SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
836 PM PDT MON MAR 16 2009
.UPDATE...WINDS ARE BEING MONITORED CLOSELY THIS EVENING AS KSBA-
KSMX SURFACE GRADIENTS HAS INCREASED TO -3.1 MB EARLIER THIS
EVENING...BUT HAVE SINCE BACKED OFF TO -2.6 MB CURRENTLY. SOME
CONCERN IS THAT A WIND ADVISORY MAY BE NEEDED FOR SOUTHERN SANTA
BARBARA COUNTY THIS EVENING. WHILE THE SURFACE GRADIENTS HAVE
INCREASED...THE LATEST MODEL SOLUTIONS INDICATE THE BEST 950 MB
AND 850 MB THERMAL GRADIENTS DEVELOPING BETWEEN NOW AND TUESDAY
MORNING. THE BEST SUBSIDENCE IS EXPECTED TO OCCUR BEHIND A
SHORTWAVE MOVING OVER THE CALIFORNIA COAST CURRENTLY. LATEST
13-KM RUC DATA INDICATES THAT THE SOME STRONGER WINDS DEVELOPING
AT 950 MB AND WITHIN THE BOUNDARY LAYER CURRENTLY. THERE IS ALSO
SOME POSSIBILITY THAT SOME WINDS COULD ALSO DEVELOP THROUGH I-5
CORRIDOR TONIGHT AS WELL...BUT WITH KLAX-KBFL GRADIENTS BEING MUCH
WEAKER...LOWER CONFIDENCE EXISTS IN WIND HEADLINE POSSIBILITY FOR
THE I-5 CORRIDOR. FOR THE CURRENT TIME...WINDS WILL BE INCREASED
SLIGHTLY IN THE CURRENT PACKAGE FOR TONIGHT.
MARINE LAYER COULD ALSO BECOME PROBLEMATIC FOR THE CURRENT PACKAGE
TONIGHT. COLD AIR ADVECTION AND A DEVELOPING OFFSHORE FLOW PATTERN
APPEARS TO BE KEEPING THE MARINE LAYER PATCHY OVER THE CENTRAL
COAST. LATEST NAM-WRF AND 13-KM RUC INDICATE THAT AN OFFSHORE FLOW
PATTERN SHOULD MINIMIZE THE MARINE LAYER...BUT A MARINE INFLUENCE
IS STILL PRESENT THIS HOUR FROM LATEST ACARS SOUNDINGS FROM KLAX.
EARLIER MODEL SOLUTIONS SUGGESTED THE POSSIBILITY OF DEVELOPING AN
EDDY CIRCULATION OVER SOUTHERN CALIFORNIA. WITH OFFSHORE GRADIENTS
DEVELOPING...BEST APPROACH IS TO TREND THE DIRECTION TOWARDS NO
MARINE LAYER. THIS AGREES WELL WITH THE MODELS DEVELOPING COLD
AIR ADVECTION OVER THE AREA LATER TONIGHT.
DESPITE WIND ISSUES THIS EVENING...CURRENT PACKAGE SEEMS IN PRETTY
DECENT SHAPE WITH BRINGING A WARM UP FOR TUESDAY. NAM-WRF 950 MB
TEMPERATURES DID INITIALIZE ABOUT A DEGREE TOO COOL VERSUS GOOD
ACARS SOUNDING COVERAGE AT KLAX DURING THE 23Z-01Z TIME PERIOD.
WITH A FIVE DEGREES OF WARMING AT 950 MB AND OFFSHORE GRADIENTS
EXPECTED TO INCREASE...PACKAGE WILL BE ALSO BE UPDATED TO SLIGHTLY
TO INCREASE TEMPERATURES OVER THE AFFECTED AREAS ON TUESDAY.
&&
.PREV DISCUSSION... /ISSUED 230 PM PDT MON MAR 16 2009/
SHORT TERM...TEMPERATURES WERE 5 TO 10 DEGREES WARMER AT LOW
ELEVATIONS AND 10 TO 20 DEGREES WARMER AT HIGHER ELEVATIONS FROM
YESTERDAY AT THIS TIME AND TREND WILL CONTINUE THROUGH WEDNESDAY.
MAX TEMPERATURES WILL LIKELY WARM 10 TO 15 DEGREES ABOVE SEASONAL
NORMAL THROUGH WEDNESDAY. TEMPERATURE TREND WILL LIKELY REVERSE
THURSDAY...EXCEPT OVER THE DESERT...WHILE THE LONG WAVE TROUGH
APPROACHES AND THE SYSTEM NORTHEAST OF HAWAII MOVES ASHORE WITHIN
THE PROGRESSIVE AND MODERATE UPPER LEVEL SOUTHWEST FLOW...THOUGH
TEMPERATURES WILL LIKELY REMAIN 5 DEGREES ABOVE SEASONAL NORMAL.
THERE IS A CHANCE A CATALINA EDDY WILL DEVELOP HAVE INCLUDED
PARTLY CLOUDY SKIES OVER THE LA BASIN EARLY MORNING AND LATE NIGHT
THURSDAY. OTHERWISE A MODERATE NORTHWEST PRESSURE GRADIENT WILL
PERSIST AND THERE IS A CHANCE THE GRADIENT WILL BECOME STRONG
WEDNESDAY AFTERNOON AS A THERMAL TROUGH INTENSIFIES NEAR SHORE.
