Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 012246
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
336 PM MST SUN MAR 1 2015

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 336 PM MST SUN MAR 1 2015

H5 UPPER AIR HAND ANALYSIS AT 12Z HAD THE POSITIVELY TILTED
WESTERN LOW CENTERED OVER THE SOUTHERN SAN JOAQUIN VALLEY.
LIGHTNING BEING SEEN IN THE LOW THIS AFTERNOON BUT SO FAR NONE IN
THE SOUTHWEST. HOWEVER THE INSTABILITY IS THERE AND APPARENT ON
RADAR AND SATELLITE IMAGERY. ANOTHER IMPORTANT FEATURE IS THE
KICKER WAVE DROPPING DOWN THE WESTERN BRITISH COLUMBIA COASTLINE
THIS AFTERNOON. DERIVED GOES IMAGERY SHOWS SOME INTERESTING BLOBS
OF ANOMALOUSLY HIGH PRECIPITABLE WATER OVER NORTHERN NEW MEXICO
AND OVER CENTRAL UTAH. THIS IS WHERE PWATS ARE 180 TO 250 PERCENT
SOGGIER THAN NORMAL. FEEDING ACROSS THE CENTRAL BAJA IS THE SUB-
TROPICAL TAP...WHICH AGAIN THE 295K-300K THETA SURFACES HAVE SHOWN
BEING TRANSPORTED INTO THIS SYSTEM. AS SUCH SURFACE DEW POINTS
HAVE RISEN ABOVE THE 32 DEGREE MARK OVER MANY OF THE SOUTHERN
VALLEYS. THIS IS NOT GOOD FOR MAKING SNOW STICK IF IT MAKES IT TO
THE GROUND...WHICH LOW LEVEL PROFILES SHOW IS UNLIKELY. AS SUCH
RAIN HAS BECOME THE PREDOMINANT PTYPE AND COULD NOT JUSTIFY THE
LONG TERM WARNING. AREAS ABOVE 7500 FEET WILL REMAIN SNOW BUT FOR
THE MOST PART ACCUMULATIONS...EXCEPT AT THE HIGHEST ELEVATIONS AND
UNDER CONVECTIVE BANDS...HAS BEEN LIGHT WITH SNOW TO LIQUID RATIOS
PROBABLY PUSHING ABOVE CLIMO OF 13:1.

THE `KICKER WAVE` BEGINS TO INTERACT WITH THE WESTERN LOW AFTER
MIDNIGHT...AND EVENTUALLY REPLACES IT BY MONDAY EVENING. THIS
INTERACTION CREATES A STRENGTHENING THERMAL GRADIENT OVER OUR REGION
TONIGHT AS THE UPPER LOW BEGINS TO DEFORM...WHICH IN RESPONSE
INDUCES A MID LEVEL JET ACROSS THE FOUR CORNERS REGION. THIS JET IN
TURN WILL PUSH A LOW LEVEL WARM FRONT FEATURE INTO THE NORTHERN CWA
VALLEYS BY SUNRISE. THIS FRONT ALONG WITH STRONG UPGLIDE WILL FOCUS
THE HEAVIER PRECIPITATION OVER OUR CENTRAL AND NORTHERN
TERRAIN..WITH SNOW LIKELY RETURNING TO THE UPPER PORTION OF THE
I-70 CORRIDOR TO VAIL PASS. FARTHER SOUTH THE DENDRITIC LAYER
WILL BE DISRUPTED BY THIS JET AND THIS SHOULD PRODUCE A GENERAL
LULL WITH JUST THE OCCASIONAL PASSING SHOWER. HEAVY SNOW IN THESE
SHOWERS NOT OUT OF QUESTION BUT WHEN AND WHERE TO HARD TO
PREDICT...SO JUST A DOWNTREND IN POPS/QPF/SNOW IN PLACE FOR NOW IN
THE LOW ELEVATIONS. GENERAL MOIST SOUTHERLY FLOW SHOULD KEEP SNOW
GOING OVER THE HIGHEST TERRAIN WITH AMOUNTS IN THE 4-8 INCH RANGE
AT PASS LEVEL. HIGHER AMOUNTS UP TOP AND LOWER AT MOUNTAIN BASES.
MILD NIGHT IN STORE WITH CLOUD AND WARM FRONT LIFTING THROUGH.

MONDAY AND MONDAY NIGHT...THE TROUGH IS EXPECTED TO SHIFT EASTWARD
ACROSS THE GREAT BASIN MONDAY. A COLD FRONT DRIVEN BY THE TROUGH
WILL PUSH INTO EASTERN UTAH LATE IN THE MORNING...ACROSS WESTERN
COLORADO DURING THE AFTERNOON...THEN EAST OF THE CONTINENTAL
DIVIDE MONDAY EVENING. WARM AIR AHEAD OF THE FRONT (7H TEMPS OF -2
TO -3 DEGS IN THE MORNING AND NEAR 0 DEGS DURING THE AFTERNOON)
WILL KEEP SNOW LEVELS ELEVATED ACROSS THE SOUTH SO WILL NOT
INCLUDE HILITES FOR ELEVATIONS BELOW ROUGHLY 7000 FEET ON MONDAY.
IN CONTRAST...MOISTURE OVERRUNNING A WARM FRONT SHOULD BRING
PERSISTENT SNOWFALL TO THE LOWER ELEVATIONS OF NORTHWEST COLORADO.
MEANWHILE...DEEP MOISTURE (7H SPECIFIC HUMIDITY OF 4 TO 4.3 G/KG)
WILL CONTINUE TO GENERATE HEAVY SNOW OVER THE HIGHER ELEVATIONS
DUE TO BOTH OROGRAPHIC AND DYNAMIC LIFT. BANDS OF HEAVY SNOW ARE
LIKELY ALONG THE COLD FRONT AS IT MOVES THROUGH THE AREA. STRONG
WINDS ALOFT WILL RESULT IN AREAS OF SNOW AND BLOWING SNOW OVER THE
HIGHER TERRAIN.

