AREA FORECAST DISCUSSION

 
 FXUS65 KSLC 040845
 AFDSLC
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE SALT LAKE CITY UT
 245 AM MDT SAT JUL 4 2009
 
 .SYNOPSIS...WEAK DISTURBANCES WILL PASS OVER NORTHERN UTAH TODAY.
 A DRIER AIRMASS WILL GRADUALLY SPREAD BACK INTO THE AREA FROM THE
 WEST SUNDAY INTO NEXT WEEK.
 
 &&
 
 .DISCUSSION...WATER VAPOR LOOP SHOWS A WEAKENING SYSTEM PROGRESSING 
 INTO THE GREAT BASIN FROM NORTHERN CALIFORNIA. FURTHER UPSTREAM A 
 DEEPER UPPER LOW WAS NEARING 140W/45N. 400-250MB ACARS WIND 
 OBSERVATIONS REVEAL A 40-60KT SOUTHWESTERLY JET FROM OFF THE 
 CALIFORNIA COAST INTO NEVADA. 00Z 700MB ANALYSIS SHOWS RIDGING 
 BUILDING BEHIND A WAVE LIFTING NORTHEAST OUT OF THE REGION. WARM 
 ADVECTION WAS IN PLACE WITH +11C AT KSLC AND +12C UPSTREAM AT KLKN. 
 
 00Z KSLC RAOB INDICATES 3 TO 5C OF WARMING BELOW 600MB AND 3C OF 
 COOLING ALOFT DURING THE PAST 24 HOURS. PRECIPITABLE WATER HAS 
 FALLEN TO SIX TENTHS OF AN INCH. STRONG DRYING WAS OBSERVED ALOFT. 
 
 GOES SOUNDER AND RUC INDICATE THAT PRECIPITABLE WATER HAS FALLEN 
 CONSIDERABLY AFTER A PAIR OF DISTURBANCES PASSED OVERHEAD DURING THE 
 LAST 36 HOURS. MORE RECENTLY...MOISTURE HAS BEEN INCREASING TO ABOUT 
 AN INCH ACROSS EASTERN NEVADA AND WESTERN UTAH IN RESPONSE TO THE 
 APPROACH OF THE NEXT SYSTEM. ISOLATED TO SCATTERED CONVECTION HAS 
 AFFECTED MUCH OF WESTERN AND CENTRAL UTAH OVERNIGHT INCLUDING WIND 
 GUSTS OF 30 TO 40 MPH. EXPECT THIS ACTIVITY TO DIMINISH TOWARD 
 SUNRISE.
 
 00Z NAM BUFKIT AND 21Z SHORT RANGE ENSEMBLES INDICATE SIMILAR 
 THERMODYNAMIC SET-UP TODAY...WITH A BIAS TOWARD SLIGHTLY DRIER 
 FORECAST SOUNDINGS. GOOD INSTABILITY REMAINS IN PLACE WITH A CHANCE 
 OF 1000 J/KG OF MUCAPE AND -2C LIFTED INDICES LIKELY ACROSS 
 NORTHERN UTAH. BEST EFFECTIVE SHEAR...ON THE ORDER OF 
 30KTS...REMAINS ACROSS NORTHERN UTAH WHERE WEAK WAVES WILL TRAVERSE 
 OVERHEAD IN MEAN WESTERLY FLOW. DOWNDRAFT CAPE WILL LIKELY BE ABOVE 
 1000 J/KG...SUGGESTING LOCALLY DAMAGING WINDS WILL BE POSSIBLE IN 
 VICINITY OF CONVECTION. HAIL CANNOT BE RULED OUT WITH THE STRONGER 
 CORES...MORE LIKELY ACROSS NORTHERN UTAH WHERE THE BETTER DEEP LAYER 
 SHEAR RESIDES. 
 
