Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 312124
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
324 PM MDT FRI JUL 31 2015

.SYNOPSIS...HIGH PRESSURE WILL REMAIN OVER THE FORECAST AREA
THROUGH SATURDAY BEFORE SHIFTING EAST. MOISTURE OVER SOUTHERN UTAH
WILL SPREAD NORTHWARD ON SUNDAY BEFORE DRIER CONDITIONS MOVE IN
BEGINNING MONDAY.

&&

.SHORT TERM (THROUGH 12Z MONDAY)...HIGH PRESSURE REMAINS OVER THE
AREA THIS AFTERNOON...WITH THE RIDGE AXIS ORIENTED NORTHWEST TO
SOUTHEAST. HIGH BASED MOISTURE REMAINS CONFINED TO SOUTHERN
UTAH...SOUTH OF I-70...WHERE PWS ARE IN THE 0.8 TO 1.0 INCH RANGE.
SOME THUNDERSTORMS HAVE DEVELOPED...PRIMARILY OVER THE HIGHER
TERRAIN...AND ARE MOVING LITTLE GIVEN THE LACK OF FLOW ALOFT.
GIVEN THE RELATIVELY DRY LOWER LEVELS EXPECT THAT LITTLE IF ANY
RAIN IS HITTING THE GROUND. STORMS SHOULD CONTINUE INTO THE EARLY
EVENING BEFORE DISSIPATING. MAXES APPEAR TO BE RUNNING NEAR
SEASONAL NORMALS ONCE AGAIN.

AS THE TROUGH NEAR 130W TRACKS NORTHWARD TONIGHT AND
TOMORROW...THE RIDGE AXIS IS EXPECTED TO BECOME MORE NORTH TO
SOUTH IN ORIENTATION...RESULTING IN RATHER LIGHT FLOW ALOFT.
LITTLE CHANGE IS EXPECTED IN THE POSITION OF THE MOISTURE OVER
SOUTHERN UTAH TOMORROW...SO SHOWERS AND STORMS SHOULD FIRE IN A
SIMILAR FASHION TO TODAY. BY SATURDAY NIGHT...FLOW ALOFT BECOMES
MORE SOUTHERLY AS A VORT MAX MOVES NORTHWARD INTO
NEVADA...SHIFTING THE RIDGE EASTWARD. THIS WILL DRAW THE MOISTURE
OVER SOUTHERN UTAH NORTHWARD ACROSS THE FORECAST AREA. THE WAVE IS
EXPECTED TO GRAZE WESTERN UTAH AS IT CONTINUES TO THE NORTH DURING
THE DAY SUNDAY. THE INCREASE IN MOISTURE AND INSTABILITY WILL
INCREASE COVERAGE OF SHOWERS AND THUNDERSTORMS ON SUNDAY...THOUGH
LOWER LEVELS WILL STILL REMAIN FAIRLY DRY.

&&

.LONG TERM (AFTER 12Z MONDAY)...SHORT WAVE THAT ORIGINATED WITHIN
THE RETURN FLOW IS RESOLVED TO REMAIN OVER FAR NORTHERN UTAH MONDAY
MORNING BEFORE DEPARTING TO THE NORTHEAST. HAVE ADDED SLIGHT CHANCE
POPS FAR NORTH/EAST TO ACCOUNT FOR POSITIONING OF THIS WAVE...AND
ANY LINGERING CONVECTION THAT WILL REMAIN TIED TO IT.
ADDITIONALLY...LOWERED MAX TEMPS FOR MONDAY AFTERNOON AS H7 TEMPS
WILL BE COOLING BEHIND THIS WAVE PER GLOBALS.

A DRIER SOUTHWESTERLY FLOW WILL THEN IMPINGE ACROSS THE EASTERN
GREAT BASIN IN RESPONSE TO A DEEPENING OF A BRITCOL CLOSED LOW AND
ITS POTENTIAL INTERACTION WITH A WEAK LOW OFF THE CALI COAST. MODELS
BEGIN TO DIVERGE SIGNIFICANTLY ON THE HANDLING OF THESE FEATURES MID
TO LATE WEEK HOWEVER.

PREVIOUS RUNS OF THE OPERATIONAL GFS TRANSLATED THE BRITCOL LOW
SOUTH INTO THE PACNW ALLOWING THE CALI LOW TO OPEN AND SWEEP
NORTHEAST THROUGH NEVADA THURSDAY...THIS OPENING A TAP OF SUB-TROP
MOISTURE TO SPREAD SOUTH TO NORTH ACROSS THE STATE ATTM. EC WAS
FURTHER EAST WITH THIS MOISTURE ADVECTION BUT HAS NOW CONFORMED TO
THE PREVIOUS GFS. THE LATEST GFS HOWEVER IS LESS AMPLIFIED AND MORE
PROGRESSIVE WITH THE BRITCOL LOW AND SLOWER WITH THE CALI LOWS
PROGRESSION AND ASSOCIATED TAP. DUE TO FORECAST SPREAD AND RUN TO
RUN INCONSISTENCIES PRESENT OPTED TO LEAVE THU/FRI GRIDS LARGELY
UNCHANGED.

&&

.AVIATION...SURFACE WINDS AT THE SLC TERMINAL WILL SWITCH BACK TO
THE SOUTHEAST BETWEEN 03Z AND 05Z. VFR CONDITIONS WILL PREVAIL
THROUGH THE TAF PERIOD.

&&

.FIRE WEATHER...HIGH BASED MOISTURE REMAINS OVER SOUTHERN UTAH THIS
AFTERNOON WITH LITTLE NORTHWARD MOVEMENT. A FEW SHOWERS HAVE
DEVELOPED AND WILL CONTINUE INTO THE EARLY EVENING. HIGH PRESSURE
WILL REMAIN IN PLACE THROUGH TOMORROW...SO CONDITIONS TOMORROW
WILL BE SIMILAR TO TODAY. AS THE RIDGE MOVES EAST SATURDAY
NIGHT/SUNDAY...MOISTURE WILL SPREAD NORTHWARD ACROSS THE FIRE
DISTRICT. COMBINED WITH A DISTURBANCE MOVING ACROSS THE GREAT
BASIN DURING THIS TIME...THIS WILL RESULT IN INCREASING COVERAGE
OF SHOWERS AND THUNDERSTORMS. A DRIER SOUTHWEST FLOW IS EXPECTED
TO DEVELOP BEGINNING MONDAY...WITH SOME GUSTY WINDS POSSIBLE BY
MIDWEEK.

&&

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

$$

SHORT TERM/FIRE WEATHER...TRAPHAGAN
LONG TERM...MERRILL
AVIATION...SCHOENING

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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