000
FXUS65 KREV 160934
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
234 AM PDT THU MAY 16 2013

.SYNOPSIS...

LOW PRESSURE OVER THE PACIFIC NORTHWEST WILL PUSH A COLD FRONT
THROUGH NORTHERN NEVADA THIS MORNING BRINGING RAIN, HIGH ELEVATION
SNOW AND MUCH COOLER TEMPERATURES. THE LOW WILL REMAIN IN PLACE
FRIDAY WITH A FEW SHOWERS AND THUNDERSTORMS POSSIBLE. TEMPERATURES
WILL WARM SLOWLY OVER THE WEEKEND AND EARLY NEXT WEEK AS HIGH
PRESSURE BUILDS INTO THE REGION. ANOTHER COLD LOW WILL BRING WIND
AND MUCH COOLER TEMPERATURES AGAIN BY THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...

AN AREA OF LOW PRESSURE SHIFTS INLAND TODAY TAPPING INTO DEEP
MOISTURE IN THE EASTERN PACIFIC. THE COLD FRONT ASSOCIATED WITH
THIS LOW WILL REACH NORTHEAST CALIFORNIA/FAR NORTHWEST NEVADA
EARLY THIS MORNING, PUSHING ACROSS RENO-CARSON-TAHOE DURING THE
MORNING COMMUTE. RAIN AND HIGH ELEVATION SNOW WILL DEVELOP ALONG
THE FRONT AND MODELS REMAIN CONSISTENT IN KEEPING THE THE HEAVIEST
PRECIPITATION NORTH OF INTERSTATE 80 WHERE THERE IS ENHANCEMENT
FROM THE JET. THE JET WILL ALSO COMBINE WITH AN EMBEDDED PV WAVE
BRINGING ISOLATED THUNDERSTORMS TO AREAS FROM SUSANVILLE-PYRAMID
LAKE NORTHWARD. PRECIPITATION TOTALS WILL MAINLY BE UNDER A
QUARTER INCH, BUT PORTIONS OF LASSEN AND PLUMAS COUNTIES AS WELL
AS THE SURPRISE VALLEY AND FAR NORTHWEST NV MAY SEE CLOSER TO A
HALF INCH. SNOW LEVELS TODAY WILL FALL BETWEEN 7500 TO 8500 FEET
MSL, WITH AN INCH OR TWO OF SLUSHY ACCUMULATION POSSIBLE ABOVE
8000 FEET. THIS INCLUDES HIGHER SIERRA PASSES SUCH AS CALIFORNIA
HIGHWAYS 4, 88, 89, AND 108 AND NEVADA HIGHWAY 431. THIS FRONT
WILL ALSO USHER IN A SIGNIFICANTLY COOLER AIR MASS WITH MAX
TEMPERATURES DROPPING 15 TO 20 DEGREES TODAY AS COMPARED TO
WEDNESDAY.

BY THIS EVENING, THE FRONT AND JET MOVE EASTWARD, WITH
PRECIPITATION DECREASING IN COVERAGE. THE UPPER LEVEL TROUGH
AXIS SHIFTS OVER THE NORTHERN SIERRA TONIGHT CAUSING SHOWERS TO
CONTINUE OVERNIGHT. THE COOLING ALOFT FROM THE CORE OF THE LOW
WILL ALSO BRING ADDITIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS ON
FRIDAY. THERE IS LITTLE UPPER LEVEL FORCING, ESPECIALLY AS MODELS
HAVE SLOWED THE TIMING IN THE NEXT JET SEGMENT REACHING THE SIERRA
TO LATE FRIDAY AFTERNOON. THEREFORE, THUNDERSTORM DEVELOPMENT WILL
BE MAINLY DEPENDENT ON SURFACE INSTABILITY AND THIS MAY BE LIMITED
BY THE ABUNDANT CLOUDS. HAVE KEPT PRECIPITATION CHANCES THE SAME,
BUT LIMITED THUNDERSTORMS TO SLIGHT CHANCE ON FRIDAY.

