Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 031615
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1015 AM MDT SUN MAY 3 2015

.UPDATE...
ISSUED AT 935 AM MDT SUN MAY 3 2015

PREVIOUS FORECAST LOOKS GOOD. COLDFRONT AT 15Z WAS INTO NORTHEAST
COLORADO...WITH THE BEST PRESSURE RISES HEADED ACROSS NEBRASKA.
THE FRONT WILL CONTINUE DROPPING ACROSS NORTHEAST COLORADO THIS
AFTERNOON. THIS WILL SET UP THE MOISTENING PROCESS WHICH WILL TAKE
SOME TIME. EXPECT SCATTERED GUSTY THUNDERSTORMS THIS
AFTERNOON...THEN BY EVENING SHOWERS AND THUNDERSTORMS WILL BECOME
LIKELY AND LOCALLY HEAVY RAIN WILL BE POSSIBLE ESPECIALLY ON THE
PAINS. A WEAK UPPER TROUGH WILL PROVIDE MARGINAL LIFT...AND
FORECAST CAPES ARE ONLY 750 OR SO... WE ARE NOT EXPECTING SEVERE
WEATHER. LATER TONIGHT LOW CLOUDS AND FOG IS EXPECTED TO
DEVELOP...THE MORNING COMMUTE COULD BE IMPACTED BY LOW
VISIBILITIES.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 221 AM MDT SUN MAY 3 2015

MOISTURE CONTINUES TO BE ENTRAINED AND STUCK UNDER THE FLAT UPPER
RIDGE OVER THE CENTRAL AND SOUTHERN ROCKIES. THE RIDGE HAS BEEN
FLATTENED BY A BROAD TROUGH PUSHING EAST OVER THE US/CANADA
BORDER. A FEW RIPPLES IN THE WESTERLY FLOW HAS HELPED ISOLATED
SHOWERS CONTINUE OVERNIGHT OVER WESTERN COLORADO AND INTO THE
NORTHERN AND CENTRAL MOUNTAINS EARLY THIS MORNING.

FLOW ALOFT WILL BE TURNING MORE SOUTHWESTERLY TODAY AS A WEAK
SHORTWAVE MOVES OVER CO...INCREASING MOISTURE. AT THE SURFACE...A
TROUGH OVER THE KS/CO BORDER WILL SLOWLY MOVE SOUTH AS HIGH
PRESSURE PUSHES DOWN ALONG THE LEE OF THE NORTHERN AND CENTRAL
ROCKIES...PUSHING A COLD FRONT INTO COLORADO STARTING MID MORNING.
NORTHERLY WINDS WILL TURN TO AN UPSLOPE NORTHEAST DIRECTION THIS
AFTERNOON TO PUSH MORE LOWER LEVEL MOISTURE IN THROUGH THE NIGHT.
THIS SHOULD PRODUCE HIGH TEMPERATURES SIMILAR TO OR A FEW DEGREES
COOLER THAN YESTERDAY. SHOWERS AND STORMS FORMING OVER THE HIGH
TERRAIN AROUND NOON WILL PUSH OFF ONTO THE ADJACENT PLAINS EARLY
AFTERNOON. WITH PW VALUES INCREASING ABOUT 0.2" OVER
YESTERDAY...LOOK FOR STORMS TO HAVE MORE MOISTURE AND WEAKER GUSTY
WINDS TODAY. NAM HAS SHOWN A DECREASE IN CAPE VALUES OVER THE LAST
MODEL RUN. EXPECT CAPE VALUES OF ABOUT 500 TO 800 J/KG TODAY FOR
THE POTENTIAL OF A FEW STRONGER STORMS HOWEVER LITTLE TO NO SEVERE
THREAT FOR TODAY. AS THE COLD FRONT CONTINUES TO PUSH SOUTH THIS
EVENING...AN EASTERLY JET PUSHES IN TO INCREASE MOISTURE EVEN MORE
AS A 700 MB CLOSED LOW FORMS OVER SOUTHEASTERN COLORADO. SCATTERED
TO NUMEROUS SHOWERS WILL FORM OVER THE PLAINS AND THE EASTERN
SLOPES AND FOOTHILLS OF THE FRONT RANGE. SEVERAL MODELS POINTING
TO CONVECTION FORMING JUST EAST OF THE DENVER AIRPORT THIS EVENING
AND PUSHING NORTHEAST THROUGH THE NIGHT. WILL HAVE A CHANCE OF
SHOWERS AND POSSIBLE THUNDERSTORMS GOING THROUGH THE NIGHT TO
ACCOUNT FOR THIS. SHOWERS WILL DECREASE WEST OF THE DIVIDE OVER
THE HIGH TERRAIN. EXPECT CLOUDS TO LOWER WITH SOME PATCHY FOG
OVERNIGHT FOR THE PLAINS WITH MOISTURE BEING PILED UP AGAINST THE
FOOTHILLS. SNOW LEVELS WILL REMAIN HIGH...NEAR 11 KFT. HAVE WARMED
TONIGHTS LOW TEMPERATURES WITH THE EXPECTED CLOUD COVER.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 344 AM MDT SUN MAY 3 2015