 WHILE NORTHERN UTAH WILL SEE THE PASSAGE OF SEVERAL WEAK 
 DISTURBANCES TO ACT AS POTENTIAL TRIGGERS...SOUTHERN UTAH WILL HAVE 
 TO RELY ON TERRAIN CIRCULATIONS (THOUGH HEIGHTS WILL GRADUALLY FALL 
 THROUGH THE DAY). THUS...POP GRIDS REFLECT BETTER CHANCES ACROSS THE 
 NORTH WITH MORE ISOLATED ACTIVITY ACROSS THE SOUTH. PRECIPITABLE 
 WATER VALUES...THOUGH LOWER THAN A COUPLE DAYS AGO...ARE STILL ABOUT 
 2 STANDARD DEVIATIONS ABOVE NORMAL FOR THIS TIME OF YEAR. 
 THUS...STRONGER STORMS WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY 
 RAINFALL. 
 
 AS THE NEXT SYSTEM BEGINS TO TAKE HOLD OF THE PACIFIC NORTHWEST 
 EARLY NEXT WEEK...STRONGER SOUTHWESTERLIES WILL DRY OUT THE REGION. 
 THIS TREND BEGINS ON SUNDAY ACROSS WESTERN UTAH AS RIDGING BUILDS 
 INTO PLACE. MONDAY SHOULD BE THE WARMEST DAY IN THE SHORT TERM AS 
 THE COLD CORE APPROACHES THE REGION BY MID WEEK. WINDS WILL LIKELY 
 BE STRONGEST TUESDAY AND WEDNESDAY...THOUGH THE EUROPEAN CONTINUES 
 TO INDICATE WEAKER 700MB FLOW (PREFERRED SOLUTION GIVEN TIME OF 
 YEAR) THAN THE GFS. STILL A CHANCE OF NEARING WIND ADVISORY LEVEL.
 
 THE EUROPEAN AND GFS (TO A LESSER EXTENT) INDICATE A PATTERN SHIFT 
 NEXT WEEKEND WITH A STRONG RIDGE BUILDING INTO THE FOUR CORNERS. 
 SUMMER HEAT COULD VERY WELL BE ON THE WAY WITH +20C 700MB FORECAST 
 AS EARLY AS FRIDAY.
 
 &&
 
 .AVIATION...SOUTHEAST WINDS SHOULD DEVELOP BY AROUND 12Z AS  
 CONVECTION ABATES. ISOLATED THUNDERSTORMS IN THE VICINITY...BUT 
 DISTANT...WILL CONTINUE TO PLAY HAVOC WITH THE WINDS UNTIL THEN. VFR 
 CONDITIONS ARE EXPECTED THROUGH THE EARLY AFTERNOON. NORTH WINDS AT 
 THE SLC TERMINAL WILL AGAIN DEVELOP AROUND 19Z WITH AFTERNOON 
 SHOWERS AND THUNDERSTORMS AGAIN DEVELOPING. THERE IS A 30 PERCENT 
 CHANCE THAT A THUNDERSTORM WILL DIRECTLY IMPACT THE TERMINAL AFTER 
 20Z AND A 40 PERCENT CHANCE THE PASSING CONVECTION WILL AGAIN CAUSE 
 WINDS AT THE AIRPORT TO BE VARIABLE AND GUSTY.
 
 &&
 
 .FIRE WEATHER...MOISTURE CONTINUES TO STREAM NORTH AROUND THE UPPER 
 RIDGE SETTLING OVER THE FIRE DISTRICT. THE AIRMASS ACROSS UTAH WILL 
 REMAIN SOMEWHAT MOIST TODAY AND ALLOW AFTERNOON AND EVENING 
 CONVECTION TO AGAIN DEVELOP. THE DEEP MOISTURE WILL BEGIN TO SLOWLY 
 DECREASE TONIGHT WITH THE AIRMASS BECOMING DRY ON SUNDAY AND VERY 
 DRY THROUGH THE EARLY PART OF THE WEEK. THE RELATIVE HUMIDITY 
 MINIMUMS WILL DROP BELOW 10 PERCENT IN MOST AREAS MONDAY THROUGH 
 THURSDAY. EXPECT POOR RECOVERY OF LESS THAN 30 PERCENT AT NIGHT AS 
 WELL.
 
 &&
 
 .SLC WATCHES/WARNINGS/ADVISORIES...
 UT...NONE.
 WY...NONE.
 
 &&
 
 $$
 
 PUBLIC...ROGOWSKI
 FIRE WEATHER...YOUNG
 AVIATION...YOUNG
 
 FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
 HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)