LONG TERM...WILL CONTINUE WITH THE COOLING TREND OVER THE ENTIRE
AREA AS THE LONG WAVE TROUGH ADVANCES EAST AND MOVES OVER THE AREA
SATURDAY AND WILL CONTINUE THE TREND SUNDAY AS NORTHWEST FLOW
FOLLOWING THE TROUGH MOVES ASHORE. TEMPERATURES WILL LIKELY COOL 5
TO 10 DEGREES BELOW NORMAL SATURDAY WITH A FEW DEGREES COOLING
SUNDAY. THERE IS A CHANCE BRISK NORTHWEST WINDS WILL DEVELOP OVER
THE ENTIRE AREA SUNDAY AS A MODERATE TO STRONG GRADIENT DEVELOPS
BETWEEN AN ADVANCING RIDGE OVER THE EASTERN PACIFIC AND DEVELOPING
LOW OVER THE SOUTHWEST. WILL CONTINUE WITH LOW POPS SUNDAY AS
GUIDANCE DIFFERED ON TIMING OF THE EASTWARD PROGRESSING SYSTEM.
TEMPERATURES WILL LIKELY MODERATE A FEW DEGREES MONDAY BUT WILL
REMAIN SEVERAL DEGREES LOWER THEN NORMAL AS A BROAD LONG WAVE TROUGH
AND NORTHWEST FLOW PERSISTS OVER THE AREA.
AVIATION...16/2349Z.
VFR CONDITIONS ARE EXPECTED AT MOST TERMINALS...EXCEPT FOR KPRB
WHERE IFR CONDITIONS COULD DEVELOP AS SOON AS 06Z THIS EVENING...OR
AS LATE AS 12Z LATE TONIGHT. THERE IS A CHANCE OF IFR CONDITIONS AT
KSMX AND KSBP THROUGH 07Z TONIGHT...AND A SLIGHT CHANCE OF MVFR
CONDITIONS AT LOS ANGELES COUNTY COASTAL TERMINALS AFTER 10Z
TONIGHT. AT KBUR...KVNY...AND KSBA...WEAK TURBULENCE AND INFREQUENT
LOW-LEVEL WIND SHEAR COULD IMPACT THE TERMINALS THROUGH 18Z TUESDAY.
KLAX...VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD WITH NO
WIND ISSUES. THERE IS A 20 PERCENT CHANCE THAT MVFR CONDITIONS COULD
DEVELOP AFTER 10Z TONIGHT. IF MVFR CONDITIONS DEVELOP...VFR
CONDITIONS SHOULD BE EXPECTED TO DEVELOP BETWEEN 17Z AND 19Z TUESDAY.
KBUR...VFR CONDITIONS ARE EXPECTED THROUGH OUT THE PERIOD WITH WEAK
TURBULENCE AND INFREQUENT WIND SHEAR ISSUES ARE POSSIBLE BETWEEN 12Z
AND 18Z TUESDAY MORNING.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
&&
$$
HALL/30
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
200 PM PDT MON MAR 16 2009
.SYNOPSIS...FAIR AND WARMER WEATHER IS EXPECTED THE NEXT FEW DAYS AS
HIGH PRESSURE CONTINUES. LOWER PRESSURE WILL DEVELOP LATER IN THE
WEEK...BRINGING COOLER WEATHER AND MORE CLOUDS.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
THE HIGH PRESSURE ALOFT IS BUILDING AND DAYTIME TEMPERATURES ARE
RESPONDING...ESPECIALLY INLAND WHERE IT IS 10-20 DEGREES WARMER THAN
THIS TIME YESTERDAY. THE NEAREST LOW CLOUDS ARE BEYOND THE ISLANDS.
THE HIGH PRESSURE RIDGE WILL PEAK OUT TUESDAY AND WEDNESDAY.
TEMPERATURES WILL HIT 70 AT THE COAST...RISE ABOVE 80 IN SOME INLAND
VALLEYS AND TOUCH 90 IN THE LOWER DESERTS. SURFACE FLOW WILL REMAIN
WEAKLY ONSHORE AND THERE ARE SOME HINTS OF A COASTAL EDDY DURING THE
NIGHTS...SO SOME LOW CLOUDS ARE EXPECTED DURING NIGHTS AND MORNINGS
NEAR THE COAST. A WEAK SHORTWAVE WILL DAMPEN THE RIDGE STARTING
THURSDAY...SO SLIGHTLY COOLER WEATHER WITH MORE COASTAL CLOUDS AND
HIGH CLOUDS ARE EXPECTED THURSDAY AND FRIDAY. AND THAT OPENS THE
DOOR FOR A VIGOROUS SHORTWAVE TROUGH TO MOVE INTO CALIFORNIA LATE
SATURDAY AND SUNDAY. THE LATEST 12Z RUN OF THE GFS SHOWS THIS SYSTEM
STAYING TOO FAR NORTH TO GIVE US PRECIP. THE 12Z EURO MODEL IS MORE
CONSISTENT FROM RUN TO RUN AND IT SHOWS LIGHT RAIN SUNDAY MORNING.
THE SYSTEM CONTAINS A LOT OF WIND...AND THAT MAY TURN OUT TO BE THE
BIGGEST WEATHER IMPACT AFTER ALL. UNLESS/UNTIL MODELS CAN CONVERGE
ON THE PRECIP SOLUTION WE WILL KEEP IT OUT OF THE FORECAST FOR NOW.
&&
.AVIATION...
