063
FXUS02 KWBC 190700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST MON FEB 19 2024
VALID 12Z THU FEB 22 2024 - 12Z MON FEB 26 2024
..OVERVIEW
NORTHERN STREAM UPPER TROUGHING AND A SOUTHERN STREAM SHORTWAVE
INTERACT LATE IN THE WORKWEEK AND DEVELOP A CENTRAL-EASTERN U.S.
SURFACE LOW/FRONTAL SYSTEM. THIS FEATURE SHOULD SPREAD RAIN AND
NORTHERN TIER SNOW TO PARTS OF THE EASTERN THIRD OF THE COUNTRY AS
A LARGER SCALE UPPER TROUGH SETTLES OVER THE EAST. MEANWHILE,
PERIODS OF UPPER RIDGING ACROSS THE WEST-CENTRAL U.S. WILL LEAD TO
MUCH ABOVE NORMAL TEMPERATURES LATE THIS WEEK INTO EARLY NEXT
WEEK. UPPER AND SURFACE LOWS MAY APPROACH THE WEST COAST AGAIN BY
THE WEEKEND, CAUSING AN INCREASE IN PRECIPITATION CHANCES THERE BY
EARLY NEXT WEEK IF NOT BEFORE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
IN THE CENTRAL TO EASTERN U.S., MODELS ARE IN REASONABLE AGREEMENT
THAT AN UPPER LOW WILL CLOSE OFF AROUND JAMES BAY FOR A TIME LATE
WEEK, WHILE A SHORTWAVE FARTHER SOUTH ALSO HELPS TO FORCE A
SURFACE LOW TRACKING QUICKLY FROM THE SOUTH-CENTRAL U.S. THURSDAY
INTO THE MID-ATLANTIC FRIDAY AND LIKELY ATLANTIC CANADA BY
SATURDAY. GFS RUNS HAVE BEEN PERSISTENTLY FAST AND THE ECMWF ON
THE SLOWER SIDE, BUT A MIDDLE GROUND CONSENSUS INITIALLY CLOSE TO
THE CMC AND EC MEAN SEEMS BEST, THOUGH THE CMC STRAYS EAST OF
CONSENSUS BY SATURDAY. THEN, MODELS HAVE TRENDED TOWARD A MORE
DEFINED SURFACE LOW REACHING JUST NORTH OF THE GREAT LAKES AROUND
SUNDAY WITH ITS ASSOCIATED FRONTS AFFECTING THE U.S., AND A BLEND
OF MODELS/MEANS SEEMS REASONABLE WITH TYPICAL MODEL SPREAD FOR THE
DAY 6-7 TIMEFRAME. THE AMPLITUDE OF THE UPPER TROUGH LOOKS TO
RELAX A BIT EARLY NEXT WEEK.
IN THE WEST, MODELS AGREE ON MEAN RIDGING WITH ITS AXIS SHIFTING
EAST SLOWLY INTO THE INTERMOUNTAIN WEST FOR THE WEEKEND.
SHORTWAVES MAY BE EMBEDDED IN THE NORTHWEST FLOW JUST EAST OF THE
RIDGE AXIS, WITH TYPICAL SPREAD FOR THESE SMALLER FEATURES. THE
TRACK OF THE UPPER LOW AND ITS ASSOCIATED SURFACE LOW(S) IN THE
EASTERN PACIFIC HAS BEEN WAFFLING FROM CYCLE TO CYCLE WITH HOW
FAST OR SLOW IT REACHES THE WEST COAST OVER THE WEEKEND/EARLY NEXT
WEEK, WITH THE NORTHERN STREAM FLOW SHOWING A DIGGING TROUGH AS
WELL POTENTIALLY COMPLICATING MATTERS. THE NEWER INCOMING 00Z
GUIDANCE OVERALL IS SHOWING A MUCH FASTER/EASTWARD TREND BRINGING
BOTH NORTHERN STREAM AND ESPECIALLY THE SOUTHERN STREAM TROUGHING
INTO THE WEST COMPARED TO THE 12/18Z CYCLE, WHICH WOULD SPREAD QPF
INTO THE WEST ON THE EARLIER SIDE.
