EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 950 PM PST WED JAN 24 2001
...SYNOPSIS...
SCATTERED SHOWERS WILL END OVERNIGHT AS A WEAKENING PACIFIC STORM
MOVES EAST INTO ARIZONA. FAIR THURSDAY. A COLDER...WETTER STORM WILL
ARRIVE ON FRIDAY AND LINGER FOR SATURDAY.
...DISCUSSION...
MUDDLED PICTURE INTO NEXT WEEK AS MDLS ARE IN LESS THAN PERFECT
AGREEMENT WITH DETAILS THRU SAT...THEN DIVERGE MORE SUBSTANTIALLY
SUNDAY AND BEYOND.
IN THE NR TERM...SCATTERED SHOWERS ALG AND W OF THE MTNS WL
GRADUALLY DECR OVERNIGHT. THIS IS HANDLED WELL BE THE ETA QPF AND IN
THE CURRENT ZONES. GREATEST COVERAGE AND AMOUNTS...GENERALLY ONE
QUARTER INCH OR LESS LIQUID EQUIVALENT ADDITIONAL...WL BE ON SW
SLOPES OF SBD MTNS AND ALG W FACING SLOPES OF CNTRL AND SRN SAN
COUNTY. CURRENT ACARS DATA AND RAWS REPORTS WOULD SUPPORT SNOW LVLS
OF 3500 TO 4000 FT. LTL CHANGE OF SNOW LVLS IS EXPECTED OVERNIGHT
WITH SHOWERS GRADUALLY ENDING BY MORNING.
FOR THU...SKIES SHOULD BE CLR TO PARTLY CLOUDY WITH AFTERNOON CU
MORE NUMEROUS NR HIGHER TERRAIN.
FOR FRI/SAT...MDLS STILL DIFFER SOMEWHAT WITH THE DETAILS IN WHAT
SHOULD BE A COLDER AND WETTER STORM FOR SW CA THAN THE ONE NOW
EXITING. LATEST ETA WOULD BRING A WKNG FRONTAL BAND AND ASSOCD RAIN
AND MTN SNOW ACROSS SW CA LATE FRI MORNING THRU EARLY FRI EVENING.
MDLS ARE TAKING DYNAMICS WITH A STRONGER SECONDARY SHORTWAVE INLAND
TO THE S OF SW CA ON SAT...INTO NRN AND CNTRL BAJA. HOWEVER...WITH
CD AIR ALF AND MOIST CYCLONIC FLOW OVR SW CA...SCATTERED TO NUMEROUS
SHOWERS SHOULD CONTINUE FOR SAT ALG WITH A CHANCE FOR THUNDERSTORMS
AND WITH SNOW LVLS NR 3000 FT SAT. AT PRESENT...THIS STORM DOES NOT
APPEAR AS STRONG AS THE ONE THAT IMPACTED SRN CA TWO WEEKS OR SO
AGO.
SUN AND BEYOND...ECMWF...NEW AVN...AND OLD MRF ARE IN RATHER
STRIKING DISAGREEMENT. WITH NO GREAT DIFFERENCES IN THE UPSTREAM
INITIALIZATION OVR THE PAC NOTED...ITS NOT CLR WHICH SOLN TO FAVOR
AT THIS TIME. SYNOPTICALLY...THE EVOLUTION FORECAST BY LAST NIGHT'S
MRF (ALSO SHOWN BY NOGAPS) WOULD APPEAR TO BE THE MOST REASONABLE.
GIVEN THE HIGH DEGREE OF UNCERTAINTY SUN AND BEYOND...WL NOT MAKE
ANY CHANGES TO THE EXTENDED.
SAN 4127
.SAN...SPECIAL WEATHER STATEMENT...SEE LAXSPSSAN.