161900Z...MDCRS SOUNDINGS CONTINUE TO SHOW THE MARINE LAYER DEPTH TO
BE AROUND 2500 FEET BUT DEPTH SHOULD LOWER TO AROUND 1200 FEET
TONIGHT. EXPECT SOME STATUS WITH BASES AROUND 800 FEET MSL TO RETURN
TO THE IMMEDIATE COAST AFTER SUNSET AND MOVE LOCALLY INLAND OVER THE
COAST AND LOWER MESA AREAS BETWEEN MIDNIGHT AND SUNRISE ON TUESDAY.
STRATUS COULD BRING CEILINGS DOWN TO NEAR OR BELOW THE LOCALIZER
RUNWAY 27 APPROACH MINIMUMS FOR KSAN AFTER MIDNIGHT. ANY STRATUS
SHOULD BREAK UP BETWEEN 15Z AND 17Z ON TUESDAY.
ABOVE THE MARINE LAYER INCLUDING THE MOUNTAINS AND DESERTS...MOSTLY
CLEAR WITH UNRESTRICTED VISIBILITIES THROUGH TUESDAY. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
HIGH RIP CURRENT RISK ORANGE COUNTY COASTAL AREAS...SEE LAXSRFSGX.
&&
$$
PUBLIC...MM
AVIATION...HORTON
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
330 AM PDT SUN MAR 15 2009
.SYNOPSIS...A DEEP MARINE LAYER WILL CAUSE LOW CLOUDS AND PATCHY FOG
WEST OF THE MOUNTAINS THIS MORNING WITH PARTIAL AFTERNOON CLEARING.
WARMER WITH A LESS EXTENSIVE MARINE LAYER MONDAY INTO THE END OF
THE WEEK UNDER HIGH PRESSURE.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
.SHORT TERM (TODAY-TUESDAY)....STRATUS WAS INTO THE COASTAL MOUNTAIN
SLOPES THIS MORNING. A WEAK UPPER DISTURBANCE WAS CAUSING VARIABLE
HIGH CLOUDINESS AND ALSO BROKE UP THE STRATUS IN THE NW AREAS.
AIRCRAFT SOUNDINGS INDICATED NW WINDS ALOFT. MODERATELY STRONG
ONSHORE GRADIENTS WITH ABOUT 7 MB SAN-IPL.
THE FLOW ALOFT WILL TURN FROM NW TO W WITH GRADUALLY INCREASING
HEIGHTS THROUGH TUESDAY. THIS WILL BRING A DECREASING MARINE LAYER
AND WARMING TREND AFTER TODAY. THE DEEP MARINE LAYER THIS MORNING
WILL BE SLOW TO BURN OFF WITH ONLY PARTIAL CLEARING AFTERNOON
CLEARING. THERE WILL BE PATCHY DENSE FOG ON THE COASTAL MOUNTAIN
SLOPES AND FOOTHILLS THIS MORNING. THERE COULD ALSO BE LOCAL DRIZZLE
FROM THICK LOW CLOUDS THIS MORNING. THE ONSHORE GRADIENTS WILL CAUSE
LOCAL BREEZY TO WINDY CONDITIONS IN THE MOUNTAINS AND DESERTS THIS
AFTERNOON AND EVENING. THE HIGH CLOUDINESS WILL DECREASE TODAY AND
THEN INCREASE AGAIN LATE TUESDAY.
&&
.LONG TERM (WEDNESDAY-SATURDAY)...A SHALLOW MARINE LAYER AND GRADUAL
WARMING TREND WILL CONTINUE INTO WEDNESDAY WHICH SHOULD BE THE
WARMEST DAY OF THE WEEK WITH MAX TEMPS INTO THE LOW 80S. A WEAK
SHORT WAVE SHOULD BRING MORE HIGH CLOUDINESS AND A LITTLE COOLING
THURSDAY AND FRIDAY. A LITTLE WARMER AGAIN SATURDAY UNDER A SHORT
WAVE RIDGE.
&&
.AVIATION...
150800Z...MARINE LAYER AROUND 5K FT. BASES AROUND 3500 FT WITH
LOCAL AT 2500 FT MSL. POSSIBLE NIGHT AND MORNING DRIZZLE. VSBY ABOVE
7SM WITH LOCAL 3-5SM IN THE MORNINGS. NIGHT AND MORNING LOW CLOUDS
COVERING THE COASTAL BASIN WILL CONTINUE THROUGH MONDAY WITH AREAS
OF STRATUS PERSISTING IN THE COASTAL AREAS THROUGH AFTERNOON.
STRATUS EXPECTED TO MOSTLY CLEAR INLAND AROUND 19Z.
&&
.MARINE...
150800Z...A LONG PERIOD SOUTH SWELL WILL INCREASE TODAY. THE SWELL
WILL GENERALLY BE AROUND 4 FEET BUT COULD GET UP TO 5 TO 6 FEET IN
THE OUTER WATERS. THE PERIOD WILL BE AROUND 18 SECONDS TODAY...
DROPPING THEREAFTER. THE SWELL WILL PEAK TODAY...WITH LITTLE CHANGE
MONDAY...DECREASING THEREAFTER.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...ATKIN
AVIATION/MARINE...WHITLOW
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
301 PM CDT MON MAR 16 2009
.DISCUSSION...CWA REMAINS UNDERNEATH A WARM ADVECTION REGIME
SPONSORED BY SFC LOW ACROSS WCTRL MANITOBA EARLY THIS AFTERNOON.
