Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 311119
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
419 AM MST SAT JAN 31 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 419 AM MST SAT JAN 31 2015

WIDESPREAD PRECIPITATION PERSISTS AS THE TROPICAL MOISTURE PLUME
CONTINUES TO STREAM FROM SOUTH TO NORTH ACROSS THE REGION. IT
APPEARS THAT THE PRECIPITATION IS GENERALLY ON THE LIGHT
SIDE...WITH FOG DEVELOPING IN MANY VALLEY AREAS. DENSE FOG HAS
BEEN REPORTED AT A FEW ASOS SITES...AND FEEL THAT THESE ARE
PROBABLY ONLY THE TIP OF THE ICE BERG SINCE THE SURFACE LEVEL IS
SO SATURATED. SO WILL EXPAND THE DENSE FOG ADVISORY FOR THIS
MORNING TO INCLUDE THE NORTHWEST CO VALLEYS...ALONG THE INTERSTATE
70 CORRIDOR...AND THE CENTRAL WESTERN VALLEYS.

AS INDICATED BY SATELLITE IMAGES...THE SOUTHWEST LOW PRESSURE CENTER
LOOKS TO BE POSITIONED OVER THE SOUTHERN CORNER OF NV EARLY THIS
MORNING. THE LOW HAS BEEN RESPONSIBLE FOR PUMPING THE MOISTURE
INTO INTO THE SOUTHWEST CONUS. THIS LOW WILL BEGIN TO DROP
SOUTHWARD TODAY...PUSHED BY THE NORTHERN BRANCH FLOW AS A
SHORTWAVE TROUGH DROPS ACROSS THE NORTHERN ROCKIES. AS THIS
HAPPENS...A DRIER NORTHWEST FLOW WILL DEVELOP OVER OUR FORECAST
AREA LATE IN THE DAY. THEREFORE WE CAN EXPECT TO SEE PRECIPITATION
WIND DOWN FROM THE NORTHWEST DURING THE AFTERNOON. SNOW WILL
LINGER OVER THE SOUTHERN MOUNTAINS THROUGH THE EVENING. BUT AS THE
FLOW BECOMES MORE NORTHERLY LATE THIS AFTERNOON INTO THIS
EVENING...THERE IS THE POTENTIAL FOR THE UNCOMPAHGRE GORGE NEAR
OURAY TO SEE A SHORT PERIOD OF HEAVY SNOW BEFORE THE DEEP MOISTURE
IS SCOURED OUT. ANY REMAINING SNOW SHOWERS WILL GRADUALLY END BY
SUNDAY MORNING. WITH THE ONGOING PRECIPITATION...EXPECT THAT TEMPS
WILL BE JUST A TAD COOLER TODAY. OVERNIGHT LOW TEMPERATURES WILL
ALSO BE A LITTLE COOLER DUE TO THE DRIER AIR MASS. BUT STILL THEY
WILL REMAIN ON THE MILD SIDE FOR THIS TIME OF YEAR.

THE NORTHWEST FLOW RELAXES ON SUNDAY AS A WEAK RIDGE EMBEDDED IN THE
FLOW PASSES OVER THE AREA. DRY CONDITIONS ARE EXPECTED.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 419 AM MST SAT JAN 31 2015

FOLLOWING A DRY SUNDAY...MOISTURE WILL BEGIN TO GENERATE SNOWFALL
ACROSS THE NORTHERN MOUNTAINS LATE SUNDAY NIGHT. THE SURGE OF
MOISTURE IN NORTHWEST FLOW ARRIVES ON THE NOSE OF A 90 KT JET AND
MID-LEVEL SHORTWAVE TROUGH. SNOW WAS INDICATED TO CONTINUE
THROUGH THE DAY ON MONDAY WITH A LULL IN ACTIVITY MONDAY EVENING.
SNOWFALL ACCUMULATIONS PRETTY LIGHT ACCORDING TO MODEL DATA SO DO
NOT PLAN ON HOISTING ANY HIGHLIGHTS AT THIS POINT.

EC AND GFS BOTH GET SNOW STARTED AGAIN ACROSS THE NORTHERN
MOUNTAINS LATER MONDAY NIGHT AND KEEP IT GOING THROUGH TUESDAY
EVENING AT LEAST. MODELS DIVERGE A BIT AT THIS POINT WITH GFS
DEPICTING A MORE ENERGETIC SHORTWAVE DEVELOPING LATE TUESDAY NIGHT
WHICH WILL GENERATE MORE WIDESPREAD PRECIPITATION FROM LATE
TUESDAY NIGHT THROUGH WEDNESDAY EVENING. IN CONTRAST...EC DRIER
AND DEPICTS A SHALLOWER SHORTWAVE TROUGH MOVING OVER THE AREA.
GIVEN MODEL DIFFERENCES DID NOT VEER FROM BLENDED FORECAST WITH
THIS MORNING/S PACKAGE.

RIDGE REBUILDS OVER THE WEST LATE IN THE WEEK BRINGING A RETURN
OF DRY WEATHER. TEMPERATURES WILL REMAIN ABOVE SEASONAL NORMS
THROUGH THE PERIOD WITH THE WARMEST READINGS ON FRIDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 419 AM MST SAT JAN 31 2015

MOISTURE SURGING NORTHWARD AHEAD OF A LOW CENTERED OVER LAS VEGAS
WILL CONTINUE TO BRING WIDESPREAD PRECIPITATION TO THE AREA...
ESPECIALLY BEFORE NOON. FOG...RAIN...AND SNOW WILL KEEP MOUNTAINS
OBSCURED AND TAF SITES IN IFR/LIFR CONDITIONS DURING THE EARLY
PART OF THE DAY.

EXPECT PRECIPITATION WILL BECOME MORE SCATTERED IN NATURE FOR ALL
BUT THE SOUTHERN AND CENTRAL MOUNTAINS AS THE STORM CENTER DROPS
SOUTHWARD INTO MEXICO LATER TODAY. DRIER AIR FILTERS INTO THE
REGION FROM THE NORTHWEST TONIGHT ENDING ALL BUT ISOLATED SHOWERS
OVER THE COLORADO DIVIDE MOUNTAINS LATE TONIGHT. HOWEVER...LOW
LEVEL MOISTURE AND NIGHTTIME COOLING IS EXPECTED TO BRING FOG TO
MOST VALLEYS DURING THE LATTER PART OF THE NIGHT. CONSEQUENTLY...
THERE IS A STRONG POSSIBILITY THAT TAF SITES WILL EXPERIENCE
PERIODS OF MVFR/IFR CIGS AND VSBY FROM 05Z TO 12Z SUNDAY.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...DENSE FOG ADVISORY UNTIL 10 AM MST THIS MORNING FOR COZ001-002-
     006>008-011-020.

     WINTER WEATHER ADVISORY UNTIL 8 PM MST THIS EVENING FOR
     COZ017>019.

     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR COZ021>023.

UT...DENSE FOG ADVISORY UNTIL 10 AM MST THIS MORNING FOR UTZ024-027.

     WINTER WEATHER ADVISORY UNTIL 8 PM MST THIS EVENING FOR UTZ028.

&&

$$

SHORT TERM...EH
LONG TERM...NL
AVIATION...NL


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