FXUS65 KREV 292128
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
128 PM PST SUN NOV 29 2009

.SHORT TERM...
INITIAL PART OF THE SHORT TERM FORECAST SHOULD BE MAINLY A TEMP
FORECAST. LOW LVL PRES GRADIENT SHOULD RELAX TONIGHT AND H700
WINDS WILL CONTINUE TO DECREASE AS UPPER LOW PULLS TO THE ESE INTO
NRN MEXICO. THIS WILL ALLOW WINDS MOST LOCATIONS...EVEN RIDGE TOPS
TO DROP TONIGHT. SNOW COVER OVER SRN PORTIONS OF THE CWA SHOULD
ALLOW FOR MAX RADIATIONAL COOLING SO LOWERED TEMPS THERE TONIGHT.
LOW LVL INVERSIONS WILL BE SLOW TO MIX MONDAY AS LIGHT LOW LVL
ERLY FLOW CONTINUES AND LITTLE IN THE WAY OF MID LVL WINDS TO AID
MIXING. SO HIGH TEMPS MONDAY WILL REMAIN AT OR BELOW GUIDANCE.

RIDGE BUILDS OVER THE RGN MONDAY INTO TUESDAY. MODELS ALL TRY TO
DROP A VORT LOBE INTO THE WRN U.S. LATE TUESDAY INTO WEDNESDAY.
GFS IS VERY WEAK WITH THIS FEATURE WHILE NAM IS A BIT STRONGER.
STILL NEITHER PRODUCES PCPN AS PWATS REMAIN AT OR BELOW 0.30
INCHES. ECMWF HAS BEEN THE MOST AGGRESSIVE WITH THIS FEATURE AND
REMAINS SO...BUT IS ABOUT 8 HOURS SLOWER THAN NAM. NOW IT DROPS THE
VORT LOBE SOUTH THROUGH CA WEST OF THE SIERRA. EVEN SO IT DOES NOT
PRODUCE ANY PCPN. SREF FROM THIS MRNG DOES NOT HINT AT ANY POPS
FOR LATE TUESDAY WEDNESDAY EITHER. WILL INCREASE CLOUD COVER A BIT
TUESDAY NIGHT AND WEDNESDAY AND SHOW A RETURN TO LIGHT LOW LVL NE
FLOW IN MOST AREAS. THIS WILL WEAKLY REINFORCE LOW LVL COOL TEMPS.
SO ONLY SLOW WARMING NOTED IN THE SHORT TERM FORECAST AFTER MONDAY.
MLF

.LONG TERM...THURSDAY THROUGH SUNDAY...
THERE REMAINS A GREAT DEAL OF UNCERTAINTY AS MEDIUM RANGE MODELS
STUGGLE WITH INCREASING ACTIVITY IN THE MID LATITUDES OF THE PACIFIC
AND HOW THAT WILL AFFECT RIDGING INTO THE EASTERN PACIFIC AND ITS
PLACEMENT.

THE OVERALL PATTERN OF THE OPERATIONAL GFS...WHICH HAS BEEN CONSISTENT
FOR THE PAST COUPLE OF DAYS WITH THIS SCENARIO...IS TO PUMP A STRONG
RIDGE UP AROUND 140W ALLOWING FALLING HEIGHTS AND AN E/W COLD FRONT
TO DROP INTO THE PACIFIC NORTHWEST FRIDAY AND EARLY SATURDAY. THE
GFS CONTINUES TO CARVE A SHARP AND DEEP POSITIVELY TILTED TROUGH
ACROSS THE WESTERN U.S. THROUGH THE WEEKEND...DRAGGING THE COLD
FRONT AND POSSIBLY A BAND OF RAIN/SNOW ACROSS NORTHEAST CA AND
WESTERN NEVADA SATURDAY INTO SUNDAY. MEANWHILE THE EC IS SIMILAR
IN THAT IT ALSO PUMPS A STRONG RIDGE UP INTO THE EASTERN PACIFIC
BUT IN SO DOING...ALLOWS ENERGY TO UNDERCUT THE RIDGE...KEEPING
THE COLDER AIRMASS CONFINED NORTH OF NORTHERN CA/NORTHERN NV BUT
BRINGING A SERIES OF WEAK MOIST SYSTEMS ACROSS NORTHERN CA AND
NORTHERN NV FOR THE WEEKEND INTO EARLY NEXT WEEK.

THE CANADIAN MODEL...GEM...FAVORS A GFS SOLUTION AND ALSO SHOWS THE 
POTENTIAL FOR A COLD FRONT DROPPING ACROSS THE AREA OVER THE 
WEEKEND.

MODELS ARE LATCHING ONTO THE POTENTIAL FOR A STRONG STORM IN THE 
EASTERN PACIFIC IN THE MID LATITUDES PROGRESSING FROM AROUND 160W 
THURSDAY TO 50N/140W AROUND SATURDAY...THE FEATURE THAT WOULD
BUILD THE RIDGE IN THE EASTERN PACIFIC LATER THIS WEEK.

WILL KEEP THE LOW CHANCE POPS ACROSS THE AREA FOR SATURDAY UP NORTH 
AND ACROSS ALL OF NORTHEAST CA AND WESTERN NEVADA INCLUDING THE 
SIERRA FOR SATURDAY NIGHT THROUGH SUNDAY AS EITHER SCENARIO HAS THE 
POTENTIAL FOR PRODUCING PRECIPITATION. THE EC WOULD POINT TO A 
MILDER RAIN/SNOW SCENARIO WHILE THE GFS SOLUTION WOULD INDICATE A 
SHOT OF SNOW ASSOCIATED WITH A RELATIVELY STRONG COLD FRONT. DAYTIME 
TEMPERATURES WERE BUMPED UP SOME FOR FRIDAY AND SATURDAY BUT WILL 
KEEP THEM ON THE LOWER SIDE...BELOW NORMAL..FOR SUNDAY. JAH
&&

.AVIATION...
VFR CONDS WITH LIGHT SFC WINDS THROUGH TUESDAY. 

KTRK...SHOULD STAY FREE OF FOG TONIGHT ALTHOUGH THERE IS A CHANCE
OF DEVELOPMENT OF A VERY SHALLOW LAYER 11Z-13Z DUE TO TODAYS
SNOWMELT...BUT DEWPOINTS ARE VERY LOW IN VERY DRY AIRMASS. EXPECT
TO SEE SOME SHALLOW FOG DEVELOPMENT TUESDAY MORNING 10Z-16Z. JAH
&&

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

$$

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