897
FXUS02 KWBC 121932
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
332 PM EDT FRI MAY 12 2023
VALID 12Z MON MAY 15 2023 - 12Z FRI MAY 19 2023
...SOME FLASH FLOODING POTENTIAL COULD LINGER IN/AROUND TEXAS
THROUGH THE FIRST HALF OF NEXT WEEK...
..EARLY SEASON HEAT WAVE TO AFFECT THE PACIFIC NORTHWEST
..OVERVIEW
THE OVERALL WEATHER PATTERN 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.
THIS PATTERN WILL RESULT IN AN EARLY SEASON HEAT WAVE 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 SHORT RANGE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT FOR THE LARGE
SCALE PATTERN WHILE EXHIBITING SOME EMBEDDED DETAIL
DIFFERENCES/ADJUSTMENTS. ONE AREA OF RECENT INCONSISTENCY HAS BEEN
WITH THE COLD FRONT PASSING THROUGH NEW ENGLAND AROUND TUESDAY.
THERE WAS A BRIEF PERIOD WHEN THE MODELS WERE SUGGESTING SOME WAVE
DEVELOPMENT OVER/OFFSHORE NEW ENGLAND OR INTO NOVA SCOTIA LATE
TUESDAY-WEDNESDAY BUT NOW THERE IS A BETTER SIGNAL FOR A DEEPENING
WAVE FARTHER NORTHEAST OF NEW ENGLAND BY EARLY WEDNESDAY. BEHIND
THIS FRONT, GUIDANCE TAKES ENERGY SHEARING INTO NORTHWESTERN
CANADA AND HAS VARYING IDEAS ON HOW IT COULD CONSOLIDATE INTO A
TROUGH (WITH POSSIBLE EMBEDDED LOW) THAT WOULD REACH SOMEWHERE
BETWEEN THE NORTHERN PLAINS AND UPPER GREAT LAKES BY DAY 7 FRIDAY.
THE ASSOCIATED FRONT SHOULD PUSH INTO THE LOWER 48 ON A SOMEWHAT
FARTHER WEST PATH THAN ITS PREDECESSOR. THE 06Z GFS WAS A BIT ON
THE WESTERN SIDE OF THE SPREAD WITH THE CORE OF THE UPPER SYSTEM
BUT THE NEW 12Z CMC ENDS UP BEING AS SLOW (WITH THE 12Z GFS COMING
IN JUST A TAD FASTER THAN THE 06Z VERSION). NOW THE 12Z UKMET
BECOMES A FAST EXTREME BY LATE IN ITS RUN ENDING EARLY THURSDAY.
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. A
COMPOSITE OF THE 00Z GFS/ECMWF/UKMET/CMC PROVIDED THE MOST
COHERENT UPDATE TO THE FORECAST DURING THE FIRST HALF OF THE
PERIOD, WITH A TREND TOWARD HALF MODELS AND HALF MEANS (06Z
GEFS/00Z ECENS) ACCOUNTING FOR THE INCREASING DETAIL UNCERTAINTY
BY THE END OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
PERSISTENT MOIST INFLOW IS LIKELY TO CONTINUE INTO THE SOUTHERN
PLAINS THROUGH AT LEAST THE EARLY PART OF NEXT WEEK. THOUGH RAIN
AMOUNTS MAY NOT BE AS HIGH AS IN THE SHORT TERM ACROSS TEXAS,
ANOTHER DAY OF ENHANCED QPF IS POSSIBLE ON MONDAY OVER WHAT IS
LIKELY TO BE VERY WET GROUND, SO A SLIGHT RISK OF EXCESSIVE
RAINFALL/FLASH FLOODING WILL BE MAINTAINED IN THIS FORECAST CYCLE
FOR DAY 4/MONDAY ACROSS SOUTH-CENTRAL TEXAS. GUIDANCE STILL
EXHIBITS SOME SPREAD BUT FOR NOW THE RELATIVELY BETTER SIGNAL FOR
HIGHER RAINFALL TOTALS GENERALLY ALIGNS WITH THE CURRENT SLIGHT
RISK AREA SO THAT REMAINS UNCHANGED THIS CYCLE. LIKEWISE, THE
SURROUNDING MARGINAL RISK AREA CONTINUES TO REFLECT A MORE DIFFUSE
GUIDANCE SIGNAL FOR WHERE HEAVIEST POCKETS OF RAINFALL MAY BE,
INCLUDING THE WESTERN PART REACHING INTO PORTIONS OF NEW MEXICO
WHERE A MONSOON-LIKE PATTERN STARTS TO SET UP. BY TUESDAY AND
BEYOND THIS MONSOONAL TYPE OF PATTERN WITH MOISTURE COMING IN
UNDERNEATH GREAT BASIN RIDGING ALOFT LOOKS TO PERSIST ACROSS THE
FOUR CORNERS STATES AND PERHAPS EVEN FARTHER NORTH THROUGH MUCH OF
NEXT WEEK, WITH TYPICAL DIURNAL ENHANCEMENT. MOISTURE ANOMALIES
VARY PER MODEL (WITH THE ECMWF SUITE SHOWING MUCH HIGHER ANOMALIES
THAN THE GFS/GEFS SUITE), BUT WITH INSTABILITY IN PLACE THERE
COULD BE LOCALIZED FLASH FLOODING. THE MARGINAL RISK OF EXCESSIVE
RAINFALL FOR DAY 5/TUESDAY OVER THE SOUTHERN HIGH PLAINS REFLECTS
MINIMAL CHANGE FROM PREVIOUS CYCLE WITH SOME PERSISTENT HINTS OF
LOCALIZED HEAVY TOTALS AND FLASH FLOODING POTENTIAL BUT
UNCERTAINTY IN SPECIFICS. TOWARD THE END OF THE WEEK THE LATEST
GUIDANCE IS SUGGESTING POTENTIAL FOR HEAVIER RAINFALL OVER PARTS
OF THE SOUTH-CENTRAL ROCKIES/HIGH PLAINS AS A FRONT DROPS INTO THE
REGION FROM THE NORTH, WITH LOW LEVEL UPSLOPE FLOW ENHANCING
ACTIVITY IF THE FRONT REACHES FAR ENOUGH SOUTH.
