Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 050946
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
346 AM MDT TUE MAY 5 2015

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 346 AM MDT TUE MAY 5 2015

MODELS REMAIN IN GOOD AGREEMENT WITH PLENTY OF PRECIP IN THE
FORECAST OVER THE NEXT FEW DAYS. SHORT RANGE MODELS...HRRR AND
RAP...HAVE PERFORMED FAIRLY WELL THIS EVENING WITH PRECIP
LOCATIONS AND IF THIS HOLDS TRUE...PRECIP WILL CONTINUE FOR THE
SAN JUANS AND PICK UP FOR THE SOUTHERN VALLEYS OVERNIGHT. ALL OF
THIS IS IN RESPONSE TO AN AREA OF LOW PRESSURE CURRENTLY CENTERED
OVER ARIZONA AND CYCLONIC FLOW THAT IS PULLING IN MOISTURE FROM
THE SOUTH ALLOWING PWATS TO REACH VALUES OVER 200% OF NORMAL.
PIECES OF ENERGY WILL EJECT FROM THE LOW AND BE THE FOCUS OF
PRECIP TODAY UNTIL THE LOW PRESSURE BECOMES AN OPEN WAVE AND MOVES
NEWRD ACROSS OUR CWA AND ITSELF BECOMES THE FOCUS OF PRECIP.

WHILE SOME THUNDERSTORMS ARE EXPECTED AND REMAIN IN THE
FORECAST...CLOUD COVER...LOW CAPE AND MARGINAL INSTABILITY WILL
LIKELY BRING MORE STRATIFORM RAIN THAN CONVECTIVE. DESPITE ALL
THAT...ANY PEAKS OF SUN THAT BREAK THROUGH WILL LIKELY SET OFF
SOME STORMS THAT WILL PRODUCE SOME HEAVY RAIN. EXPECT PRECIP TO
GET GOING AROUND NOON...IF NOT A LITTLE BEFORE...AND CONTINUE
POSSIBLY THROUGH WEDNESDAY MORNING. THE HEAVIEST PRECIP LOOKS TO
FAVOR THE CENTRAL MTNS AND AREAS N OF I-70 WHERE BEST QG ASCENT IS
LOCATED AS THE UPPER LEVEL WAVE MOVES ACROSS. THAT`S NOT TO SAY
THAT OTHER AREAS WON`T SEE PRECIP BECAUSE MUCH OF THE CWA
WILL...INCLUDING VALLEY LOCATIONS...BUT THE HEAVIEST REMAINS
FAVORED UP NORTH. SOME RUNOFF CONCERNS ARE CERTAINLY POSSIBLE IF
THE MODELS HOLD TRUE WHICH IS LOOKING MORE AND MORE LIKELY. SOME
SNOW IS ALSO EXPECTED AT ELEVATIONS ABOVE 10K FEET THOUGH ROADS
WILL LIKELY REMAIN TOO WARM FOR MUCH ACCUMULATION.

NOT MUCH REST WEDNESDAY AS THE NEXT UPPER LEVEL SHORTWAVE MOVES
ACROSS THE AREA BRINGING ANOTHER ROUND OF SHOWERS AND STORMS WITH
HIGHER TERRAIN FAVORED AT THIS TIME. WHILE PWATS WILL START
DROPPING...VALUES WILL STILL REMAIN ABOVE NORMAL. TEMPS WILL RUN
COOLER THAN NORMAL DUE TO CLOUD COVER AND PRECIP.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 346 AM MDT TUE MAY 5 2015