...WET AND UNSETTLED WEEK AHEAD WITH POTENTIAL FOR LOCALLY HEAVY
RAINFALL...

MONDAY WILL START OFF WITH AREAS OF LOW CLOUDS AND POSSIBLE FOG ON
THE EASTERN PLAINS AND FRONT RANGE FOOTHILLS WITH CONTINUED MOIST
EASTERLY UPSLOPE FLOW. WE SHOULD ALSO SEE A FEW SHOWERS...LOCAL
DRIZZLE...AND ISOLATED THUNDERSTORMS WITH A NEUTRAL TO SLIGHTLY
UNSTABLE AIRMASS IN PLACE. THE PLAINS WILL LIKELY REMAIN TOO
STABLE THROUGH MUCH OF THE DAY TO SUPPORT SURFACE BASED
CONVECTION...BUT NONETHELESS WEAK SYNOPTIC SCALE LIFT SEEN IN THE
Q-G FIELDS AND FURTHER DESTABILIZATION OF THE AIRMASS OVER THE
MOUNTAINS IN THE AFTERNOON WHERE BETTER SURFACE HEATING OCCURS
WILL RESULT IN MORE WIDESPREAD SHOWER AND STORM COVERAGE DURING
THE LATE AFTERNOON AND EVENING HOURS. THERE IS SOME POTENTIAL FOR
LOCALLY HEAVY RAINFALL...SEE HYDRO DISCUSSION BELOW. THREAT OF ANY
SEVERE WEATHER ON MONDAY LOOKS QUITE LOW CONSIDERING LACK OF
SURFACE BASED INSTABILITY AND COOL/SLIGHTLY STABLE BOUNDARY LAYER.

PRECIPITATION COVERAGE IS EXPECTED TO GRADUALLY DECREASE LATE
MONDAY NIGHT...BUT SHOWERS AND A FEW STORMS WILL QUICKLY FILL BACK
IN TUESDAY AS STRONGER SHORT WAVE TROUGH GETS KICKED NORTHEAST
INTO THE STATE. INCREASING SYNOPTIC SCALE LIFT AND A SLIGHTLY
UNSTABLE AIRMASS WILL LEAD TO INCREASED COVERAGE OF SHOWERS AND
THUNDERSTORMS. HAVE INCREASED POPS INTO THE LIKELY CATEGORY BASED
ON INCREASING CONFIDENCE OF THESE SYNOPTIC SCALE FEATURES LINING
UP WITH DAYTIME HEATING AND A VERY MOIST/SLIGHTLY UNSTABLE
ATMOSPHERE. WHILE MARGINAL INSTABILITY GENERALLY LESS THAN 1000
J/KG WILL KEEP THE SEVERE THREAT LIMITED...THERE MAY BE A THREAT
OF SHORT LIVED WEAK TORNADOES AS LOW LEVEL WIND FIELD STRENGTHENS
AND LCLS ARE ONLY EXPECTED TO BE NEAR 3000 FT AGL. WILL SEE A
CONTINUED THREAT OF LOCALLY HEAVY RAINFALL. SNOW LEVELS EXPECTED
TO AVERAGE BETWEEN 10500 AND 12000 FEET FOR MOST OF THIS PRECIP
EVENT WITH SEVERAL INCHES TO OVER A FOOT ACROSS THE HIGHER
MOUNTAIN PEAKS.

