244
FXUS02 KWBC 171901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MON OCT 17 2022
VALID 12Z THU OCT 20 2022 - 12Z MON OCT 24 2022
..OVERVIEW
A MAJOR SHIFT IN THE UPPER-LEVEL PATTERN IS EXPECTED TO OCCUR
ACROSS THE U.S. DURING THE MEDIUM RANGE PERIOD. A MUCH AMPLIFIED
UPPER LOW/TROUGH ANCHORED OVER THE EASTERN U.S. IS FORECAST TO
RETREAT BY LATE THIS WEEK AS AN ANOMALOUS RIDGE OVER THE WEST IS
FORECAST TO BE REPLACED BY MAJOR TROUGHING ARRIVING FROM THE
NORTHEASTERN PACIFIC BY THE WEEKEND. THIS WILL LIKELY RESULT IN A
RATHER AMPLIFIED TROUGH TO EXIT THE ROCKIES INTO THE PLAINS BY
EARLY NEXT WEEK. MEANWHILE, THE PRESENCE OF AN UPPER LOW WEST OF
BAJA CALIFORNIA WILL INTRODUCE UNCERTAINTY INTO THE FORECAST FOR
THE SOUTHWEST EARLY NEXT WEEK. A SMALLER SCALE UPPER LOW AND ITS
INTERACTION WITH AN OFFSHORE FRONT WILL ALSO INTRODUCE UNCERTAINTY
TO THE FORECAST ALONG THE EAST COAST FROM THE WEEKEND TO EARLY
NEXT WEEK.
..MODEL AND PREDICTABILITY ASSESSMENT
DETERMINISTIC MODEL SOLUTIONS ARE IN GOOD AGREEMENT AS THE
MEDIUM-RANGE PERIOD BEGINS ON THURSDAY. TIMING AGREEMENT REMAINS
GOOD THROUGH LATE WEEK REGARDING THE AMPLIFIED UPPER LOW/TROUGH
LIFTING OUT OF THE EASTERN U.S. BY THE WEEKEND, MODELS HAVE
GENERALLY TRENDED TOWARD AN MORE AMPLIFIED TROUGH TO DIG FASTER
ACROSS THE NORTHEASTERN PACIFIC TOWARD THE PACIFIC NORTHWEST.
MEANWHILE, MODELS CONTINUE TO SHOW POOR AGREEMENT ON THE EVOLUTION
OF AN UPPER LOW SITUATED WELL OFF BAJA CALIFORNIA AND THE DEGREE
OF INTERACTION WITH THE INCOMING MAJOR TROUGHING ACROSS THE
WESTERN U.S. THE 00Z CMC IS FASTEST IN TERMS OF THE WESTERN U.S.
TROUGH LIFTING THE BAJA UPPER LOW INTO NORTHWESTERN MEXICO BY LATE
IN THE WEEKEND. THE ECMWF AND GFS BOTH KEEP THE BAJA UPPER LOW
FARTHER OFFSHORE. BY EARLY NEXT WEEK, INCREASING SOUTHERLY FLOW
IS FORECAST FOR THE PLAINS, WITH GFS AND CMC INTRODUCING HEAVIER
RAINS ACROSS SOUTHERN TEXAS. ON THE OTHER HAND, THE ECMWF KEEPS
THE SOUTHERN PLAINS DRY. THE ECMWF IS ALSO MOST ENTHUSIASTIC IN
DEVELOPING AN UPPER LOW NEAR COASTAL SOUTHEASTERN U.S. THIS
WEEKEND INTO EARLY NEXT WEEK, WHILE THE GFS IS FASTER AND WEAKER
BRINGING THIS FEATURE P AND JUST OFF THE EAST COAST. THE CMC IS
SOMEWHERE IN BETWEEN THESE TWO EXTREMES.