ELSEWHERE, A ROUND OF RAIN IS LIKELY ACROSS THE MID-ATLANTIC
AND/OR CAROLINAS ON MONDAY WITH A SHORTWAVE IMPULSE AND SURFACE
FRONT. LIGHT RAIN IS POSSIBLE FOR THE NORTHEAST ON TUESDAY WITH
THE APPROACH/PASSAGE OF A COLD FRONT. AN INITIALLY STALLING
SURFACE FRONT AND THEN THE TRAILING PART OF THE NORTHEAST FRONT
ULTIMATELY PUSHING SOUTH CLOSE TO THE GULF COAST COULD LEAD TO
SCATTERED SHOWERS AND STORMS ACROSS THAT AREA THROUGH MUCH OF THE
WEEK. IT WILL TAKE ADDITIONAL TIME TO DETERMINE WHERE THE BEST
FOCUS FOR HEAVIER RAINFALL MAY BE. LATE IN THE WEEK A LOW
PRESSURE SYSTEM MOVING ACROSS SOUTHERN CANADA AND POSSIBLY AS FAR
SOUTH AS THE GREAT LAKES MAY BRING A FRONT ACROSS THE
NORTH-CENTRAL U.S. LATE WEEK, BRINGING POTENTIAL FOR SHOWERS AND
STORMS AHEAD OF IT ACROSS THE NORTHERN HALF OF THE PLAINS INTO THE
MIDWEST.
TEMPERATURE-WISE, EXPECT A HEAT WAVE TO PERSIST FROM THIS WEEKEND
INTO THE MEDIUM RANGE PERIOD ACROSS THE NORTHWEST AS LARGE SCALE
UPPER RIDGING PREVAILS OVER WESTERN NORTH AMERICA (THOUGH WITH A
WEAKENING EMBEDDED UPPER LOW SETTLING OVER THE REGION). HIGHS IN
THE 80S AND INTO THE LOW 90S WOULD BE 15 TO 20 DEGREES ABOVE
AVERAGE AND COULD SET RECORDS FOR MANY OF THE LOWER ELEVATIONS IN
WASHINGTON AND OREGON. TEMPERATURES ARE FORECAST TO REMAIN 10-20F
ABOVE AVERAGE IN THE WEST THROUGH ALL NEXT WEEK, THOUGH WITH HIGHS
DECREASING A BIT OVER WESTERN WASHINGTON/OREGON LATER IN THE WEEK
(BELOW RECORD LEVELS FOR HIGHS). HIGHS EAST OF THE CASCADES COULD
ACTUALLY INCREASE A BIT TOWARD THE END OF THE WEEK THOUGH, AND
POSSIBLY CHALLENGE RECORD HIGHS. MEANWHILE, THROUGHOUT NEXT WEEK
MANY WARM LOW TEMPERATURES COULD CHALLENGE DAILY AND PERHAPS EVEN
MONTHLY RECORDS FOR HIGH MINIMUM TEMPERATURES IN THE UPPER 50S AND
60S. 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 AFTER FRONTAL
PASSAGE THURSDAY-FRIDAY. 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 5-12F 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 EARLY IN THE WEEK, WITH
MORE MODERATE READINGS LIKELY THEREAFTER.
RAUSCH/TATE
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN PLAINS, MON, MAY 15.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE UPPER MISSISSIPPI
VALLEY, THE SOUTHERN PLAINS, 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 NORTHERN PLAINS, THE NORTHERN ROCKIES, AND
THE NORTHERN GREAT BASIN.
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL GREAT BASIN, THE
NORTHERN PLAINS, THE NORTHERN
GREAT BASIN, THE CENTRAL ROCKIES, THE SOUTHERN PLAINS, AND THE
SOUTHWEST.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF CALIFORNIA AND
THE SOUTHWEST, MON-WED, MAY
15-MAY 17.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE PACIFIC
NORTHWEST AND GREAT BASIN, MON-FRI,
MAY 15-MAY 19.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page