Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 041007
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
307 AM PDT TUE AUG 4 2015

.SYNOPSIS...
LOW PRESSURE MOVING INTO NORTHERN CALIFORNIA WILL BRING LOW
CHANCES FOR THUNDERSTORMS LATE THIS AFTERNOON AND TONIGHT WELL
NORTH OF INTERSTATE 80. DRIER FLOW RETURNS FOR MID WEEK BEFORE
CHANCES FOR SHOWERS AND THUNDERSTORMS RETURN ON FRIDAY AS LOW
PRESSURE APPROACHES THE SIERRA AND WESTERN NEVADA. AFTERNOON
TEMPERATURES WILL REMAIN AROUND AVERAGE THIS WEEK.

&&

.SHORT TERM...
RAISED WINDS TONIGHT SLIGHTLY, OTHERWISE NO MAJOR CHANGES TO THE
SHORT TERM FORECAST. FAIRLY ENERGETIC FLOW FOR SUMMER WILL AFFECT
THE SIERRA AND WESTERN NEVADA THIS WEEK, THE FIRST TODAY AND
TONIGHT AND THE SECOND ON FRIDAY (DISCUSSED IN THE LONG TERM
SECTION).

LOOKING OFF THE CENTRAL AND SOUTHERN CALIFORNIA COAST IN THE WATER
VAPOR SATELLITE, A MOIST PLUME IS EVIDENT TO THE SOUTH OF AN UPPER
LOW WEST OF SAN FRANCISCO. THE PLUME ACTUALLY ORIGINATES EAST OF
HAWAII AND INCORPORATES SOME OF THE MOISTURE FROM TROPICAL STORM
GUILLERMO. WITH THE MOISTURE, AN UPPER JET STREAK OF 75+ KTS IS
MOVING AROUND THE UPPER LOW AND WILL MOVE INTO NORTHERN CALIFORNIA
AND WESTERN NEVADA THIS AFTERNOON AND TONIGHT, WITH A STRENGTHENING
UPPER DISTURBANCE (CURRENTLY JUST INSIDE OF 130W) MOVING INTO
NORTHERN CALIFORNIA.

WITH THE NOSE OF THE JET STREAK PROGGED TO BE OVER TAHOE AND RENO
AND THE UPPER LOW OVER NORTHERN CALIFORNIA, THE BEST UPPER FORCING
WILL BE OVER FAR NORTHEAST CALIFORNIA AND EXTREME NORTHWEST NEVADA
THIS AFTERNOON AND EVENING. ALSO, IN THE LOW LEVELS THE LASSEN
CONVERGENCE ZONE WILL PROVIDE A FOCUS FOR A FEW THUNDERSTORMS.
THEREFORE, ISOLATED THUNDERSTORMS ARE FORECAST AFTER 2 PM THROUGH
TONIGHT WELL NORTH OF I-80. ANY STORMS SHOULD MOVE ALONG QUICKLY
WITH LITTLE RAINFALL EXPECTED TO REACH THE GROUND. FARTHER SOUTH
AND EAST WITH LITTLE LOW LEVEL FOCUS, IT JUST LOOKS LIKE COPIOUS
MID AND HIGH CLOUDS WILL SPREAD IN THIS AFTERNOON AND TONIGHT
ALONG WITH GUSTY WINDS TO 25-30 MPH THIS EVENING.

WEDNESDAY, A FEW STRAY SHOWERS COULD LINGER IN THE MORNING OVER
THE SURPRISE VALLEY AND FOR FAR NORTHERN WASHOE COUNTY AS THE MAIN
UPPER LOW SLIDES OVERHEAD. WEDNESDAY AFTERNOON THROUGH THURSDAY
WILL BRING A DRY PERIOD WITH NEAR AVERAGE TEMPERATURES. ZEPHYR
GUSTINESS IS EXPECTED FOR WEDNESDAY AFTERNOON AND EVENING
IMMEDIATELY BEHIND THE EXITING LOW, WITH LIGHTER WINDS ON THURSDAY
AS AN UPPER RIDGE BUILDS OVERHEAD.