DRYING BEGINS WEDNESDAY NIGHT AS A CLOSED LOW ALONG THE WEST COAST
DIGS SOUTHWARD DURING THE NIGHT. IN RESPONSE...FLOW BECOMES MORE
SOUTHERLY TAPPING INTO DRIER AIR OFF OF THE BAJA COAST. THE REGION
WILL SEE PRECIPITABLE WATER (PW) FALL FROM NEAR 0.50 OF AN INCH TO
AROUND 0.25 OF AN INCH ON THURSDAY AFTERNOON. AS A RESULT...EXPECT
ANY MOIST CONVECTION THURSDAY AFTERNOON/EVENING WILL BE HIGH BASED
AND ANCHORED TO HIGHER TERRAIN. SIMILAR CONDITIONS ARE EXPECTED
FRIDAY...THOUGH GFS HINTS THAT MOISTURE WILL BEGIN TO INCREASE A
BIT AS THE LOW CENTER DROPS OVER SOUTHERN CALIFORNIA FOR A SLIGHT
UPTICK IN SHOWER AND THUNDERSTORM ACTIVITY. THIS IS LESS APPARENT
IN THE ECMWF SOLUTION WHICH...IN CONTRAST TO THE GFS SOLUTION...
BEGINS MOVING THE LOW EASTWARD TO THE ARIZONA/NEVADA/UTAH TRIPLE
POINT BY 00Z/SAT.

MODEL DIFFERENCES PERSIST THROUGH THE WEEKEND WITH THE ECMWF
REMAINING THE MORE PROGRESSIVE OF THE TWO SOLUTIONS. DESPITE
DISPARITIES...BOTH SOLUTIONS INDICATED THAT THE FORECAST AREA IS
HEADED TOWARD ANOTHER COOLER AND UNSETTLED PERIOD. GIVEN THE
VARIABILITY OF THE LOW/S TRACK OVER THE PAST SEVERAL MODEL RUNS
WILL CONTINUE TO DEFER TO THE BLENDED SOLUTION WHICH KEEPS
MOUNTAINS IN THE CHANCE CATEGORY WITH LOWER POPS IN THE VALLEYS.

CONSENSUS EVEN HARDER TO COME BY MONDAY AS THE ECMWF BUILDS A
SHORTWAVE RIDGE OVER THE AREA...HAVING KICKED THE LOW OFF TO THE
GREAT LAKES REGION. IN CONTRAST...THE LOW DRIFTS NORTHWARD OVER
THE HIGH PLAINS IN THE GFS SOLUTION WITH A SHORTWAVE TROUGH
SLIDING EASTWARD ACROSS THE REGION TO BEGIN NEXT WEEK. PREDICTABLY
...THE EC SOLUTION POINTS TO QUIET AND WARMER CONDITIONS WHILE THE
GFS POINTS TO A WETTER AND COOLER DAY. GIVEN MODEL SPREAD THERE IS
NO WAY TO CONFIDENTLY SIDE WITH EITHER SOLUTION SO WILL STAY WITH
THE BLEND FOR NOW.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 346 AM MDT TUE MAY 5 2015

SCATTERED TO NUMEROUS SHOWERS...MAINLY SOUTH OF THE I-70 CORRIDOR
...WILL RESULT IN AREAS OF MOUNTAIN OBSCURATION THROUGH MIDDAY.
SOME SHOWERS WILL MOVE OVER ADJACENT AIRPORTS THIS MORNING THOUGH
EXPECT THE FLIGHT CATEGORIES WILL NOT DROP BELOW VFR.

DAYTIME WARMING WILL BRING INCREASED SHOWER COVERAGE AND INTENSITY
FROM 18Z TO 03Z ALONG WITH EMBEDDED THUNDERSTORMS. OUTFLOW WINDS
FROM 25 TO 30 MPH ARE POSSIBLE IN THE VICINITY OF STRONGER STORM
CELLS. ITS LIKELY THAT SHOWERS WILL IMPACT AIRPORTS ACROSS THE
REGION THIS AFTERNOON AND EVENING WITH MVFR VSBY AND CIGS POSSIBLE
FROM STRONGER CELLS. SHOWERS WILL DECREASE LATER TONIGHT WITH
MINIMAL IMPACT ON FLIGHT ACROSS EASTERN UTAH AND WESTERN COLORADO.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...NONE.
UT...NONE.

&&

$$

SHORT TERM...TGR
LONG TERM...NL
AVIATION...NL



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