Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 221751
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1151 AM MDT FRI AUG 22 2014

.UPDATE...
ISSUED AT 1135 AM MDT FRI AUG 22 2014

CONVECTION CONTINUES IN AREA OF ISENTROPIC LIFT OVER NORTHEASTERN
COLORADO. THIS HAD BEEN GRADUALLY LIFTING NORTH...THOUGH WITH
HEATING IT HAS BEGUN TO FILL BACK IN TOWARD THE SOUTH. WE WILL
NEED TO WATCH THE AREA BETWEEN STERLING AND AKRON AS THIS AREA
RECEIVED RAIN EARLIER THIS MORNING. FORTUNATELY THAT IS NOT A
FLOOD PRONE AREA. MEANWHILE LARGE AREA OF LIFT IS PROGRESSING
NORTHEAST FROM THE SOUTHERN AND CENTRAL MOUNTAINS AND HAS FILLED
IN PRETTY WELL WITH RAIN SHOWERS. EXPECT THE MAIN STORY TODAY WILL
BE THIS AREA OF FAIRLY STEADY RAIN MOVING NORTHEAST.

BIG QUESTION IS THE OUTLOOK FOR STRONGER THUNDERSTORMS...AND THE
ANSWER REMAINS MUDDLED BUT ORGANIZED STRONG CONVECTION IS LOOKING
LESS LIKELY. FRONTAL ZONE IS RATHER DIFFUSE...THOUGH THERE IS A
BROAD AREA OF CONVERGENCE FROM THE CURRENT NE COLORADO CONVECTION
SOUTH TOWARD THE ARKANSAS RIVER. LIFT FROM THE UPSTREAM SHORTWAVE
IS CREATING PRESSURE FALLS OVER NE COLORADO...HOLDING THIS
CONVERGENCE AREA IN PLACE BUT NOT REALLY FOCUSING IT ANY MORE.
LARGER SCALE MODELS HAVE A BETTER DEFINED FRONTAL ZONE AND BLOW UP
CONVECTION ON IT...WITH HEAVY RAIN ON THE NORTH SIDE AND A
POTENTIAL SUPERCELLS NORTH OF THE WARM FRONT SCENARIO WITH STRONG
EASTERLY WINDS. MEANWHILE THE HRRR DEVELOPS STORMS ON THE LEADING
EDGE OF THE MOUNTAIN RAIN AREA AND THEY MOVE QUICKLY TOWARD THE
NORTHEAST...WHILE THE FRONTAL ZONE CONVECTION IS LIMITED TO
KANSAS. I DO THINK THE TIGHT FRONTAL ZONE IS WRONG ALONG WITH THE
SIGNIFICANT PLUME OF MOISTURE ON LOW LEVEL EASTERLY WINDS...THAT
JUST IS NOT HAPPENING. THUS I HAVE PARED BACK THE SEVERE THREAT TO
OUR EASTERNMOST AREAS...AND IT IS PROBABLY JUST THE EASTERN PARTS
OF LINCOLN AND WASHINGTON COUNTIES AND AREAS EAST OF THERE. AREAS
FURTHER WEST AND NORTH WILL STILL HAVE A HEAVY RAIN THREAT IF
THERE IS REGENERATION ON AN EAST-WEST ZONE...AND OBVIOUSLY SOME
POTENTIAL FOR THAT TO CONTINUE. PREVIOUS OUTLOOKS OF UP TO 3
INCHES IN 2 HOURS IF THERE IS TRAINING SEEM ALRIGHT...BUT THE
THREAT SHOULD BE LIMITED TO THOSE EASTERN PLAINS AREAS AS
CONVECTION FURTHER WEST SHOULD BE QUITE A BIT WEAKER WITH FAST
CELL MOTIONS.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 318 AM MDT FRI AUG 22 2014

AN UPPER LEVEL LOW OVER CENTRAL ARIZONA WILL GRADUALLY MOVE NE
INTO THE FOUR CORNERS BY MIDDAY AND THEN INTO NE COLORADO BY EARLY
THIS EVENING. AS THIS FEATURE MOVES ACROSS A DECENT SHOT OF MID
LVL QG ASCENT WILL OCCUR AS WELL. AT THE SFC LOW PRES WILL EXTEND
FM SC WY INTO SERN CO WITH A WK SFC HIGH OVER WRN NEBRASKA. THIS
WILL ALLOW FOR ESE LOW LVL FLOW TO DVLP BY MIDDAY OVER NERN CO AND
ALLOW FOR DEEPER LOW LVL MOISTURE TO ADVECT INTO THE PLAINS.
OVERALL SHOULD SEE A GOOD CHC OF SHOWERS AND TSTMS ACROSS MUCH OF
THE AREA STARTING IN THE MTNS BY MIDDAY AND THEN SPREADING ACROSS
THE PLAINS BY EARLY EVENING.

PRECIPITABLE WATER VALUES ARE FCST TO BE AROUND AN INCH IN THE
MTNS WITH 1.25 TO 1.5 INCHES OVER THE PLAINS SO THE STORMS WILL
PRODUCE HEAVY RAIN...HOWEVER THEY WILL BE QUICK MOVING DUE TO
RATHER STG MID LVL FLOW. THERE WILL BE SOME POTENTIAL FOR TRAINING
OF CELLS OVER THE PLAINS SO COULD SEE A FEW SPOTS RECEIVE FM 2 TO
3 INCHES OF RAIN. AS FOR SVR POTENTIAL MAIN THREAT WOULD BE STRONG
WINDS DUE TO WET MICROBURSTS. ALSO CAN NOT RULE OUT A FEW
TORNADOES AS WELL AS STORM RELATIVE HELICITIES INCREASE BY LATE
AFTN INTO THE EARLY EVENING HOURS OVER THE PLAINS. AS FOR HIGHS
THIS AFTN WILL KEEP READINGS IN THE UPPER 70S TO MID 80S OVER THE
PLAINS.

