Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 161538
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
938 AM MDT THU APR 16 2015

.UPDATE...
ISSUED AT 936 AM MDT THU APR 16 2015

GRAND JCT RADAR INDICATED AN AREA OF ENHANCED PRECIPITATION ACROSS
WEST-CENTRAL CO THIS MORNING. MUCH OF THIS PRECIP WAS SNOW PER
PUBLIC REPORTS AND WEBCAM IMAGES. NOT EXPECTING ANY LONG-LASTING
ACCUMULATIONS IN THESE VALLEYS THOUGH PERIODS OF HEAVIER SNOW MAY
TEMPORARILY WHITEN GRASSY SURFACES. HI-RESOLUTION HRRR AND RAP
MODELS SHOW THIS AREA DECREASING...OR AT LEAST SLIDING NORTH AND
NORTHEAST...BY LATE MORNING. EXPECT TO SEE COVERAGE INCREASE ACROSS
ALL OF THE CENTRAL AND NORTHERN PORTIONS OF THE FORECAST AREA THIS
AFTERNOON AS CONVECTIVE INSTABILITY KICKS IN EVEN MORE.

LET THE FREEZE WARNING EXPIRE AT 9 AM THIS MORNING. SOME AREAS WHERE
SNOW IS OCCURRING MAY STILL BE IN THE UPPER 20S FOR A BIT LONGER
THOUGH...LIKE DELTA/MONTROSE/PAONIA AREAS. FREEZE WATCH REMAINS
FOR THE CORTEZ-YELLOWJACKET AREA EARLY FRI MORNING.

UPDATE ISSUED AT 613 AM MDT THU APR 16 2015

SOCIAL MEDIA REPORTS OF HOWLING WINDS IN THE STEAMBOAT SPRINGS
AREA HAVE BEEN RECEIVED EARLY THIS MORNING...PEAK GUSTS ON SENSORS
IN THE AREA SHOWING 25-35 MPH SO FAR THIS MORNING. PATTERN IS
SETTING UP FOR A POTENTIAL DOWNSLOPE WIND EVENT IN THIS REGION
LATER THIS AFTERNOON AND TONIGHT. STRONG H7 FLOW AROUND NORTH
SIDE OF THE LOW EXPECTED TO EXCEED 50 KTS AND WE HAVE SEEN THIS
TYPE OF FLOW IN THE PAST GENERATE STRONG DOWNSLOPE WINDS IN THE
STEAMBOAT AND ZIRKEL WILDERNESS AREAS. TRACK OF THE UPPER LOW WILL
PLAY CRITICAL ROLE AND MODELS STILL A BIT OUT OF PHASE IN EXACT
PATH...SO WILL CONTINUE TO MONITOR AND ADVISE LATER SHIFTS OF THIS
POTENTIAL. IN THE MEANTIME...BOOSTED SPEEDS UP A FEW CATEGORIES
FOR TODAY WITH GUSTS UP TO 50 MPH FOR THE HILLS AND GUST TO UP TO 45
FOR THE VALLEYS.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 416 AM MDT THU APR 16 2015

SPRING IN THE CENTRAL ROCKIES IS REARING ITS UGLY HEAD AS
TEMPERATURES THIS MORNING HAVE DIPPED BELOW FREEZING IN MANY
LOCATIONS WHICH HAVE ALREADY BEGUN THEIR GROWING SEASONS...WHILE
OTHERS (THE EASTERN UINTAS) HAVE ALREADY SEEN A DECENT AMOUNT OF
ACCUMULATING SNOW. A LARGE CLOSED LOW IS CURRENTLY OVER SOUTHEAST
UTAH AND WILL SLOWLY PROGRESS SOUTH TO THE FOUR CORNERS LATER THIS
MORNING. MODELS ARE IN GOOD AGREEMENT THAT SIGNIFICANT SNOW IS
GOING TO FALL AT ELEVATIONS MAINLY HIGHER THAN 9000 FT STARTING
THIS AFTERNOON ACROSS THE WEST CENTRAL COLORADO MOUNTAINS AND WILL
CONTINUE TO FALL OVER THE EASTERN UINTAS. THOUGH WINDS WILL NOT BE
FAVORABLE FOR CONSTANT SNOWFALL DURING THE ENTIRE TIME PERIOD OF
THE WINTER HAZARDS...WHEN THE DIRECTION IS RIGHT COMBINED WITH
LIFTING DUE TO THE PASSING CLOSED LOW...HEAVY WET SNOW WILL PILE
UP QUICKLY AT THESE HIGHER LOCATIONS. HAVE KEPT A CLOSE EYE ON THE
MOISTURE FIELDS OVER THE LAST FEW DAYS AND HAVE SEEN THE FORECAST
MODELS INCREASE MOISTURE FROM THE SOUTH AND NOW INCREASE MOISTURE
ACROSS WESTERN CO AND EASTERN UT AS IT WRAPS AROUND THE SLOWLY
PROGRESSING CLOSED LOW. THE SLOW MOVEMENT AND DYNAMICS OF THE LOW
SHOULD BE EFFECTIVE IN OVERCOMING THE MOUNTAIN SHADOW EFFECT. SPEC
HUMIDITY VALUES ARE NOW BEING PROGGED TO REACH AND EXCEED 4 G/KG
WHICH IS RATHER SIGNIFICANT WITH SUCH A COLD SYSTEM IN APRIL. SNOW
LEVEL IS DEFINITELY A CHALLENGE AND AM EXPECTING NORTHERN COLORADO
VALLEYS TO SEE MAINLY RAIN AND A RAIN/SNOW MIX WITH LITTLE
ACCUMULATION. AN UPTICK IN ACTIVITY IS EXPECTED THIS AFTERNOON AND
EVENING...BUT ALL FORECAST MODELS REALLY PICK UP COVERAGE IN
ACTIVITY FRIDAY AFTERNOON. CONDITIONS NORTH OF I-70 TODAY WILL BE
BREEZY AND WET MUCH OF TODAY. ELSEWHERE WILL RECEIVE SCATTERED
SHOWERS WITH THE EXCEPTION OF THE CENTRAL MOUNTAINS WHICH WILL SEE
DETERIORATING CONDITIONS TODAY.

