Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 280332
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
932 PM MDT SAT SEP 27 2014

.UPDATE...
ISSUED AT 919 PM MDT SAT SEP 27 2014

A FEW MINOR ADJUSTMENTS TO THE GRIDS FOR WINDS AND DEW POINTS. NO
OTHER CHANGES PLANNED. THUNDERSTORMS CONTINUE TO ROTATE NORTH OVER
WESTERN COLORADO BUT THE WEAK CONVECTION ON THE EASTERN EDGE OF
THE CLOUD SHIELD OVER THE PARK AND GORE RANGES AND THE UPPER
ARKANSAS VALLEY HAS DIMINISHED. WILL HANG ON TO SLIGHT CHANCES FOR
SHOWER DEVELOPMENT IN THOSE AREAS OVERNIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 317 PM MDT SAT SEP 27 2014

LATE AFTERNOON AND EVENING SHOWERS THIS EVENING OVER THE
MOUNTAINS WILL HAVE A NORTHWEST STORM MOTION AS LIGHT SOUTHERLY
FLOW ALOFT CONTINUES. MOSTLY CLEAR AND MILD CONDITIONS WILL
PREVAIL ACROSS THE PLAINS. CHANGES BEGIN HAPPENING TOMORROW AS THE
UPPER LOW OVER CALIFORNIA CONTINUES A SLOW EASTWARD TRACK AND THE
MOIST SOUTHERLY FLOW OVER UTAH THIS AFTERNOON SHIFTS OVER WESTERN
COLORADO. SHOWER ACTIVITY IS EXPECTED TO BEGIN IN THE MOUNTAINS
FIRST AND THEN SHIFT TO THE ADJACENT PLAINS LATE IN THE AFTERNOON
OR EVENING. INCREASING CLOUD COVER THROUGH THE DAY WILL HELP TO
HOLD TEMPERATURES DOWN...BUT WITH THE SURFACE LOW REMAINING IN THE
DENVER VICINITY...NO FRONTAL PASSAGE IS EXPECTED. MOISTURE LEVELS
WILL BE HIGH FOR LATE IN SEPTEMBER...SO PERIODS OF HEAVY RAIN WILL
BE POSSIBLE...BUT PRIMARILY ON THE SOUTH FACING SLOPES. WILL NOT
ISSUE ANY HIGHLIGHT AT THIS TIME.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 317 PM MDT SAT SEP 27 2014

SCATTERED RAIN SHOWERS AND THUNDERSTORMS WILL CONTINUE SUNDAY
NIGHT AS THE UPPER LOW MOVES INTO UTAH. SNOW LEVELS WILL BE
LOWERING TO ABOUT 11 THOUSAND.  THE UPPER LOW WILL BECOME
NEGATIVELY TILTED MONDAY WITH THE UPPER LEVEL SPEED MAX MOVING
INTO SOUTHERN CO...PUTTING THE LEFT EXIT REGION OVER NORTHEASTERN
CO. SOME OF THE MOISTURE MOVING OVER THE STATE WILL HAVE
CONNECTION TO TROPICAL STORM RACHEL. PRECIPITABLE WATER VALUES ARE
EXPECTED TO REACH NEAR 1.3 INCHES OVER THE EASTERN PLAINS. WITH
THE COOLER AIR MOVING ALOFT ENHANCING INSTABILITY AND GOOD
SHEAR...THE POTENTIAL IS THERE FOR SEVERE WEATHER MONDAY AFTERNOON
AND INTO THE NIGHT. LARGE HAIL...STRONG OUTFLOW WINDS AND SOME
TORNADOES WILL BE POSSIBLE IN THE SYNOPTIC SET UP...MAINLY OVER
THE EASTERN PLAINS EAST OF THE METRO AREAS. CAPE VALUES ARE
CURRENTLY PROGGED TO BE AROUND 1000 J/KG NEAR THE NORTH AND
EASTERN STATE BORDERS...MAY NEED TO KEEP AN EYE ON CLOUD COVER
THAT WILL LIMIT CAPE. OVERALL THE GFS AND GEM MODELS ARE THE
FASTER SOLUTIONS AND THE ECMWF AND NAM HAVE BEEN SLOWER. HAVE
TRENDED SLIGHTLY MORE TOWARD THE FASTER GFS SOLUTION BUT STILL DID
MORE OF A BLEND. THERES ALSO BEEN A SLIGHT SHIFT NORTH WITH THE
SYSTEM...THIS WOULD PUT THE STRONGER AND WETTER WEATHER JUST OUT
OF THE STATE INTO NE AND KS. EXPECT STRONG SOUTHERLY WINDS AHEAD
OF THE MAIN COLD FRONT...EXPECTED TO MOVE IN DURING THE
AFTERNOON. COOLER AIR WILL MOVE IN FROM THE WEST WITH SNOW LEVELS
DROPPING TO NEAR 9 THOUSAND FEET MSL. CLOUD COVER AND THE COLD
FRONT SHOULD LIMIT HEATING...THEREFORE EXPECTING HIGH TEMPS TO BE
ABOUT 10 DEGREES COOLER THAN SUNDAY. AS THE SYSTEM PUSHES EAST AND
DOWNWARD QG MOVES IN...PRECIP AND WEATHER WILL DECREASE WITH WEST
WINDS INCREASING OVER THE MOUNTAINS.

THERE WILL BE A BREAK IN WEATHER TUESDAY AS VERY BRIEF RIDGING
MOVES OVERHEAD. BUT EXPECT SIMILAR OR SLIGHTLY COOLER
TEMPERATURES. THEN THE NEXT SYSTEM WILL DROP FROM THE PACIFIC
NORTHWEST TO BRING ANOTHER CHANCE FOR SHOWERS AND THUNDERSTORMS
FOR THE AREA...WITH EVEN COOLER TEMPERATURES MOVING IN. NORTHWEST
FLOW ALOFT FOLLOWING THE SECOND TROUGH WILL KEEP NE COLORADO
DRY AND COOLER THAN NORMAL THROUGH FRIDAY BEFORE A RIDGE TO THE
WEST STARTS PUSHING EAST TO WARM IT BACK UP.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 919 PM MDT SAT SEP 27 2014

VFR THROUGH SUNDAY WITH A SLIGHT CHANCE OF LATE AFTERNOON SHOWERS
AND THUNDERSTORMS. SOME UNCERTAINTY ON WINDS LATER TONIGHT AND
SUNDAY MORNING AS A DENVER CYCLONE WILL LIKELY DEVELOP THAT WOULD
PRODUCE WEST TO NORTHWEST WINDS AT KBJC AND COULD PUSH NORTHWEST
WINDS INTO KDEN/KAPA TOWARD MORNING. WINDS WOULD LIKELY SHIFT BACK
TO SOUTHEAST AT KDEN/KAPA DURING THE DAY SUNDAY.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GIMMESTAD
SHORT TERM...DANKERS
LONG TERM...KRIEDERMAN
AVIATION...GIMMESTAD


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