Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 011040
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
440 AM MDT WED JUL 1 2015

.SYNOPSIS...HIGH PRESSURE ALOFT CENTERED ACROSS THE WESTERN GREAT
BASIN WILL SHIFT EAST TO THE FOUR CORNERS THIS WEEKEND. A GRADUAL
DRYING TREND CAN BE EXPECTED THROUGH THE END OF THE WORK WEEK...THEN
INCREASING MOISTURE AND SOMEWHAT COOLER TEMPERATURES WILL MOVE INTO
THE REGION FOR EARLY NEXT WEEK.

&&

.SHORT TERM (UNTIL 06Z SATURDAY)...AIR MASS HAS MOISTENED UP OVER
PAST 24 HRS WITH PWS NEARLY AN INCH OVER VALLEYS AND ABOUT 3/4 OF AN
INCH OVER THE HIGHER TERRAIN. ISOLATED THUNDERSTORMS WERE ABLE TO
PRODUCE ABOUT 0.25 OF AN INCH TUESDAY EVENING...DESPITE GUSTY WINDS
BEING THE MOST COMMON OCCURRENCE WITH THESE STORMS DUE TO A
RELATIVELY DRY SUB CLOUD LAYER. WITH THE SUB CLOUD LAYER MOISTENING
A LITTLE MORE OVERNIGHT AND A WEAK DISTURBANCE STILL TO MOVE ACROSS
NORTHERN UTAH THIS MORNING HAVE INCREASED POPS TO ISOLATED OR HIGHER
ACROSS MOST OF NORTHERN UTAH AND SOUTHWEST WYOMING THIS MORNING. SPC
HAS A GREATER THAN 50 PERCENT PROBABILITY THAT MOST UNSTABLE CAPE
VALUES WILL EXCEED 1000J/KG ACROSS MOST OF THE CWA THIS MORNING BUT
DECREASE ACROSS THE NORTH THIS AFTERNOON. LIFTED INDEX VALUES OF
MINUS 2 OR LOWER ALSO SUPPORT THIS INSTABILITY THIS MORNING BETWEEN
15 AND 18Z. WHILE SOME OF THESE INSTABILITY PARAMETERS ARE ALSO
PRESENT ACROSS THE SOUTH THIS MORNING BELIEVE WE NEED A LITTLE
FORCING TO REALIZE THE INSTABILITY. IN THIS CASE ITS THE DISTURBANCE
ACROSS THE NORTH WHICH IS EVIDENT IN THE 700-500 MB THETA E RIDGE
FIELD WHICH WILL PROVIDE THE LIFT.

IN THE WAKE OF THIS DISTURBANCE SIGNIFICANT DRYING WILL TAKE PLACE
WITH PWS DROPPING DOWN BELOW 0.50 OF AN INCH BY LATE TONIGHT ACROSS
EXTREME NORTHERN UTAH AND SOUTHWEST WYOMING. THIS DRIER AIR WILL
WORK ITS WAY INTO CENTRAL UTAH THURSDAY AFTERNOON BUT SOUTHERN UTAH
WILL STILL BE MOIST ENOUGH FOR ISOLATED THUNDERSTORMS. DESPITE THE
GFS SHOWING THIS DRYING MAKING IS WAY INTO SOUTHERN UTAH FRIDAY HAVE
LEFT SOME TOKEN POPS IN AS CONFIDENCE IS LOW THAT FULL DRYING WILL
TAKE PLACE.


.LONG TERM (AFTER 06Z SATURDAY)...THE NW-SE ORIENTED RIDGE AXIS WILL
START MIGRATING EASTWARD FRIDAY NIGHT AND SHOULD BE MORE VERTICALLY
SITUATED OVERHEAD AGAIN BY SATURDAY AFTERNOON. THIS WILL RESULT IN
MOISTURE STARTING TO RETURN TO SOUTHERN AND WESTERN UTAH WITH A
CORRESPONDING INCREASE IN CONVECTION. HOWEVER...THE AIRMASS WILL
REMAIN QUITE WARM...18-20C AT 700MB EXCEPT ACROSS THE FAR SOUTHWEST
WHERE IT WILL BE A BIT COOLER IN RESPONSE TO THE INCREASE IN
MOISTURE.

THE RIDGE AXIS WILL BE EAST OF UTAH FOR SUNDAY...OPENING THE DOOR TO
EVEN MORE MOISTURE. FURTHERMORE...WEAK RIPPLES IN THE FLOW ALONG THE
WESTERN AND NORTHERN PERIPHERY OF THE RIDGE COULD ALLOW FOR ENHANCED
SHOWER COVERAGE DURING THIS TIME. THIS WETTER AND UNSETTLED WEATHER
WILL YIELD A COOLING TREND THAT...ALTHOUGH IT WILL STILL BE A BIT
WARMER THAN NORMAL...WILL BRING A RESPITE FROM THE HOT TEMPERATURES
OF LATE.

THE RIDGE IS EXPECTED TO FLATTEN IN RESPONSE TO A TROUGH ALONG THE
CANADIAN BORDER SUNDAY INTO MONDAY. THE RESULTING WESTERLY FLOW WILL
THEN START TO BRING A DRIER AIRMASS INTO THE AREA. HOWEVER...IT WILL
TAKE A FEW DAYS TO EVACUATE THE MOISTURE SO WENT WITH A SLOW DRYING
TREND AS ISOLATED SHOWERS WILL STILL BE POSSIBLE HEADING INTO THE
MIDDLE OF NEXT WEEK.

&&

.AVIATION...SOUTHEAST WINDS WILL PREVAIL AT THE SLC TERMINAL THROUGH
ABOUT 15-16Z THEN SHIFT TO THE NORTHWEST. THERE IS A 20 PERCENT
CHANCE OF THUNDERSTORMS BETWEEN ABOUT 15 AND 20Z TODAY. THESE STORMS
COULD PRODUCE ERRATIC WIND GUSTS TO 30 MPH.

&&

.FIRE WEATHER...RIDGE OF HIGH PRESSURE WILL MOVE WESTWARD TODAY OVER
NEVADA ALLOWING FOR A DRIER NORTHWEST FLOW TO DEVELOP ACROSS
NORTHERN UTAH THIS AFTERNOON WHICH WILL SPREAD INTO CENTRAL AND
SOUTHERN UTAH THURSDAY INTO FRIDAY. SOME WETTING RAINS WILL OCCUR
WITH THE THUNDERSTORMS TODAY BUT AS THE AIR MASS DRIES THE CHANCE OF
ANY WETTING RAINS AFTER TODAY WILL BE SLIM IF ANY AND ONLY ACROSS
EXTREME SOUTHERN MOUNTAINS THURSDAY. THE RELATIVE HUMIDITY HAS COME
UP OVER MUCH OF THE DISTRICT AND WILL BE AT ITS HIGHEST MINIMUM
DAYTIME LEVELS TODAY...IN THE LOWER TO MID TEENS...THEN LOWER
TOWARDS 10 PERCENT THURSDAY AND FRIDAY.

AS THE RIDGE SHIFTS SOUTHEAST INTO ARIZONA SATURDAY THIS WILL OPEN
THE DOOR FOR MOISTURE TO ADVECT INTO THE REGION FROM THE SOUTHWEST.
THIS MOISTURE FEED WILL INCREASE SUNDAY THROUGH MONDAY WITH
SCATTERED SHOWERS AND THUNDERSTORMS.

&&

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

$$

CHENG/STRUTHWOLF

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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