263
FXUS02 KWBC 130700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SAT MAY 13 2023
VALID 12Z TUE MAY 16 2023 - 12Z SAT MAY 20 2023
...WARMER THAN AVERAGE TEMPERATURES WILL PERSIST ACROSS THE
NORTHWEST...
..OVERVIEW
THE OVERALL WEATHER PATTERN THROUGH NEXT WEEK WILL CONSIST OF AN
ANOMALOUSLY STRONG UPPER RIDGE OVER THE WESTERN HALF OF THE U.S.
AND INTO WESTERN CANADA THAT WILL BE PERSISTENT ASIDE FROM AN
UPPER LOW GRADUALLY SHEARING OUT/WEAKENING ATOP THE NORTHWEST
THROUGH AROUND MIDWEEK. THIS PATTERN WILL MAINTAIN WARM TO HOT
TEMPERATURES ACROSS THE NORTHWEST AND TO A LESSER EXTENT OVER
OTHER PARTS OF THE WEST. DOWNSTREAM, MEAN TROUGHING IS LIKELY
ACROSS EASTERN NORTH AMERICA, WITH INDIVIDUAL SHORTWAVES
SUPPORTING COLD FRONTS THAT DROP INTO THE NORTHERN/EASTERN PARTS
OF THE COUNTRY. MEANWHILE MOIST INFLOW CONTINUES INTO THE SOUTHERN
PLAINS, MAINTAINING SOME RISK OF EXCESSIVE RAINFALL THERE, THOUGH
THE THREAT OF WIDESPREAD FLASH FLOODING SHOULD DECREASE THROUGH
NEXT WEEK GIVEN LESS UPPER-LEVEL SUPPORT COMPARED TO THE NEAR TERM
AND SHORT RANGE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT FOR THE LARGE
SCALE PATTERN WHILE EXHIBITING SOME EMBEDDED DETAIL
DIFFERENCES/ADJUSTMENTS. SEEMINGLY THE MAIN FEATURE WITHIN THE
WESTERN RIDGE/EASTERN TROUGH PATTERN TO KEY ON FROM A MODEL
DIAGNOSTICS PERSPECTIVE IS THE POTENT SHORTWAVE WITH PERHAPS AN
EMBEDDED UPPER LOW TRACKING THROUGH SOUTH-CENTRAL CANADA ALONG
WITH A SURFACE LOW REFLECTION FOR WEDNESDAY AND BEYOND. THE 12Z
UKMET APPEARED TO BE A FAST OUTLIER WITH THIS, WITH OTHER
MODELS/ENSEMBLES GENERALLY SIMILAR WITH THEIR TIMING AND TRACK
THROUGH AROUND FRIDAY UNTIL THE 12Z ECMWF SPEEDS UP COMPARED TO
THE GFS/CMC. THE INCOMING 00Z MODEL CYCLE SEEMS TO BE PRETTY
CONSISTENT WITH THE 12/18Z CYCLE THAT WAS AVAILABLE FOR THIS
FORECAST ISSUANCE, THOUGH THERE MAY BE A SLIGHTLY FASTER TREND
WITH THE COLD FRONTAL POSITION BY DAY 7/SATURDAY COMPARED TO THE
WPC FORECAST. THE GFS SPED UP BUT THE ECMWF SLOWED UP A BIT
COMPARED TO ITS PREVIOUS RUN, AND THE CMC REMAINS ON THE SLOW
SIDE. MEANWHILE THERE ARE STILL NOTABLE SMALLER SCALE DIFFERENCES
ALOFT ACROSS THE CENTRAL U.S. AND INTO THE SOUTHEAST, WITH EFFECTS
ON QPF PLACEMENT AND AMOUNTS. THE LOW PREDICTABILITY INVOLVED WITH
SUCH FEATURES WILL MINIMIZE CONFIDENCE IN ANY SPECIFIC SOLUTION.
THE WPC FORECAST WAS BASED ON A MULTI-MODEL DETERMINISTIC BLEND
EARLY IN THE PERIOD, PHASING OUT THE UKMET AND LESSENING SOME
OTHER MODEL COMPONENTS IN FAVOR OF THE GEFS AND EC ENSEMBLE MEANS
TO A LITTLE LESS THAN HALF BY THE END OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
PERSISTENT MOIST INFLOW IS LIKELY TO CONTINUE INTO THE SOUTHERN
PLAINS THROUGH MUCH OF NEXT WEEK. THOUGH RAIN AMOUNTS SHOULD NOT
BE AS HIGH AS WITH RECENT EVENTS AND IN THE SHORT TERM ACROSS
TEXAS, SOME RAINFALL CONTINUING OVER WHAT IS LIKELY TO BE
EXTREMELY WET GROUND HAS LED TO MARGINAL RISKS IN THE EXCESSIVE
RAINFALL OUTLOOK CONTINUING INTO DAYS 4-5/TUESDAY-WEDNESDAY, WITH
SOME EASTWARD SHIFT FOR WEDNESDAY COMPARED TO TUESDAY. THERE IS
STILL A FAIR AMOUNT OF MODEL SPREAD WITH PLACEMENT OF ANY HEAVIER
TOTALS THAT MAY NOT BE RESOLVED UNTIL THE SHORT TERM OR NEAR TERM.
