090
FXUS02 KWBC 172022
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
422 PM EDT WED MAY 17 2023
VALID 12Z SAT MAY 20 2023 - 12Z WED MAY 24 2023
...WARMER THAN AVERAGE TEMPERATURES WILL PERSIST ACROSS THE
NORTHWEST THROUGH THIS WEEKEND...
..OVERVIEW
STRONG UPPER RIDGING ACROSS THE WEST WILL CONTINUE TO CAUSE WARM
TO HOT TEMPERATURES THERE THROUGH THE WEEKEND, BEFORE AN UPPER
TROUGH FINALLY SHIFTS INTO THE NORTHWEST NEXT WEEK AND SHIFTS
WARMER THAN NORMAL TEMPERATURES INTO THE NORTH-CENTRAL CONUS. A
MONSOONAL PATTERN WILL BE IN PLACE ACROSS THE WEST AS ANOMALOUSLY
HIGH MOISTURE UNDERNEATH THE RIDGE PROMOTES SCATTERED SHOWERS AND
THUNDERSTORMS. FARTHER EAST, A COLD FRONT WILL PUSH A ROUND OF
RAIN THROUGH THE EAST THIS WEEKEND, AND THEN ADDITIONAL FRONTAL
SYSTEMS MAY SPARK SHOWERS AND THUNDERSTORMS ACROSS FLORIDA IN
PARTICULAR THROUGH MUCH OF NEXT WEEK. TEMPERATURES WILL BE NEAR TO
ABOVE NORMAL OVER MOST OF THE LOWER 48 EXCEPT FOR PORTIONS OF
TEXAS WHERE DAILY RAIN CHANCES ARE HIGHEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
12Z GUIDANCE SHOWS REASONABLE CLUSTERING IN THE DAY 5-6 PERIOD AS
NORTHEASTERN PACIFIC TROUGHING MOVES INTO THE PAC NW AND GREAT
LAKES-NORTHEAST TROUGHING RELAXES. PRIOR TO THIS, THE ENSEMBLES
WERE UNCHARACTERISTICALLY IN NOTICEABLE DISAGREEMENT ON THE
SPEED/DEPTH OF A GREAT LAKES SMALL UPPER LOW ON SATURDAY -- THE
GFS REMAINED QUICKEST WHILE THE ECMWF AND SOME RUNS OF THE
CANADIAN/UKMET WERE SLOWER. THE GFS/GEFS HAS HAD A MULTI-DAY TREND
OF A SLOWER PROGRESSION WHILE THE ECMWF HAS BEEN RATHER STEADFAST,
AND AGAIN RELIED ON THE SLOWER NON-GFS CONSENSUS TO START THE
FORECAST. IN THE WEST, BETTER AGREEMENT OVERALL FAVORED A
MULTI-MODEL CONSENSUS. BY NEXT WEDNESDAY, MODELS DIVERGE IN HOW TO
HANDLE ANY SHORTWAVE OR UPPER LOW OVER NORTHWESTERN CANADA AND HOW
THAT DIGS INTO/REINFORCES THE PAC NW TROUGH, SO THE PREFERENCE
TRENDED TOWARD AN ENSEMBLE MEAN BLEND AS ANY OF THE DETERMINISTIC
SOLUTIONS HAVE BEEN TOO INCONSISTENT.
