SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 900 PM PST THU MAR 29 2001
WIND ADVISORY CONTINUES THIS EVENING ACROSS S SBA COUNTY COAST AND
ADJACENT MOUNTAINS. MONTECITO HILLS BEING HIT THE HARDEST AT THIS
TIME WITH LATEST WINDS NORTHEAST 39 GUSTING TO 53 MPH. WILL
CONTINUE ADVISORY THRU 3 AM FRI AS SUPPORT FOR STRONG WINDS BY THIS
TIME DIMINISHES. ELSEWHERE...FAIR SKIES EXCEPT FOR PATCHY MARINE
LAYER CLOUDS OVER THE CENTRAL COAST...ALONG VTU COUNTY COAST...AND
IN SAN GABRIEL VALLEY. SOME HINTS OF AN EDDY GOING ON...BUT
CERTAINLY CIRCULATION WEAKER THIS EVENING THAN FROM 24 HOURS AGO.
00Z SOUNDINGS AND RECENT ACARS DATA OVER LAX BASIN SHOWS MARINE
LAYER TO BE AROUND 1500 FEET OVER SBA COUNTY AND AROUND 2200 FEET
OVER LAX COUNTY. MESO-ETA CROSS SECTIONS SHOW THE MARINE LAYER
SHRINKING OVERNIGHT...DOWN TO BELOW 1000 FEET OVER LAX COUNTY BY
MORNING AS OFFSHORE FLOW INCREASES SOMEWHAT. HAVE BEEN LOOKING AT
RAWS DATA TO SEE ANY HINTS OF THIS BEGINNING TO HAPPEN. WINDS AT
SAUGUS HAVE SWITCHED AROUND TO EASTERLY...OTHERWISE LOW LEVEL
HUMIDITIES REMAIN HIGH. DIFFICULT TO SAY IF MESO-ETA IS ON THE
RIGHT STRACK. SOMETIMES THE MODELS OVERDO THE SHRINKING OF THE
MARINE LAYER WITH OFFSHORE FLOW. CONSIDERING LOW CLOUDS HAVE
ALREADY FORMED INLAND OVER THE SAN GABRIEL VALLEY...IT APPEARS THIS
MARINE LAYER SHRINKING PROCESS HAS NOT YET BEGUN...AND MAY NOT
HAPPEN UNTIL FRI MORNING. AM INCLINED TO BE MORE PESSIMISTIC WITH
LOW CLOUDS OVER THE LAX COUNTY VALLEYS TONIGHT.
HOW THE MARINE LAYER BEHAVES TONIGHT AND FRI WILL HAVE AN EFFECT ON
HIGH TEMPS ACROSS THE REGION FRI. MESO-ETA DOES SHOW 950 MB TEMPS
INCREASING BY 6 DEGREES OR SO OVER LAX COUNTY FOR FRI AFTERNOON.
TEMPS FRI AFTERNOON WILL LIKELY BE WARMER THAN TODAY OVER MOST
AREAS. THEN FOR SAT...IT APPEARS THAT MARINE LAYER INFLUENCE WILL BE
CONFINED TO THE IMMEDIATE COAST...WITH THE VALLEYS WARMING WELL INTO
THE 80S. UPPER RIDGE OFF THE COAST WILL LINGER THROUGH SAT TO KEEP
THE WEATHER DRY AND WARMER THAN NORMAL.
WILL ISSUE A ZONE UPDATE BY 930 PM TO ADJUST WORDING MAINLY IN THE
FIRST PERIOD FOR A FEW ZONES. OTHERWISE...THE BALANCE OF THE
FORECAST LOOKS REASONABLE...INCLUDING TEMPERATURES.
IN THE EXTENDED...THE UPPER RIDGE OFF THE COAST GRADUALLY BREAKS
DOWN SUN AND EARLY MON...THEN AN UPPER TROUGH WILL MOVE DOWN THE W
COAST AND INTO SOCAL FOR LATE MON AND TUE. IT IS A BIT TOO EARLY
TO SAY WHETHER THE DISTRICT WILL GET ANY RAIN FROM THIS UPPER TROUGH.
AT THIS TIME IT LOOKS LIKE AFFECTS WILL BE TO COOL TEMPS DOWN...DEEPEN
THE MARINE LAYER...AND INCREASE ONSHORE FLOW.
