285
FXUS02 KWBC 100550
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 AM EST FRI NOV 10 2023
VALID 12Z MON NOV 13 2023 - 12Z FRI NOV 17 2023
...HEAVY RAINFALL POTENTIAL FOR THE WEST-CENTRAL GULF COAST MONDAY
AND TUESDAY...
...MOISTURE DIRECTED INTO CALIFORNIA COULD LEAD TO HEAVY RAIN AND
SNOW TUESDAY-THURSDAY...
..OVERVIEW
IT OVERALL REMAINS RELEVENT THAT RECENT GUIDANCE HAS BEEN SHOWING
AN UPPER PATTERN TRANSITIONING FROM FAIRLY LOW AMPLITUDE MEAN FLOW
WITH PROGRESSIVE SHORTWAVES TOWARD A MORE AMPLIFIED REGIME
CONSISTING OF A DEEP EASTERN PACIFIC TROUGH, A BROAD RIDGE ALIGNED
OVER THE CENTRAL U.S., AND A TROUGH REACHING THE WESTERN ATLANTIC.
THIS EVOLUTION WILL FAVOR DRY WEATHER OVER A MAJORITY OF THE LOWER
48 AND A TREND TO WELL ABOVE NORMAL TEMPERATURES OVER THE NORTHERN
TWO-THIRDS OF THE CENTRAL U.S. INTO MIDWEST. THE MOST LIKELY AREAS
OF PRECIPITATION FOCUS DURING THE PERIOD WILL BE ALONG THE WEST
COAST, WITH GRADUALLY INCREASING COVERAGE AND INTENSITY AHEAD OF
THE AMPLIFYING PACIFIC TROUGH THAT SHOULD EVENTUALLY DIRECT AN
ATMOSPHERIC RIVER INTO CALIFORNIA IN PARTICULAR, AND ACROSS THE
SOUTHERN TIER/GULF COAST STATES WHERE MOISTURE SHOULD OVERRUN A
SLOW-MOVING FRONT OVER THE GULF OF MEXICO. A SOUTHERN STREAM
SHORTWAVE/UPPER LOW EJECTING FROM NORTHWESTERN MEXICO AFTER SUNDAY
SHOULD CONTRIBUTE TO THIS ACTIVITY, WITH THE REGION TRENDING
WETTER OVER THE PAST DAY. ALONG THE EASTERN SEABOARD, ONE OR MORE
SHORTWAVES PUSHING THROUGH THE NORTHERN TIER OF THE COUNTRY EARLY
NEXT WEEK AND FORMING THE MIDWEEK ATLANTIC TROUGH WILL LEAD TO
COOLER THAN AVERAGE TEMPERATURES BEFORE A MODERATING TREND AS THE
WEEK PROGRESSES.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE SOLUTIONS ARE REASONABLY WELL CLUSTERED VALID
EARLY NEXT WEEK, AND A COMPOSITE SOLUTION ALONG WITH THE 01 UTC
NATIONAL BLEND OF MODELS SEEMS TO PROVIDE A STEADY STARTING POINT
FOR THE FORECAST. THAT SAID, THE MOST NOTEABLE DIFFERENCE RELATING
TO THREAT MESSAGING IS WHETHER THE HEAVIEST AXIS OF RAINFALL WORKS
MORE INTO THE WEST-CENTRAL GULF COAST OR HOLD MORE OFFSHORE INTO
THE GULF. THE 06 UTC GFS AND 00 UTC CANADIAN/ECMWF AND ECMWF
ENSEMBLES SHOW MORE DEEP MOISTURE AND INLAND RAINFALL POTENTIAL
MONDAY AND TUEADAY THAN THE 06 UTC GEFS AND 00 UTC UKMET. GUIDANCE
TRENDS ARE OVERALL FAVORABLE FOR SOME RUNOFF ISSUES INTO COASTAL
AREAS GIVEN POSSIBLE DURATION AND RISING QPF AMOUNTS, ESPECIALLY
FOR URBAN FLOODING DESPITE GENERALLY LIMITED INTENSITIES AND
CONSIDERING ANTECEDENT CONDITIONS. FORECAST SPREAD THEN BECOMES
INCREASINGLY PROBLEMATIC TUESDAY ONWARD NEXT WEEK ALONG/OFF THE
WEST COAST WITH THE EXTENT OF DIGGING/PHASING OF UPPER TROUGH
ENERGIES. A SOLUTION CLOSER TO THE NICELY COMPATABLE 06 UTC GEFS/
00 UTC ECMWF ENSEMBLE MEANS OFFERS A SEEMINGLY MIDDLE OF THE ROAD
MEAN UPPER TROUGH SOLUTION JUST OFF THE WEST COAST THAT DESPITE
THE LACK OF EMBEDDED FEATURE DEPICTION SEEMS MOST PRUDENT GIVEN
THE LACK OF A COMMON MODEL SIGMAL NOR CLEAR UPSTREAM PATTERN TO
FAVOR ANY MODEL CAMP AT THIS TIME.