THUS THE WPC FORECAST WAS BASED ON A BLEND FAVORING THE 00Z
ECMWF/CANADIAN DAYS 3-4 BEFORE BRINGING IN THE GFS/GEFS AS
UNCERTAINTY INCREASED. TRENDED TOWARD A MAJORITY ENSEMBLE MEAN
BLEND BY NEXT WED NOTING THAT THE SHAPE OF THE WESTERN TROUGH WILL
VERY LIKELY CHANGE.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT IS FORECAST TO TRACK THROUGH THE EAST THIS WEEKEND
AND PRODUCE WIDESPREAD RAIN ALONG AND AHEAD OF IT, THOUGH AMOUNTS
MAY BE LIGHT TO MODEST. A LEADING SYSTEM OVER THE MID-ATLANTIC MAY
SNEAK NORTHWARD INTO SOUTHEASTERN NEW ENGLAND WITH A ROBUST PUSH
OF MOISTURE AND A CHANCE FOR SOME NEEDED BUT PERHAPS LOCALLY HEAVY
RAIN ON SATURDAY. FLASH FLOODING IS NOT EXPECTED TO BE A BIG
THREAT DUE TO THE ONGOING DRYNESS IN THE REGION AND PROGRESSIVE
NATURE. THE BACK END OF THE FRONT STALLING NEAR THE CENTRAL RIO
GRANDE VALLEY COULD FOCUS MOISTURE AND INSTABILITY THERE THAT
COULD PRODUCE SOME HEAVY RAIN RATES ATOP MOIST SOILS FROM RECENT
RAINFALL. A MARGINAL RISK WAS MAINTAINED FOR PARTS OF SOUTHWESTERN
TEXAS FOR THIS FORECAST CYCLE FOR DAY 4/SATURDAY. MEANWHILE,
SCATTERED SHOWERS AND THUNDERSTORMS ARE ALSO POSSIBLE IN THE WEST
AT TIMES THIS WEEKEND INTO NEXT WEEK ESPECIALLY IN THE
AFTERNOONS/EVENINGS WITH A COMMON DIURNAL CYCLE, AS A MONSOON-LIKE
PATTERN SETS UP WITH ANOMALOUSLY HIGH MOISTURE REMAINING OVER A
LARGE PORTION OF THE WESTERN U.S., FIRST UNDER THE UPPER RIDGE
AXIS AND THEN AS TROUGHING EDGES INTO THE NORTHWEST. CHANCES FOR
SHOWERS AND THUNDERSTORMS MAY INCREASE IN THE PLAINS BY
TUESDAY-WEDNESDAY. MEANWHILE MULTIPLE FRONTAL SYSTEMS COULD MOVE
THROUGH THE SOUTHEASTERN U.S. INCLUDING FLORIDA, WHICH COULD
PROVIDE FOCUS FOR AMPLE MOISTURE AND ENHANCE DAILY
DIURNALLY-DRIVEN SHOWERS AND THUNDERSTORMS.
COASTAL AREAS OF THE PACIFIC NORTHWEST CAN EXPECT TEMPERATURES TO
REMAIN WARMER THAN NORMAL BY AROUND 10-15 DEGREES ON SATURDAY,
BEFORE MODERATING TO AROUND NORMAL NEXT WEEK AS UPPER TROUGHING
AND A COLD FRONT OR TWO MOVE IN. INTERIOR AREAS LIKE THE GREAT
BASIN ARE LIKELY TO SEE ABOVE AVERAGE TEMPERATURES BY 15-25F
UNDERNEATH THE UPPER RIDGE AXIS, WITH HIGHS IN THE 90S THAT COULD
BE RECORD-SETTING ON SATURDAY. LOW TEMPERATURES IN THE 50S AND 60S
COULD ALSO BREAK RECORDS FOR WARM MINIMUM TEMPERATURES ACROSS
WIDESPREAD AREAS OF THE WEST OVER THE WEEKEND. THEN UPPER
TROUGHING COMING INTO THE NORTHWEST SHOULD SHIFT WARMER THAN
AVERAGE TEMPERATURES EASTWARD INTO THE NORTH-CENTRAL U.S. THROUGH
MONDAY-WEDNESDAY, MODERATING A BIT WITH ANOMALIES AROUND 10-15F
ABOVE NORMAL. MEANWHILE FARTHER SOUTH, POST-FRONTAL COOLER AIR AND
PERIODS OF RAIN AND CLOUDS COULD LEAD TO SLIGHTLY BELOW AVERAGE
TEMPERATURES FOR PARTS OF THE PLAINS AND ESPECIALLY WEST TEXAS AT
TIMES THROUGH EARLY NEXT WEEK.
FRACASSO/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
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN PLAINS, SAT, MAY 20.
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, MON-WED, MAY 22-MAY
24.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE
PACIFIC NORTHWEST, THE NORTHERN ROCKIES, THE NORTHERN GREAT BASIN,
AND THE NORTHERN PLAINS.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN
PLAINS, THE NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN.
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE
CENTRAL GREAT BASIN, THE NORTHERN PLAINS, THE NORTHERN GREAT
BASIN, THE SOUTHERN ROCKIES, THE UPPER MISSISSIPPI VALLEY, AND THE
SOUTHWEST.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF CALIFORNIA,
THE CENTRAL GREAT BASIN, THE PACIFIC NORTHWEST, THE NORTHERN
ROCKIES, AND THE NORTHERN GREAT BASIN, SAT-MON, MAY 20-MAY 22.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHERN
PLAINS AND THE NORTHERN ROCKIES, SAT-TUE, MAY 20-MAY 23.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY AND THE NORTHERN PLAINS, MON-TUE, MAY 22-MAY 23.
- HEAVY PRECIPITATION ACROSS PORTIONS OF MAINLAND ALASKA AND THE
ALEUTIANS, MON-TUE, MAY 22-MAY 23.
- FLOODING POSSIBLE ACROSS PORTIONS OF MAINLAND ALASKA, SAT-WED,
MAY 20-MAY 24.
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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