374
FXUS02 KWBC 120657
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST MON FEB 12 2024
VALID 12Z THU FEB 15 2024 - 12Z MON FEB 19 2024
..GENERAL OVERVIEW
AN OVERALL PROGRESSIVE AND QUASI-ZONAL UPPER LEVEL FLOW PATTERN
CAN BE EXPECTED ACROSS THE CONTINENTAL U.S. FOR THE END OF THE
WEEK, AND A LOW PRESSURE SYSTEM IS FORECAST TO TRACK FROM THE
GREAT LAKES TO THE NORTHEAST U.S. COAST BY FRIDAY ALONG WITH A
MODIFIED ARCTIC AIRMASS SETTLING SOUTH ACROSS THE DAKOTAS AND
MONTANA. A NORTHERN STREAM TROUGH ORIGINATING FROM CENTRAL CANADA
IS FORECAST TO DROP SOUTHWARD ACROSS THE UPPER MIDWEST AND GREAT
LAKES REGION BY SATURDAY, AND THIS WILL REINFORCE THE COLD WEATHER
PATTERN ACROSS MUCH OF THE CENTRAL AND NORTHERN PLAINS FOR THE
WEEKEND WITH A STRONG SURFACE HIGH SETTLING SOUTHWARD FROM CANADA.
FOR THE GULF COAST REGION, A SOUTHERN STREAM TROUGH WILL INDUCE
SURFACE CYCLOGENESIS OVER THE WESTERN GULF AND RESULT IN
INCREASING SHOWERS AND THUNDERSTORMS FROM TEXAS TO THE CENTRAL
GULF COAST. UNSETTLED CONDITIONS ARE ALSO EXPECTED TO MAKE A
RETURN TO PORTIONS OF THE WEST COAST REGION WITH MULTIPLE ROUNDS
OF PRECIPITATION LIKELY OVER THE UPCOMING WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MOST OF THE CONTINENTAL U.S. HAS AVERAGE MODEL AGREEMENT GOING
INTO THURSDAY, BUT THE MAIN EXCEPTION TO THIS IS ACROSS THE WEST
COAST REGION WHERE MODELS HAVE RECENTLY STRUGGLED WITH TIMING AND
LOCATION OF LEAD PACIFIC SHORTWAVE ENERGY REACHING THE COAST. THE
00Z CMC IS AT ODDS WITH THE MODEL CONSENSUS ACROSS THE NORTHEAST
PACIFIC ON THURSDAY, PORTRAYING A MUCH STRONGER UPPER LOW, WHEREAS
THE OTHER GUIDANCE SUPPORTS THE IDEA OF AN ELONGATED TROUGH OVER
BRITISH COLUMBIA AND A RIDGE AXIS JUST OFF THE COAST, SO A NON-CMC
MODEL BLEND WORKS BEST FOR THE WEST COAST EARLY IN THE FORECAST
PERIOD. INTERESTINGLY, THIS DIFFERENCE BECOMES MUCH LESS
NOTICEABLE GOING INTO FRIDAY AND THE WEEKEND ACROSS THE SAME
REGION AS THE FEATURE ON THURSDAY LIFTS NORTH AWAY FROM THE
REGION, AND FITS THE CONSENSUS BETTER. GOING INTO THE WEEKEND
ELSEWHERE ACROSS THE NATION, THE GFS IS STRONGER WITH THE TROUGH
DROPPING SOUTH FROM CENTRAL CANADA AND HAS A GREATER SURFACE HIGH
OVER THE CENTRAL/NORTHERN PLAINS REGION. BY NEXT MONDAY, THE CMC
IS CONSIDERABLY SLOWER WITH THE GULF TROUGH AND LESS AMPLIFIED
WITH THE NEXT PACIFIC STORM SYSTEM APPROACHING CALIFORNIA. TAKING
THESE FACTORS INTO ACCOUNT, THE WPC FRONTS/PRESSURES FORECAST WAS
PRIMARILY BASED ON A GFS/ECMWF/UKMET BLEND WITH SOME PREVIOUS
CONTINUITY EARLY ON, AND THEN GRADUALLY INCREASING CONTRIBUTIONS
FROM THE ENSEMBLE MEANS HEADING INTO SUNDAY AND MONDAY.
TEMPERATURES WERE ALSO REDUCED A FEW DEGREES FROM THE NBM ACROSS
THE NORTH-CENTRAL U.S. GIVEN THE STRENGTH OF THE CANADIAN SURFACE
HIGH BEHIND THE COLD FRONT, AND THIS HAS BEEN THE TREND OVER THE
PAST FEW DAYS.