TUESDAY NIGHT AND WEDNESDAY...THE UPPER LEVEL TROUGH WILL BE
KICKING NORTHEAST ACROSS THE NORTHEAST COLORADO PLAINS TAKING THE
BEST CHANCE OF SHOWERS/STORMS WITH IT. HOWEVER...THERE IS ENOUGH
INSTABILITY LINGERING IN THE STILL RATHER MOIST AND SLIGHTLY
UNSTABLE ENVIRONMENT BEHIND THE TROUGH AXIS AND POTENTIAL FOR
ANTICYCLONIC UPSLOPE FLOW TO KEEP A DECENT CHANCE OF SHOWERS AND A
FEW THUNDERSTORMS IN THE FORECAST THROUGH WEDNESDAY.

A DRIER PERIOD IS EXPECTED LATE WEDNESDAY NIGHT INTO
THURSDAY...ALTHOUGH STILL CANT RULE OUT ISOLATED TO SCATTERED
SHOWER AND STORM DEVELOPMENT AS MOISTURE DOES NOT SCOUR OUT
COMPLETELY.

FOR FRIDAY AND SATURDAY...THE STRONGER UPPER LEVEL CLOSED LOW
DROPPING INTO THE DESERT SOUTHWEST WILL KEEP THE CHANCE OF SHOWERS
AND STORMS IN THE FORECAST. THERE MAY ALSO BE A HIGHER RISK OF
SEVERE WEATHER AS WIND SHEAR INCREASES AHEAD OF THE UPPER LOW.
SEVERE THREAT WOULD LIKELY HINGE ON EVENTUAL LOCATION OF NEXT
FRONTAL SYSTEM AND IF HIGHER THETA-E RIDGE CAN BUBBLE UP ALONG THE
FRONT RANGE/HIGH PLAINS.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 935 AM MDT SUN MAY 3 2015

A COLD FRONT WILL CAUSE WINDS TO BECOME NORTHEASTERLY THIS
AFTERNOON. AFTER 21Z SCATTERED THUNDERSTORMS MAY IMPACT AREA
AIRPORTS WITH GUSTY OUTFLOW WINDS TO 30 KTS BEING THE THE PRIMARY
THREAT. AS THE EVENING PROGRESSES THUNDERSTORMS WITH HEAVY RAIN
WILL BE POSSIBLE. AFTER 05Z MVFR CONDITIONS WILL BE POSSIBLE WITH
SHOWERS AND A FEW THUNDERSTORMS...AFTER 08Z EXPECT AREAS OF IFR
WITH STRATUS AND FOG.

&&

.HYDROLOGY...
ISSUED AT 935 AM MDT SUN MAY 3 2015
THE COMBINATION OF UPPER TROUGH AND DEEPENING UPSLOPE FLOW WILL
ALLOW FOR LOCALLY HEAVY RAIN THIS EVENING...EXPECIALLY ON THE
PLAINS. WITH PRECIPITABLE WATER VALUES UP TO 0.80...EXPECT STORMS
TO PRODUCE UP TO AN INCH IN 30 MINUTES. SHOWERS MAY LINGER THROUGH
THE NIGHT...THEN ANOTHER ROUND OF STORMS WILL DEVELOP ON MONDAY.
LATEST FORECAST MODELS SUGGEST THE BEST FOCUS WILL BE OVER THE
PALMER DIVIDE AND SOUTHEAST COLORADO. AGAIN AN INCH OF RAIN IN 30
MINUTES WILL BE THREAT. MAY ADJUST CURRENT QPF FORECAST A BIT
SOUTHWARD IN AFTERNOON FORECAST.

&&

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

$$

UPDATE...RTG
SHORT TERM...KRIEDERMAN
LONG TERM...BARJENBRUCH
AVIATION...RTG
HYDROLOGY...RTG


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