SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 830 PM PDT MON APR 14 2003
COLD UPPER LOW CENTERED NEAR POINT CONCEPTION WILL MOVE THROUGH
FORECAST AREA THIS EVENING. WHILE STEADY RAINFALL WITH THE MAIN
FRONTAL BAND HAS PUSHED SOUTH AND EAST OF LOS ANGELES COUNTY...
INSTABILITY SHOWERS CONTINUE THIS EVENING ACROSS OUR FORECAST AREA.
00Z VANDENBERG SOUNDING AND ACARS DATA SHOWING FREEZLING LEVELS BELOW
5000 FEET...WHICH CORRELATES TO SNOW LEVELS AROUND 4000 FEET...
PERHAPS EVEN LOWER ON INTERIOR SLOPES AND NEAR HEAVIER SHOWERS.
LATEST 00Z MESO-ETA SOLUTION SUPPORTS THIS IDEA WITH THICKNESSES
FALLING TO BELOW 540 OVERNIGHT...AND 850 MB TEMPERATURES NEAR THE
FREEZING MARK. SEVERAL MOUNTAIN AUTOMATED STATIONS REPORTING
TEMPERATURES IN THE LOWER TO MID 30S AS WELL.
WINTER STORM WARNING REMAINS IN EFFECT FOR LA/VTU COUNTY MOUNTAINS
THROUGH TONIGHT. WHILE THE HEAVIEST SNOWFALL HAS SHIFTED EAST OF
OUR REGION...DO EXPECT SHOWERS TO LINGER MUCH OF THE NIGHT...SOME
LOCALLY HEAVY. THIS COULD RESULT IN A FEW INCHES OF ADDITIONAL
ACCUMULATION. MOUNT BALDY AND MOUNTAIN HIGH HAVE ALREADY REPORTED
AROUND A FOOT OF NEW SNOW WITH THIS STORM AS OF 8 PM.
AS UPPER LOW APPROACHES THE SOUTHERN CALIFORNIA COAST...IT HAS
BEGUN TO TAKE A SOMEWHAT NEGATIVE TILT ORIENTATION...RESULTING
IN SHOWERS DRAPING ALONG THE COASTAL AREAS OF LOS ANGELES...
VENTURA...AND SANTA BARBARA COUNTIES. LATEST CROSS SECTIONS
INDICATING A MOIST ONSHORE FLOW WITH SOME UPWARD VERTICAL MOTION
THROUGH MIDNIGHT...SO SHOWERS LIKELY TO CONTINUE NEXT 4 TO 6 HOURS...
THEN GRADUALLY TAPER OFF FROM THE NORTHWEST LATER TONIGHT.
SIGNIFICANT INFLUX OF COLD AIR ALOFT...AS EVIDENT BY THE 500 MB
TEMPERATURES FALLING TO -25 TO -28 DEGREES CELSIUS...SO LOOK FOR
POSSIBILITY OF BRIEF HEAVY RAIN AND SMALL HAIL. WITH MSAS LIFTED
INDICES AROUND 0...COULD NOT RULE OUT A STRAY THUNDERSTORM AS THE
UPPER LOW MOVES THROUGH THE REGION.
DRIER WEATHER EXPECTED ON TUESDAY...EXCPET FOR SOME LINGERING SHOWERS
ACROSS THE MOUNTAINS...ESPECIALLY NORTH FACING SLOPES. ANOTHER CHANCE
FOR RAIN ACROSS THE CENTRAL COAST BY WEDNESDAY...SPREADING TO LA BASIN
BY WEDNESDAY NIGHT.
LAX 8000. GOMBERG.
.LOX...WINTER STORM WARNING (SEE LAXWSWLOX).
