350
FXUS65 KSLC 210154
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
754 PM MDT MON MAY 20 2013
SYNOPSIS
HIGH PRESSURE WILL BUILD INTO THE REGION TOMORROW
ALLOWING DRYING AND WARMING CONDITIONS TO TAKE FORM. A DRY COLD
FRONT WILL WORK INTO THE NORTHERN THIRD WEDNESDAY.
DISCUSSION
WATER VAPOR LOOP SHOWS RIDGING QUICKLY BUILDING INTO
THE REGION AS THE LAST OF THE TROUGH PULLS EAST OF THE ROCKIES.
ACARS 400-250MB WIND OBSERVATIONS SHOW A 75-110KT CYCLONICALLY
CURVED JET OVER THE GREAT BASIN AND FOUR CORNERS REGION.
RAP...GOES...GPS SENSORS...AND 00Z SLC RAOB INDICATE PRECIPITABLE
WATER VALUES IN THE 0.20"-0.80" RANGE ACROSS THE REGION.
REGIONAL RADAR INDICATES THAT ISOLATED CONVECTION IS AFFECTING I-15
EAST ACROSS NORTHERN UTAH. UPDATED TO BUMP UP POPS. SUSPECT IT WILL
BE SHORT LIVED AS DYNAMICS CONTINUE TO PULL AWAY AND 15Z SHORT RANGE
ENSEMBLES INDICATE INSTABILITY WILL WANE THIS EVENING.
ALSO INCREASED NORTHERLY WINDS IN PRONE LOCATIONS OF CENTRAL AND
SOUTHERN UTAH AS PRESSURE GRADIENT IS CONTRIBUTING TO LOCALLY GUSTY
WINDS NEAR CANYONS AND LOCATIONS FAVORED IN DOWNSLOPE FLOW.
OTHERWISE VERY MINOR CHANGES TO TEMPERATURES OVERNIGHT. REST
UNCHANGED.
PREVIOUS DISCUSSION FOLLOWS...
DRYING CONDITIONS ARE TAKING FORM THIS AFTERNOON
ACROSS WESTERN PORTIONS...WHILE EASTERN AREAS CONTINUE TO SEE
ISOLATED TO SCATTERED SHOWERS FOCUSED OVER THE TERRAIN. UPSTREAM
RIDGING IS QUITE NOTICEABLE IN WATER VAPOR ALONG THE WEST COAST AND
THIS WILL SPREAD RAPIDLY INTO THE REGION OVER THE NEXT 24 HOURS.
WITH THAT EXPECTING FAIRLY SIGNIFICANT WARMING ON TUESDAY WITH
TEMPS CLIMBING BACK UP 5 TO 10 DEGREES ABOVE CLIMO DURING THE LATE
AFTERNOON HOURS.
SENSIBLE WEATHER AHEAD EXPECTED TO REMAIN LARGELY DRY WITH ONLY
SOME HIGH BASED CONVECTION FAR NORTHERN TERRAIN AFTERNOONS BEGINNING
WEDNESDAY. TEMPERATURES HAVE BEEN THE TRICKY DETAIL IN THE
FORECAST AS THE MID/LATE WEEK PERIOD WILL BE DEALING WITH A COLD
FRONT THAT IS EXPECTED TO SURGE THROUGH NORTHERN UTAH ON TWO
SEPARATE OCCASIONS.
DEEPENING TROUGH OFF THE PACNW COASTLINE ATTM PER WATER VAPOR TO
BE THE DRIVING FORCE OF SAID FRONTAL PASSAGES. THE TROUGH ITSELF
WILL REMAIN WELL UPSTREAM AND CLOSED...BUT THE LEADING EDGE FRONT
WILL MAKE ITS FIRST SURGE THROUGH NORTHERN PORTIONS WEDNESDAY
AFTERNOON/EVENING. WILL LIKELY SEE GUSTY POST FRONTAL WINDS ACROSS
THE NORTHWEST DESERTS AT THAT TIME...AS WELL AS NOTICED COOLING.
GLOBALS AGREE LARGELY ON THIS FEATURE THOUGH THE ECMWF A BIT MORE
AGGRESSIVE STALLING IT OUT AROUND OR JUST SOUTH OF PROVO BY 00Z.
GFS HOWEVER DEPICTS THIS FEATURE OVER THE GREAT SALT LAKE AT THAT
TIME. THE ONLY REAL SIGNIFICANCE OF THIS WOULD BE ON SAID WINDS
AND EXTENT OF LATE DAY COOLING ACROSS THE CENTRAL AND SOUTHERN
FRONT WASATCH FRONT. OPTED TO COOL AREAS NORTH OF SALT LAKE CITY
IN GOING FORECAST.
