Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KSLC 190300
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
800 PM MST SUN JAN 18 2015

.SYNOPSIS...A WEAK PACIFIC WEATHER DISTURBANCE WILL IMPACT FAR
NORTHERN UTAH AND SOUTHWEST WYOMING LATE TONIGHT THROUGH MONDAY.
HIGH PRESSURE ALOFT WILL BECOME ESTABLISHED ACROSS THE WESTERN
STATES FOR THE LATTER HALF OF THE WEEK.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS THE RIDGE FLATTENING OVER
THE EASTERN GREAT BASIN...WHILE A WAVE TRAIN HAS SET UP FROM SOUTH
OF THE GULF OF ALASKA INTO THE NORTHERN ROCKIES. AMDAR 400-250MB
WIND OBSERVATIONS INDICATE A 75-110KT WESTERLY JET OVER THE
PACIFIC NORTHWEST AND NORTHERN ROCKIES. GOES/GPS/RAP/00Z RAOB
INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN 0.15-0.20"
MOUNTAINS...TO 0.40-0.45" MOST VALLEYS. BLENDED TOTAL PRECIPITABLE
WATER PRODUCT INDICATES A TROPICAL MOISTURE TAP INTO NORTHERN
CALIFORNIA...WITH VALUES WELL ABOVE NORMAL ACROSS MUCH OF THE
WEST.

00Z KSLC RAOB SHOWS A WARM ADVECTION PATTERN IN PLACE WITH VEERING
AND INCREASING WINDS WITH HEIGHT. MIXING WAS LIMITED BY SEVERAL
LOWERING INVERSIONS...THE LOWEST ONE WITH A BASE OF ONLY 865MB. THE
HIGHER BENCHES AND MOUNTAINS WERE FULLY MIXED THIS AFTERNOON...WHILE
MANY NORTHERN VALLEY TEMPERATURES WERE AIDED BY A WARM START DUE TO
CLOUD COVER OVERNIGHT. SEE WEBSITE FOR SOME RECORD HIGH TEMPERATURES.

WHILE PORTIONS OF CENTRAL AND SOUTHERN UTAH ARE SEEING PASSING MID
AND HIGH CLOUDS...BULK OF DENSE CLOUD COVER RESTRICTED NEAR THE
IDAHO BORDER AHEAD OF THE NEXT APPROACHING SYSTEM. THESE ARE GRAZING
WEAK WAVES SO COOLING WILL COME IN STAGES. THUS...NOT EXPECTING MUCH
QPF EVEN ALONG THE IDAHO BORDER. FELT THAT POPS WERE ON TRACK AND
ONLY MADE MINOR ADJUSTMENTS TO GRIDS.

RASIED SNOW LEVELS DUE WITH SUPPORT FROM LATEST RAP BUFKIT THERMAL
PROFILES. ALSO ADDED STRATUS AND MENTION OF FOG NEAR ROOSEVELT WHERE
THEY ARE STUCK IN A STRONG INVERSION.

PREVIOUS DISCUSSION FOLLOWS...

TWO SEPARATE MID-LATITUDE SHORTWAVES OVER THE EASTERN PACIFIC THIS
AFTERNOON WILL IMPACT THE NORTHERN PORTION OF THE FORECAST AREA
LATER TONIGHT THROUGH MONDAY NIGHT. THE FIRST SYSTEM JUST OFF THE
PACIFIC NORTHWEST COAST WILL MOVE INLAND EARLY THIS EVENING...THEN
RACE EAST INTO AND THROUGH THE NORTHERN ROCKIES OVERNIGHT. THE LOW-
LEVEL BAROCLINIC BOUNDARY ASSOCIATED WITH THIS FIRST FEATURE WILL
SAG SOUTH INTO EXTREME NORTHERN THIS EVENING AND THEN STALL LATE
TONIGHT. LIGHT PRECIP WILL FORM ALONG THIS BOUNDARY NEAR THE THE
IDAHO BORDER THIS EVENING...THEN REMAIN ON THE COOL SIDE OF THE
BOUNDARY THROUGH LATE TONIGHT.

THE SECOND SHORTWAVE WILL REACH THE PACIFIC NORTHWEST COAST LATE
TONIGHT...THEN TURN TO THE EAST-SOUTHEAST AS A LOW-AMPLITUDE UPPER
RIDGE FORMS JUST OFF THE COAST. THIS SHORTWAVE WILL GRAZE NORTHERN
UTAH/SOUTHWEST WYOMING LATE MONDAY/MONDAY EVENING. THIS DYNAMIC
FEATURE SHOULD ENERGIZE THE LOW-LEVEL BAROCLINIC BOUNDARY AND CREATE
A FAIRLY BROAD AREA OF LIGHT PRECIP OVER THE NORTHERN QUARTER OF
UTAH AND SOUTHWEST WYOMING. THE ASSOCIATED SURFACE COLD FRONT WILL
GRADUALLY STRENGTHEN MONDAY AFTERNOON...THEN SURGE SOUTH INTO
CENTRAL UTAH MONDAY EVENING. THIS FRONT WILL LOSE MUCH OF THE PRECIP
AS IT MOVES SOUTH WITH THE LOSS OF DYNAMIC LIFT AS THE UPPER
SHORTWAVE RACES OFF TO THE SOUTHEAST.