ADDED NORTHERN SAN JUANS TO A WINTER STORM WATCH STARTING TONIGHT
AS WE ANTICIPATE FLOW CHANGING TO WEST NORTHWESTERLY. STRONG
NORTHERLY FLOW FRIDAY EVENING WILL ALSO BE FAVORABLE FOR THIS AREA
TO RECEIVE HEAVY SNOW IF THE LOW STAYS ON TRACK. CONFIDENCE IS
MODERATE ON CURRENT SOLUTIONS EVEN A COUPLE DAYS OUT DUE TO THE
LOW TRACKING SO SLOWLY ACROSS THE REGION.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 416 AM MDT THU APR 16 2015

MEANDERING LOW WILL CONTINUE TO WREAK HAVOC ON THE FORECAST AS WE
START OFF THIS EXTENDED PERIOD. DEEP NORTHERLY FLOW ON THE BACK
SIDE OF THE...EXPECTED TO BE EXITING LOW PRESSURE SYSTEM...MAY
KEEP LOCALLY HEAVY SNOW FALLING ACROSS THE NORTHWEST SAN JUAN
MOUNTAINS AND OTHER FAVORED NORTH FACING SLOPES IN WESTERN
COLORADO. THIS SYSTEM LOOKS TO LINGER OVER THE AREA UNTIL MIDDAY
SATURDAY...BEFORE A KICKING WAVE DROPS INTO MONTANA LATE SATURDAY
AFTERNOON AND EVENING. THIS SYSTEM SHOULD KICK THE LOW OUT INTO
THE PLAINS WITH SOMEWHAT MOIST NW FLOW HOLDING IN PLACE THROUGH
THE REMAINDER OF THE WEEKEND. SO EXPECT UNSETTLED CONDITIONS TO
CONTINUE OVER THE NORTHERN AND CENTRAL MOUNTAINS WITH ADDITIONAL
LATE SEASON SNOWFALL ANTICIPATED...ESPECIALLY ABOVE THE 9K LEVEL.
SLIGHT INCREASE IN HEIGHTS EXPECTED AS WE MOVE INTO THE NEW WORK
WEEK...WHICH WILL MODIFY TEMPS UP A BIT. HOWEVER...ENOUGH PACIFIC
MOISTURE STREAMING INTO THE REGION TO KEEP ISOLATED TO SCATTERED
POPS ROLLING THROUGHOUT THE PERIOD...GENERALLY FOCUSED ON THE
HIGHER TERRAIN. ANOTHER STRONG CLOSED LOW BEING ADVERTISED BY BOTH
THE GFS AND ECMWF LATE NEXT WEEK PROMISES TO BRING MORE WIDESPREAD
PRECIPITATION TO THE REGION AS WE CLOSE THE WEEK OUT. EXPECT
TEMPS TO BE RUNNING NEAR TO SLIGHTLY BELOW NORMAL THROUGH THIS
PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 416 AM MDT THU APR 16 2015

A STRONG LOW PRESSURE SYSTEM WILL BE DROPPING SOUTH INTO THE FOUR
CORNERS AREA TODAY AND WILL MEANDER SLOWLY ENE ACROSS COLORADO FOR
THE NEXT 24 HOURS. EXPECT WIDESPREAD SHOWERS TO DEVELOP ACROSS THE
REGION BY THIS AFTERNOON...WITH LOCALLY HEAVY SNOW EXPECTED OVER
THE MOUNTAINS THROUGH SATURDAY. CIGS WILL BE DROPPING THROUGHOUT
THE REGION WITH AREAS OF MVFR AND IFR CONDS ANTICIPATED LATER
TONIGHT. MOUNTAINS WILL BECOME OBSCURED...ESPECIALLY NEAR SHOWERS.
GUSTY EASTERLY WINDS CAN BE EXPECTED ACROSS WESTERN COLORADO AND
EASTERN UTAH THROUGH FRIDAY MORNING.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL NOON MDT SATURDAY FOR COZ004-009-
     013.

     WINTER STORM WARNING UNTIL NOON MDT SATURDAY FOR COZ010-012.

     WINTER STORM WATCH FROM LATE TONIGHT THROUGH SATURDAY MORNING
     FOR COZ018.

     FREEZE WATCH FROM LATE TONIGHT THROUGH FRIDAY MORNING FOR COZ021.

UT...WINTER STORM WARNING UNTIL 6 AM MDT SATURDAY FOR UTZ023.

&&

$$

UPDATE...JAD
SHORT TERM...JAM
LONG TERM...JDC
AVIATION...JDC


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