MARTIN
AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 253 AM CST THU JAN 25 2001
MAIN FORECAST CONCERNS ARE ENDING LAKE EFFECT IN NORTHWEST INDIANA
THIS MORNING...TEMPERATURES...AND SNOW EVENT FOR FRIDAY AND FRIDAY
NIGHT.
ACARS SOUNDINGS OUT OF ORD SHOW 850 MB WARM ADVECTION HAS BEGUN WITH
850 MB TEMPS RISING FROM -13 TO -11 DEG LAST FEW HOURS. WITH
BACKING LOW LEVEL WINDS...GOES IR LOOP SHOWS CLOUD BANDS OVER THE
LAKE SHIFTING EASTWARD WITH TIME...AND WESTERN EDGE OF CLOUDS AND
RADAR DETECTABLE SNOW JUST ABOUT COMPLETELY OUT OF PORTER COUNTY.
WILL BASE FORECAST WORDING ON LAST MINUTE RADAR/SATELLITE OBS...BUT
WILL MOST LIKELY BE ABLE TO START THE DAY SUNNY FOR ALL COUNTIES.
UPPER LEVEL RIDGE BUILDS ACROSS THE AREA TODAY...WITH 1036 MB
SURFACE HIGH OVER WESTERN IOWA AT 06Z MOVING SOUTHEAST INTO THE
LOWER OHIO VALLEY BY THIS EVENING. SUBSIDENCE WILL ALLOW FOR
ABUNDANT SUNSHINE ACROSS THE FORECAST AREA TODAY...WITH SURFACE
WINDS BACKING TO SOUTHWEST THIS AFTERNOON. FWC/MAV TEMPERATURE
GUIDANCE IN FAIRLY GOOD AGREEMENT AND LOOK OK. FAVOR COOLER MAV
MAXES FRIDAY...WITH CLOUDS AND PRECIPITATION WORKING AGAINST
CONTINUED WARM ADVECTION.
WATER VAPOR SHOWS OUR NEXT WEATHER MAKER MOVING ACROSS SOUTHERN
CALIFORNIA. MODELS FAIRLY SIMILAR IN MOVING THIS SOUTHERN STREAM
TROF INTO WESTERN KANSAS AND OKLAHOMA BY THIS EVENING...THEN
NORTHEAST INTO IOWA AND MISSOURI OVERNIGHT AND PHASING IT WITH
NORTHERN STREAM ENERGY DROPPING SOUTHEAST OUT OF THE DAKOTAS. ETA/AVN
DIVERGE WITH THEIR SOLUTIONS OF THE SURFACE LOW TRACK...WITH THE
ETA TAKING THE LOW FROM NORTHERN IOWA ACROSS WISCONSIN FRIDAY
AFTERNOON AND THE AVN TAKING IT FARTHER SOUTH...FROM NORTHEAST
MISSOURI TO NORTHEAST ILLINOIS. GIVEN THE STRENGTH OF THE SOUTHERN
STREAM WAVE...TEND TO THINK THAT THE ETA IS A BIT TOO FAR NORTH.
PREFER BLEND OF ETA/AVN TRACKS WITH AN ELONGATED SFC LOW PASSING
NEAR IL/WI BORDER. NOT A MAJOR STORM BY ANY MEANS...WITH INITIALLY
DRY AIR TAKING SOME TIME TO MOISTEN. PCPN LOOKS TO BEGIN BY
AFTERNOON...THEN TAPER OFF LATE EVENING AS TROF PASSES. QPF AND
ISENTROPIC PROGS INDICATE AN INCH OR TWO OF ACCUMULATION
POSSIBLE...WITH HIGHEST AMOUNTS TOWARD WI BORDER.
NEW MRF ABOUT 12 HOURS SLOWER WITH SYSTEM IN MONDAY/TUESDAY EXTENDED
FORECAST...WITH NOGAPS VERY SIMILAR. THICKNESS PROGS STILL SUPPORT
RAIN...CHANGING TO SNOW AT THE END.
.CHI...NONE.
RATZER