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 291002
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
402 AM MDT MON SEP 29 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 402 AM MDT MON SEP 29 2014

A STRONG STORM SYSTEM WILL RACE ACROSS THE CENTRAL ROCKIES THIS
AFTERNOON AND TONIGHT BRINGING SHOWERS AND THUNDERSTORMS. SOME THE
STORMS COULD BE SEVERE WITH DAMAGING WINDS...HAIL AND TORNADOES. A
BROAD UPPER LEVEL LOW IS OVER THE GREAT BASIN. WATER VAPOR SHOWING
AT LEAST THREE WAVES ROTATING AROUND IT. THE STRONGEST ONE...THE ONE
THAT WILL AFFECT COLORADO...IS NEAR LAS VEGAS NEVADA. THIS STRONG
SHARP WAVE WILL QUICKLY MOVE EASTWARD TODAY. SOUTHERLY FLOW AHEAD OF
IT WILL BECOME STRONG.

THERE WILL BE STRONG ASCENT AHEAD OF THE TROUGH THIS AFTERNOON AND
EARLY EVENING. EXPECT ENOUGH LIFT THIS MORNING TO PRODUCE SHOWERS
AND POSSIBLY A FEW WEAK STORMS. AS LIFT AND INSTABILITY INCREASE...
CONVECTION WILL BECOME WIDESPREAD OVER CENTRAL COLORADO THIS
AFTERNOON AND SPREAD OVER THE EASTERN PLAINS THIS EVENING. BECAUSE
OF THE INSTABILITY...SCATTERED STORMS SHOULD FORM PRIOR TO THE MAIN
SWATH OF SHOWERS AND STORMS. CAPES OF UP TO 1500 J/KG WILL BE
POSSIBLE THIS AFTERNOON OVER THE PLAINS IF TEMPERATURES CLIMB INTO
THE LOWER 70S AND DEW POINTS ARE IN THE MID 50S. THIS INSTABILITY
COMBINED WITH VERY GOOD SHEAR WILL LIKELY PRODUCE A FEW SEVERE
STORMS WITH DAMAGING WIND...HAIL AND POSSIBLY TORNADOES. BEST CHANCE
FOR SEVERE STORMS WILL BE EAST OF A LINE FROM GREELEY TO DENVER
INTERNATIONAL AIRPORT. THOUGH CAN`T RULE OUT SEVERE STORMS WEST TO
THE FOOTHILLS.

MODELS IN GOOD AGREEMENT IN SHOWING A LINE OF CONVECTION MOVING
ACROSS NORTHEAST COLORADO THIS EVENING. WEST PARTS OF THE AREA WILL
START TO SEE DRYING AND SUBSIDENCE LATE THIS EVENING...WHICH WILL
SPREAD EAST OVERNIGHT. BY TUESDAY MORNING...EXPECT DRY CONDITIONS
ACROSS THE AREA.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 402 AM MDT MON SEP 29 2014