LAX 0000. SIRARD.
.LAX...WIND ADVISORY...SEE LAXNPWLAX.
SMALL CRAFT ADVISORY...SEE LAXCWFLAX.
AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 300 AM CST FRI MAR 30 2001
THE LARGE WAVE OVER THE CENTRAL U.S. DOMINATES THE WEATHER FOR THE
FORECAST AREA OF NORTHEAST ILLINOIS AND NORTHWEST INDIANA. SHORT
WAVES MOVING EAST ACROSS THE REGION WILL KEEP THE CLOUDS TRAPPED
UNDER THE WEAK INVERSION THIS MORNING AND DURING THE DAY. A
NORTHEAST TO EAST FLOW IS EVIDENT FROM ACARS SOUNDINGS AND WOLCOTT
PROFILER DATA. A STRONG JET ON THE NORTHWEST COAST AS SEEN ON THE
300 MB AND WATER VAPOR LOOPS WILL PUSH SOUTHEAST AS A SHORT WAVE
MOVE SOUTHEAST FROM CANADA. THIS WAVE WILL CREATE ENOUGH BAROCLINIC
INSTABILITY TO CAUSE CYCLOGENESIS IN SOUTHERN SASKATCHEWAN. HEIGHT
FALLS ARE IN ALBERTA AT 00 UTC AT 500 MB. THIS LOW WILL BRING RAIN
INTO THE FORECAST AREA SATURDAY. THICKNESS FORECASTS SUGGEST SNOW
FOR SATURDAY NIGHT INTO SUNDAY. WITH A MIX ON SUNDAY MAINLY AROUND
ROCKFORD.
WARM FRONT SHOWERS MOVE IN ON MONDAY NIGHT AND MORE RAIN MOVES IN ON
WEDNESDAY AHEAD OF ANOTHER LOW IN THE DAKOTAS. WILL USE THE AVN AS
MODEL OF CHOICE TONIGHT.
.CHI...NONE.
$$
WHW
AREA FORECAST DISCUSSION
NWS GRAY ME
AFDGYX 245 AM EST FRI MAR 30 2001
TUFF CALL THIS MRNG WITH RESPECT TO W/W/A DECISION...SINCE THE AMS
APPEARS AS THO IT WL BE BORDERLINE CD ENUF TO SUPPORT SN FOR A GUF
PTN OF THE FA LONG ENUF TO PUT DOWN A DECENT ACCUMULATION.
MODELS IN FAIRLY GUD AGREEMENT WITH RESPECT TO THE LARGER FTRS THRU
THE FCST PD. THE MAIN FCST PROBLEM LIES WITH TDY (AND TNGT FOR ERN
ZNS AND THE MTNS).
PCPN ALREADY GOING IN THE SRN PTN OF THE FA...AND SINCE THE PCPN IS
LITE...IT IS TAKING VARIOUS FORMS. FURTHER S...ORH IS NOW SN...AND
EXPECT A TYPICAL WAA PCPN BURST TO DEVELOP THIS MRNG ACRS NH AND
LATER THIS MRNG INTO THIS AFTN IS ME. ACARS SOUNDINGS (AS WELL AS
THE 30/00Z GYX RAOB) SUGGEST THAT THERE IS PLENTY OF ROOM FOR EVAP
COOLING TO CHANGE PCPN TO SN AS THE INTENSITY INCREASES.
THE QUESTION IS HOW LONG THE PCPN CAN REMAIN SN (ESP FOR PTNS OF
INTERIOR SRN NH AND INTERIOR SWRN AND CNTRL ME). MODEL SOUNDINGS
SUGGEST THAT THIS CUD OCCUR AS LT AS 16-18Z FOR SRN NH AND EVEN
LATER FOR INTERIOR CRNTL ME. GIVEN THE AMT OF INFLO ASSOCIATED WITH
THE MID LEVEL S/W...AS WELL AS THE AMT OF WAA...WUD EXPECT THAT
THERE WL BE A PD OF +SN FOR JUST ABT EVERYONE THIS AM.
