Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 182134
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
334 PM MDT SAT APR 18 2015

.SYNOPSIS...NORTHWESTERLY FLOW WILL PREVAIL THROUGH THE WEEKEND.
HIGH PRESSURE WILL BUILD EARLY NEXT WEEK BEFORE AN UNSETTLED
WEATHER PATTERN DEVELOPS FOR THE LATTER PORTION OF THE WEEK.

&&

.SHORT TERM (THROUGH 00Z WEDNESDAY)...EXITING STORM SYSTEM
CONTINUES EASTWARD ACROSS COLORADO THIS AFTERNOON. ASSOCIATED
THICK CLOUD COVER HAS LEFT UTAH. HOWEVER...THERE IS ENOUGH
LINGERING MOISTURE AND INSTABILITY IN THE WAKE OF THE SYSTEM TO
ALLOW FOR A FEW SHOWERS ACROSS THE EASTERN QUARTER OR SO OF THE
CWA. WARMING TREND CONTINUES WITH TEMPERATURES RUNNING UP TO 5F
ABOVE SEASONAL NORMS.

WEAK TROUGH MOVING DOWN THE CALIFORNIA COAST TONIGHT INTO TOMORROW
MORNING WILL BRING SOME WEAK SHORTWAVE ENERGY ACROSS UTAH TONIGHT
INTO TOMORROW MORNING...RESULTING IN A VERY SLIGHT CHANCE OF
SHOWERS LINGERING INTO THE OVERNIGHT HOURS. THE WAVE SHOULD ALSO
SLOW THE WARMING OF THE AIRMASS...SO THE TREND OF INCREASING
TEMPERATURES SHOULD SLOW JUST A BIT. ENOUGH MOISTURE AND
INSTABILITY SHOULD STILL BE AROUND FOR AFTERNOON CONVECTION OVER
THE HIGHER TERRAIN.

HIGH PRESSURE IS EXPECTED TO BUILD FOR THE FIRST PART OF THE
UPCOMING WEEK. HOWEVER...THE AIRMASS DOES NOT DRY OUT MUCH SO AT
LEAST AN OUTSIDE THREAT OF CONVECTION OVER THE TERRAIN REMAINS.
THE WARMING TREND WILL CONTINUE THROUGH TUESDAY...WITH MAXES
EXPECTED TO RUN AT LEAST 10F ABOVE CLIMO BY THEN.

&&

.LONG TERM (AFTER 00Z WEDNESDAY)...MODEL TO MODEL AND RUN TO RUN
CONSISTENCY CONTINUES TO VARY...CONTINUING THE TREND OF CHALLENGING
LONG TERM FORECASTS. TO START...A TROUGH WILL BE APPROACHING THE
PACIFIC NORTHWEST TUESDAY EVENING...WHILE ANOTHER TROUGH SITS OFF
THE COAST OF SOUTHERN CALIFORNIA. THESE TWO TROUGHS WILL GRADUALLY
PUSH EASTWARD THROUGH EARLY THURSDAY.

THE PACIFIC NORTHWEST TROUGH WILL REALLY STRUGGLE TO MAKE MUCH
HEADWAY AS IT INTERACTS WITH THE RIDGE OVER THE INTERIOR WEST AND
MAY EVENTUALLY SPLIT...WITH THE BEST DYNAMICS RIDING NORTH AND EAST
OVER THE TOP OF THE RIDGE INTO CANADA. MEANWHILE...THE SOUTHERN
TROUGH WILL GRADUALLY MOVE INTO THE DESERT SOUTHWEST THURSDAY INTO
FRIDAY. BY EARLY NEXT WEEKEND...ANOTHER FAIRLY SIMILAR SCENARIO IS
EXPECTED...WITH THE NORTHERN TROUGH SPLITTING AROUND THE TOP OF THE
RIDGE AND THE SOUTHERN PORTION OF THE TROUGH PROGRESSING ACROSS THE
DESERT SOUTHWEST.

WHAT DOES THIS MEAN FOR THE SENSIBLE WEATHER ACROSS THE CWA? MAINLY
THAT IT IS HARD TO FOCUS IN ANY PARTICULAR FEATURE AT THIS POINT DUE
TO POOR MODEL TO MODEL AND RUN TO RUN CONSISTENCY ON RATHER SUBTLE
FEATURES GIVEN THE CONVECTIVE NATURE OF THE FORECAST. PREVIOUS
PACKAGE TRENDS MATCH THE CURRENT FORECAST WELL...WITH GRADUALLY
INCREASING POPS FROM WEDNESDAY THROUGH FRIDAY. THE MAIN MODE OF
PRECIPITATION WILL LIKELY BE CONVECTIVE...SO MAXIMUM COVERAGE OF
PRECIPITATION WILL LIKELY BE DURING THE AFTERNOON/EVENING.

&&

.AVIATION...WEST TO NORTHWEST WINDS WILL CONTINUE AT THE SLC
TERMINAL THROUGH 03-05Z BEFORE SHIFTING TO THE TYPICAL SOUTHERLY
DRAINAGE WIND. THERE IS A 20 PERCENT CHANCE THE WIND SHIFT WILL BE
AS LATE AS 07Z.

&&

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

$$

SHORT TERM...TRAPHAGAN
LONG TERM/AVIATION...KRUSE

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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