Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 220330
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
930 PM MDT TUE APR 21 2015

.UPDATE...
ISSUED AT 930 PM MDT TUE APR 21 2015

A FEW RAIN SHOWERS MOVED OFF THE FOOTHILLS EARLIER IN THE
EVENING...BUT THINGS ARE CLEARING OUT NOW. NORTHEAST WINDS ARE
MOVING ACROSS THE NORTHEAST PLAINS AS HIGH PRESSURE BUILDS OVER
THE NORTHERN AND CENTRAL PLAINS. THE STAGE SEEMS TO BE SETTING UP
FOR STRONGER SHOWER ACTIVITY TOMORROW AFTERNOON. WINDS SHOULD BE
POST-FRONTAL AND OUT OF THE SOUTH-SOUTHEAST IN THE MORNING. THIS
WILL HOLD LOW LEVEL MOISTURE UP AGAINST THE FOOTHILLS TO FEED INTO
THE AFTERNOON CONVECTION. NOT MANY CHANGES TO THE FORECAST
PACKAGE OTHER THAN REMOVE THE MENTION OF THIS EVENINGS SHOWERS.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 340 PM MDT TUE APR 21 2015

UPPER RIDGE BUILDING OVER THE EASTERN GREAT BASIN/FOUR CORNERS
REGION AND THE LARGE UPPER TROUGH CAMPED OVER THE EASTERN U.S.
WILL KEEP NORTHEAST COLORADO UNDER NORTHWEST 700-400MB FLOW OF
25-40 KTS THROUGH 12Z/WED. UNLIKE YESTERDAY AT THIS TIME...QG
VERTICAL VELOCITY AND VORTICITY FIELDS DO NOT INDICATE ANY FORCING
MECHANISMS IMMEDIATELY UPSTREAM OF THE CWA. FURTHERMORE THE
EXTENSIVE SNOW FIELD IN SOUTH CENTRAL WY SURROUNDING LARAMIE
CLEARLY VISIBLE ON SATELLITE IMAGERY CONTINUES TO PLAY AN
IMPORTANT ROLE IN SUPPRESSING CONVECTION/CLOUD DEVELOPMENT
DOWNSTREAM OVER WELD...MORGAN AND EASTERN PORTIONS OF ADAMS AND
ARAPAHOE COUNTIES. AT THE SAME TIME...UPRIGHT CONVECTION IS NOW
UNDERWAY WITH CONVECTIVE TEMPS BEING REACHED OVER THE HIGHER
TERRAIN OF THE FRONT RANGE MTNS AND FOOTHILLS ACCORDING TO SATELLITE
AND RADAR. WITH THE 25-35 DEG F DEWPOINT SPREADS IN THESE AREAS...
THESE DEVELOPING SHOWERS ARE MORE LIKELY TO GENERATE GUSTY OUTFLOW
WINDS RATHER THAN WETTING RAINFALL. STILL WOULD NOT RULE OUT A STRAY
CG STRIKE OR TWO BUT OVERALL THE RISK OF T-STORM FORMATION REMAINS
LOW.

DURING THE NEXT FEW HOURS...SHOULD SEE A FEW SHOWERS MOVE OFF THE
FOOTHILLS AND TRACK EAST-SOUTHEASTWARD OVER THE ADJACENT I-25
CORRIDOR. THIS POORLY ORGANIZED CONVECTION WILL PROBABLY PRODUCE
MORE WIND THAN WETTING RAINFALL. CONVECTIVE GUST POTENTIAL LOW TO
MODERATE TODAY WITH POSSIBLE GUSTS IN THE 25-35 KT RANGE. FOR THE
MOST PART...DO NOT SEE ANY OF THESE SHOWERS SURVIVING MUCH BEYOND A
CHEYENNE-TO-LIMON LINE WHERE THE BOUNDARY LAYER ENVIRONMENT REMAINS
TOO DRY AND CAPPED. THE SHOWERS MENTIONED ABOVE SHOULD QUICKLY WIND
DOWN DURING THE EARLY EVENING HOURS WITH THE LOSS OF SOLAR HEATING.
HOWEVER...MODEL RH FIELDS AND NAM SYNTHETIC SATELLITE IMAGERY SHOW A
BAND OF MID-LEVEL CLOUD NW-SE ACRS CENTRAL PORTIONS OF THE CWA.
AFTER MIDNIGHT...SHOULD SEE SKIES GRADUALLY CLEAR. LOWS TONIGHT
GENERALLY 2-3 DEG C WARMER THAN AVERAGE.