ANOTHER WARM DAY AS TEMPS SOAR WELL PAST NORMAL VALUES BY 20/25
DEGREES IN PARTS OF ERN CWA. MID LVL HEIGHTS ARE RISING SLIGHTLY
AS MAIN PUNCH OF UPPER JET CORE AIMS FROM PACNW INTO NE MONTANA
ATTM. NO SIGNIFICANT LIFT AVAILABLE..SYNOPTIC OR MESOSCALE...TO
TAKE ADVANTAGE OF SLIGHTLY ABOVE NORMAL PWAT LEVELS.
TONIGHT/TUESDAY...SFC LOW OVER ONTARIO WILL DRAG A COLD FRONT
INTO NWRN CWA BY 12Z. NAM12 COND PRESS DEFICITS ALONG 280/285K SFC
SUGGEST AN AREA OF LOW CLOUDS WILL ACCOMPANY FRONT. A FEW OF THE
GEFS MEMBERS SHOW SOME MEASURABLE PRECIP SKIRTING NRN TIER OF CWA
THRU 18Z. LATEST SREF SUGGESTS LESS THAN 20 PERCENT POPS. OMEGA
PRESSURE ADVECTION IS LIMITED SO WILL LEAVE POPS OUT OF FCST FOR
NOW. FOG POTENTIAL FOR THIS EVENING ACROSS NWRN CRNR CWA AS SFC
T/TD DEPRESSIONS LOWER WITHIN CONVERGENT AREA ASSOCIATED WITH SFC
BDRY. SHOULD BE A 3 TO 4 HR WINDOW OF VISIBILITY LESS THAN 3 MILES
BEFORE MIXING INCREASES IMMEDIATELY BEHIND FRONT. MAX TEMPS ABOUT
5 TO 10 DEGREES LOWER AS 85H CAA CONTINUES THROUGHOUT DAY.
EXTENDED...WED THRU SATURDAY...GFS/EC IN DECENT AGREEMENT THROUGH
FRIDAY. DRY FCST AS WEST...THEN NORTHWEST..MID LVL FLOW
ESTABLISHES ACROSS REGION AND DEEP LAYER DRYING OCCURS. MDL
DIFFERENCES ARISE BY FRIDAY AFTERNOON AND LINGER INTO WEEKEND. EC
PUSHES PRECIP THROUGH QUICKLY BY EARLY SAT...THEN KEEPS FCST DRY.
GFS MAINTAINS A FAIRLY DAMP FCST THRU WEEKEND COURTESY OF STRONG
WAA AND A PROGRESSION OF MORE UNSTABLE AIR INTO THE CWA BY SUNDAY.
&&
.AVIATION.../18Z TAF ISSUANCE/
SHALLOW FOG/HAZE WILL LINGER AT KAXN EARLY THIS AFTERNOON FOR A
SHORT TIME....CLEARING BY 17Z-18Z. VFR CONDITIONS WITH PASSING
CIRRUS CLOUDS CAN BE EXPECTED THIS AFTERNOON ELSEWHERE.
SOUTH/SOUTHWEST WINDS AROUND 12 KTS GUSTING 16-22 KT CAN BE EXPECTED
THROUGH THE 18Z-22Z TIME FRAME AT KMSP/KRNH/KEAU WITH THE EASTERN
HALF OF THE REGION STILL IN A STRONG PRESSURE GRADIENT. MODELS
SUGGEST THIS GRADIENT SHOULD RELAX IN THE LATE AFTERNOOON...AFTER
THE 22Z/23Z TIME FRAME. TAMDAR SOUNDINGS AT KMPX SHOW 2000 FT WINDS
AT 18 KT...2500 FT WINDS AT 23 KT.
A WEAK SURFACE TROUGH WILL PASS ACROSS THE AREA OVERNIGHT...AND
BRING LIGHT/VARIABLE WINDS AND ANOTHER CHANCE FOR FOG
DEVELOPMENT...STARTING THE EARLIEST AT KAXN...THEN KSTC. BETWEEN
15Z AND 18Z...SCT-BKN MVFR LEVEL CLOUDS WILL LIKELY ACCOMPANY A WEAK
FRONT NEAR THE END OF THE TAF PERIOD...BUT LOW CONFIDENCE ON
MVFR...SO LEFT VFR FOR NOW.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
99/99
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
130 PM CDT MON MAR 16 2009
.UPDATE...FOR 18Z AVIATION DISCUSSION BELOW
&&
.DISCUSSION...
RUC13 DEPICTS RELATIVE INVERSION ACROSS NWRN CWA WITH 925 THERMAL
TROUGH BEING OVERTAKEN BY WAA AT 85H. BRISK WIND OFF DECK SHOULD
MINIMIZE POTENTIAL OF ANYTHING MORE DENSE. MECHANICAL MIXING
SHOULD WIPE OUT FG WITHIN NEXT HOUR OR SO. DROPPED HRLY TEMPS A
TAD ACROSS SRN CWA MORE IN LINE WITH LATEST LAV AND CURRENT OBS.
&&
.AVIATION.../18Z TAF ISSUANCE/
SHALLOW FOG/HAZE WILL LINGER AT KAXN EARLY THIS AFTERNOON FOR A
SHORT TIME....CLEARING BY 17Z-18Z. VFR CONDITIONS WITH PASSING
CIRRUS CLOUDS CAN BE EXPECTED THIS AFTERNOON ELSEWHERE.
