053
FOUS30 KWBC 191938
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
338 PM EDT MON OCT 19 2026
DAY 1
VALID 16Z MON OCT 19 2026 - 12Z TUE OCT 20 2026
..THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHWEST...
AFTERNOON HEATING COMBINED WITH UNSEASONABLY HIGH MOISTURE FOR
MID-OCTOBER (PWATS 0.75-1.0", 2-2.5 STANDARD DEVIATIONS ABOVE THE
MEAN) WILL LEAD TO SUFFICIENT INSTABILITY (~1000 J/KG CAPE) OVER
SOUTHEASTERN ARIZONA/SOUTHWESTERN NEW MEXICO TODAY TO SUPPORT SOME
MORE ROBUST THUNDERSTORMS CAPABLE OF LOCALLY HEAVY DOWNPOURS. THE
HI-RES GUIDANCE SHOWS THE POTENTIAL FOR HOURLY RATES OF 1"+ WHICH
COULD LEAD TO SOME ISOLATED INSTANCES OF FLASH FLOODING, ESPECIALLY
FOR URBAN AREAS AS WELL AS TERRAIN SENSITIVE AREAS SUCH AS BURN
SCARS, BOX/SLOT CANYONS, AND DRY WASHES/ARROYOS.
PUTNAM
DAY 2
VALID 12Z TUE OCT 20 2026 - 12Z WED OCT 21 2026
..SOUTHWEST
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.
ANOMALOUS MOISTURE WILL REMAIN IN PLACE TUESDAY AHEAD OF AN UPPER-
LOW DIGGING SOUTHWARD JUST OFF THE WEST COAST. HOWEVER,
INSTABILITY LOOKS TO REMAIN RATHER LOW IN THE PERIOD COMPARED TO
MONDAY WHICH SHOULD LIMIT THE POTENTIAL FOR MORE ROBUST
STORMS/LOCALLY HEAVY RAINFALL RATES. THE RISK FOR HEAVY RAINFALL
AND FLASH FLOODING IS NON-ZERO, BUT APPEARS TO BE BELOW THE 5
PERCENT THRESHOLD AT THE PRESENT TIME.
PUTNAM
DAY 3
VALID 12Z WED OCT 21 2026 - 12Z THU OCT 22 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST AND FOUR CORNERS REGION WEDNESDAY/WEDNESDAY NIGHT...
..SOUTHWEST AND FOUR CORNERS REGION
A NORTHERN STREAM UPPER-LOW WILL DIG SOUTHWARD ALONG THE WEST
COAST AS STRONGER FLOW REMAINS IN PLACE IN THE SOUTHERN STREAM
ACROSS THE NORTHEASTERN PACIFIC/BAJA CALIFORNIA. THESE MERGING
FEATURES WILL SHIFT EASTWARD BY WEDNESDAY FURTHER INTO THE
SOUTHWEST/FOUR CORNERS REGION. MEANWHILE, ALREADY ANOMALOUS
MOISTURE IN PLACE WILL BE AUGMENTED BY ADDITIONAL MOISTURE FROM
REMNANT TRUDY IN THE PACIFIC, BRINGING PWATS OF 0.75-1.5" (UPWARDS
OF 3-4 STANDARD DEVIATIONS ABOVE MID-OCTOBER MEANS DEPENDING ON
LOCATION). THE COMBINATION OF ANOMALOUS MOISTURE AND COOLING MID-
LEVELS WILL LEAD TO SUFFICIENT INSTABILITY (UPWARDS OF 1000 J/KG)
FOR THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL ACROSS PORTIONS OF
THE SOUTHWEST INTO THE FOUR CORNERS REGION. THE RISK FOR AT LEAST
SCATTERED INSTANCES OF FLASH FLOODING LOOKS LIKELY GIVEN THE
ANOMALOUS MOISTURE IN PLACE, ESPECIALLY FOR URBAN AREAS AS WELL AS
TERRAIN SENSITIVE AREAS SUCH AS BURN SCARS, SLOT/BOX CANYONS, AND
DRY WASHES/ARROYOS. THE INFLUX OF WARM, MOIST AIR WILL ALSO KEEP
SNOW LEVELS VERY HIGH, AS MUCH AS 12000 TO 13000 FEET, LIMITING ANY
SNOW TO ONLY THE HIGHEST PEAKS. WITH RAIN INTO HIGHER ELEVATIONS,
THERE IS THE POTENTIAL THAT THE RAIN/WARMER AIR COULD LEAD TO
SNOWMELT WHERE SNOW HAS ALREADY FALLEN WHICH WOULD RAISE THE
PROSPECTS OF DOWNSTREAM ISSUES AS WELL, MOST LIKELY IN VICINITY OF
THE SAN JUAN RANGE IN SOUTHWEST COLORADO.
