Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 241152
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
552 AM MDT FRI APR 24 2015

.SYNOPSIS...AN UNSETTLED WEATHER PATTERN WILL REMAIN OVER THE
FORECAST AREA TODAY. A COLD AND ENERGETIC PACIFIC STORM SYSTEM WILL
IMPACT THE REGION THIS WEEKEND. HIGH PRESSURE WILL RETURN EARLY NEXT
WEEK.

&&

.SHORT TERM (THROUGH 12Z MONDAY)...SOUTHWEST FLOW OVER THE FORECAST
AREA WILL INCREASE TODAY AS AN UPSTREAM TROUGH...CURRENTLY CENTERED
OVER THE WEST COAST STATES...APPROACHES THE AREA. CURRENT GOES
ESTIMATE SHOWS 0.3-0.4 INCHES OF PWAT OVER MUCH OF UTAH...WHILE
VALUES OVER FAR SOUTHERN NEVADA ARE 0.5-0.6 INCHES. THIS MORE MOIST
AIRMASS IS EXPECTED TO SPREAD INTO THE AREA LATER TODAY.

ISOLATED WEAK SHOWERS ARE CURRENTLY EVIDENT ON RADAR IMAGERY...BUT
EXPECT CONVECTION TO INCREASE LATER THIS EVENING AS DAYTIME HEATING
FURTHER DESTABILIZES THE AIRMASS. BECAUSE THE AIRMASS WILL BE MORE
MOIST THAN IT WAS YESTERDAY...RAINFALL POTENTIAL WILL INCREASE WHILE
THE OCCURRENCE OF GUSTY OUTFLOW WINDS WILL BE A BIT LESS. GREATER
LARGE-SCALE FORCING WITH THE APPROACH OF THE TROUGH AND THE
ASSOCIATED COLD FRONT WILL LEAD TO INCREASING COVERAGE OF
SHOWERS/THUNDERSTORMS BY THE MIDDLE OF THE AFTERNOON. THE FRONT WILL
ENTER NORTHWEST UTAH THIS AFTERNOON BEFORE MAKING TO CENTRAL UTAH
THIS EVENING.

THE TROUGH ITSELF IS STILL PROGGED TO JUST GRAZE NORTHERN UTAH THIS
EVENING AS IT WEAKENS AND EJECTS NORTHEAST IN FAVOR OF A DEEPENING
WAVE UPSTREAM. THIS WILL LEAVE THE COLD FRONT STALLED NEAR CENTRAL
UTAH WHERE MODELS CONTINUE TO LIGHT UP THE BOUNDARY OVERNIGHT DUE IN
PART TO THE MOISTURE AND INCREASING LOW-LEVEL CONVERGENCE.

PRECIPITATION IS EXPECTED TO FILL IN EVEN MORE TOMORROW WITH THE
APPROACH OF THE DEEPER TROUGH. THE TROUGH IS ACTUALLY PROGGED TO
ELONGATE BEFORE ENDING UP AS A CLOSED LOW OVER NORTHWEST NEW MEXICO.
HOWEVER...IT SHOULD MAINTAIN ENOUGH ENERGY TO PUSH A DECENT COLD
FRONT THROUGH UTAH LATE TOMORROW AFTERNOON THROUGH TOMORROW NIGHT.
THE BEST COLD PUSH WILL BE AT THE LOWER LEVELS AS MODELS DEVELOP A
DECENT NORTHWEST SURFACE GRADIENT BEHIND THE FRONT.
HOWEVER...THERMAL ADVECTION AT 700-500MB IS NOT VERY STRONG...DUE
PARTIALLY TO THE SPLITTING NATURE OF THE STORM AND PARTIALLY TO THE
COOLER AIR ALOFT THAT WILL HAVE MOVED INTO THE AREA WITH THE INITIAL
COLD FRONT TODAY. ALTHOUGH GUSTY NORTHWEST WINDS ARE LIKELY TO OCCUR
BEHIND THE FRONT....THE STRONGEST WINDS SHOULD REMAIN CONFINED TO
FAVORED DOWNSLOPE AREAS AS A RESULT. HOWEVER...WITH THE MOISTURE IN
PLACE AND THE LOW-LEVEL FORCING THAT WILL ACCOMPANY THE
FRONT...EXPECT FAIRLY WIDESPREAD PRECIPITATION TOMORROW AND TOMORROW
NIGHT.

PRECIPITATION WILL START WINDING DOWN ACROSS FAR WESTERN UTAH BY
SUNDAY. HOWEVER...WITH NORTHWEST FLOW STILL IN PLACE FROM THE
SURFACE THROUGH 700MB...SHOWERS SHOULD PERSIST ALONG THE SPINE OF
UTAH AND I-15 CORRIDOR. IN ADDITION...THE EASTERN VALLEYS COULD
STAND TO SEE A FEW SHOWERS AS WELL WITH MOISTURE SPREADING INTO THE
AREA AROUND THE CLOSED LOW. BY SUNDAY NIGHT...THE LOW WILL TRACK
FARTHER SOUTHEAST ACROSS NEW MEXICO WHILE A DRIER AND MORE STABLE
AIRMASS SPREADS INTO UTAH FROM THE WEST...ALLOWING FOR A QUICK
DOWNWARD TREND IN PRECIPITATION.