SOUTH/SOUTHWEST WINDS AROUND 12 KTS GUSTING 16-22 KT CAN BE EXPECTED
THROUGH THE 18Z-22Z TIME FRAME AT KMSP/KRNH/KEAU WITH THE EASTERN
HALF OF THE REGION STILL IN A STRONG PRESSURE GRADIENT. MODELS
SUGGEST THIS GRADIENT SHOULD RELAX IN THE LATE AFTERNOOON...AFTER
THE 22Z/23Z TIME FRAME. TAMDAR SOUNDINGS AT KMPX SHOW 2000 FT WINDS
AT 18 KT...2500 FT WINDS AT 23 KT.
A WEAK SURFACE TROUGH WILL PASS ACROSS THE AREA OVERNIGHT...AND
BRING LIGHT/VARIABLE WINDS AND ANOTHER CHANCE FOR FOG
DEVELOPMENT...STARTING THE EARLIEST AT KAXN...THEN KSTC. BETWEEN
15Z AND 18Z...SCT-BKN MVFR LEVEL CLOUDS WILL LIKELY ACCOMPANY A WEAK
FRONT NEAR THE END OF THE TAF PERIOD...BUT LOW CONFIDENCE ON
MVFR...SO LEFT VFR FOR NOW.
&&
.PREV DISCUSSION...
/ISSUED 915 AM CDT MON MAR 16 2009/
RUC13 DEPICTS RELATIVE INVERSION ACROSS NWRN CWA WITH 925 THERMAL
TROUGH BEING OVERTAKEN BY WAA AT 85H. BRISK WIND OFF DECK SHOULD
MINIMIZE POTENTIAL OF ANYTHING MORE DENSE. MECHANICAL MIXING
SHOULD WIPE OUT FG WITHIN NEXT HOUR OR SO. DROPPED HRLY TEMPS A
TAD ACROSS SRN CWA MORE IN LINE WITH LATEST LAV AND CURRENT OBS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
99/99
AREA FORECAST DISCUSSION...UPDATED
NWS RALEIGH NC
1106 AM EDT SUN MAR 15 2009
.SYNOPSIS...
COLD SURFACE HIGH PRESSURE WILL MAINTAIN ITS INFLUENCE OVER OUR
REGION TODAY THEN GRADUALLY WEAKEN TONIGHT AND MONDAY.
MEANWHILE...SEVERAL UPPER LEVEL DISTURBANCES IN THE SOUTHWEST FLOW
ALOFT WILL CONTINUE TO CAUSE PERIODS OF RAIN OVER OUR AREA THROUGH
MONDAY. WEATHER CONDITIONS ARE EXPECTED TO GRADUALLY IMPROVE TUESDAY
INTO WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1100 AM SUNDAY...
SURFACE WEDGE REMAINS IN PLACE THIS MORNING ALTHOUGH THE 12Z KGSO
RAOB SHOWS THE DEPTH OF THE COOL SFC BASED AIRMASS HAS DECREASED
ALOFT. SEVERAL 12Z AMDAR AIRCRAFT SOUNDINGS AT KRDU INDICATE A
SIMILAR EROSION OF THE WEDGE AIRMASS FROM ABOVE. IN FACT...ONLY
THE 100M WIND FROM THE KRAX AND TRDU TERMINAL RADAR INDICATE A
NORTHERLY COMPONENT TO THE WIND ABOVE THE SFC. THE 1000-850
THICKNESSES FROM KGSO ALSO INDICATE THE WARMING ALOFT AS
THICKNESSES HAVE WARMED 21M FROM SAT 12Z TO 1341M.
LATEST SAT AND RADAR TRENDS INDICATE A LARGE AREA OF PRECIPITATION
MOVING INTO CENTRAL NC FROM THE WEST. THIS AREA OF PRECIPITATION
IS ASSOCIATED WITH A DEEP LAYER OF ASCENT IN A VERY MOIST AIRMASS.
AT THE LOWER LEVELS GOOD MOISTURE ADVECTION AND LOW LEVEL
ISENTROPIC LIFT IS SYNDICATED WITH A MODEST AMOUNT OF 850 MB
CONVERGENCE OVER THE CAROLINAS. THIS IS FURTHER ENHANCED BY A
MID LEVEL SHORTWAVE THAT IS SHEARING OUT ACROSS THE SOUTHERN
APPALACHIANS AND SOME DIVERGENCE ALOFT ASSOCIATED WITH THE
ENTRANCE REGION OF A 115 KT JET ANALYZED ON THIS MORNINGS UPPER
AIR ANALYSIS. MOST SHORT NWP GUIDANCE IS CONSISTENT IN BRINGS
THIS AREA OF RAIN ACROSS CENTRAL NC THIS AFTN. THE PRECIPITATION
AMOUNTS AND COVERAGE SHOULD DECREASE A BIT FROM THE WEST LATE THIS
AFTN AS UPPER LEVEL SUPPORT SHIFTS NE OF THE AREA. WILL KEEP POPS
AT 100 PERCENT.
TEMPS AREA ALREADY RUNNING CLOSE TO OR NEAR FCST HIGHS IN MANY
LOCATIONS. ONSET OF RAIN SHOULD SLOW THE UPWARD TREND OF TEMPS BUT
EXPECT HIGHS TO BE 3 TO 5 DEGREES WARMER THEN YESTERDAY IN THE SE
ZONES DECREASING TO A MODEST 2 DEGREE INCREASE IN THE NW. -BLAES
TONIGHT...MID LEVEL S/W AND ASSOCIATED SURFACE LOW WILL LIFT E-EN
AWAY FROM REGION. EXPECT WIDESPREAD RAIN EARLY TO GIVE WAY TO
WIDESPREAD DRIZZLE AND FOG. ANY RAIN OCCURRING AFTER 06Z MONDAY
SHOULD BE SPOTTY AND MAINLY OCCURRING EAST OF HIGHWAY 1. AS ONE
USUALLY EXPECTS IN RESIDUAL CAD EVENTS...TEMPS TONIGHT WILL CHANGE
LITTLE FROM AFTERNOON LEVELS AS TEMPS ONLY COOL 3-5 DEGREES. -WSS
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 320 AM SUNDAY...
