950
FXUS02 KWBC 230723
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
323 AM EDT SAT MAR 23 2024
VALID 12Z TUE MAR 26 2024 - 12Z SAT MAR 30 2024
..HEAVY RAIN THREAT ACROSS THE SOUTHEAST TUESDAY-WEDNESDAY
...HEAVY RAIN AND SNOW POSSIBLE ACROSS MUCH OF THE WEST BY MIDWEEK
AND BEYOND...
..OVERVIEW
AS SNOW STARTS TO EXIT THE UPPER MIDWEST ON TUESDAY, THE MAIN
FOCUS FOR POTENTIALLY HAZARDOUS WEATHER WILL BE MUCH FARTHER SOUTH,
AS HEAVY RAIN AND THUNDERSTORMS ARE LIKELY AHEAD OF A COLD FRONT
TRACKING ACROSS THE SOUTHEASTERN U.S. TUESDAY-THURSDAY. MEANWHILE,
ONE OR MORE PACIFIC SYSTEMS SHOULD BRING INCREASING TOTALS OF RAIN
AND MOUNTAIN SNOW TO THE WEST COAST STATES AND THEN INTO THE
ROCKIES MID-LATE WEEK. SOME OF THIS MOISTURE MAY REACH THE NORTHERN
PLAINS BY FRIDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
WHILE MODEL GUIDANCE IS MORE AGREEABLE ACROSS THE CONUS THAN A DAY
AGO, THERE ARE CERTAINLY STILL SOME DIFFERENCES THAT IMPACT
SENSIBLE WEATHER. IN THE EAST, MINOR VARIATIONS ARE SEEN IN THE
MODELS THROUGH THURSDAY OR SO, THOUGH THE DETAILS DO IMPACT QPF
AXES AND AMOUNTS IN THE SOUTHEAST. THERE ARE SOME INCREASING
DIFFERENCES BY FRIDAY-SATURDAY WITH SOUTHERN STREAM ENERGY
DEVELOPING LOW PRESSURE IN THE WESTERN ATLANTIC. THESE ARE
GENERALLY WITHIN NORMAL SPREAD FOR THE DAY 6-7 TIMEFRAME. THE 12Z
GFS SURFACE LOW POSITION SEEMED TO MATCH BEST WITH THE ENSEMBLE
MEANS, WHILE OTHER MODELS WERE SLOWER. THE INCOMING 00Z SUITE SHOWS
LESSENING SPREAD IN THE UPPER/SURFACE LOWS.
IN THE WEST, THE MAIN OUTLIER WAS THE 12Z UKMET, SHOWING MUCH LESS ENERGY
COMING FROM THE PACIFIC AND A DISPLACED SURFACE LOW POSITION BY
WEDNESDAY. THE CMC WAS IN MUCH BETTER ALIGNMENT COMPARED TO A DAY
AGO, WITH AN ECMWF/GFS/CMC BLEND GENERALLY REASONABLE. BY DAY
7/SATURDAY THERE BECOME MORE DIFFERENCES IN EJECTING ENERGY INTO
THE CENTRAL U.S., SO QUICKLY TRANSITIONED TO THE ENSEMBLE MEANS
COMPRISING JUST OVER HALF THE BLEND BY DAY 7 AFTER MAINTAINING MORE
DETERMINISTIC MODELS THROUGH DAY 6.
..WEATHER/HAZARDS HIGHLIGHTS
SOME SNOW MAY LINGER ACROSS NORTHERN PARTS OF THE UPPER MIDWEST ON
TUESDAY AS THE SURFACE LOW TRACKS ACROSS THE UPPER GREAT LAKES.
