986
FXUS02 KWBC 121842
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EST MON FEB 12 2024
VALID 12Z THU FEB 15 2024 - 12Z MON FEB 19 2024
...INCREASINGLY WET PATTERN ACROSS CALIFORNIA THIS WEEKEND INTO
EARLY NEXT WEEK...
..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
MODELS CONTINUE TO SHOW GOOD AGREEMENT THROUGH MOST OF THE PERIOD
ACROSS THE U.S. ON THE LARGE SCALE, WITH SOME LINGERING
UNCERTAINTIES IN THE DETAILS OF INDIVIDUAL SYSTEMS. MODELS HAVE
TRENDED STRONGER OFF THE PACIFIC NORTHWEST COAST ON THURSDAY WITH
A COMPACT UPPER LOW WHICH SHOULD WEAKEN AND LIFT NORTHWARD BY
FRIDAY AS THE NEXT TROUGH MOVES TOWARDS THE REGION. ALSO SOME
TIMING DIFFERENCES WITH SHORTWAVES THROUGH THE GREAT
LAKES/NORTHEAST BUT MINOR AND COULD BE HANDLED WITH A GENERAL
MODEL BLEND. THE CMC IS NOTICEABLY SLOWER WITH TROUGHING ACROSS
THE GULF SUNDAY-MONDAY. THERE ARE ALSO UNCERTAINTIES WITH THE NEXT
TROUGH/UPPER LOW INTO THE WEST COAST, WITH THE CMC WEAKER WITH THE
OVERALL TROUGH VS THE GFS AND ECMWF (WITH SUPPORT FROM THE
ENSEMBLE MEANS) SHOW A CLOSED LOW BREAKING OFF FROM THE LARGER
SCALE FLOW AND MOVING IN TOWARDS SOUTHERN CALIFORNIA. THE WPC
BLEND FOR TODAY WAS BASED ON A GENERAL MODEL COMPROMISE THROUGH
DAY 5, REPLACING THE CMC AND UKMET WITH THE ENSEMBLE MEANS DAYS
6-7 TO HELP SMOOTH OUT THE LATER PERIOD DIFFERENCES. OVERALL, THIS
MAINTAINS GOOD CONTINUTIY WITH THE PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
LOOKING AHEAD TO THURSDAY AND FRIDAY, A WEAK LOW PRESSURE SYSTEM
IS EXPECTED TO DEVELOP OVER THE WESTERN GULF IN ADVANCE OF AN
APPROACHING SOUTHERN STREAM UPPER TROUGH ENERGY AND ADVECT
INCREASING MOISTURE NORTHWARD AND OVER A DEVELOPING WARM FRONT.
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, BUT GIVEN AN OVERALL DECREASING TREND IN
AMOUNTS AND HIGH FLASH FLOOD GUIDANCE ACROSS THAT REGION, DID GO
AHEAD AND REMOVE THE MARGINAL RISK ON THE DAY 4/THURSDAY ERO. THE
HEAVY RAINFALL SIGNATURE QUICKLY INCREASES ACROSS PARTS OF 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. FOR FRIDAY, DID MAINTAIN THE MARGINAL
RISK AREA ALONG THE TEXAS GULF COAST REGION ON THE DAY 5 ERO 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 SOME
MOISTURE ALSO EXTENDING 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.
SANTORELLI/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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