MONDAY...SHORT TERM MODEL GUIDANCE LIFT ANOTHER S/W ACROSS THE SE
U.S. THIS FEATURE EXPECTED TO TRACK A LITTLE FARTHER SE THAN THOSE
OF THE PAST COUPLE OF DAYS. IN ADDITION...FLOW ABOVE 3000FT BECOMES
MORE WESTERLY IN THE WAKE OF THE SYSTEM THAT EXITS THIS EVENING.
EVEN THOUGH EXPECT ANOTHER ROUND OF RAIN MONDAY MORNING...RAINFALL
INTENSITY WILL BE LIGHT WITH AMOUNTS VARYING FROM A THIRD OF AN INCH
IN THE SE TO LESS THAN A QUARTER OF AN INCH IN THE NW (AND THIS MAY
BE GENEROUS IN THE NW). TEMPS WILL REMAIN BELOW NORMAL IN THE
RESIDUAL CAD AIRMASS BUT PERIODS OF NO PRECIP AND A VARIABLE NEAR
SURFACE FLOW WILL ALLOW FOR SOME RECOVERY IN TEMPS. HIGHS MONDAY
AFTERNOON EXPECTED TO RANGE FROM THE UPPER 40S NW TO THE MID 50S
SE. -WSS
MONDAY NIGHT AND TUESDAY: THE WELL DEFINED NEARLY STATIONARY UPPER
LOW OVER KANSAS THIS MORNING IS FORECAST TO ACCELERATE EASTWARD
THROUGH THE MID ATLANTIC STATES MONDAY NIGHT... IN RESPONSE TO AN
UPSTREAM KICKER TROUGH ALOFT OVER THE NORTHERN ROCKIES AT THE
MOMENT. THE APPROACH AND PASSAGE OF THIS TROUGH ALOFT SHOULD FINALLY
SHUNT THE DEEP MOISTURE AXIS SOUTHEASTWARD AND OFFSHORE. IN
ADDITION... THERE ARE HINTS OF MULTIPLE CAD EROSION PROCESSES BY
THIS TIME... AS CAA AT H85 (DIFFERENTIAL THERMAL ADVECTION) FROM
LATE MONDAY ONWARD SHOULD GRADUALLY WEAKEN THE CAD INVERSION AND
PROMOTE SHEAR-INDUCED MIXING OF DRIER AIR ALOFT DOWNWARD INTO THE
RESIDUALLY SATURATED NEAR SURFACE CAD AIRMASS. HOWEVER... MODEL
CROSS SECTIONS INDICATE RESIDUAL CAD/LOW LEVEL MOISTURE MAY LINGER
WITHIN A VERY LIGHT WIND PATTERN AT THE SURFACE... AND ACCORDINGLY
MAINTAIN LOW STRATUS AND/OR FOG OVERNIGHT AND INTO TUESDAY... UNTIL
MID MARCH SOLAR HEATING ASSISTS WITH THE EROSION BY LATER TUESDAY
AFTERNOON. OVERNIGHT LOWS GENERALLY IN THE MIDDLE 40S. HIGH
TEMPERATURES TUESDAY RETARDED BY THE LINGERING LOW CLOUDS (MOSTLY
CLOUDY SKIES) UNTIL AT LEAST EARLY AFTERNOON... GENERALLY UPPER 50S
TO LOWER 60S.
TUESDAY NIGHT: SHORTWAVE RIDGING ALOFT WILL PROMOTE CONTINUED DRY
DEEP LAYER MOISTURE/CLEAR SKIES... WHICH IN CONJUNCTION WITH THE
PRESENCE OF AN ACCOMPANYING SURFACE RIDGE AXIS AND SATURATED SOIL
SHOULD LEAD TO RADIATION FOG DEVELOPMENT OVERNIGHT. LOW TEMPERATURES
IN THE LOWER 40S EXPECTED. -MWS
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 430 AM SUNDAY...
WEDNESDAY AND WEDNESDAY NIGHT: MORNING FOG IS EXPECTED TO LIFT INTO
A SCATTERED FLAT STRATOCUMULUS DECK WITH DIURNAL HEATING. THE
COMBINATION OF PARTLY SUNNY SKIES AND RETURN FLOW AROUND THE
AFOREMENTIONED RIDGE AXIS AS IT SETTLES TO OUR SOUTHEAST... SHOULD
ALLOW TEMPERATURES TO CLIMB INTO THE UPPER 60S PER DRY ADIABATIC
TEMPERATURE SCHEMES THROUGH ABOUT 3 THSD FT. A SHORTWAVE TROUGH
ALOFT IS FORECAST TO AMPLIFY SOUTHEASTWARD ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES WEDNESDAY NIGHT... AND PROPEL AN ATTENDANT
SURFACE COLD FRONT TOWARD THE WESTERN SLOPES OF THE CENTRAL
APPALACHIANS BY THURSDAY MORNING. THIS DOES NOT PRESENTLY LOOK TO BE
A CLASSIC CASE OF RISING OVERNIGHT THICKNESSES AND (MOS) NUMBER
BUSTING TEMPERATURES ON THE NIGHT BEFORE A COLD FRONT... OWING TO A
RELATIVELY LAX MSLP GRADIENT AND WEAK LOW LEVEL WAA AHEAD OF THE
STILL RELATIVELY DISTANT COLD FRONT. HOWEVER... THE CURRENT FORECAST
OF UPPER 40S MAY NEED TO BE ADJUSTED UPWARD A CATEGORY IF LATER
MODELS INDICATE MORE OF THAT NIGHT BEFORE A COLD FRONT SIGNAL.
