545
FXUS02 KWBC 190701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM 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 NORTHERN
PERIHERY OF THE PRECIPITATION SHIELD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
12/18/00 UTC GUIDANCE CYCLE SOLUTIONS FOR BOTH THE OVERALL PATTERN
EVOLUTION/SCOPE AND OVERALL SENSIBLE WEATHER THREAT FOCUS FOR THE
MAIN FLOW EMBEDDED SYSTEMS SEEM REASONABLY WELL CLUSTERED THROUGH
MUCH OF NEXT WEEK, BOLSTERING FORECAST CONFIDENCE. LOCAL DETAIL
AND FOCUS ALWAYS OFFER MORE CHALLENGE, BUT AN ONGOING COMPOSITE OF
THE LATEST GFS/ECMWF/UKMET/CANADIAN AND GEFS/ECMWF ENSEMBLE MEANS
ALONG WITH THE NBM AND WPC CONTINUITY PROVIDES A SOLID FORECAST
BASIS WITH SIMILAR THREAT FOCUS SIGNALS TO EVALUATE NEEDED ACTION
THAT SEEMS CONSISTENT WITH A PATTERN WITH ABOVE NORMAL
PREDICTABILITY.
..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 LOOKS TO
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. DAY 5/TUESDAY
SLIGHT AND A SURROUNDING MARGINAL RISK AREAS HAVE BEEN INTRODUCED
FOR THE LOWER MISSISSIPPI VALLEY GIVEN SLOW PATTERN TRANSLATION
AND CONTINUED VERY FAVORABLE UPPER AND MOIST LOWER ATMOSHERIC
SUPPORT, ALBEIT WITH A SLIGHTLY MORE BROADLY DEFINED GUIDANCE
FOCUS. IN SOME AREAS ACROSS THE MIDWEST, PRECIPITATION MAY START
AS FREEZING RAIN OR MIXED PRECIPITATION, BUT 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 THE WARMER TEMPERATURES AND SNOWMELT, AREAL AND
STREAM FLOODING MAY BE A CONCERN.
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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