Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 300415
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1015 PM MDT MON JUN 29 2015

.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL REMAIN ANCHORED ACROSS
THE GREAT BASIN THROUGH THE WEEK. THE CENTER OF THE HIGH PRESSURE
WILL SHIFT TO THE FOUR CORNERS REGION THIS WEEKEND...ALLOWING
MOISTURE ALONG WITH MODESTLY COOLER TEMPERATURES TO MOVE INTO THE
REGION BY EARLY NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A RIDGE CENTERED OVER THE
EASTERN GREAT BASIN. AMDAR 400-250MB WIND OBSERVATIONS SHOW A
50-115KT ANTICYCLONIC JET FROM ALONG THE PACIFIC NORTHWEST OVER
THE CANADIAN ROCKIES AND INTO THE PLAINS. GOES/GPS/RAP/00Z SLC
RAOB INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN
0.60"...TO 0.75"-1.00" ACROSS MOST VALLEYS.

CONVECTION FROM THE CENTER OF THE RIDGE EASTWARD HAS
DISSIPATED...WITH LINGERING ACTIVITY ON THE WESTERN PERIPHERY.
UPDATED FORECAST TO MAINTAIN LOW POPS ALONG THE NEVADA BORDER...WITH
NO MENTION ELSEWHERE. HRRR-3KM IS STRUGGLING IN A VERY SIGNIFICANT
WAY IN THIS WEAK TRIGGER UNSTABLE ATMOSPHERE AND IS TOO COLD POOL
DOMINANT. BEST CONVECTIVE GUIDANCE IVE SEEN BY FAR WAS OUR WRF-
ARW4N RUN AT 12Z THIS MORNING.

BOOSTED OVERNIGHT LOWS WITH COMBINATION OF PERSISTENCE AND LAMP
GUIDANCE. ADJUSTED SKY BASED ON IR WHICH REFLECTS PATCHY CONVECTIVE
DEBRIS ACROSS MUCH OF THE STATE.

&&

PREVIOUS DISCUSSION...
THE STRONG UPPER RIDGE CENTERED OVER THE GREAT BASIN WILL REMAIN
THE DOMINANT FEATURE THROUGH THE SHORT TERM FORECAST PERIOD. A
SHORTWAVE MOVING EAST ACROSS THE NORTHERN ROCKIES ON TUESDAY WILL
FLATTEN THE RIDGE A BIT...BUT WILL HAVE LITTLE IMPACT ON SENSIBLE
WEATHER. WILL LOWER TEMPS A FEW DEGREES FOR TUESDAY...WITH STILL
SOLID DYNAMIC SUBSIDENCE LIMITING MOST CONVECTION TO THE HIGHER
TERRAIN DURING THE AFTERNOON/EARLY EVENING HOURS.

A SECONDARY SHORTWAVE DIGGING SOUTHEAST INTO THE NORTH PLAINS STATES
WILL FORCE THE RIDGE WEST INTO THE WESTERN GREAT BASIN WEDNESDAY
NIGHT THROUGH THURSDAY. A DRIER AND STILL VERY WARM NORTH-NORTHWEST
FLOW ON THE EAST SIDE OF THE RIDGE WILL KEEP TEMPS WELL ABOVE NORMAL
WITH LIMITED HIGH TERRAIN SHOWERS/THUNDERSTORMS DURING THE
AFTERNOON/EARLY EVENING HOURS.

DRIER AIRMASS BECOMES WELL ESTABLISHED OVER THE CWA BY FRIDAY WITH
MODELS INDICATING PWS IN THE 0.25-0.5 INCH RANGE. THE DRY AND STABLE
AIRMASS IS EXPECTED TO LIMITED ANY AFTERNOON/EARLY EVENING
CONVECTION TO THE HIGHER TERRAIN.

THE RIDGE AXIS IS PROGGED TO SHIFT EAST OVER THE WEEKEND. THIS WILL
ALLOW SOME MOISTURE TO SLOWLY MOVE BACK IN AS TEMPERATURES WARM.
THUS...AFTERNOON CONVECTION IS ONCE AGAIN POSSIBLE OVER THE HIGHER
TERRAIN. BY SUNDAY...THE RIDGE AXIS WILL BE EAST OF THE AREA. THE
SOUTHERLY FLOW THAT DEVELOPS WILL ALLOW TROPICAL MOISTURE TO BE
DRAWN INTO THE AREA. GFS IS STILL SLOWER WITH THE ARRIVAL OF
MOISTURE COMPARED TO THE GFS...MOVING THE BRUNT OF THE MOISTURE IN
EARLY MONDAY AS OPPOSED TO DURING THE DAY SUNDAY IN THE EC. CURRENT
POP TREND IN THE FORECAST COVERS THE INCREASE IN MOISTURE WELL WITH
ABOVE CLIMO POPS FOR MOST LOCATIONS BY SUNDAY AND EVEN HIGHER ON
MONDAY. THE INCREASE IN MOISTURE WILL ALSO RESULT IN A DOWNWARD
TREND IN TEMPERATURES FOR MONDAY.

&&

.AVIATION...VFR CONDITIONS AT KSLC TERMINAL WITH A GUSTY
SOUTHEAST DRAINAGE WIND OVERNIGHT.

&&

.FIRE WEATHER...THE UPPER RIDGE CENTERED OVER THE GREAT BASIN WILL
MAINTAIN THE HOT/DRY CONDITIONS IN THE VALLEYS...WITH ISOLATED
CONVECTION GENERATING MINIMAL RAIN AND LIGHTNING/ERRATIC WINDS
OVER THE HIGH TERRAIN THROUGH THE BALANCE OF THE WEEK.

A TRANSITION TO MORE ACTIVE CONVECTION WILL BEGIN THIS WEEKEND AS
THE CENTER OF THE UPPER RIDGE SHIFTS TOWARDS THE FOUR CORNERS
REGION. TEMPERATURES WILL REMAIN WELL ABOVE NORMAL OVER THE
WEEKEND WITH AN INCREASE IN HUMIDITIES AND CONVECTION DURING THE
LATTER HALF OF THE WEEKEND. BY EARLY NEXT WEEK MORE SEASONAL
TEMPERATURES...HIGHER RH VALUES AND AN INCREASING AREAL COVERAGE
OF SHOWERS/STORMS IS EXPECTED AS A MOIST SOUTHERLY FLOW DEVELOPS
ACROSS THE GREAT BASIN FOR THE FIRST HALF OF THE WEEK.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

$$

PUBLIC...ROGOWSKI/TRAPHAGAN
FIRE WEATHER...CONGER
AVIATION...ROGOWSKI

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)



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