ON WEDNESDAY... UPPER RIDGE TO OUR WEST SHIFTS EAST ACRS COLORADO
DURING THE DAY. TRANSPORT WINDS WEAKEN AS THEY BACK FROM
NORTHWESTERLY IN THE MORNING TO WEST-SOUTHWESTERLY IN THE AFTERNOON.
SELY SFC FLOW EAST OF THE MTNS AROUND A STG SFC HIGH IN ERN NEBRASKA
DRIVES LOW-LEVEL MOISTURE UP INTO NERN COLORADO THROUGH THE DAY. THIS
SAME SELY FLOW ON THE PLAINS PRODUCES A DENVER CYCLONE WITH A
CONVERGENCE BNDRY FORMING TO ITS SOUTH ACRS ERN AND SRN SECTIONS OF
THE DENVER METRO AREA IN THE AFTERNOON. THESE BNDRYS OFTEN ACT AS A
FOCUS FOR CONVECTIVE STORM DEVELOPMENT. THOUGH SHEAR DOES NOT APPEAR
STRONG...MESOSCALE MODELS SHOW SFC/BNDRY LAYER CAPES APPROACHING A
1000 J/KG IN THE VCNTY OF THIS CONVERGENCE ZONE. THAT SAID...SHOULD
SEE SHOWERS BEGIN FORMING IN THE HIGH COUNTRY AROUND MIDDAY WITH
STRONG SOLAR HEATING AND AS MID-LEVEL MOISTURE FLOWING IN FROM THE
WEST. NOT LONG AFTER THAT SHOULD SEE ISOLATED SHOWERS MOVING OFF THE
FOOTHILLS AND FORMING ON THE PALMER DIVIDE ONCE CONVECTIVE TEMPS IN
THE LOWER 60S ARE REACHED. MID TO LATE AFTERNOON STORMS FIRING IN
THE VICINITY OF THE DENVER CYCLONE AND ITS TRAILING CONVERGENCE
BNDRY WILL HAVE THE POTENTIAL TO PRODUCE SMALL HAIL AND WIND GUSTS
TO AROUND 40 KTS. OTHER STORMS IN THE AREA MAY ALSO PRODUCE SIMILAR
GUSTS TOGETHER WITH BRIEF LIGHT TO MODERATE RAINFALL. HIGHS ON
WEDNESDAY SIMILAR TO TODAY WITH 60S ON THE PLAINS AND MAINLY 50S IN
THE HIGH COUNTRY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 340 PM MDT TUE APR 21 2015

LONG TERM WEATHER THROUGH THE WEEKEND LOOKS TO BE UNSETTLED AS
SEVERAL DISTURBANCES WILL BE MOVING ACROSS THE REGION THROUGH NEXT
SUNDAY. TEMPERATURES WILL BE AROUND SEASONABLE NORMALS WITH
READINGS IN THE 60S THROUGH THE WEEKEND ACROSS THE PLAINS.

LINGERING SHOWERS AND A FEW STORMS WEDNESDAY EVENING SHOULD
DISSIPATE BEFORE MIDNIGHT WITH LACK OF ANY UPPER AIR SUPPORT AS
RIDGE AXIS SHIFTS OVER EASTERN COLORADO. THE NEXT UPPER LEVEL LOW
WHICH WILL MOVE ACROSS THE DESERT SOUTHWEST WILL TRACK RAPIDLY
ACROSS SOUTHERN COLORADO LATE THURSDAY AND FRIDAY. THIS SYSTEM
APPEARS MORE PROGRESSIVE AND A BIT LESS MOISTURE ASSOCIATED WITH
IT THAN FROM PREVIOUS MODEL RUNS. APPEARS TO BE MOVING TO FAST TO
PULL IN ANY SIGNIFICANT LOW LEVEL MOISTURE. STILL GOOD CHANCE FOR
SHOWERS/STORMS ESPECIALLY OVER FAR EASTERN PLAINS OF COLORADO AND
IN THE MOUNTAINS WITH MODEST UPPER LEVEL ASCENT.

THE NEXT PACIFIC SYSTEM MOVES ACROSS COLORADO LATE SATURDAY AND
SUNDAY. THERE ARE DIFFERENCES IN THE MODEL TRACKS AND AVAILABLE
MOISTURE BUT AGAIN FAVORS LOCATIONS EAST OF THE FRONT RANGE. WILL
INCREASE POPS OVER EASTERN COLORADO AS MODELS ARE SHOWING A
STRONGER SYSTEM THIS WEEKEND. APPEARS MORE SIGNIFICANT DRYING AND
SOME WARMING BY EARLY NEXT WEEK AS STRONGER RIDGE MOVES INTO THE
ROCKY MOUNTAIN REGION.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z WEDNESDAY EVENING)
ISSUED AT 930 PM MDT TUE APR 21 2015

CLEARING SKIES AND WINDS TRANSITIONING TO SOUTHERLY ARE EXPECTED
FOR THE REST OF TONIGHT. FOR TOMORROW AFTERNOON WILL NEED TO ADD
THE MENTION OF SHOWERS AND THUNDERSTORMS TO THE DENVER AREA
AIRPORTS.

&&

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

$$

UPDATE...DANKERS
SHORT TERM...BAKER
LONG TERM...ENTREKIN
AVIATION...DANKERS


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