Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 301117
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
516 AM MDT MON MAR 30 2015

.SYNOPSIS...A WEAK WEATHER DISTURBANCE WILL MOVE EAST INTO NORTHWEST
ARIZONA TODAY. A VERY WARM SOUTHWEST FLOW ALOFT ON TUESDAY WILL BE
FOLLOWED BY A SERIES OF COLD PACIFIC WEATHER DISTURBANCES FOR THE
MIDDLE TO LATTER HALF OF THE WORK WEEK.

&&

.SHORT TERM (THROUGH 12Z THURSDAY)...A MEAN RIDGE REMAINS OVER THE
WESTERN CONUS THIS MORNING WHILE BEING UNDERCUT BY A SHORTWAVE
DISTURBANCE CURRENTLY CENTERED NEAR THE SOUTHERN SIERRA NEVADA. THIS
DISTURBANCE IS EXPECTED TO WEAKEN AS IT APPROACHES UTAH...BUT
MAINTAIN ENOUGH ENERGY TO PRODUCE A FEW SHOWERS OVER MAINLY THE HIGH
TERRAIN DURING THE DAYTIME HOURS...WITH ENOUGH INSTABILITY PRESENT
TO ALLOW A THREAT OF THUNDERSTORMS. VERY LITTLE PRECIPITATION IS
EXPECTED TO REACH THE GROUND AS DEEP MOISTURE IS LACKING...WITH
MODELS INDICATING BARELY MORE THAN A THIRD OF AN INCH OF PWAT.
OTHERWISE...EXPECT TEMPERATURES TO TREND WARMER TODAY.

SOUTHWEST FLOW WILL INCREASE TOMORROW AS THE RIDGE SHIFTS EAST AHEAD
OF A TROUGH ARRIVING OVER THE PACIFIC NORTHWEST. CONTINUED WARMING
OF THE AIRMASS COMBINED WITH GOOD MIXING DUE TO STRENGTHENING WINDS
ALL POINT TO A VERY WARM DAY TOMORROW. MODELS INDICATE H7
TEMPERATURES OVER SLC TOMORROW AFTERNOON WILL BE +6 OR +7C. THIS
WILL LIKELY BE A NEW HDOY FOR MANY AREAS...AND TEMPERATURES IN SOME
LOCALES MAY NEAR OR EXCEED RECORD HIGHS FOR THE DAY.

THE TROUGH WILL PUSH A COLD FRONT THROUGH UTAH TOMORROW NIGHT INTO
WEDNESDAY MORNING. THIS WILL BE QUITE THE SIGNIFICANT FRONT WITH
GOOD LOW-LEVEL FORCING. MODELS STILL INDICATING A 12-15C DROP IN H7
TEMPERATURES ACROSS NORTHERN UTAH FROM 00Z TO 12Z WEDNESDAY. THIS
WILL BRING TEMPERATURES DOWN BELOW NORMAL FOR WEDNESDAY ACROSS
NORTHERN UTAH. TIGHT SURFACE GRADIENT PLUS A PERIOD OF STRONG COLD
ADVECTION WILL LEAD TO BREEZY TO WINDY CONDITIONS IN THE POSTFRONTAL
ENVIRONMENT ESPECIALLY IN EXPOSED AREAS AND FAVORED DOWNSLOPE
REGIONS OF NORTHERN AND CENTRAL UTAH. THE FRONT WILL LOSE SOME OF
ITS PUSH AS IT REACHES SOUTHERN UTAH SINCE THE BULK OF THE UPPER
SUPPORT IS EXPECTED TO REMAIN NORTH OF UTAH. ALSO BECAUSE OF THE
LACK OF UPPER SUPPORT...AS WELL AS A CONTINUED DEARTH OF
MOISTURE...ANY PRECIPITATION WILL LIKELY REMAIN FAIRLY ISOLATED.

THE FRONT WHICH WILL BE NEAR THE ARIZONA BORDER WILL ATTEMPT TO LIFT
NORTH WEDNESDAY NIGHT...OR AT LEAST PIVOT COUNTER-CLOCKWISE AS THE
FLOW ALOFT STARTS TO BACK. THIS IS IN ADVANCE OF THE NEXT TROUGH
WHICH WILL CROSS NORTHERN CALIFORNIA AND NEVADA WEDNESDAY NIGHT.