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
$$
AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 1245 PM CDT MON APR 14 2003
AVIATION DISCUSSION FOR 18Z TAF ISSUANCE
GUSTY SOUTHWEST GRADIENT FLOW OVER FORECAST AREA THIS
AFTERNOON...BETWEEN HIGH PRESSURE ALONG THE EAST COAST AND LOW
PRESSURE OVER UPPER MIDWEST/NORTHERN PLAINS. AS LOW LEVELS MIX OUT
WILL SEE GUSTS INTO THE MID-UPPER 20S...THOUGH LOOKS LIKE STRONGEST
WINDS WILL REMAIN WEST OF THE FORECAST AREA ACROSS IOWA THIS
AFTERNOON. WITH GRADIENT TONIGHT WILL KEEP SOME GUSTS INTO THE
TEENS...THEN BRING WINDS BACK UP DURING THE MORNING TUES. 12 UTC
SOUNDINGS FROM MANY PLAINS LOCATIONS SHOWS VERY DRY ATMOSPHERE...AND
VISIBLE SATELLITE PICS SHOWING ALMOST NO CLOUD COVER ACROSS
REGION...EXCEPT SOME VERY THIN CIRRUS ACROSS IA. EXPECT THESE VFR
CONDITIONS TO CONTINUE THROUGH 18Z TUES.
RATZER
DISCUSSION FOR 1000 AM ZONE UPDATE
...RECORD BREAKING WARMUP THIS AFTERNOON...
12Z ANALYSIS SHOWS 925 MB HEIGHT GRADIENT OVER NORTHERN ILLINOIS
WITH +20C AT DVN. GRADIENT DOESNT RELAX AT 850 MB WITH TEMPERATURES
ALREADY +14C AT DVN/ILX/LOCAL ACARS SOUNDINGS. RUC THETA-E CROSS
SECTIONS SHOW MIXING TO 850 MB NEAR ROCKFORD...AND 800 MB OVER
NORTHWEST INDIANA. WAS INITIALLY SURPRISED TO SEE THIS TREND IN THE
RUC FORECAST...BUT WITH SUBSIDENCE INVERSION SEEN ON DVN...AND
HEIGHT RISES AT 500 MB...THIS WOULD TEND TO MAKE SOME SENSE.
RUC FORECASTS +16 AT 850 AND +10 AT 800 MB AT 21Z. THIS WOULD MIX TO
A UNIFORM +30/31C HIGH TEMPERATURE ACROSS CWA. WILL BUMP HIGH
TEMPERATURES UP TO MID 80S ACROSS ENTIRE CWA. RECORDS ARE (SOON TO
BE WERE) 79/83 SET IN 1941 AT ROCKFORD/OHARE RESPECTIVELY.
OTHER ISSUE THIS AFTERNOON IS THE WINDS. WITH TIGHT HEIGHT/MSLP
GRADIENT ALREADY SEE 30 KNTS AT 950 MB ON LOCAL ACARS SOUNDINGS.
ACARS SOUNDINGS FURTHER WEST REVEAL 40 KNTS AT 875 MB...SO WILL HAVE
HIGHEST WINDS MENTIONED IN NORTHWEST ZONES. GENERALLY EXPECT 15 TO
25 MPH SOUTHWEST WINDS...WITH SOME GUSTS OVER 30 ESPECIALLY NEAR
ROCKFORD.
WEAK SHORTWAVE APPROACHING THE AREA IS ALLOWING FOR SOME MID/HI
CLOUD DEVELOPMENT OVER IOWA. THOUGH BETTER SUBSIDENCE OVER OUR
AREA...SUSPECT SOME DEBRIS TO BE ADVECTED OVER AREA LATE THIS
AFTERNOON.
.CHI...GALE WARNING FOR NORTH THIRD OF LAKE MICHIGAN THIS AFTERNOON.
A SMALL CRAFT ADVISORY THIS AFTERNOON FOR NEARSHORE WATERS.
ROGOWSKI
SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NWS BILLINGS MT
AFDBIL 235 PM MDT MON APR 14 2003
.SHORT TERM...VALID FOR TUE AND WED...