A DRYING AND SLOW WARMING TREND IS ON TRACK FOR THE WEEKEND AS A
RIDGE BUILDS INTO THE EASTERN PACIFIC. THE FORECAST WILL REMAIN
DRY FOR THE WEEKEND WITH HIGH TEMPERATURES RETURNING TO NEAR
NORMAL ON SATURDAY. DF

.LONG TERM...SUNDAY THROUGH WEDNESDAY...

MODELS CONTINUE TO ADVERTISE THE DEVELOPMENT OF A COLD TROUGH FOR
THE MIDDLE TO LATTER HALF OF NEXT WEEK WITH DECENT CONTINUITY OVER
THE PAST SEVERAL DAYS WITH REGARD TO THE LARGE SCALE PATTERN. THIS
FITS WILL THE FORECAST STRONG NEGATIVE PNA INDEX CENTERED AROUND MAY
18-20TH AND AN OVERALL TREND OF DEEPER 500MB HEIGHTS OVER THE
WESTERN U.S. IN RESPONSE TO A MORE AMPLIFIED RIDGE EXTENDING FROM
THE ALEUTIANS TO THE EAST PACIFIC. EVENTUAL CENTER OF ANOMALY
REMAINS NEAR OR JUST NORTH OF 40N WHICH WOULD RESULT IN A COOLER BUT
BREEZY AND MOSTLY DRY PATTERN. HOWEVER UPPER LOW WILL BE CLOSE
ENOUGH TO WARRANT SOME CHANCE OF SHOWERS NORTH OF I-80 BY LATE IN
PERIOD.

FLAT RIDGE WILL BE IN PLACE FOR MONDAY WHICH WILL LIKELY BE THE
WARMEST DAY. AS TROUGH DROPS INTO PLACE ON TUE-WED, WINDS WILL BE ON
THE INCREASE WITH FORECAST SOUNDINGS SHOWING A VERY DRY AIRMASS,
ESPECIALLY SOUTH OF I-80. SOME MOISTENING WILL TAKE PLACE ACROSS THE
FAR NORTH AS CENTER OF UPPER LOW GETS CLOSER. MAIN CHANGE WAS TO
COOL TEMPERATURES WEDNESDAY AND THE PRELIMINARY DAY 8 WITH BELOW
NORMAL READINGS BECOMING LIKELY. IN FACT, SOME SOLUTIONS ARE QUITE
COLD AND WOULD RESULT IN TEMPERATURES FALLING 10-15 DEGREES BELOW
NORMAL. SO THERE IS A POSSIBILITY THAT OUR TEMPERATURES MAY STILL BE
TOO WARM. AS MENTIONED IN THE PREVIOUS FORECAST, SNOW LEVELS COULD
GET QUITE LOW ACROSS OUR NORTHERN AREAS WHERE SHOWERS WOULD BE
CAPABLE OF PRODUCING SOME LIGHT SNOW FOR HIGHER ELEVATIONS. HOHMANN

&&

.AVIATION...

LOW PRESSURE OFF THE OREGON COAST WILL PUSH INTO CALIFORNIA TODAY.
THE SYSTEM HAS A DEEP MOISTURE FEED WHICH IS EXPECTED TO BRING
WIDESPREAD RAIN (AND SNOW ABOVE 7500 FEET) TO THE NORTHERN
SIERRA/NORTHEAST CALIFORNIA AND NORTH OF INTERSTATE 80.

THE DEEP MOISTURE WILL MEAN SIGNIFICANT TERRAIN OBSCURATION AND
PERIODS OF MVFR/IFR VISIBILITIES IN THE SIERRA AND OUT INTO NORTHERN
NEVADA, ESPECIALLY NORTH OF A SUSANVILLE TO WINNEMUCCA LINE.
ISOLATED TO SCATTERED SHOWERS WILL PERSIST TONIGHT AS THE UPPER LOW
MOVES INLAND.

SIERRA TAF SITES KTRK/KTVL MAY EXPERIENCE BRIEF PERIODS OF MVFR
CONDITIONS THROUGH THIS EVENING WITH RESTRICTIONS LESS LIKELY AT
KMMH AND WESTERN NV TAF SITS OF KRNO/KCXP. WEST TO SOUTHWEST WINDS
WILL GUST 15-20KT WITH RIDGE WINDS DOWN A BIT TODAY, GENERALLY
30-40KT. HOHMANN

&&

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

$$

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