379
FXUS02 KWBC 011923
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
323 PM EDT TUE NOV 01 2022
VALID 12Z FRI NOV 04 2022 - 12Z TUE NOV 08 2022
...SYSTEM EMERGING FROM THE ROCKIES TO BRING A POTENTIAL FOR HEAVY
RAIN TO PORTIONS OF THE PLAINS...
...LATE WEEK ATMOSPHERIC RIVER EVENT LIKELY TO BRING AN EPISODE OF
HEAVY PRECIPITATION TO PARTS OF THE NORTHWEST...
..OVERVIEW
GUIDANCE CONTINUES TO SHOW AN AMPLIFIED PATTERN LATE THIS WEEK
INTO THE EARLY WEEKEND AS AN UPPER TROUGH AND EMBEDDED LOW MOVES
FROM THE ROCKIES INTO THE PLAINS AND A STRONG RIDGE BUILDS NEAR
THE EAST COAST. STRONG NORTH PACIFIC FLOW PUSHING INTO WESTERN
NORTH AMERICA WILL HELP TO ACCELERATE THE PLAINS SYSTEM
NORTHEASTWARD, DEFLECTED BY THE EAST COAST RIDGE THAT WILL BECOME
CENTERED OVER THE WESTERN ATLANTIC. IN RESPONSE TO A STRONG UPPER
RIDGE THAT BUILDS OVER AND NEAR ALASKA, BY SUNDAY-TUESDAY THE MEAN
PATTERN OVER THE EASTERN PACIFIC THROUGH WESTERN TWO-THIRDS OF THE
LOWER 48 SHOULD BECOME BROADLY CYCLONIC. THE LEADING PLAINS SYSTEM
WILL SUPPORT A HEAVY RAIN THREAT OVER PARTS OF THE CENTRAL U.S.
LATE THIS WEEK INTO THE EARLY WEEKEND. MEANWHILE THE NORTHWEST
ATMOSPHERIC RIVER EVENT SHOULD BE MOST PRONOUNCED AROUND
FRIDAY-FRIDAY NIGHT, WITH THE PATTERN POTENTIALLY SUPPORTING
MULTIPLE DAYS OF LESS EXTREME BUT STILL MEANINGFUL RAIN/MOUNTAIN
SNOW OVER THE WEST THEREAFTER.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
GENERALLY, THE LATEST GUIDANCE HAS TRENDED WEAKER AND FASTER WITH
UPPER-LEVEL ENERGY PROPAGATING ACROSS THE CONUS DURING THE MEDIUM
RANGE PERIOD. THE AMPLIFIED TROUGH OVER THE SOUTHERN PLAINS ON DAY
3 HAS EXPERIENCED A CONSISTENT WEAKENING OVER THE LAST 3 RUNS OF
THE EC AND GFS. THIS WEAKER/MORE PROGRESSIVE TREND IN THE UPPER
TROUGH CONTINUES THROUGH DAY 5 AT WHICH TIME IT'S FORECAST TO BE
FIRMLY IN EASTERN CANADA. IT'S WORTH NOTING THAT THERE'S ABOVE
AVERAGE ENSEMBLE SPREAD WITH RESPECT TO THE TIMING AND INTENSITY
OF THIS TROUGH AS EARLY AS DAY 3. THIS TRANSLATES INTO THE AXIS OF
HIGHEST QPF BEING FARTHER DOWNSTREAM OVER THE MISSISSIPPI
VALLEY/SOUTHEAST ON DAYS 3 & 4 THEN MORE BROAD OVER THE UPPER
MIDWEST/GREAT LAKES THAN WHERE THE OVERNIGHT GUIDANCE HAD IT. A
QPF BLEND CONSISTING OF THE 13Z NBM AND THE OVERNIGHT SOLUTION WAS
USED TO ACCOUNT FOR THE UNCERTAINTY IN THIS MORNING'S MODEL SUITE.
THIS MORNING'S GUIDANCE WAS SLIGHTLY MORE PROGRESSIVE WITH THE
AMPLIFYING UPPER TROUGH IN THE EASTERN PACIFIC THIS WEEKEND. THIS
SPEED-UP IN THE SYNOPTIC PATTERN APPEARS TO PROMOTE A MORE
PROGRESSIVE SOLUTION TO THE ATMOSPHERIC RIVER EVENT OVER THE
NORTHWEST THIS WEEKEND WITH QPF FORECAST TO SPREAD SOUTHWARD DOWN
THE WEST COAST AT A FASTER RATE. THERE'S MORE RUN-TO-RUN
CONSISTENCY WITH THE EVOLUTION OF THIS WESTERN TROUGH SO A GENERAL
MODEL BLEND SUFFICED HERE. A GENERAL MODEL BLEND OF THE 00Z
EC/CMC/UKMET AND 06 GFS WAS USED THROUGH DAY 4, BEFORE ENSEMBLE
MEANS ARE INTRODUCED ON DAY 5. THE ENSEMBLE MEANS ACCOUNT FOR A
MAJORITY OF THE BLEND ON DAYS 6 & 7.
