Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 231150
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
550 AM MDT SAT MAY 23 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 355 AM MDT SAT MAY 23 2015

A RATHER WET WEEKEND IS IN STORM FOR MUCH OF THE AREA. AS
HAPPENED FRIDAY THE CLOSED LOW APPROACHING FROM THE SW WILL
CONTINUE ITS SLOW MOVEMENT. A FEW SIGNIFICANT VORT LOBES WILL
ROTATE AROUND THE LOW CENTER AND BE THE MAIN FOCUS FOR STRONGER
CONVECTIVE DEVELOPMENT. FCST SOUNDINGS SHOW SOME MID-LEVEL
WARMING LAST NIGHT AND TODAY...AND THIS DECREASES THE PROJECTED
CAPE FROM THE 600+ J/KG ON YESTERDAY`S 00Z SOUNDING TO A
PROJECTED CAPE OF ABOUT 430 J/KG LATE THIS AFTERNOON. SO THE
ENVIRONMENT WILL NOT BE QUITE AS CONDUCIVE TO DEEP CONVECTION AS
ON FRIDAY.

STILL...THE PVA ASSOCIATED WITH THOSE VORT MAXES SHOULD CARRY
ENOUGH LIFT TO HELP GENERATE BETTER THAN GARDEN VARIETY
THUNDERSTORMS THIS AFTERNOON AND EVENING. THE FIRST VORT MAX SHOWS
ITSELF IN THE MODELS WITH INCREASING PRECIP OVER THE EASTERN
PORTION OF THE SAN JUAN MTS WHICH ROTATES NORTH AND OVER
KGUC...KASE TO KSBS THRU EARLY AFTERNOON. THE NEXT LOBE APPEARS
MORE DISTINCT. AS THE MAIN LOW CENTER REACHES THE CO/UT BORDER
THIS AFTERNOON...THIS DISTURBANCE MOVES THROUGH THE BASE OF THE
LOW OVER THE FOUR CORNERS AND INTO THE SAN JUAN MTS FROM MID-
AFTERNOON THROUGH THE EVENING.

AS THE LOW CENTER MOVES THROUGH SW CO LATE TONIGHT AN EVEN
STRONGER TROUGH DIVES DOWN ITS WESTERN SIDE AND HELPS KICK THE
MAIN LOW NE INTO EASTERN WY BY SUNRISE SUNDAY. THE CWA FINALLY IS
UNDER THE WESTERN HALF OF THE STORM WITH WINDS ALOFT SHIFTING TO
THE NW SUNDAY MORNING...AS THE MAIN TROUGH CONTINUES TO DRAG
THROUGH THE AREA THROUGHOUT THE DAY...WHICH KEEP BROAD AREAS OF
PRECIP OVER THE CWA AND MOVING WITH IT.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 355 AM MDT SAT MAY 23 2015

WRAPAROUND MOISTURE ON THE BACK SIDE OF CLOSED LOW WILL CONTINUE TO
BRING ADDITIONAL SHOWERS/STORMS SUNDAY NIGHT INTO MEMORIAL DAY.
ASSOCIATED WITH THE MOISTURE WILL BE AN EMBEDDED DISTURBANCE THAT
ENHANCES THE CONVECTIVE SHOWERS. THE WET BULB ZERO LINE AND THE
700 MB TEMP SUGGEST THIS LEADS TO SNOW FOR THE MOUNTAIN PASSES
OVER THE PARK/GORE RANGES TOWARD MONARCH PASS. SOME OF THE SNOW
WILL BE MELTING AS IT FALLS...SO FORECASTING AMOUNTS WILL BE
CHALLENGING. POTENTIAL IMPACTS INCLUDE SLUSH OR SNOW COVERED
ROADS ABOVE 9K FEET.

A FLAT RIDGE MOVES ACROSS THE CENTRAL ROCKIES ON TUESDAY AHEAD OF
ANOTHER TROUGH OVER THE WEST COAST STATES. AREAL COVERAGE OF
SHOWERS/STORMS WILL BE LESS PROMINENT AND MAINLY TERRAIN DRIVEN.
THE WEST COAST TROUGH SLOWLY APPROACHES THE ROCKY MOUNTAIN STATES
AND COULD BE OVER COLORADO BY NEXT FRIDAY. UNLIKE PREVIOUS
TROUGH THAT ADVECTED MOISTURE INTO COLORADO...THE MEDIUM RANGE
MODELS SEEM TO AGREE THAT THE DRY SLOT WILL BE POSITIONED OVER UTAH
AND WRN COLORADO. CONVECTIVE POTENTIAL WOULD BE LOWER WITH LESS
SHOWER ACTIVITY IF THIS DOES VERIFY. NOT FULLY CONFIDENT IN THIS
SOLUTION...BUT THE PATTERN DOES HAVE A DISORGANIZED APPEARANCE AND
DYNAMICAL LIFT FROM ANY "FEATURE" WILL BE WEAK. WITH RESPECT TO
TEMPS...WARMING TREND IS EXPECTED WITH VALUES RETURNING TO NEAR
NORMAL FOR LATE MAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 550 AM MDT SAT MAY 23 2015

WITH THE UPPER LEVEL SYSTEM DIRECTLY OVER WRN COLORADO
TODAY...NUMEROUS SHOWERS/STORMS WILL EXIST. PASSING SHOWERS/STORMS
WILL LOWER CIGS TO BELOW ILS BREAKPOINTS FOR THE MOUNTAIN SKI
COUNTRY TAF SITES. IN ADDITION...LOCALIZED AND BRIEF +TSRA COULD
LOWER VIS INTO THE 3-5SM RANGE. MOUNTAIN TOPS WILL BE OBSCURED AT
TIMES. SHOWERS/STORMS WILL DECREASE IN AREAL COVERAGE AFTER
03Z...BUT EXPECT SCATTERED COVERAGE TO PERSIST.

&&

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

$$

SHORT TERM...CC
LONG TERM...PF
AVIATION...PF


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