TEMPERATURES WILL REMAIN NEAR TO ABOVE NORMAL TODAY...BUT COOLER
THAN YESTERDAY DUE TO INCREASING CLOUD COVER AND THE ARRIVAL OF THE
COLD FRONT THIS AFTERNOON. THE FRONT AND CONTINUED CLOUD COVER ARE
EXPECTED TO COMBINED FORCES TO BRING TEMPERATURES BELOW NORMAL
TOMORROW. SUNDAY WILL BE THE COLDEST DAY...WITH 700MB TEMPERATURES
BOTTOMING OUT BETWEEN 12-18Z. SNOW LEVELS ARE EXPECTED TO FALL AS
LOW AS 6000FT LATE SATURDAY NIGHT INTO SUNDAY WITH SIGNIFICANT
ACCUMULATIONS POSSIBLE ON THE HIGHER PEAKS. ALTHOUGH SOME
ACCUMULATION IS EXPECTED LATER THIS AFTERNOON AND OVERNIGHT...THE
BULK OF IT WILL OCCUR WITH THE STORM TOMORROW/NIGHT. WINTER WEATHER
HIGHLIGHTS MAY BE NEEDED IF ACCUMULATIONS ARE EXPECTED TO CAUSE
SIGNIFICANT IMPACTS. WILL LET THE DAY SHIFT MAKE THE DECISION AFTER
COORDINATION WITH PARTNERS.

.LONG TERM (AFTER 12Z MONDAY)...THE LOW WILL CONTINUE TO EXIT THE
REGION THROUGH THE DAY MONDAY...AS A RIDGE SHIFTS OVER THE GREAT
BASIN. ENOUGH MOISTURE LOOKS TO LINGER OVER THE EASTERN HALF OF UTAH
TO POTENTIALLY ALLOW SOME CONVECTIVE INITIATION ALONG THE UINTAS AND
PERHAPS CENTRAL SPINE OF UTAH...SO HAVE MAINTAINED SOME SLIGHT
CHANCE POPS IN THE HIGHER TERRAIN THROUGH MONDAY AFTERNOON.

THE HIGH AMPLITUDE RIDGE SHIFTS OVERHEAD THROUGH TUESDAY...LEADING
TO A FAST DRYING AND WARMING TREND. BY WEDNESDAY AND THURSDAY...THE
AIRMASS LOOKS TO BE THE WARMEST OF THE CALENDAR YEAR SO FAR FOR
UTAH...WITH 700MB TEMPERATURES GENERALLY IN THE 6-10C RANGE.
THURSDAY ALSO LOOKS TO BE CATEGORIZED BY AN INCREASING SOUTHWESTERLY
FLOW AS A TROUGH MOVES THROUGH THE PACIFIC NORTHWEST...WHICH SHOULD
LEAD TO INCREASED SURFACE WINDS AND GOOD MIXING.

THE EXACT FATE OF THE AFOREMENTIONED TROUGH IS SOMEWHAT
UNCERTAIN...THOUGH MODELS SEEM TO BE IN GOOD AGREEMENT THAT IT WILL
NOT SIGNIFICANTLY IMPACT UTAH OR SOUTHWEST WYOMING. THERE HAVE BEEN
TWO MAJOR SOLUTIONS THAT GLOBAL MODELS HAVE FLIP-FLOPPED AROUND
RECENTLY FOR THIS TROUGH. ONE HAS THE TROUGH SLIDING NORTH OF THE
CWA...FLATTENING THE RIDGE AND PERHAPS PUSHING A WEAK COLD FRONT
THROUGH THE AREA...WITH SOMEWHAT COOLER TEMPERATURES HEADING INTO
THE WEEKEND. THE OTHER MAJOR MODEL SOLUTION IS THAT THE TROUGH
CLOSES OFF AND LINGERS OVER THE PACIFIC NORTHWEST...WITH AT LEAST
ONE ADDITIONAL VERY WARM DAY ON FRIDAY.

&&

.AVIATION...A COLD FRONT WILL MOVE THROUGH THE SALT LAKE CITY
TERMINAL LATER TODAY...WITH THE MOST LIKELY TIMING OF 21-23Z.
SOUTHERLY WINDS ARE EXPECTED TO BECOME GUSTY AHEAD OF THIS
FRONT...WITH WEST-NORTHWESTERLY WINDS BEHIND THE FRONT. A WESTERLY
CROSSWIND COMPONENT IS POSSIBLE FOR A COUPLE HOURS JUST AHEAD OF AND
BEHIND THE FRONT. SHOWER ACTIVITY WILL ALSO INCREASE THROUGH THIS
AFTERNOON AND EVENING...WITH CEILINGS LIKELY TO DROP BELOW 7000FT.
GUSTY ERRATIC WINDS AND MVFR CONDITIONS IN MODERATE TO HEAVY
RAINFALL ARE ALSO POSSIBLE WITH THE STRONGER SHOWERS AND
THUNDERSTORMS.

&&

.FIRE WEATHER...A MOIST PACIFIC STORM SYSTEM WILL BEGIN IMPACTING
UTAH LATE TODAY. AN INITIAL COLD FRONT WILL PUSH INTO NORTHERN AND
CENTRAL UTAH THIS AFTERNOON AND EVENING...THOUGH SCATTERED SHOWERS
ARE POSSIBLE ACROSS MOST OF THE STATE THROUGH THE DAY.

A STRONGER COLD FRONT WILL MOVE THROUGH THE STATE SATURDAY AND
SATURDAY NIGHT...WITH WIDESPREAD WETTING RAIN...ACCUMULATING
SNOWFALL IN THE HIGHER TERRAIN...AND GUSTY NORTH WINDS BEHIND THE
FRONT. PRECIPITATION WILL LINGER INTO SUNDAY BEFORE MOSTLY ENDING
SUNDAY NIGHT.

A SIGNIFICANT WARMING AND DRYING TREND IS ON TAP FOR MONDAY THROUGH
THURSDAY...WITH LIGHT WINDS EARLY IN THE WEEK...FOLLOWED BY
INCREASING SOUTHWESTERLY WINDS WEDNESDAY AND THURSDAY.

&&

.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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