OPERATIONAL MODELS AGREE IN PINWHEELING THE CLOSED UPPER LOW/NEG
TILT TROUGH NORTHEASTWARD ACROSS WYOMING AND NORTHERN GREAT PLAINS
ON TUESDAY...PLACING NRN COLORADO IN A DRIER ZONAL FLOW. TUESDAY
LOOKS DRY EAST OF THE MTNS WITH PREVAILING WLY/DOWNSLOPE FLOW.
WHEREAS MTN AREAS...PARTICULARLY AREAS WEST OF THE CONTINENTAL
DIVIDE...REMAIN IN A MORE FAVORABLE POSITION TO SEE LIGHT
OROGRAPHIC AND/OR CONVECTIVE PCPN BY LATE IN THE DAY IN ADVANCE
OF A MID-LEVEL PERTABATION FORMING IN THE LEFT FRONT QUAD OF A
90+ KT JET DIVING SEWRD ACRS THE CENTRAL GREAT BASIN. MODELS SHOW
THE JET CARVING OUT A POSITIVE TILT LONGWAVE TROUGH OVER THE
GREAT BASIN TUESDAY NIGHT/WEDNESDAY...AND SWINGING ACRS ERN
COLORADO WEDNESDAY NIGHT. MODEL QG VERTICAL VELOCITY FIELDS
INDICATE WEAK TO MODERATE LARGE SCALE ASCENT OVER THE FORECAST
AREA DURING THE DAY WEDNESDAY AS A 80-100KT JET PASSES JUST TO OUR
SOUTH. COOLING ALOFT WILL STEEPEN LAPSE RATES AND CYCLONIC
UPSLOPE FLOW BEHIND A COLD FRONT THAT PASSES THROUGH THE DENVER
METRO AREA DURING THE MORNING WILL PROVIDE ADDITIONAL LIFT FOR
WIDESPREAD CLOUD COVER AND PRECIPITATION BY THE AFTERNOON. ALL
THIS POINTS TO A COOL...WET DAY WITH MODEL GUIDANCE INDICATING
HIGHS ONLY IN THE 60S AT LOWER ELEVATIONS AND 30S TO LOWER 50S IN
THE HIGH COUNTRY. MTN AREAS ROUGHLY ABOVE TIMBERLINE COULD SEE A
MIX OF RAIN/SNOW DURING THE DAYLIGHT HOURS WITH SPOTTY LIGHT SNOW
ACCUMULATION BY LATE AFTERNOON. BY EVENING WITH THE THERMAL
TROUGH PASSING OVERHEAD...SNOW LEVEL IS EXPECTED TO LOWER TO
AROUND THE 9500 OR 10K FOOT LEVEL. HOWEVER...MOISTURE APPEARS TO
BE ON THE DECLINE AT THAT TIME WITH DRIER STABLE AIR SPREADING
IN BEHIND THE TROUGH. HIGH MTN AREAS COULD STILL END UP WITH A
FEW INCHES OF SNOW BY LATE WEDNESDAY NIGHT. MODEL RAIN TOTALS ON
THE PLAINS VARY ANYWHERE FROM A COUPLE TENTHS OF AN INCH TO AROUND
0.75 INCH BY MID-EVENING WEDNESDAY...WITH THE GREATER AMOUNTS
SCATTERED ACRS THE NERN CORNER OF THE STATE.

BY THURSDAY...TROUGH MOVES EAST AND FLOW ALOFT GOES
NORTHWESTERLY. AS A RESULT EXPECT SLIGHTLY WARMER TEMPERATURES
WITH MUCH MORE SUNSHINE.

FRIDAY THROUGH SUNDAY...LARGE UPPER RIDGE BUILDING OVER THE WEST
COAST GRADUALLY SHIFTS EAST OVER THE GREAT BASIN BY WEEKS END. THE
CWA REMAINS UNDER THE INFLUENCE OF NORTHWEST FLOW ALOFT...BUT
TEMPERATURES ARE FORECAST TO GRADUALLY WARM A FEW DEGS EACH DAY WITH
PLENTY OF SUNSHINE. HOWEVER BY SUNDAY...COULD SEE TEMPERATURES
DIP SOME WITH PASSAGE OF A WEAK MOSTLY DRY COLD FRONT.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 402 AM MDT MON SEP 29 2014

LOW CLOUDS WITH CEILINGS OF 500 TO 2000 FEET WILL PREVAIL THROUGH
14Z...THEN SCATTER OUT. A STRONG STORM SYSTEM WILL MOVE ACROSS THE
DENVER AREA THIS AFTERNOON AND EVENING. THIS WILL BRING SHOWERS AND
THUNDERSTORMS...WITH A VERY GOOD CHANCE FOR A THUNDERSTORM BETWEEN
21Z AND 01Z. HEAVY RAIN...STRONG WINDS...AND HAIL WILL BE POSSIBLE
WITH THE STRONGEST STORMS...EVEN A TORNADO CAN`T BE RULED OUT. WEST
TO NORTHWEST WINDS WILL BECOME LIGHT AROUND 14Z...AND THEN SHIFT TO
THE NORTHEAST BY 18Z.

THE THREAT FOR THUNDERSTORMS WILL END AROUND 02Z. SKIES WILL BECOME
SCATTERED SHORTLY AFTER WITH SOUTHWEST WINDS PREVAILING.

&&

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

$$

SHORT TERM...MEIER
LONG TERM...BAKER
AVIATION...MEIER



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