AIRMASS ACROSS MUCH OF THE AREA REMAINS CAPPED PER LATEST ACARS
SOUNDING. AS A RESULT...NO PRECIPITATION HAS MADE IT TO THE GROUND
THIS AFTERNOON. MOISTURE STREAMING UP FROM THE SOUTH REMAINED
IN THE FAR WESTERN ZONES. THE SHORT WAVE MOVING THROUGH CA/OR PER
WATER VAPOR APPEARS WILL BE THE MAIN PRECIPITATION PRODUCER AS IT
SLIDES AROUND THE TROUGH AXIS...BUT THIS WONT BE UNTIL LATE TONIGHT AND
TOMORROW. FEEL THE ETA/GFS IS TOO QUICK WITH THE PRECIPITATION AND HAVE
BACKED OFF ON THE TIMING A BIT.
ONCE THIS SYSTEM DEVELOPS...A 700MB LOW MOVING INTO THE AREA WILL
RESULT IN A WIDESPREAD PRECIPITATION EVENT. EXPECT MOST OF THE PRECIP TO
FALL WEST AND NORTH OF BIL UNTIL TUESDAY NIGHT/WED. THEN ANOTHER 700MB
LOW WILL HEAD OUT OF CO AND INTO NE. THIS SHOULD WRAP PRECIPITATION
INTO THE EASTERN ZONES. NORTHWEST FLOW DEVELOPING ON THE BACK SIDE OF
THE LOW WILL BRING OROGRAPHICALLY ENHANCED PRECIPITATION ON THE
NORTH SIDE OF THE BEAR TOOTHS AND BIG HORNS. MODELS FORECAST SNOW
LEVELS TO LOWER TO 4-5K FEET BY TUESDAY AFTERNOON AND THEN LOWER
SNOW LEVELS TO NEAR 3K FEET BY WEDNESDAY MORNING. THERE IS A LOT OF
MOISTURE WITH THIS SYSTEM WHICH COULD RESULT IN A HEAVY SNOW EVENT FOR
THE WESTERN MOUNTAINS. HOWEVER DONT FEEL CONFIDENT ENOUGH GIVEN THE
MODEL ERRORS TO POST ANY HIGHLIGHTS.
MOORE
.LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON...
MEDIUM RANGE MODELS NOT IN GREAT AGREEMENT...SO CONFIDENCE LOW FOR THIS
PACKAGE. GENERALLY LIKE THE IDEA OF SPLIT FLOW INTO THE WEEKEND...
KEEPING POPS MOSTLY ON THE LOWER SIDE. NEW GFS DIFFERS WITH THIS BY
DRAGGING SHORTWAVE THROUGH. WILL LEAN WITH ECWMF SPLIT FLOW FOR NOW...
KEEPING MOST PRECIP AND ENERGY TO THE SOUTH OF FORECAST AREA. LOOKS
LIKE ANOTHER TROUGH WILL AFFECT ZONES BY MONDAY PER GFS (AGAIN
CONFIDENCE LOW). WILL PUT IN A CHANCE FOR PRECIP. SCARLETT
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 040/048 032/042 029/055 029/058 031/060 040/060 037/060
46/W 63/O 20/E 00/B 00/B 00/B 03/W
LVM 035/042 028/045 026/051 026/054 028/057 034/054 035/054
69/O 93/S 23/W 00/B 00/B 00/B 03/W
HDN 040/050 031/043 031/055 031/058 033/060 041/061 039/061
36/W 76/O 20/E 00/B 00/B 00/B 03/W
MLS 040/050 030/039 034/052 034/055 036/060 044/062 041/062
24/W 66/O 20/E 00/B 00/B 00/B 03/W
4BQ 040/052 030/036 032/052 032/055 034/059 042/060 040/060
26/W 77/S 20/E 00/B 00/B 00/B 03/W
BHK 038/050 032/038 034/050 034/053 036/059 043/060 042/060
24/W 66/O 30/E 00/B 00/E 00/B 03/W
SHR 037/046 032/038 028/055 028/058 030/058 039/059 039/059
26/W 76/S 20/E 00/B 00/B 00/B 03/W
.BYZ...
MT...NONE.
WY...NONE.