Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 271545
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
945 AM MDT SAT JUN 27 2015

.SYNOPSIS...HIGH PRESSURE WILL STRENGTHEN ACROSS THE REGION
THROUGH THE WEEKEND...AND REMAIN OVER THE WESTERN STATES THROUGH
NEXT WEEK.

&&

.DISCUSSION...MORNING WATER VAPOR AND H5 ANALYSIS PLACE THE AXIS
OF A STRONG UPPER LEVEL RIDGE ACROSS WESTERN UTAH...GRADUALLY
STRENGTHENING. H7 TEMP IN THE 12Z KSLC RAOB REMAINED JUST A TOUCH
OVER +16 C WITH GUIDANCE SUGGESTING +18 C BY 00Z THIS EVE...+19 C
BY 00Z MON AND +20 C BY 00Z TUE. NEEDLESS TO SAY THE PRIMARY
TALKING POINT REGARDING SENSIBLE WEATHER ACROSS THE AREA REMAINS
FOCUSED ON THE RECORD CHALLENGING HEAT FOR THE NEXT FEW DAYS.
SHOULD JUST TOUCH TRIPLE DIGITS TODAY AREAS ALONG THE WASATCH
FRONT WITH TEMPS FURTHER CLIMBING A DEGREE OR TWO EACH DAY THROUGH
MON. TEMPS LIKELY PLATEAUING TODAY AND REMAINING VERY HOT ACROSS
THE SOUTH INTO EARLY NEXT WEEK.

WEAK MID AND HIGH LEVEL MOISTURE ADVECTION CONTINUES THIS MORNING
WITH FOCUS ALONG AND WEST OF THE RIDGE AXIS...BUT STARTING TO SEE
THIS INFUSE AROUND MUCH OF THE MID LEVEL HIGH CIRCULATION AS SOME
IS NOW ADVECTING INTO THE EAST WITHIN THE PREVIOUSLY DRY
NORTHWESTERLY FLOW ALOFT. AFTERNOON THERMALS WILL LIKELY INDUCE
ISOLATED HIGH BASED CONVECTION ALONG THE MOUNTAIN SPINE FROM THE
UINTAS SOUTH INTO THE SOUTHERN MOUNTAINS...WITH WEAK SOUTHERLY
DRIFT POTENTIALLY ALLOWING ONE OR TWO OF THESE CELLS TO MOVE OVER
ADJACENT VALLEYS TO THE SOUTH. HAVE ISOLATED DRY THUNDERSTORM
WORDING IN FORECAST THOUGH A HUNDREDTH OR SO OF RAIN IS POSSIBLE
OVER THE HIGH TERRAIN...BUT PRIMARY OUTCOME FROM ANY CELLS THAT DO
DEVELOP WILL BE GUSTY/MICROBURST WINDS AND A FEW DRY LIGHTNING
STRIKES. A SIMILAR DIURNALLY DRIVEN CONVECTIVE THREAT WILL
CONTINUE THROUGH MONDAY AS THE MEAN PLACEMENT OF THE RIDGE WILL
VARY LITTLE THROUGH THAT TIME.

GOING FORECAST HANDLES THIS WELL AND HAVE MADE NO UPDATES THIS
MORNING. PREVIOUS LONG TERM DISCUSSION BELOW...

...THE PERSISTENT HIGH OVER THE GREAT BASIN IS FORECAST TO BEGIN
TO ELONGATE E-W ON TUE WITH THE CENTER REMAINING OVER SRN UT. THIS
INCREASES THE WLY FLOW ACROSS THE NORTH WITH EVEN A NWLY COMPONENT
AT LOWER LEVELS GENERATING A WEAK FRONTAL BOUNDARY THAT PUSHES
THRU THE NRN CWA TUE AFTN/EVE. MOISTURE WILL TEND TO FOCUS ALONG
THIS WEAK FEATURE BRINGING AN INCREASE IN THE COVERAGE OF
CONVECTION AS IT DRIFTS SWD.

THIS ALSO BRINGS SLIGHT COOLING TO NORTHERN UT AND PROBABLY THE
MTNS DUE TO THE INCREASE IN CONVECTION.

MED RANGE MODELS DIVERGE AT THIS POINT WITH THE LATEST EC TAKING
THE HIGH WESTWARD THRU THU WITH THE INCREASING NLY FLOW OVER THE
CWA BRINGING A STRONG DRYING TREND AND CLEARING THE STATE OF
CONVECTION BY THU AFTN. THE GFS EVENTUALLY DOES THIS TOO BUT IT
TAKES UNTIL SAT AND IT LEAVES SOME MOISTURE OVER THE EAST.
CONFIDENCE IS NOT GOOD IN EITHER SOLUTION AND FORECAST IS A
COMPROMISE BUT LEANS TOWARDS THE DRIER EC.

MODELS CONTINUE TO DIVERGE THRU THE WEEKEND WITH THE EC BRINGING
THE HIGH BACK INTO THE ERN GREAT BASIN AND WARMING TEMPS BACK UP
WHILE THE GFS HAS A COOLER AND DRIER NWLY FLOW. CONFIDENCE IN THE
FORECAST IS EVEN LOWER AT THIS POINT BUT KEPT GRIDS LEANING
TOWARDS THE DRIER SOLUTION.

&&

.AVIATION...LIGHT SOUTHEASTERLY WINDS WILL DECREASE AND SHIFT TO
NORTH BETWEEN 16Z AND 18Z WITH A 20 PERCENT CHANCE OF SHIFTING
BETWEEN 15Z AND 16Z. VFR CONDITIONS WILL PREVAIL UNDER EITHER MOSTLY
CLEAR SKIES OR HIGH THIN CLOUDS THROUGH THE TAF PERIOD.

&&

.FIRE WEATHER...EXCESSIVE HEAT AND LOW RH WILL PREVAIL ACROSS THE
REGION TODAY WITH A SLIGHT DOWNWARD TREND IN TEMPERATURES ACROSS THE
SOUTH SUNDAY AND MONDAY WHILE TEMPERATURES WILL INCREASE A COUPLE
MORE DEGREES SUNDAY AND MONDAY ACROSS THE NORTH. THE MAIN CONCERN
DURING THIS HOT SPELL WILL BE THE INFUSION OF MID-HIGH LEVEL
MOISTURE WHICH WILL BRING A THREAT OF HIGH-BASED THUNDERSTORMS TO
MAINLY THE HIGH TERRAIN EACH AFTERNOON AND EVENING. THESE
THUNDERSTORMS WILL BE ISOLATED WITH LIGHTNING AND GUSTY ERRATIC
WINDS BEING THE MAIN THREAT.

A SLIGHT INCREASE IN THUNDERSTORM COVERAGE OCCURS LATER MONDAY
THROUGH WEDNESDAY AS A WEAK DISTURBANCE TEMPORARILY FLATTENS THE
RIDGE OF HIGH PRESSURE AND FOCUSES WHAT LITTLE MOISTURE THERE IS FOR
A SLIGHTLY HIGHER CHANCE OF THUNDERSTORMS. THE RIDGE IS EXPECTED TO
SHIFT WESTWARD IN THE WAKE OF THIS DISTURBANCE WHICH WILL ALLOW A
DRIER NORTHWEST FLOW TO SET IN FOR THE END OF THE WEEK. TEMPERATURES
WILL REMAIN HOT.

&&

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

$$

MERRILL/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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