542
FXUS65 KVEF 170526
AFDVEF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
1026 PM PDT TUE SEP 16 2025
KEY MESSAGES
*SEASONABLY WARM TO HOT AND DRY CONDITIONS TO PERSIST THROUGH
MIDWEEK.
*INCREASING MOISTURE ASSOCIATED WITH THE REMNANTS OF MARIO WILL
GRADUALLY MOVE INTO THE REGION, SETTING THE STAGE FOR PERIODS OF
SHOWERS AND THUNDERSTORMS THURSDAY INTO THE WEEKEND. HEAVY RAIN
AND HIGH RAINFALL RATES WILL LEAD TO AN INCREASED RISK OF FLASH
FLOODING.
DISCUSSION
ELONGATED WEAK UPPER RIDING WILL CONTINUE TO EXTEND OVER THE
REGION THROUGH TOMORROW. THIS WILL GENERALLY PROMOTE DRY
CONDITIONS AND THE CONTINUATION OF SUMMER-LIKE TEMPERATURES NEAR
TO SLIGHTLY ABOVE NORMAL. THIS WILL BEGIN TO CHANGE LATE WEDNESDAY
AS UPPER AND MID-LEVEL MOISTURE BEGIN TO ENCROACH FROM THE SOUTH.
FROM THURSDAY INTO THE WEEKEND, SHORT AND MEDIUM RANGE ENSEMBLES
POINT TO GRADUALLY INCREASING MOISTURE FROM SOUTH TO NORTH. THIS
IS ALL ASSOCIATED WITH MARIO, WHICH IS IN THE PROCESS OF RAPIDLY
WEAKENING OVER THE EAST PACIFIC. AS A WEAK UPPER TROUGH INTERACTS
WITH AND SHEARS OFF THIS MOISTURE, IT WILL RAPIDLY SURGE
NORTHWARD, FIRST ALONG THE CALIFORNIA COAST AND AREAS INLAND.
HOWEVER IT WILL TAKE MORE TIME TO ARRIVE ACROSS THE DESERTS OF
SOUTHERN CALIFORNIA, NEVADA, AND ARIZONA, OWING THE MOUNTAINOUS
TERRAIN UPWIND AND ORIENTATION OF UPPER FLOW. THIS WILL ALLOW THE
MID AND UPPER ATMOSPHERE TO MOISTEN FIRST, WHICH WILL MANIFEST AS
RATHER EXPANSIVE CLOUD COVER. DESPITE RATHER IMPRESSIVE MOISTURE
CONTENT, EVIDENT BY PWATS ON THE ORDER OF 1-1.5 INCHES OR BETTER,
THE ABUNDANCE OF CLOUDS WILL ACT TO LIMIT DAYTIME HEATING AND
ASSOCIATED INSTABILITY. WHILE THERE WILL CERTAINLY BE SOME SHOWER
AND AT LEAST ISOLATED THUNDERSTORM ACTIVITY, THIS LEADS TO A FAIR
AMOUNT OF UNCERTAINTY WITH RESPECT TO THUNDERSTORM COVERAGE AND
THE ATTENDANT THREAT OF FLASH FLOODING. STILL, WITH ANY STORMS
THAT DO MANAGE TO DEVELOP, RAINFALL RATES OF 2-3 INCHES PER HOUR
CAN BE EXPECTED GIVEN THE TROPICAL NATURE OF THE AIRMASS IN PLACE.
ENSEMBLES ARE IN GENERAL AGREEMENT MAINTAINING RATHER DEEP
MOISTURE ACROSS THE DESERT SOUTHWEST AT LEAST INTO SATURDAY. THE
EC ENSEMBLE HOLDS ONTO THIS MOISTURE A BIT LONGER, AND GIVEN THE
GENERAL WEAKNESS OF THE UPPER TROUGH, THIS APPEARS TO BE A
REASONABLE SOLUTION, SO EXPECT THURSDAY AFTERNOON THROUGH SATURDAY
TO BE THE MOST ACTIVE PERIOD FOR SHOWER AND THUNDERSTORM
ACTIVITY. FROM SUNDAY INTO NEXT WEEK, MODEST MOISTURE WILL LINGER
WITH ISOLATED TERRAIN INDUCED SHOWERS AND STORMS EACH AFTERNOON AT
LEAST INTO MIDWEEK. THESE LOOK TO BE LARGELY DIURNAL AND WILL
LIKELY DIMINISH EACH NIGHT WITH THE LOSS OF DAYTIME HEATING.
AVIATION...FOR HARRY REID...FOR THE 06Z FORECAST PACKAGE
WINDS
WILL FOLLOW TYPICAL DIURNAL DIRECTIONAL PATTERNS WITH SUSTAINED
SPEEDS OF 10 KNOTS OR LESS. SOUTHWESTERLY WINDS WILL BECOME LIGHT
AND VARIABLE DURING THE EARLY MORNING HOURS. THESE LIGHT AND
VARIABLE WINDS WILL CONTINUE INTO THE LATE MORNING WHEN WINDS WILL
SETTLE IN FROM A MORE EASTERLY DIRECTION THROUGH THE AFTERNOON
AND INTO THE EARLY EVENING. HIGH CLOUDS WILL BEGIN TO PUSH INTO
SOUTHERN NEVADA OVERNIGHT TONIGHT, WITH MID-LEVEL CLOUDS MOVING IN
TOMORROW EVENING. TEMPERATURES ARE NOT EXPECT TO REACH 100
DEGREES, BUT WILL CLIMB TO THE UPPER 90S BETWEEN 21 AND 01Z.
FOR THE REST OF SOUTHERN NEVADA, NORTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA...FOR THE 06Z FORECAST PACKAGE... HIGH CLOUDS WILL
PUSH INTO THE AREA FROM THE SOUTH OVERNIGHT AND THROUGHOUT THE DAY
TOMORROW. MID-LEVEL CLOUDS WILL BEGIN TO INCREASE LATE TOMORROW
AFTERNOON/EARLY TOMORROW EVENING. THERE IS A LOW CHANCE THAT
SHOWERS WILL BEGIN TO PUSH INTO THE AREA AS EARLY AS TOMORROW
EVENING. HOWEVER, CHANCES FOR SHOWERS WILL INCREASE DURING THE
OVERNIGHT HOURS AS MOISTURE MOVES INTO THE AREA. CONFIDENCE
REGARDING WHETHER OR NOT ANY OF THESE SHOWERS WILL IMPACT
TERMINALS IS LOW AT THIS TIME. OUTSIDE OF INFLUENCE FROM ANY
SHOWERS, WHICH MAY RESULT IN ERRATIC GUSTY WINDS, WINDS ACROSS THE
REGION WILL FOLLOW TYPICAL DIURNAL DIRECTIONAL TRENDS WITH SPEEDS
OF 12 KNOTS OR LESS. THE ONE EXCEPTION TO THIS WILL BE THE
WESTERN MOJAVE DESERT TOMORROW NIGHT WHEN BREEZY SOUTHWESTERLY
WINDS WILL PICK UP.
SPOTTER INFORMATION STATEMENT
SPOTTERS ARE ENCOURAGED TO REPORT
ANY SIGNIFICANT WEATHER OR IMPACTS ACCORDING TO STANDARD OPERATING
PROCEDURES.
DISCUSSION...AUSTIN
AVIATION...STESSMAN
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