UPPER SUPPORT WILL BE LOST WEDNESDAY NIGHT FOR A TIME ALLOWING THE
FRONT TO RECEDE BACK TO THE NV/UT BORDER FOR THURSDAY. THIS TO BE
SHORT IN TIME HOWEVER AS YET ANOTHER LOBE WILL FORCE THE FRONT
BACK THROUGH MUCH OF NORTHERN UTAH THURSDAY NIGHT INTO THE
MORNING. AGAIN...ECMWF A BIT MORE AGGRESSIVE WITH THIS BUT BIG
PICTURE REMAINS THE SAME WITH COOLING TEMPS THURSDAY NIGHT.
THE SOUTHERN TWO THIRDS OF THE STATE WILL REMAIN SOUTH OF THESE
FRONTAL PASSAGES ALL WEEK. OUTCOME OF THIS WILL BE ABOVE NORMAL
TEMPS...DRY HUMIDITY AND BREEZY/GUSTY CONDITIONS. SEE FIRE WEATHER
DISCUSSION FOR MORE DETAIL ON THAT.
HOLIDAY WEEKEND LOOKS WARM AND LARGELY DRY OUTSIDE OF ISOLATED
HIGH BASED CONVECTION OVER THE TERRAIN. WILL BE PROVIDING MORE
DETAIL ON THIS AS TIME NEARS.
AVIATION
THERE IS A 20 PERCENT CHANCE THAT CEILINGS AT THE SLC
TERMINAL WILL DROP BELOW 7000FT BETWEEN 03Z AND 05Z DUE TO ISOLATED
PASSING SHOWERS. OTHERWISE...VFR CONDITIONS SHOULD PREVAIL THROUGH
THE EVENING. NORTHERLY WINDS ARE GENERALLY EXPECTED TO REMAIN IN THE
7 TO 10 KNOT RANGE...BEFORE SWITCHING TO THE SOUTHEAST BETWEEN 03Z
AND 05Z.
FIRE WEATHER
LINGERING MOISTURE AND INSTABILITY WILL MAINTAIN
ISOLATED SHOWERS/THUNDERSTORMS ACROSS NORTHERN AND EASTERN UTAH INTO
EARLY THIS EVENING. HIGH PRESSURE ALOFT WILL MOVE OVER THE FIRE
DISTRICT FOR LATER TONIGHT THROUGH TUESDAY. WARMER AND DRIER
CONDITIONS WILL DEVELOP WITH ISOLATED MOUNTAIN CONVECTION POSSIBLE
LATE TUESDAY.
THE NEXT PACIFIC STORM SYSTEM WILL SETTLE INTO THE PACIFIC NORTHWEST
TUESDAY. THE COLD FRONT ASSOCIATED WITH THIS STORM WILL REACH
EASTERN NEVADA BY LATE TUESDAY. AHEAD OF THE FRONT RAPID WARMING AND
DRYING WILL TAKE PLACE...FIRST ACROSS SOUTHWEST UTAH...THEN OVER THE
REMAINDER OF THE STATE TUESDAY NIGHT/WEDNESDAY. THE FRONT WILL MOVE
EAST ACROSS NORTHERN UTAH WEDNESDAY. THE MAIN IMPACT FROM THIS
FEATURE WILL BE MODESTLY COOLER TEMPS FOR THE WEST-CENTRAL THROUGH
NORTHWEST PORTIONS OF THE STATE. ANY SHOWERS/THUNDERSTORMS THAT
DEVELOP WILL BE CONFINED TO THE FAR NORTHWEST CORNER OF THE STATE
LATE WEDNESDAY AFTERNOON AND EVENING.
A SECOND BETTER ORGANIZED COLD FRONT WILL ENTER THE REGION THURSDAY.
THIS SECOND FRONT...MUCH LIKE THE FIRST...WILL GENERATE LITTLE IN
THE WAY OF SHOWERS/STORMS ACROSS THE FAR NORTH AND WEST LATE
THURSDAY. TEMPS WILL COOL FURTHER BEHIND THIS FRONT...WITH THE MAIN
IMPACT CENTERED ON THE FAR NORTHERN FIRE ZONES. BREEZY AND WARM
CONDITIONS WILL CONTINUE OVER THE SOUTHERN AND EASTERN ZONES
THROUGHOUT THE WEEK...WITH WARM/DRY CONDITIONS RETURN TO THE NORTH
FOR THE WEEKEND.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
PUBLIC...ROGOWSKI/MERRILL
FIRE WEATHER...CONGER
AVIATION...VERZELLA
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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