THURSDAY NIGHT, THE AFOREMENTIONED UPPER LOW WEST OF SAN FRANCISCO
WILL PIVOT AND APPROACH THE CALIFORNIA COAST. THIS WILL BEGIN TO
SPREAD UPPER FORCING OVER THE SIERRA AND FAR WESTERN NEVADA, WITH
CHANCES FOR SHOWERS OR EVEN A FEW THUNDERSTORMS INCREASING EARLY
FRIDAY MORNING. MORE ON THIS FAIRLY POTENT SYSTEM IN THE LONG TERM
SECTION. SNYDER

.LONG TERM...FRIDAY THROUGH MONDAY...
THE MAIN FOCUS WILL BE ON THE POTENT UPPER LOW FOR FRIDAY. MODELS
REMAIN VERY CONSISTENT WITH THIS FEATURE WHICH IS REMARKABLE FOR AN
UPPER LOW. THEY HAVE EVEN COME INTO BETTER AGREEMENT ON TIMING WITH
THE LOW MOVING THROUGH FRIDAY EVENING. CONFIDENCE IS MUCH HIGHER
THAN AVERAGE FOR A FEATURE LIKE THIS.

THE OTHER TREND IN THE MODELS IS THEY ARE TRENDING MORE MOIST. THE
FORCING WITH THE UPPER LOW WILL BE STRONG WITH GOOD JET SUPPORT, MID-
UPPER LEVEL FRONTAL FORCING AND LOW-LEVEL CONVERGENCE. INSTABILITY
IS NOT THE GREATEST IN THE MID-LEVELS, BUT THE STRONG FORCING WILL
RESULT IN THUNDERSTORMS. THE STORMS WILL LIKELY START EARLY AND LAST
THROUGH THE DAY, WITH SOME POSSIBLE STRATIFORM RAINS IN THE
DEFORMATION ON THE NORTH SIDE OF THE LOW FRIDAY NIGHT. WITH THE
INCREASED MOISTURE SHOWING UP IN THE MODELS, SOME FROM TS GUILLERMO,
IT IS LOOKING LESS LIKE A FIRE WEATHER THREAT AND MORE SEVERE
WEATHER.

AS THE LOW PULLS AWAY SATURDAY, A FEW STORMS ARE POSSIBLE IN THE
LASSEN CONVERGENCE ZONE. HOWEVER, SOUTHWEST FLOW THEN RESUMES WITH
DRYING FURTHER SOUTH. SUNDAY AND MONDAY BOTH LOOK DRY UNDER
SOUTHWEST FLOW WITH LIMITED MOISTURE. A RETURN TO THE AFTERNOON
ZEPHYR IS EXPECTED SATURDAY THAT WILL CONTINUE THROUGH MONDAY.
WALLMANN

&&

.AVIATION...
VFR CONDITIONS EXPECTED AT AREA TERMINALS WITH ISOLD TS POSSIBLE
NORTH OF KSVE AND GERLACH TODAY. THERE WILL BE AN EXTENSIVE MID AND
HIGH CLOUD DECK MOVING IN LATE THIS AFTERNOON WITH SOME SPRINKLES
INTO TONIGHT, BUT STILL VFR. WINDS WILL BE LOCALLY GUSTY THIS
AFTERNOON AT AREA TERMINALS WITH PEAK GUSTS TO 25 KTS POSSIBLE FROM
THE SW 22-04Z.

&&

.FIRE WEATHER...
ISOLATED TS POSSIBLE TODAY NORTH OF SUSANVILLE/GERLACH, AND THESE
WOULD BE ON THE DRY SIDE, BUT INSTABILITY IS WEAK. BEST CHANCES
WOULD ACTUALLY BE IN THE EVENING HOURS WITH JUST AN EXTENSIVE CLOUD
DECK FURTHER SOUTH AS A WAVE MOVES THROUGH. LOCALLY GUSTY AFTERNOON
SW WINDS WITH PEAK GUSTS TO 30 MPH. TYPICAL AFTERNOON ZEPHYR BREEZES
ARE EXPECTED WED/THU WITH SEASONABLE HUMIDITY ALTHOUGH SOME MID
SLOPES WILL SEE ONLY FAIR RECOVERY.

THE UPPER LOW FOR THURSDAY NIGHT INTO FRIDAY CONTINUES TO LOOK GOOD
WITH THE MODELS SHOWING MORE MOISTURE. ISOLATED HIGH-BASED AND FAST-
MOVING THUNDERSTORMS ARE POSSIBLE THURSDAY NIGHT WITH ONLY FAIR
HUMIDITY RECOVERY. THEN THE MOISTURE REALLY INCREASES WITH THE LOW.
THE STORMS SHOULD BECOME STRONGER DURING THE DAY FRIDAY AS WELL AND
WILL QUICKLY TRANSITION TO WET. OF COURSE, WHILE THIS IS
HIGHER CONFIDENCE THAN NORMAL WITH AN UPPER LOW, IT IS AN
UPPER LOW SO THINGS CAN STILL CHANGE IN THE NEXT 3 DAYS. WALLMANN

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.
&&

$$

FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/RENO (ALL LOWER CASE)



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