Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KBOU 282146
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
346 PM MDT SUN SEP 28 2014

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 246 PM MDT SUN SEP 28 2014

MAIN AREA OF SHOWERS AND STORMS IS DEVELOPING ALONG THE FRONT
RANGE LATE THIS AFTERNOON AND WILL CONTINUE TO PUSH NORTHEAST
ACROSS THE AREA THROUGH THE EVENING HOURS. THE MOST WIDESPREAD
ACTIVITY SHOULD OCCUR TOWARD THE NORTHERN PORTIONS OF THE CWA BUT
EVEN FARTHER SOUTH TOWARD LIMON THERE IS A CHANCE THE CAP COULD
BREAK. CAPE IS LIMITED TO ABOUT 800 J/KG OR LESS...SO EVEN IF THE
CAP BREAKS ON THE PLAINS ANY SEVERE THREAT IS RATHER LOW. BIGGEST
THREAT WOULD BE STRONG AND GUSTY OUTFLOW WINDS TO AROUND 50 MPH AS
MID LEVEL FLOW STRENGTHENS. BEHIND THIS MORE ORGANIZED BATCH OF
PRECIP...THERE IS SOME SHORT TERM STABILIZATION BUT STILL CANT
RULE OUT REDEVELOPMENT OF ISOLATED OR SCATTERED SHOWERS/STORMS
INTO THE EVENING. OVERNIGHT...AIRMASS IS EXPECTED TO GRADUALLY
STABILIZE WITH ONLY A FEW SHOWERS/STORMS POSSIBLE NORTHERN BORDER
AREA. ENOUGH CLEARING AND WEAK DENVER CYCLONE COULD BRING SOME
STRATUS/PATCHY FOG DEVELOPMENT LATE TONIGHT.

MONDAY WILL BE A MORE ACTIVE WEATHER DAY WITH POTENTIAL FOR SEVERE
STORMS ON THE PLAINS. STRONG UPPER LEVEL TROUGH WILL BEGIN TO
ADVANCE EAST ACROSS THE NORTHERN/CENTRAL ROCKIES AND BECOME
NEGATIVELY TILTED BY 00Z. LARGE SCALE Q-G LIFT ASSOCIATED WITH
THIS TROUGH WILL MOVE EAST AND NORTHEAST ACROSS THE AREA IN THE
AFTERNOON. AT THE SAME...DAYTIME HEATING WILL ACT TO DESTABILIZE
AIRMASS WITH CAPES EXPECTED TO REACH 1000 J/KG OR MORE OVER THE
EASTERN PLAINS. LOW LEVEL SOUTHERLY FLOW INCREASES SIGNIFICANTLY
OVER THE EASTERN PLAINS AIDING LOW LEVEL WIND SHEAR. 0-1KM
HELICITY INCREASES TO 100-150 M/S2 21Z-00Z AND 0-3KM HELICITY UP
TO 120-200 M/S2. THE STRONG LOW LEVEL WINDS FIELDS AND LOWER LCLS
COMBINED WITH STRONG MID LEVEL WIND SHEAR COULD RESULT IN TORNADO
THREAT ON THE EASTERN PLAINS. AT THIS TIME...MAIN THREAT WOULD BE
ALONG AND EAST OF A LINE FROM ROUGHLY FORT MORGAN TO LIMON...BUT
MODELS TYPICALLY SCOUR MOISTURE TOO FAR AND TOO QUICKLY TO THE
EAST WITH THESE STRONG AND NEGATIVELY TILTED UPPER TROUGHS SO
THAT COULD EVEN BE REFINED A BIT FARTHER WEST. WE WILL CONTINUE TO
MONITOR THIS SEVERE THREAT THROUGH TOMORROW. LOOKS LIKE CAPE AND
PERHAPS ADDITIONAL STRATUS DEVELOPMENT MONDAY MORNING WOULD BE THE
LIMITING FACTORS FOR SEVERE WEATHER DEVELOPMENT. FARTHER
WEST...CAPES ARE LESS THAN 500 J/KG BUT CONSIDERABLE LIFT SHOULD
RESULT IN GOOD SHOWER/STORM COVERAGE BY AFTERNOON.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 246 PM MDT SUN SEP 28 2014

