012
FXUS02 KWBC 130655
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 AM EST TUE FEB 13 2024
VALID 12Z FRI FEB 16 2024 - 12Z TUE FEB 20 2024
***MAJOR ATMOSPHERIC RIVER EVENT POSSIBLE FOR PORTIONS OF
CALIFORNIA SUNDAY INTO MONDAY WITH HEAVY RAIN AND SIERRA SNOW***
..GENERAL OVERVIEW
BROAD CYCLONIC FLOW ALOFT IS EXPECTED ACROSS THE NORTH-CENTRAL
U.S. FOR THE END OF THE WEEK, AND MAINLY ZONAL FLOW ACROSS MUCH OF
THE COUNTRY EAST OF THE ROCKIES WITH A RIDGE AXIS OVER THE
INTERMOUNTAIN WEST. THE TROUGH OVER THE GREAT LAKES AMPLIFIES
FURTHER GOING INTO THE WEEKEND, AND A SOUTHERN STREAM UPPER TROUGH
IS PROGGED TO ENTER THE GULF REGION BY SATURDAY AND INDUCE A
RELATIVELY WEAK SURFACE LOW THAT SHOULD TRACK ACROSS FLORIDA AND
THEN OFFSHORE. MEANWHILE, A BIG SURFACE HIGH FROM CANADA WILL BE
SETTLING SOUTHWARD ACROSS THE PLAINS AND THEN EVENTUALLY THE DEEP
SOUTH REGION BY LATE SUNDAY WITH COLDER TEMPERATURES ACCOMPANYING
IT. THE WEST COAST WILL LIKELY BECOME QUITE UNSETTLED GOING INTO
THE WEEKEND AND NEXT MONDAY WITH INCREASING CHANCES OF A MAJOR
ATMOSPHERIC RIVER EVENT FOR PORTIONS OF CENTRAL AND SOUTHERN
CALIFORNIA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
OVERALL, THE 00Z MODEL GUIDANCE SUITE IS IN BETTER AGREEMENT
ACROSS THE CONTINENTAL U.S. COMPARED TO THE SAME TIME FRAME
YESTERDAY, ESPECIALLY FOR THE WEST COAST. THERE ARE SOME MODEST
TIMING DIFFERENCES WITH THE ARRIVAL OF THE UPPER TROUGH ACROSS THE
GREAT LAKES, WITH THE CMC FASTER AND THE GFS SLOWER AND MORE
AMPLIFIED. THE CMC REMAINS A WEAKER SOLUTION WITH THE CLOSED
UPPER LOW NEAR CALIFORNIA EARLY NEXT WEEK AND CENTERED WELL TO THE
NORTH OF WELL CLUSTERED ECMWF AND GFS GUIDANCE, BUT IT HAS TRENDED
MORE IN LINE WITH THE MODEL CONSENSUS WITH THE GULF COAST LOW.
THE FRONTS/PRESSURES WERE PRIMARILY DERIVED FROM A
GFS/ECMWF/UKMET/SOME CMC FRIDAY-SATURDAY, AND THEN DROPPING THE
CMC AFTER SATURDAY AND GRADUALLY INCREASING THE ENSEMBLE MEANS,
WHICH ACCOUNTED FOR ABOUT 40-50% OF THE FORECAST BLEND GOING INTO
EARLY NEXT WEEK DUE TO THE GREATER MESOSCALE DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
THE LOW PRESSURE SYSTEM DEVELOPING OVER THE GULF FRIDAY NIGHT HAS
GRADUALLY TRENDED SOUTH OVER THE PAST FEW DAYS OF MODEL RUNS, WITH
CONSEQUENTIAL RAINFALL MAINLY CONFINED TO THE TEXAS COASTAL REGION
AND THE NORTHERN FLORIDA PANHANDLE. ALTHOUGH RAINFALL TOTALS ARE
GENERALLY EXPECTED TO BE UNDER TWO INCHES FOR BOTH OF THESE AREAS,
THERE MAY BE JUST ENOUGH HIGHER RAINFALL RATES TO WARRANT A
MARGINAL RISK AREA FOR SOUTHERN TEXAS ON FRIDAY, AND POTENTIAL
EPISODES OF TRAINING CONVECTION ACROSS NORTHERN FLORIDA ON
SATURDAY TO JUSTIFY A MARGINAL RISK THERE.
