Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 221052
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
452 AM MDT MON SEP 22 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 452 AM MDT MON SEP 22 2014

TROUGH PASSING OVER COLORADO TODAY. MODELS ARE PRETTY GOOD WITH
THE TIMING OF THE TROUGH THOUGH THERE ARE SOME DISAGREEMENTS AS TO
THE PLACEMENT OF CONVECTION. NAM COMPARES WITH THE CURRENT PATTERN
PRETTY MISERABLY...GFS HAS TOO LITTLE THIS MORNING AND TOO MUCH
THIS EVENING. HRRR LOOKS PRETTY REASONABLE BRINGING THE UPSTREAM
BATCH OF SHOWERS OVER DENVER AT MIDDAY...THEN GENERATING ISOLATED
THUNDERSTORMS OVER THE MOUNTAINS AND NORTHERN PART OF THE PLAINS
IN THE MID TO LATE AFTERNOON AS THERE IS SLIGHT COOLING ALOFT
BEHIND THE TROUGH. WILL GENERALLY GO WITH THIS IDEA...THOUGH I
HAVE SOME RESERVATIONS ABOUT MOISTURE AVAILABILITY. PLAINS REMAIN
COOL AND DRY AND WHILE SOUTHERLY WINDS ARE INCREASING THERE IS NOT
BETTER MOISTURE AT THE SURFACE UNTIL YOU GET TO TEXAS. SO THE
MOISTURE WILL HAVE TO BE COMING WITH THE SHOWER BAND. THERE WILL
BE SOME OF THIS GOING ON...BUT MODEL FORECAST MOISTURE ON THE
PLAINS DURING THE DAY LOOKS OVERDONE.

MOISTURE UNCERTAINTY IMPACTS THE PROSPECTS FOR STRONG STORMS.
WIND PROFILE IN THE MODELS IS GOOD FOR SUPERCELLS ALONG AND BEHIND
THE TROUGH AXIS ON THE PLAINS THIS AFTERNOON...NAM HAS CAPES OF
1000-1500 J/KG WHICH WOULD PRESENT A DECENT THREAT OF SEVERE
WEATHER. BUT THIS IS WITH DEW POINTS IN THE MID 50S WHICH LOOKS
PRETTY UNLIKELY...ESPECIALLY IN THE AIR BEHIND THE TROUGH WHERE
ANY REMAINING SURFACE MOISTURE SHOULD BE MIXING OUT. THERE ALSO
MAY BE MORE OF A WIND SHIFT THAN THE MODELS ARE SHOWING AS A
DENVER CYCLONE BOUNDARY THAT GETS PICKED UP WITH THE TROUGH AXIS
AND MOVES EAST TURNING INTO A DRYLINE SEEMS QUITE POSSIBLE. NAM/GFS
MOS DEW POINTS OF 45-50 ONLY GIVE CAPES AROUND 500 J/KG...AND I
THINK THIS IS MORE LIKELY. GIVEN THE WIND PROFILE AND FAST MOVING
STORMS...MAYBE STILL A SMALL WIND THREAT.

FOR TONIGHT THERE MAY BE SOME SHALLOW CONVECTION IN LINGERING LIFT
IN THE NORTHERN PART OF THE AREA FOR A WHILE...BUT SUBSIDENCE AND
CLEARING SHOULD BE COVERING THE AREA BY MORNING. COULD BE A
MOUNTAIN WAVE SETUP WITH SOME WARMING ALOFT BY 12Z...THOUGH SPEEDS
ARE MARGINAL SO PROBABLY JUST A BIT GUSTIER THAN WOULD OTHERWISE
BE EXPECTED. WITH JUST A LITTLE COOLING ALOFT...SNOW LEVEL SHOULD
STAY ABOVE TIMBERLINE.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 452 AM MDT MON SEP 22 2014

TUESDAY AND TUESDAY NIGHT...THE STORM SYSTEM WLL PASS TO THE
NORTH AND EAST WITH A NORTHWESTERLY FLOW ALOFT OVER THE REGION.
ENOUGH MID LEVEL INSTBY AND MOISTURE WILL BE PRESENT FOR SOME
LINGERING SHOWERS/TSTMS IN THE HIGH COUNTRY AND FAR NORTHEAST
PLAINS THROUGH EARLY TUESDAY EVENING. WEDNESDAY THROUGH
THURSDAY...AN UPPER LEVEL RIDGE WILL BUILD OVER THE GREAT
BASIN/CENTRAL ROCKIES WITH A DRY AND SUBSIDENT NORTHERLY FLOW
ALOFT OVER NORTHEAST COLORADO. TEMPERATURES WILL CLIMB BACK INTO
THE MID TO UPPER 80S. BY FRIDAY...THE RIDGE AXIS IS PROGGED TO
SHIFT TO THE EAST WITH A WEAK SLY FLOW ALOFT OVER THE STATE.
SUBTROPICAL MOISTURE WILL START TO ADVECT BACK INTO COLORADO. SOME
POPS GET INTRODUCED BACK INTO THE HIGH COUNTRY BY FRIDAY
AFTN...WITH A BETTER CHANCE OF SHOWERS/TSTMS FOR THE REST OF
NORTHEAST AND NORTH CENTRAL COLORADO OVER THE WEEKEND AHEAD OF THE
NEXT UPPER TROUGH WHICH IS EXPECTED TO MOVE ACROSS NRN PORTIONS OF
CA/NV BY SUNDAY.
&&

.AVIATION...(FOR THE TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 452 AM MDT MON SEP 22 2014

VFR CONDITIONS WILL PREVAIL THROUGH TONIGHT...THOUGH INSTRUMENT
APPROACHES TO KDEN MAY BE NEEDED AT TIMES AS SHOWERS MOVE THROUGH.
MOST LIKELY TIME FOR THIS IS BETWEEN 16Z AND 22Z. SOUTH WINDS THIS
MORNING WILL LIKELY SHIFT TO NORTH DURING THE MIDDLE OF THE DAY AS
A DENVER CYCLONE STRENGTHENS AND THEN SHIFTS EAST. THIS PATTERN
COULD BE DISRUPTED WITH WIND SHIFTS DUE TO SHOWER ACTIVITY
HOWEVER.

&&

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

$$

SHORT TERM...GIMMESTAD
LONG TERM...COOPER
AVIATION...GIMMESTAD



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