THE BEST MOISTURE FLUX
AND HIGHEST PW ANOMALIES ARE EXPECTED. RAINFALL RATES IN THIS
REGION HAVE THE POTENTIAL TO REACH 0.5-1" PER HOUR. ANOTHER SLIGHT
RISK AREA IS IN PLACE IN ON MONDAY FOR PART OF SOUTHERN CALIFORNIA
FROM CONCEPTION TO ANAHEIM, INCLUDING THE TRANSVERSE RANGES AND
THE LOS ANGELES METRO AREA. THE ATMOSPHERIC RIVER AND ASSOCIATED
ANOMALOUS MOISTURE FLUX WILL BE DIRECTED AT THE TERRAIN AND COULD
PRODUCE 2 TO LOCALLY 4 INCHES OF RAINFALL. HEAVY SNOW IS EXPECTED
FOR THE SIERRA SUNDAY THROUGH TUESDAY, THEN MODERATE SNOW IS
FORECAST FARTHER INLAND ACROSS THE HIGHER TERRAIN OF THE
INTERMOUNTAIN WEST AND EVENTUALLY THE ROCKIES.
AFTER THE BRIEF COLD SPELL ACROSS THE NORTH-CENTRAL U.S. ON
SATURDAY, A WARMING TREND IS EXPECTED GOING INTO SUNDAY, AND
ESPECIALLY EARLY NEXT WEEK AS THE UPPER TROUGH LIFTS OUT AND MORE
WESTERLY FLOW FROM THE PACIFIC MOVES IN AND MODIFIES THE AIR MASS.
HIGH TEMPERATURES COULD BE 15-25 DEGREES ABOVE AVERAGE ACROSS
PORTIONS OF THE CENTRAL PLAINS AND MIDWEST BY TUESDAY. CLOUDS AND
PRECIPITATION ACROSS THE WEST COAST REGION WILL TEND TO HOLD
TEMPERATURES MORE IN CHECK, WITH SLIGHTLY BELOW AVERAGE READINGS
LIKELY.
DOLAN/HAMRICK
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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