..WEATHER/HAZARD HIGHLIGHTS
THE LEADING SYSTEM EMERGING FROM THE ROCKIES INTO THE PLAINS WILL
BRING AN EPISODE OF HEAVY RAIN POTENTIAL TO PARTS OF THE CENTRAL
U.S. LATE THIS WEEK AND INTO THE WEEKEND. SOME STRONG CONVECTION
IS POSSIBLE OVER PARTS OF THE PLAINS AS WELL, PER THE LATEST
OUTLOOKS FROM THE STORM PREDICTION CENTER. THE EXPERIMENTAL DAY 4
EXCESSIVE RAINFALL OUTLOOK REFLECTS THE BEST POTENTIAL FOR
HEAVIEST RAINFALL DURING FRIDAY-FRIDAY NIGHT, OVER AND JUST EAST
OF PORTIONS OF THE SOUTH-CENTRAL PLAINS/LOWER AND MIDDLE
MISSISSIPPI VALLEY. A BAND OF MODERATE TO HEAVY RAINFALL MAY
DEVELOP ALONG A FRONT EXTENDING NORTHWARD INTO THE MIDWEST AS
WELL. HEAVY RAINFALL SHOULD BECOME LESS WIDESPREAD OVER THE
COURSE OF THE WEEKEND AS THE SUPPORTING DYNAMICS LIFT
NORTHEASTWARD. THE PORTION OF THE SURFACE FRONT STALLING OVER THE
LOWER MISSISSIPPI VALLEY MAY PROVIDE THE BEST FOCUS FOR LINGERING
AREAS OF SIGNIFICANT RAINFALL. THIS EVENT MAY FEATURE A
COMBINATION OF FLASH FLOOD THREATS (IN MAINLY URBANIZED/METRO
REGIONS) WHERE THE HEAVIEST RAIN OCCURS BUT ALSO BENEFICIAL
RAINFALL GIVEN THE LONG-TERM DROUGHT OVER THE REGION. MONITOR
STORM PREDICTION CENTER OUTLOOKS FOR LATEST INFORMATION ON SEVERE
POTENTIAL.
THE OTHER SIGNIFICANT PRECIPITATION FOCUS WILL BE OVER THE
NORTHWEST LATE THIS WEEK INTO THE WEEKEND, DUE TO AN ATMOSPHERIC
RIVER EVENT ASSOCIATED WITH STRONG WESTERLY FLOW REACHING INTO THE
REGION. A PERIOD OF HEAVY RAIN/MOUNTAIN SNOW APPEARS LIKELY WITH
HIGHEST TOTALS TENDING TO BE DURING FRIDAY-FRIDAY NIGHT. SOME
SIGNIFICANT PRECIPITATION SHOULD CONTINUE INTO THE WEEKEND BUT THE
SOUTHWARD PROGRESSION OF THE PACIFIC JET (EXTENDING THE
PRECIPITATION SHIELD GRADUALLY FARTHER SOUTH) SHOULD BE SUFFICIENT
TO ALLOW FOR A SOMEWHAT LIGHTER TREND. A PERIOD OF STRONG WINDS
WILL BE POSSIBLE IN THIS EVENT AS WELL. SOMEWHAT LESS EXTREME BUT
STILL SIGNIFICANT PRECIPITATION WILL REACH INTO THE NORTHERN
ROCKIES. THE PATTERN MAY SUPPORT CONTINUATION OF SOME
PRECIPITATION OVER THE NORTHERN HALF OF THE WEST THROUGH THE FIRST
HALF OF NEXT WEEK. SNOW LEVELS OVER FAR NORTHERN AREAS MAY TREND
NOTABLY LOWER DEPENDING ON THE SOUTHWARD EXTENT OF COLD AIR
PUSHING DOWN FROM WESTERN CANADA.
CONFIDENCE IS NOT VERY HIGH THUS FAR, BUT GUIDANCE SUGGESTS THAT A
SYSTEM REACHING THE NORTHWEST LATE IN THE WEEKEND MAY LEAD TO
PLAINS/UPPER MIDWEST LOW PRESSURE BY NEXT TUESDAY. THIS SYSTEM
COULD PRODUCE SOME SNOW OVER THE NORTHER TIER. NEAR THE EAST
COAST, BY VERY LATE IN THE PERIOD SOME MOISTURE COULD APPROACH
FROM THE ATLANTIC AS AN UPPER LOW NEAR THE BAHAMAS RETROGRADES
TOWARD FLORIDA.
THE SOUTHERN THREE-FOURTHS OF THE WEST WILL SEE A BROAD AREA OF
DAYTIME HIGHS 10-25F BELOW NORMAL CONTINUE THROUGH FRIDAY.
DOUBLE-DIGIT ANOMALIES SHOULD BECOME MORE SCATTERED DURING THE
WEEKEND AS TEMPERATURES MODERATE BUT MOST AREAS SHOULD REMAIN
BELOW NORMAL FOR HIGHS. THE EVOLVING UPPER PATTERN SHOULD SUPPORT
A PUSH OF COLD AIR REACHING THE NORTHERN HIGH PLAINS/EASTERN
SLOPES OF THE ROCKIES BY NEXT MONDAY-TUESDAY, POSSIBLY PUSHING
HIGHS DOWN TO 20-35F BELOW NORMAL OVER MONTANA. PERSISTENCE OF
MEAN TROUGHING ALOFT TO SOME DEGREE SHOULD KEEP THE WEST BELOW
NORMAL EARLY NEXT WEEK WITH MINUS 5-15F ANOMALIES FOR HIGHS. WHILE
IT WILL FEEL MORE LIKE WINTER OVER THE WEST, THE EAST WILL SEE
TEMPERATURES MORE TYPICAL FOR EARLIER IN THE FALL. EXPECT A BROAD
AREA OF PLUS 10-25F ANOMALIES THAT SHOULD PRODUCE SOME DAILY
RECORDS, WITH MORNING LOWS TENDING TO BE SLIGHTLY MORE EXTREME
THAN THE DAYTIME HIGHS.
KEBEDE/RAUSCH
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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