&&

.LONG TERM (AFTER 12Z THURSDAY)...THE BEST MID-LEVEL MOISTURE AND
INSTABILITY MOVES OVER THE FORECAST AREA THROUGH THE DAY
THURSDAY...AS THE BULK OF THE TROUGH MOVES DIRECTLY OVER THE AREA
BETWEEN 12Z THURSDAY AND 00Z FRIDAY. PRECIP CHANCES STILL LOOK GOOD
FOR THE HIGHER TERRAIN OF NORTHERN AND CENTRAL UTAH...WITH COVERAGE
PERHAPS A LITTLE MORE SPOTTY OVER THE VALLEY LOCATIONS. THE LOW
LEVEL COLD AIR ALSO MAKES ITS BEST PUSH OF THE STORM THROUGH THE DAY
THURSDAY...AND SNOW LEVELS WILL LIKELY FALL TO THE VALLEY FLOORS
ACROSS MUCH OF NORTHERN UTAH THURSDAY...WITH 700MB TEMPS DROPPING TO
ABOUT -10C.

THE TROUGH IS FORECAST TO EXIT THROUGH THURSDAY NIGHT...AND FRIDAY
MORNING WILL LIKELY BRING THE COLDEST TEMPERATURES OF THE
WEEK...ESPECIALLY IF SKIES CLEAR SUFFICIENTLY BEFORE SUNRISE. THE
00Z GFS CLEARS THE SKIES MORE SLOWLY THAN PREVIOUSLY ADVERTISED...AS
THE TROUGH LAGS A BIT BEFORE EXITING...BUT HAVE KEPT THE FORECAST
TILTED TOWARD THE FASTER SOLUTION SHOWN IN THE ECMWF AND CANADIAN
MODELS. A HARD FREEZE IS CURRENTLY FORECAST FOR THE CACHE VALLEY AND
PARTS OF THE NORTHERN WASATCH FRONT...WHICH IS A CONCERN CONSIDERING
THE VERY WARM LATE WINTER AND EARLY SPRING THE STATE HAS
EXPERIENCED.

SHORTWAVE RIDGING BEGINS BUILDING OVER THE REGION FRIDAY AFTER THE
TROUGH EXITS INTO THE CENTRAL CONUS. HOWEVER...FRIDAY SHOULD NOT BE
SIGNIFICANTLY WARMER THAN THURSDAY...WITH COOL LOW LEVEL AIR
LINGERING ACROSS THE AREA...A COLD START IN THE MORNING...AND
RELATIVELY POOR MIXING IN THE VALLEY LOCATIONS. THE WARMING TREND
SHOULD BE MUCH MORE SIGNIFICANT ON SATURDAY...AS SOUTHWESTERLY FLOW
AND WARM ADVECTION BOTH INCREASE THROUGH THE DAY...WHICH SHOULD HELP
MAX TEMPERATURES TO BOUNCE BACK ABOVE NORMAL VALUES.

GLOBAL MODELS BEGIN TO DIVERGE STARTING SATURDAY NIGHT...LEADING TO
A LOWER CONFIDENCE FORECAST FOR DAYS 6 AND 7. A BROAD TROUGH IS
LIKELY TO SWING INTO THE PACIFIC NORTHWEST THROUGH SATURDAY AND
SATURDAY NIGHT...WITH CONTINUED MILD SOUTHWESTERLY FLOW OVER UTAH
THROUGH THE OVERNIGHT HOURS. THE GFS AND CANADIAN PROGRESSIVELY MOVE
THIS TROUGH THROUGH THE GREAT BASIN SUNDAY AND SUNDAY
NIGHT...PUSHING A COLD FRONT THROUGH UTAH...WITH MOISTURE AND
TEMPERATURES FAIRLY SIMILAR TO THE PREVIOUSLY MENTIONED
WEDNESDAY/THURSDAY TROUGH. HOWEVER...THE ECMWF CLOSES THIS TROUGH
OFF A BIT AND DIGS IT SOUTHWARD ALONG THE CALIFORNIA COAST...WHICH
KEEPS UTAH AND SOUTHWEST WYOMING IN THE WARM SECTOR SUNDAY THROUGH
TUESDAY...WITH WARM/DRY CONDITIONS AND GUSTY SOUTHERLY WINDS FOR THE
BEGINNING OF THE WEEK. CURRENT FORECAST IS A MUDDLING OF THESE TWO
ADMITTEDLY INCOMPATIBLE SOLUTIONS...BUT IS TILTED A LITTLE MORE
TOWARD THE COOLER AND MORE PROGRESSIVE GFS/CANADIAN MODELS.

&&

.AVIATION...WINDS AT THE SLC TERMINAL ARE EXPECTED TO SWITCH TO THE
NORTHWEST BETWEEN 17Z AND 19Z...THEN INCREASE TO 6 TO 9 KNOTS AFTER
19Z. VFR CONDITIONS WILL PREVAIL UNDER MOSTLY CLEAR SKIES.

&&

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

$$

CHENG/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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