Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 261625
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1025 AM MDT WED AUG 26 2015

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL CROSS THE REGION FROM SOUTH
TO NORTH TODAY. HIGH PRESSURE WILL RETURN FOR THE LATTER HALF OF
THE WEEK INTO THE UPCOMING WEEKEND.

&&

.DISCUSSION...MORNING WATER VAPOR AND H5 ANALYSIS INDICATES MID
LEVEL RIDGING CENTERED OVER THE NORTHERN ROCKIES AND A DEEPENING
UPPER LOW OFF THE PACNW. THIS IS ALLOWING FOR DEEP SOUTHWESTERLY
FLOW ACROSS THE EASTERN GREAT BASIN AND INTER MOUNTAIN
REGION...WITH SUITABLE STREAMLINES TO ADVECT DEEP MOISTURE ACROSS
THE AREA. WITHIN THIS FLOW A MID LEVEL LOW IS TRANSLATING NORTH
AND EAST THROUGH UTAH THIS MORNING...WITH CIRCULATION CENTERED
OVER WEST CENTRAL UTAH ATTM. SURFACE DEWPOINTS REMAIN NOTABLE
...WITH 50S TO 60 THE NORM ACROSS THE FORECAST AREA /INDICATIVE
OF A PRIMED BOUNDARY LAYER/. PWAT VALUES RANGE FROM 1 TO 1.4 WITH
VALUES MOST PROLIFIC ACROSS THE SOUTH AND WEST TIED TO THE LOW.

ALTHOUGH INSTABILITY WILL BE LARGELY SUPPRESSED DUE TO LOW/MID
LEVEL LAPSE RATES REMAINING ON THE ORDER OF 5.5C...FORCING WILL
CONTINUE TO INCREASE ALONG THE NORTHERN/EASTERN PERIPHERIES OF THE
LOW TODAY ALLOWING FOR WIDESPREAD SHOWERS ACROSS MUCH OF THE
AREA. FAVORABLE LOW LEVEL FLOW EXISTS FOR OROGRAPHIC ENHANCEMENT
ALONG THE GRAND STAIRCASE ATTM AND WILL FOR THE NEXT SEVERAL
HOURS. ADDITIONALLY KPGA BUFR SHOWS POTENTIAL FOR WARM RAIN
PROCESSES ACROSS THE SOUTH AS A DEEP WARM CLOUD
LAYER IS IN PLACE...RELATIVELY SHALLOW INSTABILITY THROUGH THE
LAYER EXISTS...AND WEAK UNI-DIRECTIONAL SW FLOW COULD ENHANCE
RATES. NOTING THE HEAVIEST RETURNS ACROSS THIS REGION FROM
ROUGHLY KANAB TO KPGA NORTH TO BRYCE CANYON ACROSS THIS FAVORED
AREA...AND SPOTTERS HAVE REPORTED STEADY MODERATE TO HEAVY RAIN IN
THE KANAB AREA. OPTED TO ISSUE AN AREAL FLOOD WARNING ACROSS SOUTH
CENTRAL UTAH AS MOST ALL BASINS /INCLUDING WAHWEAP AND THE PARIA/
WILL LIKELY SEE IN EXCESS OF A HALF INCH OF RAIN OVER THE NEXT
SEVERAL HOURS...ENOUGH TO FILL THE BASINS AND ALLOW FOR STEADY
RISES WITHIN THE NORMALLY DRY WASHES ON INTO THE RIVER CHANNELS.
WILL CONTINUE TO MONITOR FOR FLASH FLOOD POTENTIAL OF THE MORE
FLASHY BASINS WITHIN THE WARNING AREA IF LOCAL CONVECTION BECOMES
A BIT DEEPER AND PRECIP RATES INCREASE.

DUE TO EXTENSIVE COVERAGE OF RAIN ACROSS THE SOUTH...INCREASED
MORNING POPS TO CATEGORICAL...BUT IN GENERAL LEFT LIKELY POPS FOR
MUCH OF THE FORECAST AREA. NORTHEASTWARD TRANSLATION OF THE LOW
WILL TEND TO FOCUS PRECIP AND CENTRAL AND NORTHERN UTAH INTO THE
AFTERNOON HOURS...AND WILL LIKELY SEE A NET DOWNTURN IN COVERAGE
AND EXTENT OF PRECIP ACROSS THE SOUTH AS SUBSIDENCE BEGINS TO
DOMINATE IN WAKE OF THE LOW PASSAGE. THE MAIN FORECAST PROBLEM IN
THE SHORT TERM IS MONITORING THE POTENTIAL OF REDEVELOP ACROSS THE
SOUTH LATE DATE IF AND WHEN CLOUD COVER BEGINS TO THIN ALLOWING
INSTABILITY TO TICK UP.

OUTSIDE OF THOSE UPDATES NOTED GOING FORECAST REMAINS ON TRACK.

&&

.AVIATION...IN GENERAL THE KSLC TERMINAL WILL CONTINUE TO SEE
PERIODIC LIGHT TO MODERATE RAIN SHOWERS IN VFR CONDITIONS INTO THE
EARLY EVENING HOURS. THIS SAID...A 10 PERCENT CHANCE EXISTS FOR
THUNDER AT THE TERMINAL AFTER 19-20Z. WINDS ARE EXPECTED TO REMAIN
SOUTHERLY THROUGH EARLY AFTERNOON...WITH A 60 PERCENT CHANCE OF
SHIFTING TO THE NORTHWEST AFTER 20Z.

&&

.FIRE WEATHER...A DISTURBANCE EMBEDDED WITHIN A MONSOONAL SURGE
WILL MOVE NORTHWARD ACROSS THE REGION TODAY CREATING WIDESPREAD
SHOWERS AND SCATTERED THUNDERSTORMS. INSTABILITY SHOWERS AND
THUNDERSTORMS WILL CONTINUE INTO THURSDAY...BUT MAINLY OVER THE
HIGHER TERRAIN AND BY FRIDAY AND SATURDAY ONLY ISOLATED MOUNTAIN
THUNDERSTORMS ARE EXPECTED. A STRONG TROUGH IS EXPECTED TO REMAIN
OFF THE PACIFIC NORTHWEST COAST THIS WEEKEND WHICH WILL CAUSE A
MAINLY DRY AND BREEZY SOUTHWEST FLOW TO PREVAIL ACROSS UTAH. THE
TROUGH WEAKENS MONDAY AS SOME ENERGY EJECTS NORTHEAST ACROSS THE
NORTHERN ROCKIES WHICH WILL PUSH A COLD FRONT INTO NORTHERN UTAH.
HOWEVER...A BROAD TROUGH WILL REMAIN OVER THE PACIFIC NORTHWEST
AND NORTHERN ROCKIES THROUGH MIDWEEK WHICH WILL KEEP UTAH UNDER A
DRY AND BREEZY REGIME.

&&

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

$$

PUBLIC...MERRILL


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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