THE WPC FORECAST FOR FRONTS/PRESSURES WAS BASED ON A BLEND OF THE
DETERMINISTIC 00Z EC/EC MEAN, 00Z CMC/CMC MEAN, AND THE 06Z
GFS/GEFS. THIS APPROACH MAINTAINED GOOD CONTINUITY WITH THE
PREVIOUS FORECAST ASIDE FROM TYPICAL NUDGES REFLECTING LATEST
TRENDS.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
THE CONTIGUOUS U.S. SHOULD OVERALL BE RATHER DRY ON THURSDAY, WITH
THE EXCEPTION OF LINGERING LIGHT LAKE EFFECT RAIN/SNOW DUE TO
UPPER LEVEL ENERGY AND THE WESTERLY FLOW ACROSS THE RELATIVELY
WARM GREAT LAKES COMPARED TO THE COLD AIR TEMPERATURES. SOUTH
FLORIDA MAY SEE A FEW RAIN SHOWERS AS WELL. BY LATE IN THE WEEK
THROUGH NEXT WEEKEND, THE UPPER TROUGH ARRIVAL/AMPLIFICATION
ACROSS THE WEST AND AN ASSOCIATED SURFACE FRONT PUSHING ACROSS THE
REGION SHOULD PRODUCE A NOTABLE INCREASE IN PRECIPITATION COVERAGE
AND INTENSITY. THE BEST FOCUS WILL BE OVER FAVORED WINDWARD
TERRAIN OVER THE PACIFIC NORTHWEST ON FRIDAY AND THEN EXTENDING
SOUTHEASTWARD INTO THE NORTHERN/CENTRAL ROCKIES AND WASATCH OVER
THE WEEKEND, WITH HIGHER ELEVATION SNOW AND LOWER ELEVATION RAIN.
CONFIDENCE IN A MEANINGFUL PRECIPITATION EVENT IS BECOMING FAIRLY
GOOD, BUT EXACT AMOUNTS OF RAIN/SNOW AND TIMING WILL STILL NEED TO
BE REFINED WITH TIME. PRECIPITATION MAY ALSO BE POSSIBLE ACROSS
THE SOUTHWEST FRIDAY AND ESPECIALLY SATURDAY DEPENDING ON THE
TRACK OF THE SOUTHERN STREAM LOW AND ITS EVENTUAL POSSIBLE
PHASING. BY EARLY NEXT WEEK, RAIN CHANCES MAY INCREASE FOR THE
CENTRAL U.S. AS GULF MOISTURE STREAMS IN AHEAD OF A COLD FRONT.
MEANWHILE SOME RAIN MAY BE POSSIBLE ALONG OR NEAR THE EAST COAST
THIS WEEKEND INTO MONDAY, BUT WITH LOW CONFIDENCE ON HOW MUCH RAIN
COULD FALL ONSHORE.
THE AMPLIFIED WESTERN RIDGE IN PLACE FOR THE EARLY PART OF THE
PERIOD WILL CAUSE WARMER THAN AVERAGE TEMPERATURES ACROSS THE
NORTHWEST IN PARTICULAR, WITH HIGHS COMMONLY 10-20F ABOVE AVERAGE,
POTENTIALLY LEADING TO SOME DAILY RECORD HIGHS THROUGH THURSDAY.
CONVERSELY, THE ANOMALOUS UPPER LOW/TROUGH IN THE EAST SHOULD
PRODUCE RATHER COLD TEMPERATURES MORE COMMON TO NOVEMBER AND
DECEMBER FROM THE PLAINS EASTWARD FOR THURSDAY. BELOW NORMAL
TEMPERATURES BY 10-20F WILL BE WIDESPREAD AND TRANSLATE INTO LOWS
IN THE 30S SPREADING SOUTH POSSIBLY ALL THE WAY TO THE GULF COAST
(MOBILE, ALABAMA FOR EXAMPLE), WHICH COULD SET LOW TEMPERATURE
RECORDS ACROSS THE SOUTHEAST. AS THE UPPER LEVEL PATTERN RELAXES
AROUND FRIDAY AND THEN TRANSITIONS TO A WESTERN TROUGH/EASTERN
RIDGE PATTERN, ABOVE NORMAL TEMPERATURES SHOULD GET PUSHED INTO
THE CENTRAL U.S., WITH THE NORTH-CENTRAL PLAINS SEEING HIGHS OF
10-20F ABOVE AVERAGE. TEMPERATURES ARE ALSO EXPECTED TO GRADUALLY
WARM IN THE MIDWEST TO NORTHEAST EARLY NEXT WEEK. MEANWHILE BELOW
AVERAGE TEMPERATURES PARTICULARLY FOR HIGHS ARE LIKELY ACROSS THE
WEST GIVEN THE TROUGH ALOFT.
KONG/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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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