THE WPC FORECAST USED A BLEND OF THE 12/18Z DETERMINISTIC GUIDANCE
FAVORING THE ECMWF EARLY IN THE PERIOD, WITH GRADUAL TRANSITION TO
ABOUT HALF EC/GEFS ENSEMBLE MEANS BY THE DAY 6-7 PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
PRECIPITATION SHOULD INCREASE IN COVERAGE AND INTENSITY OVER THE
OHIO VALLEY TO GREAT LAKES THURSDAY UNDER THE INFLUENCE OF A
COUPLE OF LOW PRESSURE/FRONTAL SYSTEMS. PRECIPITATION IS MOST
LIKELY TO BE RAIN EXCEPT IN THE FAR NORTHERN TIER. RAINFALL
AMOUNTS OF AN INCH OR TWO ARE LIKELY IN THE OHIO VALLEY, WITH
LOCALLY HIGHER AMOUNTS. SOME COMPETING FACTORS ARE IN PLACE
REGARDING WHETHER THIS RAINFALL WILL CAUSE A FLASH FLOODING
THREAT. SOME INSTABILITY COMBINED WITH GOOD DYNAMICAL SUPPORT
(LEFT EXIT REGION OF THE JET) MAY LEAD TO HIGH RAINFALL RATES. THE
SURFACE LOW AND SHORTWAVE HELPING TO FORCE THE PRECIPITATION
SHOULD BE MOVING RATHER QUICKLY, BUT THE WEST TO EAST TRACK MEANS
THAT RAIN HAS THE POTENTIAL TO TRAIN WEST TO EAST. ANTECEDENT
CONDITIONS IN TERMS OF SOIL MOISTURE AND STREAMFLOWS ARE
INCREDIBLY DRY FROM THE OHIO RIVER NORTHWARD BUT CLOSER TO NORMAL
FARTHER SOUTH. THE WPC FORECAST MAINTAINS A SOMEWHAT BROAD
MARGINAL RISK ACROSS THE OHIO VALLEY TO CENTRAL APPALACHIANS
CONSIDERING THESE FACTORS, WITH THE EXPECTATION THAT THE AREA
COULD CHANGE OVER TIME AND POSSIBLY EMBED A SLIGHT RISK AT A
FUTURE TIME IF THE POSITIONING OF A HEAVY/TRAINING QPF AXIS
BECOMES CLEARER. THE PRECIPITATION SHOULD REACH THE EAST
THURSDAY-FRIDAY WITH SNOW POSSIBLE IN PARTS OF THE NORTHEAST.
NORTHERN NEW ENGLAND HAS A RELATIVELY HIGHER PROBABILITY OF SEEING
NOTABLE SNOW ALONG WITH THE POTENTIAL FOR A PERIOD OF BRISK WINDS.
THERE IS STILL UNCERTAINTY WITH THE SNOW AMOUNTS AND PLACEMENT, SO
CONTINUE TO MONITOR FORECASTS. BEHIND THIS SYSTEM, PARTS OF THE
GREAT LAKES MAY SEE MOSTLY LIGHT SNOW FROM A COMBINATION OF LAKE
EFFECT ACTIVITY AND ONE OR MORE WAVES/FRONTAL SYSTEMS.
THE WEST WILL SEE A BREAK FROM PRECIPITATION AROUND
THURSDAY-FRIDAY WITH A BOUT OF RIDGING ALOFT. AN EASTERN PACIFIC
UPPER LOW AND ITS SURFACE REFLECTION WILL MEANDER AND GRADUALLY
DRIFT CLOSER TO THE WEST COAST, PERHAPS SPREADING PRECIPITATION
CHANCES TO CALIFORNIA BY LATE FRIDAY-SATURDAY DEPENDING ON HOW
CLOSE THE LOWS GET TO THE COAST. BY SUNDAY MODEL GUIDANCE IS MORE
AGREEABLE THAT PRECIPITATION SHOULD SPREAD INTO THE PACIFIC
NORTHWEST AND CALIFORNIA WITH SOME MOISTURE SPREADING FARTHER
INLAND INTO THE INTERMOUNTAIN WEST AS WELL.
AREAS FROM THE PLAINS EASTWARD WILL SEE ABOVE NORMAL TEMPERATURES
THURSDAY WITH THE EXCEPTION OF A COOLER FLORIDA PENINSULA.
TEMPERATURES LOOK TO MODERATE CLOSER TO AVERAGE IN THE EAST LATE
WEEK AFTER A COLD FRONTAL PASSAGE OR TWO, LIKELY REACHING BELOW
AVERAGE FOR HIGHS IN THE NORTHEAST SATURDAY. MEANWHILE RENEWED
UPPER RIDGING IN THE WEST-CENTRAL U.S. WILL PROMOTE TEMPERATURES
WARMING EVEN FURTHER BY THE WEEKEND INTO EARLY NEXT WEEK FOR MUCH
OF THE PLAINS AND MISSISSIPPI VALLEY. TEMPERATURES 15-30F ABOVE
NORMAL FOR LATE FEBRUARY WILL BE COMMON AS FORECAST HIGHS GET INTO
THE 80S FOR MUCH OF TEXAS EARLY NEXT WEEK WITH 50S REACHING AS FAR
NORTH AS THE DAKOTAS. MEANWHILE THE WESTERN U.S. SHOULD BE NEAR TO
SLIGHTLY ABOVE NORMAL UNTIL EARLY NEXT WEEK WHEN THE UPPER LOW
APPROACHES AND COOLS TEMPERATURES, ESPECIALLY HIGHS.
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, 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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