THURSDAY AND THURSDAY NIGHT: THERE ARE SOME MINOR TIMING DIFFERENCES
IN THE MEDIUM RANGE GUIDANCE REGARDING THE TIMING OF THE COLD
FRONTAL PASSAGE AND ASSOCIATED CHANCE OF SHOWERS IN CENTRAL NC...
BUT THE GENERAL CONSENSUS FAVORS THE THURSDAY AFTERNOON AND EVENING
TIME FRAME. SINCE MID LEVEL (H85-5) LAPSE RATES ARE PROJECTED TO
ONLY MARGINALLY EXCEED 5.5 C/KM AND RESULTANTLY LIMIT BUOYANCY...
THUNDER WILL BE OMITTED FOR NOW. HIGH TEMPERATURES EXPECTED TO CLIMB
INTO THE UPPER 60S TO LOWER 70S... AS LOW LEVEL THICKNESSES SURGE
INTO THE 1360S TO AROUND 1370... SOME 30 METERS ABOVE AVERAGE. THE
FRONT IS FORECAST TO SETTLE INTO THE SAVANNAH BASIN BY FRIDAY
MORNING... WITH CAA IN ITS WAKE EXPECTED TO KNOCK TEMPERATURES BACK
INTO THE 40 TO 45 DEGREE RANGE BY SUNRISE FRIDAY.
FRIDAY THROUGH SATURDAY: WILL MAINTAIN A DRY FORECAST THIS PERIOD...
AS COOL SURFACE HIGH PRESSURE BUILDS OVERHEAD BENEATH A PROGRESSIVE
TROUGH ALOFT OVER THE EASTERN US. HOWEVER... A QUICK GLANCE AT THE
LATEST ECMWF SUGGESTS THE UPPER TROUGH MAY LAG AND PROVIDE FOR A
CHANCE OF SHOWERS ON FRIDAY... THEN DRY THINGS OUT FRIDAY NIGHT AND
SATURDAY. THIS NEW... OUTLIER SOLUTION AT PRESENT... WILL NEED TO BE
CONSIDERED IN SUBSEQUENT FORECASTS. -MWS
&&
.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AS OF 733 AM SUNDAY...
LIFR/IFR CONDITIONS WILL PERSIST ACROSS CENTRAL NORTH CAROLINA
THROUGH MONDAY MORNING...AND POSSIBLY INTO MONDAY NIGHT. COLD HIGH
PRESSURE CONTINUES TO EXTEND ACROSS THE AREA FROM THE
NORTH-NORTHEAST WHILE SW FLOW AT AND ABOVE 3000FT PULLS WARM MOIST
AIR OVER THE COOL STABLE AIR NEAR THE SURFACE. THIS SCENARIO WILL
MAINTAIN LOW CLOUDS OVER CENTRAL NC THROUGH AT LEAST MONDAY MORNING.
PERTURBATIONS IN THE FLOW ALOFT WILL CAUSE PERIODS OF RAIN WITH
POCKETS OF MODERATE RAIN. AT THIS TIME...MODERATE RAIN APPEARS
LIKELY ACROSS CENTRAL NC THROUGH 20Z SUNDAY.
TONIGHT...RAIN IS EXPECTED TO TAPER OFF TO WIDESPREAD DRIZZLE ALONG
WITH AREAS OF FOG. FOG SHOULD REDUCE THE VISIBILITY TO AROUND A MILE
OR TWO AT MOST LOCALES WITH POCKETS OF DENSE FOG (A HALF MILE OR
LESS VISIBILITY) POSSIBLE. MAY SEE A BRIEF WINDOW OF LOW LEVEL WIND
SHEAR IN THE FAY VICINITY AFTER 06Z MON AS LOW LEVEL JET INCREASES
TO NEAR 30KTS AT 2000FT.
MONDAY...ANOTHER PERTURBATION ALOFT IS EXPECTED TO CROSS TO OUR
SOUTH-SOUTHEAST. THIS SHOULD BRING ANOTHER BATCH OF LIGHT TO
MODERATE RAIN TO THE SE COUNTIES OF CENTRAL NC WITH SPOTTY RAIN
FARTHER NORTH AND WEST. CEILINGS MAY IMPROVE TO THE HIGH END IFR OR
LOW END MVFR BY LATE MONDAY.
