Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 211048
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
448 AM MDT SUN SEP 21 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 448 AM MDT SUN SEP 21 2014

A LARGE AREA OF LIFT IS DEVELOPING FROM SOUTHERN COLORADO ACROSS
UTAH AND NEVADA AHEAD OF THE CALIFORNIA TROUGH. THE UPPER RIDGE IS
SHIFTING VERY SLOWLY EASTWARD...WITH SOUTHERLY FLOW ALOFT
DEVELOPING OVER WESTERN COLORADO. MEANWHILE EAST TO SOUTHEAST
WINDS HAVE DEVELOPED AS WE COME UNDER THE INFLUENCE OF PRESSURE
FALLS TO THE WEST. THIS HAS BROUGHT DRIER AIR INTO NORTHEASTERN
COLORADO FOR THE TIME BEING.

THIS PATTERN WILL SHIFT VERY SLOWLY EASTWARD TODAY...WITH LIFT
INCREASING OVER THE MOUNTAINS AND EVENTUALLY EAST CENTRAL
COLORADO. THE LOW LEVEL MOISTURE BOUNDARY WILL PROBABLY NOT MOVE
MUCH THIS MORNING...BUT WINDS SHOULD GET A MORE SOUTHERLY
COMPONENT THIS AFTERNOON AND START TO ADVECT THE LOW LEVEL
MOISTURE BACK IN...AT LEAST NEAR THE FRONT RANGE. SOME VARIETY OF
DENVER CYCLONE CIRCULATION WILL EXIST...PROVIDING SOME CONVERGENCE
IN THIS AREA AS WELL. INSTABILITY WILL BE LIMITED TO THE MOUNTAINS
WITH CAPE VALUES BELOW 500 J/KG. PLAINS WILL BE TOO COOL AND DRY
FOR SURFACE BASED CONVECTION...THOUGH ELEVATED SHOWERS ON THE EDGE
OF THE AREA OF LIFT SHOULD OCCASIONALLY DRIFT OVER THE PALMER
DIVIDE REGION AND EVENTUALLY THE DENVER AREA. KEEPING THE HIGHER POPS
NEAR THE MOUNTAINS STILL LOOKS GOOD...I TOOK THE MENTION OF
THUNDER OUT FOR THE NORTHEAST PLAINS TODAY.

THIS EVENING THE LIFT WILL CONTINUE TO SHIFT EASTWARD WHILE THE
LOW LEVEL MOISTURE RETURNS FROM THE SOUTH. THIS SHOULD BE MORE
FAVORABLE FOR SHOWER DEVELOPMENT...HOWEVER BY THIS TIME THERE WILL
BE STRONG SOUTHERLY FLOW AT LOW LEVELS VEERING TO MORE OF A
SOUTHWEST FLOW AT MID LEVELS AS THE RIDGE AXIS CONTINUES TO MOVE
EAST. THIS WILL BRING SOME DOWNSLOPE DRYING AT LOW LEVELS THAT
COULD OFFSET THIS PERIOD OF BETTER LIFT. THERE MAY BE A SWEET SPOT
IN THE LATE AFTERNOON OR EVENING WHERE THE SHOWERS DO WELL...BUT
THE DRYING WILL LIKELY BE WINNING BY LATER IN THE NIGHT.

ALL THIS APPEARS TO BE PRETTY WELL COVERED...I MADE SOME MINOR
TIMING ADJUSTMENTS IN ADDITION TO LIMITING THE THUNDERSTORM
COVERAGE AND INCREASING THE WINDS TONIGHT A BIT. THE STRONG LOW
LEVEL FLOW WITH LIGHT WINDS ALOFT DOES CREATE AN ENVIRONMENT THAT
COULD FAVOR TRAINING/BACKBUILDING CELLS ALONG THE FOOTHILLS OR
DOWNSTREAM FROM CONVERGENCE AREAS LIKE THE DENVER CYCLONE BOUNDARY
OR THE MOSQUITO RANGE. WITH PRECIPITABLE WATER AROUND AN
INCH...LITTLE OR NO WARM CLOUD DEPTH AND CAPE...AND FAST CELL
MOTIONS...IT SEEMS LIKE THE FLOOD THREAT IS LOW...WITH TRAINING
OVER THE BURN AREAS THE MAIN POSSIBILITY. HEAVY RAIN POTENTIAL IS
THERE BUT MOST LIKELY IN THE FAVORED MOUNTAIN AREAS WHERE
CAPE/MOISTURE WILL BE BEST...I.E. SOUTH PARK AND THE SURROUNDING
MOUNTAINS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 448 AM MDT SUN SEP 21 2014

