905
FXUS02 KWBC 191900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST FRI JAN 19 2024
VALID 12Z MON JAN 22 2024 - 12Z FRI JAN 26 2024
...EXCESSIVE RAIN AND FLOODING POTENTIAL TO INCREASE FROM THE
SOUTH-CENTRAL TO EASTERN U.S. NEXT WEEK...
..HEAVY PRECIPITATION FOR CALIFORNIA/WEST
..OVERVIEW
GUIDANCE CONTINUES TO INDICATE THAT THE LARGE SCALE PATTERN ALOFT
NEXT WEEK WILL SHIFT NOTABLY FROM THIS WEEK'S FRIGID PATTERN, AS A
RIDGE SHIFTS FROM THE CENTRAL U.S. INTO THE EAST AND MEAN
TROUGHING BECOMES ESTABLISHED IN THE WESTERN TO CENTRAL U.S.. THIS
WILL PROMOTE WARM AND MOIST INFLOW LIKELY FROM BOTH THE PACIFIC
AND THE GULF, WITH WARMING TEMPERATURES IN THE EASTERN HALF OF THE
COUNTRY. AS SHORTWAVES TRACK THROUGH THE WESTERN TROUGH, MULTIPLE
ROUNDS OF PRECIPITATION ARE LIKELY IN THE WEST INTO NEXT WEEK,
WITH HEAVY RAIN INTO CALIFORNIA IN PARTICULAR. MULTIPLE DAYS OF
HEAVY RAIN AND POTENTIAL FOR FLASH FLOODING ARE EXPECTED ACROSS
THE SOUTH-CENTRAL U.S. NEXT WEEK AMID THE STALLING UPPER FLOW
PATTERN, WITH EJECTING SHORTWAVES AND FAVORABLE UPPER JET SUPPORT
ACTING TO DEVELOP FRONTAL WAVES TO INCREASE AND FOCUS MOISTURE AND
INSTABILITY RETURN ON THE WESTERN PERIPHERY OF A SLOW TO DISLODGE
EASTERN U.S. SURFACE RIDGE. EXPECT WIDESPREAD ACTIVITY TO ALSO
SPREAD TO THE MIDWEST/GREAT LAKES AND THE SOUTHEAST/EAST THROUGH
MID-LATER NEXT WEEK, WITH SNOW/ICE POTENTIAL ON THE NORTH SIDE OF
THE PRECIPITATION SHIELD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE REMAINS ABOVE AVERAGE FORECAST CONFIDENCE ON THE OVERALL
SYNOPTIC PATTERN NEXT WEEK AMIDST GOOD AGREEMENT IN THE
DETERMINISTIC GUIDANCE AND ENSEMBLES ON A FAIRLY BLOCKY PATTERN
WITH TROUGHING OVER THE WEST, AND RIDGING ACROSS THE EAST. THERE
IS PLENTY OF VARIABILITY STILL IN THE SMALLER SCALE DETAILS OF
INDIVIDUAL SHORTWAVES/SYSTEMS, WHICH HAS IMPLICATIONS FOR EXACT
QPF AMOUNTS ACROSS THE SOUTH AND INTO THE EASTERN U.S.. THE
UPDATED FORECAST FOR TODAY USED A BLEND OF THE DETERMINISTIC
GUIDANCE THROUGH DAY 5, INCREASING TO ABOUT 50% ENSEMBLE MEANS
LATE PERIOD TO HELP SMOOTH OUT SOME OF THE MORE UNCERTAIN FLOW
DETAILS. THIS APPROACH MAINTAINS A VERY CONSISTENT FORECAST WITH
THE PREVIOUS WPC SHIFT.