TUESDAY WILL LIKELY BE OUR TRANSITION FROM MVFR TO VFR CONDITIONS AS
DRIER AIR ALOFT HELPS TO SCOUR OUT LOW LEVEL MOISTURE. VFR
CONDITIONS EXPECTED TO PERSIST WEDNESDAY THROUGH THURSDAY.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...WSS/MWS
LONG TERM...MWS
AVIATION...WSS
AREA FORECAST DISCUSSION
NWS SALT LAKE CITY UT
305 PM MDT MON MAR 16 2009
.SYNOPSIS...A MILD WESTERLY FLOW WILL PERSIST ACROSS THE GREAT
BASIN THROUGH MIDWEEK. A WEAK DISTURBANCE IS EXPECTED TO CROSS THE
REGION DURING THE LATE WORK WEEK...FOLLOWED BY A STRONGER COLD
FRONT NEXT WEEKEND.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS AN UPPER LOW OVER THE GULF OF
ALASKA. FLAT RIDGING WAS DOMINATING OVER THE SOUTHWEST CONUS...WITH
THE NEXT DISTURBANCE LOCATED NEAR 150W/30N. ACARS 400-250MB WIND
OBSERVATIONS REVEAL A SOUTHWESTERLY 120-150KT JET OVER THE PACIFIC
NORTHWEST. 12Z 700MB ANALYSIS PLACED A BAROCLINIC ZONE STRETCHING
FROM SOUTHWEST TO NORTHEAST ACROSS THE PACIFIC NORTHWEST.
SOUTHWESTERLY FLOW ON THE COLD SIDE WAS PARALLEL TO THE FRONT.
-17C WAS LOCATED OVER BRITISH COLOMBIA...WITH +3 TO +5C WITHIN THE
THERMAL RIDGE FROM SOUTHERN CALIFORNIA INTO SOUTHERN NEVADA.
LOCALLY...COLD ADVECTION WAS IN PLACE WITH -1C AT KSLC AND -3C
UPSTREAM AT KLKN.
12Z KSLC RAOB INDICATES +3 TO 5C OF WARMING THROUGH THE COLUMN
DURING THE PAST 24 HOURS. THE PRECIPITABLE WATER VALUE WAS STEADY AT
THREE TENTHS OF AN INCH.
PRESSURE RISES OF 3 TO 5MB/3HR ACROSS SOUTH CENTRAL CANADA AS A WAVE
RACES NORTHEAST ALONG THE BAROCLINIC ZONE. WITH PARALLEL FLOW AT
700MB ALONG THE BOUNDARY DO NOT EXPECT THE FRONTAL ZONE TO DROP INTO
THE REGION TOO QUICKLY.
WITH THE UPPER LEVEL JET NEAR THE IDAHO BORDER...MAINTAIN GOOD BIT
OF CLOUD COVER AND LOW POPS ACROSS FAR NORTHERN FORECAST AREA
TONIGHT INTO TOMORROW. IF IT DOES PRECIPITATE...QPF IS QUITE LOW.
MUCH OF CENTRAL AND SOUTHERN UTAH SHOULD REMAIN CLEAR/SUNNY.
LOW PRESSURE TO THE NORTH SHOULD MAINTAIN SOUTHERLY FLOW TONIGHT.
FOR FORECAST LOWS...STARTED WITH LAST NIGHTS TEMPERATURES AND
TWEAKED THEM TOWARD NAM MOS TO REFLECT SLIGHT COOLING ALOFT ACROSS
THE NORTH.
SHALLOW COOLING TAKES PLACE TOMORROW NIGHT AS THE BOUNDARY SAGS
SOUTH. FLOW BECOMES MORE NORTHERLY WITH LOWERING PRESSURE TO OUR
SOUTH...WHICH SHOULD BREAK THE STRING OF WARM NIGHTS.
WARMING ALOFT OCCURS WEDNESDAY WITH RIDGING BUILDING IN AHEAD OF THE
NEXT DISTURBANCE CURRENTLY NEAR 150W/30N. MID AND HIGH LEVEL CLOUD
COVER BUILDS IN FROM THE SOUTHWEST AS A RESULT OF THE APPROACHING
SYSTEM. KEPT SLIGHT CHANCE FOR PRECIPITATION IN THE MOUNTAINS
FRIDAY. MOISTURE IS RICH WITH THIS SYSTEM PER LATEST BLENDED
PRECIPITABLE WATER LOOP...BUT DYNAMICS WILL BE QUITE WEAK AS IT
LIFTS OVER THE GREAT BASIN. GFS SEEMS TO BE OVER-INFLATING OMEGA
VALUES. JUDGING BY THE RANDOMNESS OF VORTICITY MAXIMA IT APPEARS TO
BE ASSOCIATED WITH THE CONVECTIVE SCHEME.
GFS/EUROPEAN CONTINUE TO INDICATE THE NEXT SYSTEM OF INTEREST
ARRIVES FOR NEXT WEEKEND...THOUGH TIMING AND AMPLITUDE REMAIN A
CHALLENGE. FOR NOW HAVE SPLIT THE DIFFERENCE AS FAR AS TIMING GOES.
THE SYSTEM APPEARS TO BEGIN TO WARM ALOFT/WEAKEN AS IT MOVES
OVERHEAD...THOUGH BOTH MODELS INDICATE IT WILL BE QUITE COLD ALOFT
AS IT MOVES INLAND FROM THE PACIFIC. THE MAIN CONCERN AT THIS POINT
WILL BE GUSTY PRE-FRONTAL WINDS...WITH BOTH MODELS INDICATING 700MB
WINDS MAY EXCEED 50KTS. WILL HIGHLIGHT IN THE HAZARDOUS WEATHER
OUTLOOK AND CONTINUE TO MONITOR THIS WEEK.
&&
.AVIATION...LIGHT NORTHWEST WINDS ARE EXPECTED TO RETURN TO THE KSLC
TERMINAL BETWEEN 17-18Z TODAY. THAT SAID...A 30 PERCENT CHANCE
EXISTS THAT LIGHT DRAINAGE WINDS WILL SWITCH TO NORTHWEST AS EARLY
AS 16Z THIS MORNING.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI
AVIATION...TRAPHAGAN
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
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