BY TONIGHT AS MAIN DISTURBANCE MOVES QUICKLY NE SHOULD SEE PRECIP
CHANCES DECREASE ALONG THE FRONT RANGE BY EARLY EVENING AND THEN
BY MIDNIGHT OVER THE FAR NERN PLAINS. SOME MOISTURE MAY LINGER IN
THE NRN MTNS OVERNIGHT SO WILL KEEP IN A CHC OF SHOWERS MAINLY
NORTH OF I-70.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 318 AM MDT FRI AUG 22 2014

A DRIER SOUTHWESTERLY FLOW ALOFT WILL BE OVER NERN CO EARLY
SATURDAY FOLLOWING THE PASSAGE OF THE UPPER LEVEL TROUGH. THIS
WILL BE SHORT LIVED...AS ANOTHER SYSTEM OVER SRN IDAHO AT 12Z
SATURDAY MAKES ITS WAY ACROSS MONTANA/WYOMING LATE SATURDAY
AFTERNOON AND SATURDAY NIGHT. THE FLOW ALOFT OVER COLORADO WILL
INCREASE FM THE WEST WITH SCATTERED SHOWERS AND THUNDERSTORMS IN
THE MOUNTAINS. ALONG THE FRONT RANGE FOOTHILLS...URBAN CORRIDOR
AND ADJACENT PLAINS WILL MINIMIZE THE POPS SOUTH AND EAST OF
DENVER WITH HIGHER POPS TO THE NORTH AND WEST....AS THE TROF AXIS
BRUSHES ACROSS THE STATE. SUNDAY AND SUNDAY NIGHT...A DRIER
WESTERLY FLOW ALOFT WILL BE OVER THE CWA. IT WILL BE STABLE AND
COOLER FOLLOWING THE PASSAGE OF A COLD FRONT SATURDAY NIGHT INTO
SUNDAY MORNING. THE NAM12/ECMWF GENERATE LITTLE QPF OVER THE
REGION ON SUNDAY WHILE THE GFS DOES REFLECTS MORE SUBTROPICAL
MOISTURE EMBEDDED IN THE FLOW. WL LEAN TOWARD THE NAM12/ECMWF
SOLUTIONS WITH MINIMAL POPS MAINLY OVER THE MOUNTAINS IN THE
AFTN/EVNG. SUNDAY NIGHT INTO MONDAY...THE FLOW ALOFT BECOMES MORE
SOUTHWESTERLY WHICH MAY HELP TAP INTO THE SUBTROPICAL MOISTURE
OVER ERN AZ/NEW MX. POPS STILL ON THE LOW SIDE MONDAY
AFTERNOON/EVENING. THE NEXT SYSTEM IS PROGGED TO DROP OUT OF THE
NORTHERN ROCKIES AND ACROSS COLORADO TUESDAY AND TUESDAY NIGHT.
THE TROUGH AXIS AND ITS ASSOCIATED COLD FRONT WILL PASS ACROSS
NORTHERN COLORADO ON TUESDAY. IT WILL BE COOLER WITH A BETTER
CHANCE OF SHOWERS AND TSTMS AT THAT TIME. WEDNESDAY INTO
THURSDAY...AN UPPER RIDGE DEVELOPS OVER THE WESTERN U.S. WITH A
DRIER NORTHWESTERLY FLOW ALOFT OVER COLORADO. AS A RESULT...LESS
POPS WITH MODERATING TEMPERATURES FOR THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z SATURDAY MORNING)
ISSUED AT 1135 AM MDT FRI AUG 22 2014

SHOWERS WILL BE FAIRLY WIDESPREAD AROUND THE DENVER AREA THROUGH
THIS EVENING...WITH EMBEDDED THUNDERSTORMS. THE THREAT OF VERY
HEAVY RAIN WITH IFR CONDITIONS IS NOW LOOKING LOW...BUT THERE
SHOULD BE ENOUGH RAIN TO LOWER CEILINGS/VISIBILITIES WITH AREAS
OF MVFR IN THE LATE AFTERNOON AND EVENING. IT APPEARS THAT
CLEARING WILL BE SLOWER ON SATURDAY MORNING...BUT THERE IS STILL A
LOW CHANCE OF IFR/LIFR FOG FOR A FEW HOURS IF IT DOES CLEAR OUT
EARLY ENOUGH. FOR THE REST OF SATURDAY VFR CONDITIONS ARE EXPECTED
WITH ONLY ISOLATED LATE AFTERNOON THUNDERSTORMS.

&&

.HYDROLOGY...
ISSUED AT 318 AM MDT FRI AUG 22 2014

STORMS WILL MOVE QUICKLY TODAY HOWEVER THERE WILL BE SOME POTENTIAL
FOR TRAINING OF STORMS OVER NORTHEAST COLORADO AS A FEW LOCATIONS
COULD SEE UP TO 2 INCHES OF RAIN IN LESS THAN HOUR.  IN THE
FOOTHILLS AND MTNS ISOLATED AMOUNTS UP TO AN INCH IN LESS THAN AN
HOUR WILL BE POSSIBLE WITH SOME MINOR FLOODING IN THE BURN SCARS.

&&

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

$$

UPDATE...GIMMESTAD
SHORT TERM...RPK
LONG TERM...COOPER
AVIATION...GIMMESTAD
HYDROLOGY...RPK


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