Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 231750
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1150 AM MDT THU APR 23 2015

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 301 AM MDT THU APR 23 2015

A PAIR OF LOW CIRCULATIONS TO THE SOUTHEAST...THE FIRST OVER
SOUTHERN CALIFORNIA AND THE OTHER OFF THE COAST OVER THE EASTERN
PACIFIC...WILL MERGE EARLY IN THE DAY. THIS EFFECTIVELY SLOWS ANY
EASTWARD PROGRESS OF THE MERGING SYSTEMS TODAY. AS A RESULT...
DRIER AIR MENTIONED IN THE PREVIOUS DISCUSSION WILL CONTINUE TO
FILTER INTO THE AREA CAUSING PRECIPITABLE WATER (PW) TO DIP TO
BETWEEN 0.25 AND 0.30 INCHES. CONSEQUENTLY...EXPECT SHOWER AND
THUNDERSTORM COVERAGE WILL BE REDUCED WITH MOUNTAINS FAVORED.
VALLEYS MAY SEE SOME SPRINKLES AND OUTFLOW WINDS TO 30 MPH.

DIURNAL COOLING WILL BRING ABOUT AN END TO MOIST CONVECTION THOUGH
A FEW SHOWERS MAY LINGER OVER THE AREA IN RESPONSE TO A WEAK
SHORTWAVE PASSING OVERHEAD DURING THE NIGHT. MEANWHILE...THE
CALIFORNIA LOW WILL OPEN AND PHASE WITH THIS FEATURE PASSING WELL
SOUTH OF THE FORECAST AREA.

IT APPEARS FRIDAY WILL BE MORE ACTIVE AS AN ENERGETIC SHORTWAVE
TROUGH SWEEPS ACROSS THE GREAT BASIN. MOISTURE LEVELS INCREASE
AHEAD OF THIS SYSTEM WITH PW VALUES RISING TO BETWEEN 0.35 AND
0.40 INCHES. DAYTIME HEATING COMBINED WITH JET LEVEL DIVERGENCE
WILL BRING INCREASED SHOWER AND THUNDERSTORM COVERAGE. 7H FLOW
INCREASES AS THE HEIGHT GRADIENT TIGHTENS AHEAD OF THE
APPROACHING TROUGH SO OUTFLOW WINDS SHOULD BE A BIT STRONGER THAN
TODAY.

TEMPERATURES RISE SEVERAL DEGREES ABOVE NORMAL THIS AFTERNOON WITH
INCREASED SUNSHINE AS COMPARED TO YESTERDAY WHILE OVERNIGHT LOWS
DIP TO NEAR NORMAL. INCREASED CLOUDS AND SHOWERS WILL COOL IT DOWN
A BIT FRIDAY THOUGH HIGHS WON/T BE FAR FROM NORMAL.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 301 AM MDT THU APR 23 2015

PIECES OF ENERGY WILL KEEP PRECIPITATION IN THE PICTURE FRIDAY
NIGHT THROUGH NOON SATURDAY BEFORE THE NEXT STORM MOVES IN. QPF
WILL BE GENERALLY LIGHT WITH MORE SHOWERY TYPE RAIN/STORMS THAN A
PROLONGED SOAKING RAIN. HOWEVER...THE NEXT COLD FRONT LOOKS TO
CHANGE ALL THAT.

WIDESPREAD PRECIP WILL OVERSPREAD THE AREA SATURDAY EVENING AS AN
UPPER LEVEL TROUGH ORIGINATING FROM THE PACNW CLOSES OFF AN UPPER
LEVEL LOW. PREVIOUS MODEL RUNS HAD THE LOW CLOSING OFF SOONER BUT
THE END RESULT IS THE SAME...PRECIP. AS MENTIONED IN THE PREVIOUS
AFD...PWATS CONTINUE TO RANGE IN THE .5 TO .6 INCH RANGE WHICH IS
HIGHER THAN USUAL FOR THIS TIME OF YEAR. EXAMINATION OF THE H3
LEVEL SHOWS PLENTY OF ASSOD DIVERGENCE ALOFT WHICH WILL ALSO AID
IN LARGE SCALE ASCENT EVEN WITHOUT ANY APPRECIABLE JET STREAM
SUPPORT. HEAVIEST PRECIP AMTS LOOK TO FALL LATE SATURDAY NIGHT
THROUGH MONDAY MORNING AS THE CLOSED LOW MOVES DIRECTLY OVER THE
CWA. OF COURSE...ANY DEVIATIONS FROM THIS COURSE WILL CHANGE QPF
AND EXPECTED WX...MAYBE DRAMATICALLY IF MODELS START CHANGING
THEIR TUNE. DESPITE POSSIBLE DEVIATIONS IN LATER MODEL
RUNS...CONFIDENCE REMAINS HIGH THAT A STORMY AND WET WEEKEND IS IN
STORE.

ONE THING NOT TOUCHED ON IS SNOWFALL. H7 TEMPS (NEAR 10,000 FEET) LOOK
TO DROP TO OR BELOW FREEZING SUNDAY MORNING...RIGHT IN THE MIDDLE
OF THE EXPECTED HEAVIEST PRECIP. SIGNIFICANT ACCUMULATING SNOW IS
CERTAINLY POSSIBLE IN THIS SCENARIO WITH 6 INCHES TO MAYBE EVEN A
FOOT IN THE REALM OF POSSIBILITY. SAN JUANS ARE CURRENTLY FAVORED
FOR THE HEAVIER SNOW THOUGH THE CENTRAL AND NORTHERN MTNS WILL
LIKELY SEE SOME SNOW TOO. WITH LATE SEASON SNOWFALL CRITERIA NOW
IN PLACE...WINTER HIGHLIGHTS LOOK MORE AND MORE LIKELY.

PRECIP WILL END MONDAY MORNING EXCEPT FOR THE DIVIDE WHICH WILL
SEE SOME RESIDUAL SNOW/RAIN. AFTER THAT...HIGH PRESSURE BUILDS IN
BRINGING A RETURN TO MORE SPRING-LIKE CONDITIONS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1150 AM MDT THU APR 23 2015

SCATTERED -SHRA WITH A FEW -TSRA WILL FIRE OVER THE HIGH TERRAIN
AND TRACK TOWARD THE NORTHEAST AT A RATE OF 10-15KTS. THE REGION
EAST OF A LINE FROM K20V-KASE-KTEX WILL BE THE REGION OF HIGHEST
SHOWERS AND THUNDERSTORM POTENTIAL FROM 18Z-02Z TODAY. OUTFLOW
WINDS TO 30-35KTS WILL BE POSSIBLE FROM NEARBY -SHRA/-TSRA TODAY.

VFR IS EXPECTED TO PREVAIL AT ALL TAF SITES...ALTHOUGH PASSING
STORMS WILL LOWER CIGS TO BELOW ILS BREAKPOINTS AT KASE/KEGE/KRIL.

DISSIPATING -SHRA IS EXPECTED AFTER 02Z...BUT SHORT WAVE ENERGY
WILL BE APPROACHING THE FOUR CORNERS REGION OVERNIGHT. THIS
SHORT WAVE COULD TRIGGER ISOLATED -SHRA AROUND KDRO/KTEX AFTER
09Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&

$$

SHORT TERM...NL
LONG TERM...TGR
AVIATION...PF



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