THE THREAT FOR PRECIP WILL SHIFT INTO EXTREME SOUTHERN UTAH MIDWEEK.
A SPLITTING UPPER TROUGH ALONG THE WEST COAST TUESDAY WILL CONTINUE
SOUTHEAST INTO THE DESERT SOUTHWEST WEDNESDAY. THIS FEATURE WILL
INTERSECT WITH THE EARLY WEEK BAROCLINIC BOUNDARY AND LIKELY BECOME
THE FOCUS FOR ADDITIONAL PRECIP NEAR THE UTAH/ARIZONA BORDER. MODELS
STILL DIFFER SLIGHTLY ON WHERE THE PRECIP WILL FOCUS PRECIP...THOUGH
THE GENERAL IDEA OF KEEPING PRECIP NEAR OR SOUTH OF THE BORDER LOOKS
GOOD FOR THIS FORECAST PACKAGE.

12Z GFS TRENDED TOWARDS CURRENT AND PREVIOUS SOLUTIONS OF
ECMWF/GEM/GEFS ENSEMBLE MEAN REGARDING LARGE SCALE PATTERN EVOLUTION
LATE NEXT WEEK...THOUGH THE IDEA REMAINS SIMILAR AS ALWAYS. A HIGH
AMPLITUDE BLOCKING PATTERN WILL SET UP ALONG THE WEST COAST FRIDAY
INTO THE WEEKEND LEAVING THE EASTERN GREAT BASIN BENEATH A STABLE
NORTHERLY FLOW.

HIGH OVER LOW BLOCK SETTING UP FRIDAY INTO THE WEEKEND...AS A
SPLITTING SHORT WAVE THU INTO FRI WILL SEND THE NORTHERN ENERGY UP
AND AROUND THE RIDGE WHILST THE SOUTHERN ENERGY RETROGRADES
SOUTHWEST AROUND THE STRENGTHENING EASTERN PACIFIC HIGH. THIS AIDING
THE BLOCK. SENSIBLY WE SHOULD SEE A GRADUAL WARMING OF TEMPS INTO
NEXT WEEKEND...AND DRY CONDITIONS WITH ANY NORTHERN BRANCH ENERGY
ONLY MINIMALLY GRAZING THE NORTHEAST.

CONSISTENCY IN EVOLUTION OF THE BLOCK THEREAFTER DEGRADES MODEL TO
MODEL THOUGH AM TENDING TO LEAN AWAY FROM THE GFS IDEA OF
TRANSLATING THE HIGH CIRCULATION OVERHEAD VS. KEEPING IT FURTHER
WEST AS DEPICTED IN THE EC/GEM. SENSIBLY THIS DIFFERENCE FACTORS
PRIMARILY INTO TEMPS...H7 CLIMBING TO +5 C BY NEXT MONDAY /GFS/ VS.
A MORE MODERATE 0 C /EC AND GEM/. WARMED TEMPS SOME BUT NOT TO THE
EXTENT OF THE GFS. EC AND GEM SOLUTIONS WOULD ALSO INCREASE CHANCES
OF SHORT WAVE ENERGY GRAZING THE NORTH AS IT ROLLS OVER THE HIGH
BEGINNING SUNDAY AND HAVE MAINTAINED SLIGHT CHANCE OVER THE NORTHERN
MOUNTAINS AS SUCH.

BOTTOM LINE...NO SIGNIFICANT STORMS EXPECTED OVER THE NEXT 7-10 DAYS
EASY. LACK OF VALLEY SNOW MOST AREAS AND ONLY MODERATE WARMING ALOFT
SHOULD KEEP VALLEY/BASIN INVERSIONS MODERATELY STRONG AT BEST AND

&&

.AVIATION...CEILINGS AT THE SLC TERMINAL ARE EXPECTED TO DROP BELOW
7000FT BETWEEN 07Z AND 10Z...WITH A SLIGHT CHANCE THAT CEILINGS STAY
ABOVE 7000FT THROUGH 12Z. THERE IS ALSO A 40 PERCENT CHANCE OF MVFR
CEILINGS THROUGH THE DAY MONDAY. SURFACE WINDS SHOULD GENERALLY
REMAIN 7 KNOTS OR BELOW THROUGH MUCH OF THE TAF PERIOD.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

$$

PUBLIC...ROGOWSKI/CONGER/MERRILL
AVIATION...SCHOENING

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.