WINDS SHIFT TO THE WEST WITH TROFPA MONDAY NIGHT AND SNOW LEVELS
WILL LOWER AS 7H TEMPERATURES DECREASE IN ITS WAKE. MODELS SUGGEST
A DECREASE IN SNOWFALL RATES ACROSS WESTERN COLORADO WITH A LULL
IN ACTIVITY POSSIBLE OVER EASTERN UTAH. GUIDANCE NUMBERS FOR MONDAY
AFTERNOON HIGHS CAME IN PRETTY MILD SO BOOSTED HIGHS A BIT. CLOUDS
AND WIND WILL MODERATE LOWS MONDAY NIGHT WHICH APPEARED WELL
REPRESENTED IN PREVIOUS FORECAST.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 336 PM MST SUN MAR 1 2015

A SECONDARY TROUGH ROLLS ACROSS THE REGION TUESDAY DRIVING ANOTHER
COLD FRONT...THIS ONE MUCH COLDER THAN THE FIRST...NORTH TO SOUTH
ACROSS THE AREA. 7H TEMPS AS LOW AS -20 DEG C WERE INDICATED BY
MODELS ACROSS THE NORTH BY MIDNIGHT TUESDAY. DYNAMIC AND OROGRAPHIC
LIFT COMBINED WITH STEEP LAPSE RATES WILL CAUSE SNOWFALL TO
INCREASE IN BOTH AREAL COVERAGE AND INTENSITY. CONSEQUENTLY...
APPEARS REASONABLE TO CONTINUE HILITES ACROSS WESTERN COLORADO
THROUGH TUESDAY AFTERNOON. MODELS A BIT DIVIDED ON HOW LONG SNOW
WILL CONTINUE INTO TUESDAY NIGHT ACROSS NORTHERN COLORADO SO WILL
NOT MAKE ANY CHANGES TO HILITES FOR THAT AREA AT THIS TIME. BEFORE
THIS IS ALL OVER...STILL LOOKING AT FEET OF SNOW FOR A NUMBER OF
MOUNTAIN AREAS THROUGHOUT EASTERN UTAH AND WESTERN COLORADO.

RESIDUAL MOISTURE WILL FUEL LINGERING SNOW SHOWERS ALONG THE
DIVIDE WEDNESDAY WITH SNOW FINALLY ENDING WEDNESDAY NIGHT.
THEREAFTER FOLLOWS A PERIOD OF DRY NORTHWEST FLOW WHICH SHOULD
LAST UNTIL SATURDAY AFTERNOON. EC AND GFS DIFFER WITH ENERGY
ASSOCIATED WITH A SHORTWAVE DROPPING OUT OF THE NORTHWEST SATURDAY
AFTERNOON WITH MORE AMPLIFIED EC GENERATING SNOWFALL ACROSS MUCH
OF THE NORTH AND DIVIDE MOUNTAINS FROM THROUGH SATURDAY NIGHT. THE
GFS...ON THE OTHER HAND...INDICATED A MUCH WEAKER SYSTEM PROVIDING
ONLY A GLANCING BLOW TO THE DIVIDE MOUNTAINS DURING THIS PERIOD.
BOTH INDICATED A DRY SUNDAY HOWEVER.

EXPECT UNSEASONABLY COOL TEMPERATURES TO SLOWLY MODERATE TOWARD
NEAR NORMAL LEVELS BY THE WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1042 AM MST SUN MAR 1 2015

WIDESPREAD LOW CLOUDS AND PRECIP WILL CONTINUE TODAY ACROSS THE
ENTIRE AREA. FLIGHT CONDITIONS WILL FLUCTUATE FROM VFR TO BELOW
IFR AS BANDS SET UP. THIS WILL OCCUR THROUGH THE DAY AND INTO THE
OVERNIGHT. CONDITIONS WILL CHANGE RAPIDLY THROUGH THE DAY FOR ALL
TAF SITES.  AFTER 06Z THIS EVENING IFR CIGS AND VSBYS IN SNOWFALL
AND FOG WILL PREVAIL AT KEGE...KASE...KTEX...KDRO...WITH OCNL MVFR
AT ALL OTHER AIRPORTS. MOUNTAINS WILL BE OBSCURED THE NEXT 24
HOURS.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER STORM WARNING UNTIL 5 PM MST TUESDAY FOR COZ009-010-012-
     017>019.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 9 AM MST WEDNESDAY
     FOR COZ004-005.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 5 PM MST TUESDAY
     FOR COZ001-002.

     WINTER WEATHER ADVISORY UNTIL 5 PM MST TUESDAY FOR COZ014.

     WINTER STORM WARNING UNTIL 9 AM MST WEDNESDAY FOR COZ003-013.

     WINTER WEATHER ADVISORY UNTIL 8 AM MST MONDAY FOR COZ008.

     WINTER STORM WARNING UNTIL MIDNIGHT MST MONDAY NIGHT FOR COZ023.

UT...WINTER STORM WARNING UNTIL 5 PM MST TUESDAY FOR UTZ025-028.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 5 PM MST TUESDAY
     FOR UTZ023.

&&

$$

SHORT TERM...15/NL
LONG TERM...NL
AVIATION...TGR


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