ONE SUCH UNCERTAINTY IS THE ECMWF MODEL SUITE CONTINUING TO
INDICATE MODERATE WITH PERHAPS POCKETS OF HEAVY QPF EXTENDING
FARTHER WEST INTO NEW MEXICO AND EVEN ARIZONA COMPARED TO OTHER
GUIDANCE, WITH HIGHER PRECIPITABLE WATER ANOMALIES AS WELL. WITH
OTHER MODELS DRIER, LIMITED THE ERO AREAS MAINLY TO TEXAS FOR NOW,
BUT A MONSOON-LIKE PATTERN SETTING UP FARTHER WEST PROMOTING SOME
LOCALLY HEAVY RAIN AMOUNTS IS NOT COMPLETELY RULED OUT. AREAS OF
RAIN FARTHER NORTH IN A MONSOONAL TYPE OF PATTERN WITH MOISTURE
COMING IN UNDERNEATH GREAT BASIN RIDGING ALOFT ARE ALSO UNCERTAIN
IN TERMS OF PLACEMENT AND AMOUNTS. BUT BY THE LATTER PART OF NEXT
WEEK, A LOW PRESSURE SYSTEM MOVING ACROSS SOUTHERN CANADA AND
POSSIBLY AS FAR SOUTH AS THE GREAT LAKES SHOULD BRING A COLD FRONT
ACROSS MUCH OF THE CENTRAL U.S., SERVING TO FOCUS RAIN AND
THUNDERSTORMS ALONG AND AHEAD OF IT WITH SLIGHTLY MORE
PREDICTABILITY, WITH RAIN CHANCES GRADUALLY PROGRESSING SOUTH AND
EAST WITH TIME COINCIDENT WITH THE FRONT'S MOVEMENT. THIS FRONT
COULD BRING SOME UPSLOPE FLOW OVER PARTS OF THE SOUTH-CENTRAL
ROCKIES/HIGH PLAINS, ENHANCING POTENTIAL RAINFALL AMOUNTS THERE.
AHEAD OF THIS COLD FRONT, SOME SCATTERED SHOWERS AND STORMS ARE
POSSIBLE ACROSS THE GULF COAST STATES THROUGH MUCH OF THE WEEK AS
MOISTURE POOLS ALONG A COUPLE OF WEST-EAST ORIENTED FRONTS. THE
NORTHEAST COULD SEE A ROUND OF RAIN ON TUESDAY BUT THEN IS LIKELY
TO SEE DRY CONDITIONS UNTIL MOISTURE IS DRAWN INTO THE EAST LATE
WEEK AHEAD OF THE CENTRAL U.S. COLD FRONT.
TEMPERATURE-WISE, EXPECT WARM TO HOT TEMPERATURES TO PERSIST
ACROSS THE WEST AS LARGE SCALE UPPER RIDGING PREVAILS ON THE
WHOLE. THE NORTHWEST (THE PACIFIC NORTHWEST INTO THE GREAT BASIN)
IS LIKELY TO SEE THE HIGHEST TEMPERATURE ANOMALIES OF 10-20
DEGREES ABOVE AVERAGE PERSIST THROUGH MUCH OF THE WEEK, THOUGH
WITH PERHAPS SOME SLIGHT MODERATION LATE WEEK FOR THE PACIFIC
NORTHWEST WHILE AREAS INLAND MAY SLIGHTLY WARM. THE HIGHEST
POTENTIAL FOR RECORD HIGHS HAS NOW PHASED INTO THE SHORT RANGE
PERIOD, BUT RECORD HIGH MINIMUM TEMPERATURES IN THE 50S AND 60S
COULD CONTINUE TO BE WIDESPREAD THROUGH MID- AND LATE WEEK ACROSS
THE WEST, PERHAPS EVEN CHALLENGING MONTHLY RECORDS. THE WARMING
TREND OVER THE NORTHERN GREAT BASIN BY FRIDAY-SATURDAY MAY ONCE
AGAIN REACH RECORD HIGHS THOUGH. FARTHER SOUTH, HIGHS IN THE 90S
ARE LIKELY IN THE CALIFORNIA CENTRAL VALLEY WITH HIGHS ABOVE 100F
IN THE DESERT SOUTHWEST (THOUGH THE LATTER IS NOT TERRIBLY
ANOMALOUS FOR MAY). WARMER THAN AVERAGE TEMPERATURES SHOULD EXPAND
ACROSS MUCH OF THE NORTHERN TIER EARLY-MID WEEK, FOLLOWED BY A
COOLING TREND THURSDAY-SATURDAY AFTER THE FRONTAL PASSAGE. THE
NORTHEAST TO MID-ATLANTIC SHOULD SEE VARIABLE ABOVE OR BELOW
NORMAL TEMPERATURES DEPENDING ON FRONTAL PROGRESSION. CURRENTLY
ANTICIPATE THE MOST NOTABLE ANOMALIES BEING ON THE COOL SIDE OF
NORMAL BY 5-15F OVER THE NORTHEAST DURING WEDNESDAY INTO EARLY
THURSDAY AFTER A TUESDAY FRONTAL PASSAGE. THE CLOUDY AND RAINY
CONDITIONS OVER THE SOUTHERN HIGH PLAINS SHOULD KEEP HIGHS 5-15F
BELOW NORMAL ESPECIALLY FOR THE FIRST HALF OF THE WEEK, WITH MORE
MODERATE READINGS LIKELY THEREAFTER.
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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