..WEATHER/HAZARDS HIGHLIGHTS
MOISTURE OVERRUNNING THE COLD FRONT THAT IS FORECAST TO STALL OVER
THE NORTHWESTERN GULF (BUT TRACK A BIT MORE PROGRESSIVELY THROUGH
FLORIDA) WILL LEAD TO SOME RAIN ACROSS THE SOUTH-CENTRAL TO
SOUTHEASTERN QUADRANT OF THE U.S. CONTINUING INTO NEXT WEEK. THE
HIGHEST RAINFALL TOTALS ARE LIKELY TO WORK ACROSS THE WEST-CENTRAL
GULF COAST MONDAY-TUESDAY AND POTENTIALLY EVEN INTO THE
SOUTHEAST/FLORIDA BY LATER NEXT WEEK, WITH EASTERN PACIFIC AND
GULF MOISTURE COMBINING. LIMITED INSTABILITY WILL BE IN PLACE
THROUGH EARLY NEXT WEEK SINCE THE REGION WILL BE IN A POST-FRONTAL
AIRMASS, SO RAIN RATES SHOULD NOT BE TOO HIGH. BY MONDAY THOUGH,
THERE MAY BE MORE SUPPORT FOR CONVECTION FROM TEXAS INTO THE LOWER
MISSISSIPPI VALLEY AS MID-UPPER LEVEL ENERGY APPROACHES AND
POSSIBLY INCREASES INSTABILITY, AND THE POTENTIAL FOR HEAVIER RAIN
TOTALS HAS TRENDED UPWARD AS THE GUIDANCE INDICATES THIS MID-UPPER
ENERGY MAY BE STRONGER AND TRACK SLOWER OVER THE REGION. SOME OF
THE DETERMINISTIC GUIDANCE HAS BECOME PARTICULARLY AGGRESSIVE WITH
RAINFALL TOTALS ALONG THE WEST-CENTRAL GULF COAST AROUND MONDAY.
HOWEVER, WITH THE HEAVIEST RAINFALL EXPECTED TO REMAIN ALONG THE
GULF COAST, AND ANTECEDENT CONDITIONS ALREADY VERY DRY, THE RISK
FOR FLASH FLOODING SHOULD REMAIN RELATIVELY LOW, BUT THERE HAS
BEEN AN INCREASE IN MODEL FORECAST TOTALS TO CONSIDER.
ACCORDINGLY, SMALL MARGINAL THREAT AREAS HAVE BEEN INTRODUCED IN
THE WPC EXCESSIVE RAINFALL OUTLOOK FOR MONDAY AND TUESDAY TO
CAPTURE SOME THREAT FOR COASTAL COMMUNITIES.
ROUNDS OF FRONTAL SYSTEMS AND SHORTWAVES PUSHING THROUGH THE
NORTHWEST WILL MAINTAIN PRECIPITATION CHANCES ACROSS THE PACIFIC
NORTHWEST AND THE NORTHERN ROCKIES THROUGH EARLY NEXT WEEK.
MODERATE TO HEAVY AMOUNTS MAY BE DIRECTED INTO THE NORTHERN PARTS
OF THE OLYMPICS AND CASCADES, WITH LOWER ELEVATION RAIN AND HIGHER
ELEVATION SNOW. STARTING MONDAY AND ESPECIALLY BY
TUESDAY-THURSDAY, UPPER TROUGHING WILL DEEPEN OVER THE EASTERN
PACIFIC AND DIRECT MOISTURE PLUMES/ATMOSPHERIC RIVERS INTO THE
WEST, ESPECIALLY CALIFORNIA. EXPECT HEAVY LOWER ELEVATION RAIN AND
HIGHER ELEVATION SNOW, ESPECIALLY FOR FAVORED SLOPES OF THE
SIERRA. WHILE CONFIDENCE IS SOMEWHAT ABOVE AVERAGE IN A PERIOD OF
ENHANCED PRECIPITATION ASSOCIATED WITH THE OVERALL UPPER TROUGH,
IT IS MUCH LOWER IN TERMS OF SPECIFICS (TIMING, COVERAGE, AMOUNTS
OVER PARTICULAR LOCATIONS) DUE TO MODEL SPREAD AND VARIABILITY OF
INDIVIDUAL SHORTWAVE ENERGIES AND LARGER SCALE UPPER TROUGH
PROGRESSINS AND STREAM PHASINGS.
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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