..WEATHER/HAZARDS HIGHLIGHTS
LOOKING AHEAD TO THURSDAY AND FRIDAY, A LOW PRESSURE SYSTEM IS
EXPECTED TO DEVELOP OVER THE WESTERN GULF IN ADVANCE OF
APPROACHING SOUTHERN STREAM UPPER TROUGH ENERGY AND ADVECT
INCREASING MOISTURE NORTHWARD AND OVER A DEVELOPING WARM FRONT,
AND THIS WILL LIKELY RESULT IN WIDESPREAD SHOWERS AND
THUNDERSTORMS ACROSS SOUTHERN TEXAS AND INTO THE CENTRAL GULF
COAST REGION. THE GUIDANCE FAVORS SOUTH TEXAS FOR SOME LOCAL
DOWNPOURS STARTING OVERNIGHT THURSDAY, AND A MARGINAL RISK IS
SHOWN FOR THE DAY 4 ERO GIVEN INITIAL GROWING ENSEMBLE
PROBABILITIES. THE HEAVY RAINFALL SIGNATURE QUICKLY INCREASES
ACROSS THE SOUTH/SOUTHEAST FRIDAY AND NEXT WEEKEND AS A MAIN
FRONTAL LOW TRACKS EASTWARD ACROSS THE NORTHERN GULF OF MEXICO AND
FLORIDA UNDERNEATH A NORTHERN STREAM ARCTIC FRONT DIGGING DOWN
THROUGH THE CENTRAL THEN EASTERN STATES. THEREFORE, A MARGINAL
RISK AREA IS PLANNED FOR MUCH OF THE TEXAS GULF COAST REGION ON
DAY 5 (FRIDAY) WHERE THE MODEL SIGNAL IS STRONGEST FOR HEAVIEST
QPF.
GUIDANCE HAS SLOWLY CONVERGED ON A MORE SIMILAR SOLUTION FOR THE
FOCUS AND ONSET OF ORGANIZED PRECIPITATION DEVELOPMENT ACROSS THE
WEST COAST IN AN EMERGING AND INCREASING WET PATTERN LATER THIS
WEEK AND LIKELY EXTENDING INTO THE BEGINNING OF NEXT WEEK.
MULTIPLE PACIFIC SYSTEMS WILL INITIALLY STRUGGLE TO WORK EASTWARD
GIVEN THE UPPER RIDGE AXIS IN PLACE OVER THE INTERMOUNTAIN WEST,
BUT THERE SHOULD BE ENOUGH MOISTURE ADVECTION TO FUEL A MODERATE
RAIN EVENT INTO THE PACIFIC NORTHWEST/NORTHERN CALIFORNIA TO CLOSE
OUT THE WEEK. THERE WILL LIKELY BE ADDITIONAL ROUNDS OF
PRECIPITATION ACROSS THIS REGION GOING INTO THE WEEKEND AND BEYOND
BASED ON LATEST MODEL GUIDANCE. A MARGINAL RISK OF EXCESSIVE
RAINFALL IS PLANNED FOR PORTIONS OF THE WASHINGTON/OREGON COASTAL
RANGES AND THE WEST FACING SLOPES OF THE CASCADES ON THURSDAY, AND
FOR COASTAL AREAS OF NORTHERN CALIFORNIA ON FRIDAY. EXPECT SNOW
FOR THE HIGHER TERRAIN, ESPECIALLY FOR THE SIERRA, WITH
DIMINISHING SUPPORT FARTHER INLAND ACROSS THE INTERMOUNTAIN WEST
AND ROCKIES.
TEMPERATURES ARE EXPECTED TO BE GENERALLY 5 TO 15 DEGREES ABOVE
MID-FEBRUARY AVERAGES ACROSS MUCH OF THE EAST-CENTRAL U.S. ON
THURSDAY. MEANWHILE, A STRONG COLD FRONT DROPPING SOUTH FROM
WESTERN CANADA IS EXPECTED TO HERALD THE ARRIVAL OF AN ARCTIC
AIRMASS ACROSS THE NORTHERN PLAINS AND BRING A RETURN TO BELOW
AVERAGE TEMPERATURES FROM MONTANA TO THE DAKOTAS AND NEBRASKA
THROUGH THE END OF THE WEEK, PERHAPS UP TO 20 DEGREES BELOW
AVERAGE ACROSS PORTIONS OF MONTANA, BUT NOT AS COLD AS THE
PREVIOUS ARCTIC BLAST BACK IN MID-JANUARY. COLD TEMPERATURES WITH
THIS FRONT WILL GRADUALLY MODIFY ACROSS THE CENTRAL TO EASTERN
U.S. GOING INTO NEXT WEEKEND. THERE WILL LIKELY BE SOME LAKE
EFFECT SNOW TO CLOSE OUT THE WORK WEEK INTO NEXT WEEKEND WITH THE
MUCH COLDER AIRMASS CROSSING THE GREAT LAKES. THE PROSPECT OF
NORTHERN STREAM FLOW AMPLIFICATION NEXT WEEKEND AND FRONTAL WAVE
DEVELOPMENT OFFERS AT LEAST MODEST SNOW POTENTIAL FROM THE OHIO
VALLEY THROUGH THE NORTHEAST.
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
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