A WEAK UPPER TROUGH IS EXPECTED TO MOVE EASTWARD ACROSS COLORADO
MONDAY INTO MONDAY NIGHT. ON TUESDAY AND TUESDAY NIGHT AND UPPER
RIDGE MOVES IN FROM THE WEST. ZONAL FLOW ALOFT IS PROGGED MONDAY
AND MONDAY EVENING...WITH WEAK WEST-NORTHWESTERLY FLOW ALOFT AT
12Z TUESDAY MORNING. THE FLOW ALOFT IS PROGGED TO BE
NORTHWESTERLY...THEN NORTHERLY...EVEN NORTH-NORTHEASTERLY THE
REST OF TUESDAY AND TUESDAY NIGHT. UPWARD QG MOTION IS PROGGED
MONDAY AND MONDAY EVENING...THEN WEAK DOWNWARD MOTION IS PROGGED
TUESDAY AND TUESDAY NIGHT. THE LOW LEVEL WINDS SHOULD FOLLOW
NORMAL DIURNAL PATTERNS ON MONDAY. BY MONDAY OVERNIGHT...
DOWNSLOPING IS PROGGED AFTER THE UPPER TROUGH PASSAGE. THIS WILL
CONTINUE TUESDAY INTO TUESDAY NIGHT. MOISTURE IS STILL PROGGED TO
BE PLENTIFUL MONDAY AND MONDAY NIGHT. BUT NOW...TUESDAY`S MOISTURE
PROGS SHOW MORE THAN YESTERDAY`S 00Z MODEL RUNS INDICATED. IT
DOES DRY OUT UNTIL TUESDAY NIGHT. PRECIPITABLE WATER VALUES ARE IN
THE 0.50 TO 1.20 INCH RANGE MONDAY AND MONDAY EVENING...THEN THEY
DECREASE INTO THE 0.30 TO 1.00 INCH RANGE LATER TUESDAY. THE DEW
POINT READINGS ARE PROGGED IN THE 40S F WEST TO 60 F EAST MONDAY
INTO TUESDAY MORNING. DEW POINTS DROP INTO THE 30 F WEST TO 50 F
EAST RANGE BY LATE TUESDAY. THERE IS FAIRLY DECENT CAPE PROGGED
OVER THE EASTERN TWO-THIRDS OF THE CWA LATE DAY MONDAY. THERE IS
VERY LITTLE CAPE PROGGED ON TUESDAY. THE QPF FIELDS SHOW
MEASURABLE RAINFALL FOR THE MOUNTAINS MONDAY THROUGH MONDAY
EVENING. THERE IS MEASURABLE RAINFALL OVER THE REST OF THE CWA
MONDAY AFTERNOON AND EVENING. TUESDAY IS MUCH DRIER WITH JUST A
TAD OF MEASURABLE RAINFALL OVER THE MOUNTAINS IN THE AFTERNOON.
WILL GO WITH 30-60% POPS MONDAY AND MONDAY EVENING...THEN NEARLY
NO POPS UNTIL TUESDAY AFTERNOON. 0-20%S POPS ARE GOOD FOR LATE DAY
TUESDAY. FOR TEMPERATURES...MONDAY`S HIGHS ARE 2-4 C WARMER THAN
TODAY`S HIGHS. TUESDAY`S HIGHS AT UP 1-3 C FROM MONDAY`S. FOR THE
LATER DAYS...WEDNESDAY THROUGH SATURDAY...UPPER RIDGING DOMINATES
WEDNESDAY THROUGH FRIDAY. IT IS DRY WEDNESDAY AND THURSDAY...THEN
MOISTURE SLOWLY INCREASES FRIDAY AFTERNOON INTO SATURDAY NIGHT.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 448 AM MDT SUN SEP 21 2014

VFR CONDITIONS WILL PREVAIL TODAY THOUGH CEILINGS WILL REQUIRE
INSTRUMENT APPROACHES TO KDEN. SCATTERED SHOWERS COULD PRODUCE
AREAS OF MVFR CONDITIONS LATER THIS AFTERNOON AND TONIGHT. THERE
WILL BE A DENVER CYCLONE CIRCULATION TODAY...EXPECT INCREASING
SOUTHERLY WINDS TO PREVAIL AT KDEN/KAPA WITH NORTHERLY WINDS AT
KBJC...BUT THE BOUNDARY MAY MOVE OVER KDEN/KAPA AT TIMES.

&&

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

$$

SHORT TERM...GIMMESTAD
LONG TERM...RJK
AVIATION...GIMMESTAD


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