..WEATHER/HAZARDS HIGHLIGHTS
THE WEST COAST STATES CAN EXPECT ROUNDS OF PRECIPITATION NEXT
WEEK. EARLY WEEK, AN ATMOSPHERIC RIVER IS FORECAST TO BRING
MOISTURE TO CALIFORNIA AND SINK SOUTH GRADUALLY, WHILE A POTENT
SHORTWAVE AND THE LEFT EXIT REGION OF THE JET STREAM WILL PROVIDE
UPPER-LEVEL DYNAMICAL SUPPORT. THESE SHOULD COMBINE WITH SOME
INSTABILITY SNEAKING ONSHORE, LEADING TO PERIODS OF HIGH RAIN
RATES LIKELY REACHING OVER HALF AN INCH PER HOUR. A SLIGHT RISK
AREA WAS HELD FOR THE DAY 4/ERO MONDAY GIVEN THIS SETUP, WITH
FOCUS ON SOUTHERN CALIFORNIA. THE SIERRA NEVADA WILL RECEIVE HEAVY
SNOW AND RAIN AND SNOW ARE EXPECTED FARTHER EAST INTO THE
INTERMOUNTAIN WEST AND THE SOUTHWEST WHERE A MARGINAL RISK AREA
HAS BEEN DENOTED. MEANWHILE, THE PACIFIC NORTHWEST WILL SEE
PERIODIC PRECIPITATION NEXT WEEK AND PERHAPS WITH MORE EMPHASIS
LATE NEXT WEEK WITH STRONGER SYSTEM APPROACH.
DEEPLY INCREASING MOISTURE AHEAD OF THE WESTERN U.S. UPPER
TROUGHING WILL INCREASINGLY SPREAD RAIN INTO THE SOUTH-CENTRAL
U.S. EARLY NEXT WEEK. RAIN TOTALS ARE FORECAST TO QUICKLY RAMP UP
ON MONDAY AND LAST THROUGH MIDWEEK FOR THE SOUTHERN PLAINS INTO
THE LOWER MISSISSIPPI VALLEY/GULF COAST, AND THESE HEAVY TOTALS
COULD PRODUCE FLASH FLOODING CONCERNS. A SLIGHT RISK REMAINS FOR
DAY 4/MONDAY FOR SOUTHEAST TEXAS INTO WESTERN LOUISIANA WHERE THE
BEST POTENTIAL FOR INSTABILITY TO PRODUCE HIGH RAIN RATES AND WITH
GLOBAL MODELS AND ENSEMBLE PROBABILITIES SUPPORTING UPWARDS TO
LOCAL 3-6" AMOUNTS, WITH A MARGINAL RISK EXTENDING FARTHER NORTH
IN OKLAHOMA AND OVER THE LOWER MISSISSIPPI VALLEY. ON DAY
5/TUESDAY, A SLIGHT AND A SURROUNDING MARGINAL RISK AREA HAVE BEEN
INTRODUCED FOR THE LOWER MISSISSIPPI VALLEY GIVEN SLOW PATTERN
TRANSLATION AND CONTINUED VERY FAVORABLE UPPER AND MOIST LOWER
ATMOSPHERIC SUPPORT, ALBEIT WITH A SLIGHTLY MORE BROADLY DEFINED
GUIDANCE FOCUS. THERE IS SOME INCREASING PROBABILITIES FOR
FREEZING RAIN ACROSS PARTS OF THE LOWER/MID-MISSISSIPPI VALLEY
INTO THE MIDWEST, ESPECIALLY PARTS OF THE OZARKS ON MONDAY. WINTRY
PRECIP SHOULD THEN TRANSITION TO RAIN AS WARM AIR SPREADS FARTHER
NORTH. THE GREAT LAKES TO NORTHERN NORTHEAST SEEM MOST LIKELY TO
SEE PERSISTENT WINTRY WEATHER WITH OVERALL SYSTEM/PATTERN
EVOLUTION. PRECIPITATION SHOULD START SPREADING MORE EARNESTLY
ACROSS THE MIDWEST/GREAT LAKES AND THE SOUTHEAST/EAST INTO
MID-LATER NEXT WEEK AFTER A DRY PERIOD, AND GIVEN MUCH WARMER
TEMPERATURES AND SNOWMELT, AREAL AND STREAM FLOODING MAY BE A
CONCERN.
SANTORELLI/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
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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