..SOUTHERN CALIFORNIA
FURTHER WEST, PACIFIC MOISTURE WILL STREAM NORTHEASTWARD TOWARDS
SOUTHERN CALIFORNIA AS THE UPPER-LOW DROPS SOUTHWARD. SHOWERS AND
STORMS ARE LIKELY WITHIN STRONGER LOW TO MID-LEVEL FLOW AHEAD OF AN
APPROACHING OFFSHORE LOW/COLD FRONT. STORM COVERAGE LOOKS TO
GENERALLY REMAIN AT LEAST A BIT PROGRESSIVE OVERALL AS THE
FRONT/FLOW PUSHES EASTWARD, THOUGH THERE IS THE POTENTIAL FOR SOME
LOCALLY HEAVY TOTALS AS STORMS TRAIN/BACKBUILD WITHIN THE MEAN
SOUTHERLY FLOW. EXPECT AT LEAST AN ISOLATED RISK FOR FLASH
FLOODING, ESPECIALLY FOR MORE TERRAIN SENSITIVE AREAS SUCH AS BURN
SCARS.
PUTNAM
DAY 4 AND DAY 5
VALID 12Z THU OCT 22 2026 - 12Z SAT OCT 24 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST THURSDAY...
1930Z UPDATE: THE INHERITED SLIGHT RISK ON THURSDAY OVER THE
SOUTHWEST STILL LOOKS IN GOOD SHAPE. MODELS REMAIN IN AGREEMENT
THAT A HEAVY RAINFALL EVENT IS LIKELY, WITH THE POSSIBILITY OF AT
LEAST LOCALLY SIGNIFICANT IMPACTS. THE MARGINAL RISK ON DAY 5 WAS
ADJUSTED SLIGHTLY WESTWARD BASED ON MODEL TRENDS LINGERING
INSTABILITY/MOISTURE OVER NM.
CHENARD
..PREVIOUS DISCUSSION
MAINTAINED THE SLIGHT RISK AREA IN PARTS OF THE SOUTHWEST ON
THURSDAY AS A DEEP MID/UPPER LEVEL LOW MOVES ACROSS THE REGION.
HEAVY TO POTENTIALLY EXCESSIVE RAINFALL REMAINS A CONCERN GIVEN THE
MAGNITUDE OF THE TROPICAL MOISTURE BEING ADVECTED INTO THE REGION. DEEP
SOUTHERLY FLOW AHEAD OF THE APPROACHING TROUGH WILL ADVECT
AN AIRMASS WITH PRECIPITABLE WATER VALUES THAT APPROACH RECORD
VALUES FOR THE LATTER PART OF OCTOBER. THERE IS STILL SPREAD IN THE
AMOUNT OF INSTABILITY AVAILABLE BY THEN BUT THE OVERALL UPTICK IN
MODEL QPF OVER THE PAST COUPLE OF RUNS IS INDICATIVE OF THE MODELS
ARE DOING BETTER AT CAPTURING THE STEEPENING LAPSE RATES WITH THE
UPPER LOW ON THURSDAY SHOULD ALSO PRODUCE SOME DESTABILIZATION.
BY FRIDAY, THE TROUGH AXIS HAS HAVE MADE ITS WAY ACROSS THE
SOUTHERN ROCKIES AND EMERGED OUT OVER THE ADJACENT HIGH PLAINS.
SOME OF THE MOISTURE WILL BE LOST IN THE COMPLEX TERRAIN AS THE
SYSTEM MOVES EASTWARD...BUT ADDITIONAL LOW LEVEL MOISTURE SHOULD
START BEING DRAWN OUT OF THE GULF TO SUPPORT A LOWER-END RISK OF
EXCESSIVE RAINFALL LINGERING OVER PORTIONS OF NEW MEXICO AND
PORTIONS OF ADJOINING STATES.
EVEN THOUGH CONFIDENCE ON THE EXACT DETAILS REMAIN LOW GIVEN WE
ARE 4 TO 5 DAYS OUT, THERE IS GROWING CONFIDENCE IN A HEAVY RAIN
AND FLASH FLOOD THREAT OVER THE SOUTHWEST REGION BEGINNING ON DAY 3
WHICH CONTINUES INTO THURSDAY. THE INGREDIENTS IN PLACE STILL
SUGGEST THAT AT LEAST LOCALLY SIGNIFICANT IMPACTS ARE A
POSSIBILITY. TRENDS WILL CONTINUE TO BE MONITORED AND CAN NOT RULE
OUT THE NEED FOR EMBEDDED MDT RISK AREA(S) IF/WHERE ENOUGH
INSTABILITY MATERIALIZES.
BANN
DAY 1 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/94EPOINTS.TXT
DAY 2 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/98EPOINTS.TXT
DAY 3 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/99EPOINTS.TXT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page