MODELS HAVE A PRETTY DECENT UPPER TROUGH AXIS PUSH ACROSS THE
FORECAST AREA MONDAY EVENING. MAINLY WESTERLY FLOW ALOFT FOLLOWS
THE TROUGH PASSAGE TUESDAY INTO WEDNESDAY. JET LEVEL WIND SPEEDS
GET FAIRLY BRISK ON WEDNESDAY...CLOSE TO 100 KNOTS. A WEAKER UPPER
TROUGH IS PROGGED TO MOVE ACROSS THE CWA LATE WEDNESDAY AFTERNOON
/EARLY EVENING. DOWNSLOPING FOLLOWS LATE WEDNESDAY NIGHT. THERE IS
STRONG SYNOPTIC SCALE ENERGY FOR THE CWA EARLY MONDAY EVENING...
THEN DECENT DOWNWARD MOTION PROGGED WELL INTO TUESDAY. THE ENERGY
IS BENIGN THEN INTO TUESDAY OVERNIGHT...WITH INCREASING UPWARD
MOTION ON WEDNESDAY AND WEDNESDAY EVENING AHEAD OF THE NEXT UPPER
TROUGH. THE BOUNDARY LAYER FLOW WILL BE DOWNSLOPING MONDAY EVENING
AFTER THE UPPER TROUGH MOVES ACROSS. THIS CONTINUE INTO TUESDAY
MORNING...WITH NORMAL DIURNAL PATTERNS TO KICK IN BY AFTERNOON
INTO THE OVERNIGHT PERIOD. WEDNESDAY`S UPPER FEATURE BRINGS A COLD
FRONT AND UPSLOPE TO THE PLAINS WEDNESDAY AFTERNOON. FOR MOISTURE
...IT IS SIGNIFICANT MONDAY EVENING...AND EVEN AFTER TROUGH
PASSAGE THERE IS PLENTY TO STAY OVER THE WESTERN CWA THROUGH
MONDAY NIGHT. ON TUESDAY...THERE IS SOME MOISTURE AROUND...
ESPECIALLY OVER THE WESTERN CWA...THEN MOISTURE INCREASES
EVERYWHERE TUESDAY NIGHT THROUGH WEDNESDAY EVENING...THEN SOME
DRYING. PRECIPITABLE WATER VALUES ARE IN THE 0.50 TO 1.20 INCH
RANGE WEST TO EAST FOR THE CWA MONDAY EVENING. VALUES ARE IN THE
0.30 TO 0.80 INCH RANGE TUESDAY AND WEDNESDAY. THERE IS FAIRLY
DECENT CAPE OVER THE FAR NORTHEAST CORNER MONDAY EVENING. THERE IS
ALMOST NO CAPE LATE DAY TUESDAY. THERE IS SOME CAPE...MINOR FOR
WEDNESDAY AFTERNOON...MAINLY OVER THE PLAINS. THE QPF FIELDS ARE
LOADED WITH MEASURABLE RAINFALL MONDAY EVENING...ESPECIALLY OVER
THE NORTHEAST CORNER. THERE IS A BIT OF MEASURABLE OVER THE
MOUNTAINS TUESDAY INTO WEDNESDAY. THERE IS MEASURABLE OVER ALL THE
CWA WEDNEDAY AFTERNOON AND EVENING. CERTAINLY...THERE WILL BE SNOW
LEVEL ISSUES IN THE ALPINE AREAS...THE LOWEST ELEVATIONS WILL
OCCUR WITH THE WEDNESDAY AFTERNOON/EVENING TROUGH. FOR POPS...WILL
KEEP WITH THE CURRENT THINKING...VERY HIGH OVER THE NORTHEAST
CORNER MONDAY EVENING. WILL NEED 30-60%S FOR THE WEDNEDAY/
WEDNESDAY EVENING TROUGH. TEMPERATURE-WISE...TUESDAY`S HIGHS ARE
CLOSE TO MONDAY`S. WEDNESDAY`S HIGHS ARE UP TO 6 C COOLER THAN
TUESDAY`S FROM THE NAM...WITH ONLY A TAD COOLER ON THE GFS. FOR
THE LATER DAYS...THURSDAY THROUGH SUNDAY...THERE IS UPPER RIDGING
OVER THE SOUTHWESTERN UNITES STATES ALL FOUR DAYS WITH WEAK
NORTHWESTERLY FLOW ALOFT FOR OUR CWA. THE AIRMASS IS PRETTY DRY
ALL FOUR DAYS. NO POPS.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z MONDAY LATE AFTERNOON)
ISSUED AT 246 PM MDT SUN SEP 28 2014

LINE OF SHOWERS AND A FEW STORMS TRYING TO ORGANIZE ALONG THE
FOOTHILLS AT THIS TIME WITH MAIN THREAT OF THUNDER 22Z-02Z FOR
THE FRONT RANGE AIRPORTS. THEN ONLY A SLIGHT CHANCE AFTER THAT
BATCH OF SHOWERS/STORMS MOVES THROUGH. WILL MONITOR DENVER CYCLONE
OVERNIGHT AND POTENTIAL FOR FOG DEVELOPMENT...BUT SOME MIXING AND
MID LEVEL CLOUD COVER COULD PREVENT FOG FROM FORMING. ON
MONDAY...GOOD CHANCE OF STORMS 20Z-00Z AS AIRMASS DESTABILIZES AND
LARGE SCALE LIFT MOVE ACROSS SO TEMPOS WARRANTED FOR MONDAY IN
THAT TIME FRAME. STRONGER WIND GUSTS TO AROUND 35 KTS WILL BE
POSSIBLE WITH THE STRONGER SHOWERS/STORMS.

&&

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

$$

SHORT TERM...BARJENBRUCH
LONG TERM...RJK
AVIATION...BARJENBRUCH



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.