000
FXUS65 KSLC 150221
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
821 PM MDT TUE MAY 14 2013

.SYNOPSIS...A WEAK UPPER LEVEL DISTURBANCE WILL MOVE THROUGH UTAH
TONIGHT THROUGH WEDNESDAY. BEHIND THIS A STRONGER TROUGH WILL MOVE
INTO THE GREAT BASIN LATE IN THE WEEK BRINGING COOLER TEMPERATURES
FOR THE WEEKEND.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A CLOSED LOW OPENING UP AS IT
APPROACHES FROM CENTRAL CALIFORNIA. ACARS 400-250MB WIND
OBSERVATIONS SHOW A 85-115KT WESTERLY JET ALONG THE CANADIAN
BORDER...WITH A 50-85KT CYCLONIC JET ASSOCIATED WITH THE APPROACHING
WAVE. RAP...GOES...GPS SENSORS...AND 00Z SLC RAOB INDICATE
PRECIPITABLE WATER VALUES IN THE 0.26"-0.60" RANGE ACROSS THE REGION.

GIVEN COMBINATION OF INSTABILITY INDICATED TO LAST THROUGH THE NIGHT
BY THE 15Z SHORT RANGE ENSEMBLES...AND APPROACH OF THE
AFOREMENTIONED DISTURBANCE...FELT IT WAS PRUDENT TO MAINTAIN SLIGHT
CHANCE POPS FOR THE NORTHERN AND EASTERN ZONES OVERNIGHT. 00Z KSLC
RAOB INDICATES GUSTY WINDS MORE LIKELY THREAT THAN ACTUAL RAINFALL.

ALSO RAISED WINDS OVERNIGHT ACROSS THE NORTH WITH THE ARRIVAL OF THE
NEXT COLD FRONT...WITH AGREEMENT BY BOTH THE HRRR-3KM AND LOCAL 4KM
WRF-ARW.

ONLY VERY MINOR CHANGES TO TEMPERATURES AND SKY COVER OVERNIGHT.
REST UNCHANGED.

PREVIOUS DISCUSSION FOLLOWS...
AN UPPER LEVEL RIDGE IS DRIFTING SLOWLY EAST ACROSS THE EASTERN
GREAT BASIN TODAY AS A WEAK UPPER LEVEL SHORTWAVE MOVES INTO
SOUTHERN NEVADA. A SHALLOW FRONTAL BOUNDARY HAS PUSHED INTO CENTRAL
UTAH WHERE IT IS EXPECTED TO STALL. MODEST INSTABILITY HAS DEVELOPED
ACROSS MUCH OF THE STATE...SBCAPE OF 250-500 J/KG...AND ISOLATED
CONVECTION HAS FORMED OVER SOUTHERN MOUNTAINS AND THE BOOK CLIFFS.
HRRR RUNS HAVE CONSISTENTLY DEVELOPED ISOLATED CONVECTION ACROSS
ACROSS EAST CENTRAL AND NORTHEAST NEVADA LATE THIS AFTERNOON AND
EVENING AND AS WELL AS INTO PORTIONS OF NORTHERN UTAH.  WITH MODEST
CONVERGENCE AND INSTABILITY ALONG LEADING EDGE OF APPROACHING
SHORTWAVE WILL CONTINUE WITH MENTION OF ISOLATED THUNDERSTORMS THIS
EVENING ACROSS THE NORTH.  THE PRIMARY IMPACT OF ANY STORMS WOULD BE
GUSTY OUTFLOW WINDS IN THEIR VICINITY.  ALSO ADDED A MENTION OF
ISOLATED STORMS FOR EAST CENTRAL AND SOUTHEAST VALLEYS AS STORMS ARE
EXPECTED TO DRIFT OFF OF THE HIGH TERRAIN AND INTO THESE AREAS.

FOR WEDNESDAY...EXPECT HIGH TEMPERATURES TO GENERALLY BE A FEW
DEGREES COOLER IN MOST LOCATIONS ACROSS THE STATE BEHIND WAVE AS IT
MOVES SLOWLY EAST INTO CO.  WILL CONTINUE WITH MENTION OF ISOLATED
CONVECTION OVER UTAH/S HIGH TERRAIN AS WELL AS THE MOST NORTHERN
VALLEYS. INSTABILITY LOOKS TO BE MORE CONFINED TO THE NORTH ON
WEDNESDAY.

FOR THE LATTER PORTION OF THE WEEK INTO THE WEEKEND THE FOCUS SHIFTS
TO AN APPROACHING TROUGH WHICH WILL IMPACT THE GREAT BASIN.  THE
ECMWF AND CANADIAN GEM ARE FASTER WITH THE TROUGH THAN THE GFS AND
HAVE LEANED IN THEIR DIRECTION WITH THE FORECAST. AHEAD OF THIS
TROUGH GUSTY SOUTH WINDS CAN BE EXPECTED ACROSS WEST CENTRAL AND
SOUTHWEST UTAH ON THURSDAY.  TROUGH WILL THEN USHER MUCH COOLER AIR
INTO THE STATE FOR FRIDAY THROUGH THE WEEKEND. HIGH TEMPERATURES FOR
THE WEEKEND WILL BE 10-15 DEGREES COOLER THAN TOMORROW/S HIGHS IN
MANY AREAS ACROSS THE STATE. TROUGH WILL MOVE SLOWLY THROUGH THE
STATE FRIDAY THROUGH SATURDAY NIGHT AND BRING INCREASED COVERAGE OF
SHOWERS AND THUNDERSTORMS TO THE STATE.  THE GREATEST COVERAGE AT
THIS TIME APPEARS TO BE FROM FRIDAY AFTERNOON THROUGH SATURDAY
MORNING.

ON THE BACK SIDE OF THIS TROUGH THE MEDIUM RANGE MODELS CONTINUE TO
INDICATE THE THREAT FOR A SECONDARY WAVE TO DROP INTO UTAH BEFORE
SHORTWAVE RIDGING AND WARMER TEMPERATURES RETURN FOR THE MIDDLE OF
NEXT WEEK.

&&

.AVIATION...THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGH THE
EVENING WITH SCATTERED CLOUDS. NORTHWEST WINDS ARE EXPECTED TO SHIFT
TO THE SOUTHEAST BETWEEN 04Z AND 06Z. THERE IS A 10 PERCENT CHANCE
THAT ISOLATED SHOWERS IN THE VICINITY OF THE TERMINAL WILL RESULT
IN PERIODS OF GUSTY AND/OR ERRATIC WINDS LATE THIS EVENING.
THERE IS ALSO A 40 PERCENT CHANCE THAT THE NORTHWEST WINDS REMAIN
PREDOMINATE OVERNIGHT...REINFORCED BY OUTFLOW ARRIVING FROM THE
WEST DESERT.

&&

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

$$

PUBLIC...ROGOWSKI/GRAHAM
AVIATION...ROGOWSKI

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