MEANWHILE FARTHER SOUTH, AMPLE MOISTURE AND A STRONG JET ALOFT WILL
SUPPORT HEAVY RAIN. THIS IS LIKELY TO BE ONGOING IN PARTS OF THE
SOUTHEAST AS THE PERIOD BEGINS EARLY TUESDAY, WITH MODEL GUIDANCE
INDICATING A SQUALL LINE CROSSING MISSISSIPPI AND ALABAMA. THIS
COULD PRODUCE RAIN RATES THAT SUPPORT SLIGHT RISK LEVELS IN THE
EXCESSIVE RAINFALL OUTLOOK FOR TUESDAY, THOUGH AREAL COVERAGE OF
HEAVY QPF SEEMS TO BE LESS SO COMPARED TO MONDAY (NOW IN THE SHORT
RANGE). THE MAIN CHANGE WITH THE TUESDAY SLIGHT RISK FROM THE
PREVIOUS ISSUANCE WAS TO EXPAND TO THE CENTRAL GULF COAST WHERE
INSTABILITY SHOULD BE HIGHEST. SOME RAIN EXTENDING INTO TENNESSEE
AND KENTUCKY AND OVER TO THE SOUTHERN APPALACHIANS IS COVERED BY A
MARGINAL RISK. THEN ON WEDNESDAY, THE POTENTIAL FOR HEAVY RAIN
CONTINUES TO SHIFT EASTWARD AS THE COLD FRONT(S) PRESS TOWARD THE
EASTERN SEABOARD. MODELS VARY TREMENDOUSLY ON THE PLACEMENT AND
AMOUNTS OF RAINFALL ON WEDNESDAY IN THE EAST. THE FIRST TAKE AT THE
WEDNESDAY EXCESSIVE RAINFALL OUTLOOK INDICATES A MARGINAL RISK
ACROSS PORTIONS OF FLORIDA ACROSS GEORGIA AND INTO THE CAROLINAS.
IF SOME MODELS LIKE SOME GFS RUNS VERIFY, WITH MULTI-INCH TOTALS
ACROSS A SWATH INLAND IN THOSE STATES, THIS WOULD NEED TO BE
UPGRADED. BUT SOME MODELS SHOW MUCH LIGHTER QPF WITH A SWATH MORE
COASTAL OR OFFSHORE. GIVEN THE SPREAD, WILL NOT GO FOR MORE THAN A
MARGINAL RISK AT THIS POINT. SOME POTENTIALLY HEAVY RAIN COULD
LINGER INTO THURSDAY, CURRENTLY MOST LIKELY OVER THE EASTERN
CAROLINAS, BUT WITH CONTINUED UNCERTAINTY. RAIN TOTALS ARE ALSO
UNCERTAIN FOR THE MID-ATLANTIC/NORTHEAST WEDNESDAY-THURSDAY.
FARTHER WEST, SOME SNOW IS LIKELY IN THE INTERMOUNTAIN WEST ON
TUESDAY. DEEPER MOISTURE STARTS TO STREAM INTO THE WEST COAST LATE
TUESDAY AND ESPECIALLY WEDNESDAY AS UPPER TROUGHING AND LOW
PRESSURE APPROACH. RAIN RATES COULD BE HIGH ENOUGH TO BE CONCERNING
FOR FLOODING ACROSS PORTIONS OF CALIFORNIA INTO WESTERN OREGON, SO
HAVE A MARGINAL RISK DELINEATED THERE FOR WEDNESDAY. HEAVY SNOW IS
LIKELY IN HIGHER ELEVATIONS MIDWEEK AND BEYOND, STRETCHING INTO
THE INTERMOUNTAIN WEST AS WELL. THERE IS A GENERAL SIGNAL FOR
PRECIPITATION TO EXPAND INTO THE NORTH-CENTRAL U.S., POSSIBLY IN
THE FORM OF SNOW AGAIN, BY FRIDAY.
MUCH COLDER THAN AVERAGE TEMPERATURES (MORE COMPARABLE TO JANUARY)
ARE LIKELY FOR THE NORTHERN AND CENTRAL HIGH PLAINS IN THE WAKE OF
THE STRONG PLAINS/MIDWEST STORM. HIGHS WILL ONLY BE IN THE 20S AND
30S FOR THESE AREAS ON TUESDAY. THE CENTRAL U.S. WILL SEE A
WARMING TREND GOING INTO THE MIDDLE AND LATE PART OF NEXT WEEK,
THOUGH MONTANA AND THE DAKOTAS WILL STILL REMAIN CHILLY BY LATE
MARCH STANDARDS. THE WEST SHOULD SEE GENERALLY COOLER THAN AVERAGE
HIGHS AND NEAR AVERAGE LOWS NEXT WEEK. THE EAST MAY SEE MIXED ABOVE
AND NEAR NORMAL TEMPERATURES UNTIL LATE WEEK WHEN THE RELATIVE
WARMTH FROM THE CENTRAL U.S. EXPANDS EAST.
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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