FOR THE WEST COAST REGION, MOST OF THE RAINFALL WILL LIKELY REMAIN
OFFSHORE UNTIL THE 6-12Z TIME PERIOD SATURDAY MORNING, BUT THERE
ARE SOME MODEL DIFFERENCES IN ARRIVAL OF THE HEAVIER RAINFALL, SO
THE MARGINAL RISK AREA IS MAINTAINED FOR THE DAY 4 PERIOD
FRIDAY-FRIDAY NIGHT FOR COASTAL PORTIONS OF NORTHWESTERN
CALIFORNIA. A MORE SUBSTANTIAL AXIS OF HEAVIER RAINFALL IS
BECOMING MORE LIKELY ACROSS THIS REGION GOING INTO SATURDAY AND
SATURDAY NIGHT WITH SOME RAINFALL TOTALS APPROACHING TWO INCHES,
AND THEREFORE GREATER CONFIDENCE IN HAVING A MARGINAL RISK FOR THE
DAY 5 PERIOD. LOOKING AHEAD TO SUNDAY AND MONDAY, A MAJOR
ATMOSPHERIC RIVER EVENT IS BECOMING MORE EVIDENT IN THE LATEST
MODEL GUIDANCE AS A SLOW MOVING PACIFIC LOW APPROACHES CALIFORNIA,
WITH ANOMALOUS MOISTURE FLUX DIRECTED TOWARDS THE COASTAL TERRAIN.
RIGHT NOW, IT APPEARS THE HIGHEST RAINFALL TOTALS LATE IN THE
FORECAST PERIOD WOULD BE MOST FAVORED FOR THE TRANSVERSE RANGES
WHERE SEVERAL INCHES OF RAINFALL IS A GOOD POSSIBILITY, SO THIS
WILL CONTINUE TO BE MONITORED CLOSELY. HEAVY SNOW IS ALSO LIKELY
FOR THE SIERRA AND NORTHERN CALIFORNIA MOUNTAINS DURING THIS TIME
PERIOD.
THE SURFACE HIGH SETTLING SOUTH FROM WESTERN CANADA WILL LIKELY BE
ACCOMPANIED WITH TEMPERATURES RUNNING ABOUT 10-20 DEGREES BELOW
MID-FEBRUARY AVERAGES ACROSS MUCH OF THE NORTH-CENTRAL U.S. ON
FRIDAY BEHIND THE COLD FRONT. HOWEVER, IT APPEARS THAT THIS
AIRMASS WILL NOT BE AS COLD AS THE ARCTIC AIR INTRUSION BACK IN
MID-JANUARY. THIS AIRMASS THEN SETTLES ACROSS THE SOUTH-CENTRAL
U.S. AND INTO THE OHIO VALLEY GOING INTO SATURDAY WITH HIGHS
GENERALLY 5-15 DEGREES BELOW AVERAGE, BUT A WARMER TREND ACROSS
THE NORTHERN PLAINS AND MIDWEST AS THE AIRMASS MODIFIES BY SUNDAY
AND INTO EARLY NEXT WEEK. IN FACT, MOST OF THE NATION SHOULD BE
BE WARMER THAN AVERAGE BY NEXT TUESDAY EAST OF THE ROCKIES,
PERHAPS UP TO 20 DEGREES ABOVE ACROSS PORTIONS OF THE CENTRAL AND
SOUTHERN PLAINS, AND SLIGHTLY BELOW AVERAGE FOR THE WEST COAST.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page