Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 232144
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
344 PM MDT MON MAR 23 2015

.SYNOPSIS...A SECOND SYSTEM WILL CROSS MAINLY NORTHERN UTAH AND
SOUTHWEST WYOMING TUESDAY. STRONG HIGH PRESSURE ALOFT WILL RETURN
FOR THE LATTER HALF OF THE WEEK.

&&

.SHORT TERM (THROUGH 00Z FRIDAY)...
WATER VAPOR LOOP SHOWS A NEGATIVELY TILTED TROUGH OVER THE
PACIFIC NORTHWEST INTO THE EASTERN GREAT BASIN. AMDAR 400-250MB
WIND OBSERVATIONS SHOW A 75-115KT CYCLONIC JET FROM NORTHERN
CALIFORNIA INTO THE CENTRAL ROCKIES. GOES/GPS/RAP/12Z SLC RAOB
INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN 0.15-0.20"
EASTERN AND SOUTHERN MOUNTAINS TO 0.33-0.50" VALLEYS. BLENDED
TOTAL PRECIPITABLE WATER PRODUCT INDICATES AN ABNORMALLY MOIST
AIRMASS ACROSS THE NORTHERN ROCKIES AND GREAT BASIN.

RAP 850-700MB THICKNESS/SATURATED EQUIVALENT POTENTIAL
TEMPERATURE/STREAMLINES INDICATE THE FRONTAL ZONE NEAR INTERSTATE 70
WITH SHIFT INTO SOUTHERN UTAH TONIGHT BEFORE WASHING OUT. WINDS
SHOULD THEREFORE NOT BE AN ISSUE WITH THIS FEATURE ACROSS THE FAR
SOUTH.

MEANWHILE ADDED MENTION OF THUNDER INTO THE EARLY EVENING
HOURS...THOUGH SHORT RANGE ENSEMBLES INDICATE INSTABILITY WANES
RAPIDLY AFTER SUNSET. SUPPORT FOR SHOWER ACTIVITY DIMINISHES AFTER
THE EVENING AS THE WAVE LIFTS THROUGH. THUS STILL EXPECTING A BREAK
FOR MUCH OF THE OVERNIGHT PERIOD INTO TOMORROW MORNING.

WARM ADVECTION PRECIPITATION REDEVELOPS ACROSS THE NORTH TOMORROW
MORNING AHEAD OF THE NEXT FEATURE WHICH APPROACHES FROM THE PACIFIC
NORTHWEST. HIGHER TERRAIN ALONG IDAHO BORDER WILL BE MOST FAVORED
FOR ACCUMULATIONS DURING THIS TIME.

SHORTWAVE SLIDES THROUGH TOMORROW AFTERNOON AND EVENING...SUPPORTING
THE PASSAGE OF THE NEXT COLD FRONT. WITH STRENGTHENING PRESSURE
GRADIENT AND 35-45KTS OF NORTHWESTERLY FLOW AT 700MB...GUSTY WINDS
WILL BE A CONCERN POST FRONTAL IN FAVORED DOWNSLOPE AND CANYON AREAS
OF EAST CENTRAL AND SOUTHERN UTAH LATE TOMORROW AFTERNOON THROUGH
WEDNESDAY MORNING.

SHOWERS REDEVELOP ACROSS THE NORTH WITH BUILDING INSTABILITY FOR THE
AFTERNOON BUT ITS NOTEWORTHY THAT INSTABILITY PARAMETERS ARE MUCH
WEAKER THAN TODAY FROM THE SHORT RANGE ENSEMBLES.

RIDGING BUILDS IN THURSDAY BRINGING BENIGN WEATHER AND THE START OF
A WARM TREND.

&&

.LONG TERM (AFTER 00Z FRIDAY)...
THE HIGH AMPLITUDE RIDGE WILL BE THE DOMINANT FEATURE THROUGH THE
END OF THE WEEK...WITH THE RIDGE AXIS SHIFTING FROM THE WESTERN
GREAT BASIN TO DIRECTLY OVERHEAD OF UTAH/SOUTHWEST WYOMING THROUGH
THE DAY FRIDAY. THIS WILL BE ACCOMPANIED BY SIGNIFICANT
WARMING/DRYING ALOFT...WITH MAX TEMPERATURES RETURNING TO MORE
THAN 10 DEGREES FAHRENHEIT ABOVE CLIMATOLOGICAL NORMALS FOR
FRIDAY AND SATURDAY. SATURDAY WILL LIKELY BE THE WARMEST DAY OF
THE FORECAST PERIOD...POTENTIALLY AIDED BY INCREASING FLOW AND
MIXING AHEAD OF A SHORTWAVE TROUGH MOVING INTO THE WEST COAST.

MODELS HAVE BEEN FAIRLY INCONSISTENT IN HOW TO HANDLE THIS NEXT
SHORTWAVE...AND THE 12Z RUNS TODAY HAVE BEEN NO EXCEPTION. THE GFS
BRINGS THIS FEATURE THROUGH THE FORECAST AREA AS A WEAK OPEN WAVE ON
SUNDAY...WHICH WOULD LIKELY INITIATE SOME SHOWERS ACROSS THE CWA.
THE ECMWF AND CANADIAN CUT THIS UPPER LEVEL TROUGH OFF INTO A CLOSED
LOW...SLOWLY DIGGING IT INTO SOUTHERN UTAH AND ARIZONA LATE SUNDAY
THROUGH MONDAY. THIS INCREASES MOISTURE A BIT...BUT IS GENERALLY A
DRIER SOLUTION THAN THE GFS. HAVE SLIGHTLY INCREASED POPS AND
SLIGHTLY COOLED TEMPERATURES FOR SUNDAY AND MONDAY...BUT CONFIDENCE
IN THE DETAILS REMAINS LOW AT THIS TIME.

&&

.AVIATION...THERE IS A 40 PERCENT CHANCE OF ADDITIONAL SHOWERS OR
THUNDERSTORMS IMPACTING THE SLC TERMINAL BETWEEN 22Z AND 02Z...WITH
ERRATIC WINDS AND CEILINGS BELOW 7000FT AS THE MOST LIKELY IMPACTS
ACCOMPANYING THESE STORMS. OTHERWISE...CEILINGS SHOULD GENERALLY
REMAIN ABOVE 7000FT AWAY FROM SHOWERS...AND WINDS SHOULD REMAIN
NORTHWESTERLY THROUGH AT LEAST 04Z...LIKELY SWITCHING TO THE
SOUTHEAST BETWEEN 05Z AND 08Z.

&&

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

$$

SHORT TERM...ROGOWSKI
LONG TERM/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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