AFT THIS...AS ACARS SOUNDINGS TO THE S SHOW...+1/+2C AIR ARRIVE
BETWEEN 4.5KFT AND 7KFT...BRINGING -PL INTO THE EQUATION. WUD
EXPECT THIS TO OCCUR FOR INTERIOR SRN NH AND INTERIOR SWRN AND CNTRL
ME AS THE BEST WAA AND VV/S OCCUR. MODEL QPFS SUGGEST THAT UP TO
0.6 TO 0.7 CUD FALL BEFORE THE MIX WITH -PL. THIS CUD GET SOME OF
THE HIER ELEVATION IN THE ABOVEMENTIONED AREAS TO WINTER STORM
NUMBERS.
FURTHER SE...ESP ALG THE NH AND SWRN ME CST...WUD EXPECT THAT EVEN
WITH THE +SN EARLY...THIS AREAS SHUD CHANGE TO -RA...EVEN WITH THE
BEST UVV/S. SUM TREPIDATION HERE...BUT WL GO WITH A MIN ADVISORY
FOR HIER TRRN. SINCE MUCH LESS LIQUID EXPECTED THAT PRVS...WL DROP
THE FLOOD WATCH HERE AS WELL.
FOR THE MIDCST...INCLUDING PWM...WL BE A BATTLE BETWEEN SN AND RA
WITH THE WARMER BOUNDARY TEMPS. SPOKE WITH CAR...AND WL KEEP AMTS
IN THE WINTER WEATHER ADVISORY RANGE HERE. WL WACTH THE PROGRESS OF
THE CHANGE TO DETERMINE THE STATE OF THIS ADVISORY.
IN THE MTNS...WL GO WITH A MIN WARNING SINCE THE UPSLOPE COMPONENT
SHUD COMPENSATE FOR LESSER QPF DUE TO THE STROM TRACK.
AS FOR TEMPS...WUD EXPECT THAT THE COOLER NGM NUMBERS WL BE
BETTER...BASED ON THE FACT THAT TEMPS AWAY FM THE CST MAY NOT CHANGE
MUCH SINCE THE WIND DIRECTION DOES NOT FAVOR IT.
FOR TNGT...WUD EXPECT THE PCPN TO TAPER TO A LITE MIX FROM SW TO
NE. WL NOT TRY TO TIME THIS IN THE MTNS...SNCE THE UPSLOPE
COMPONENT CUD KEEP THE PCPN GOING HERE WELL INTO THE NGT. FOR MOST
PLACES...WUD EXPECT LTL TEMPS CHANGE.
FOR SAT...IN THE BROAD CYCLONIC FLO...WL KEEP A MENTION OF -SHSN IN
THE MTNS AND FOOTHILLS...AND PROBABLY A MIN CHC OR NON-POP PCPN FOR
OTHER ZNS. TEMPS ARE CLOSE...AND IN THE NLY FLO...WUD EXPECT LTL IN
THE WAY OF RISE IN TEMPS FOR MAXES.
NEXT EVENT PROBABLY HOLDS OFF TIL SUN NIGHT OR MON.
ON THE COASTAL WATERS...WINDS INCRG TO GLW LATER THIS MRNG. THO
THERE MAY BE SUM GUSTS TO STM LAT THIS AFTN AND EARLY TNGT...WUD
EXPECT GLW SHUD HOLD IT.
THANKS FOR THE COORD BTV AND CAR!
PRELIM WRKZFP/WRKCWF AVBL. AS ALWAYS...COMMENTS/OPINIONS WELCOME.
.GYX...WINTER STORM WARNING TODAY AND TONIGHT MEZ007>009-012>014
NHZ001>004
WINTER STORM WARNING TODAY AND THIS EVENING NHZ005>009
WINTER WEATHER ADVISORY FOR TODAY MEZ018>022-MEZ023>028-NHZ014
GLW
HAYES
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 830 PM PST THU MAR 29 2001
.OVERVIEW...
STRONG ZONAL FLOW CONTINUES ACROSS THE ERN PAC WITH A FLAT LONG WAVE
RIDGE CENTERED NEAR 140W AND EMBEDDED PROGRESSIVE SHORT WAVES MOVING
THROUGH. WHILE A LITTLE WEAK WITH THE STRENGTH OF THE JET ACROSS THE
N PAC PER ACARS DATA...MODELS ONCE AGAIN APPEAR RATHER WELL
INITIALIZED. BUT SHORT TERM MODELS ARE SIGNIFICANTLY FASTER AND
WETTER WITH THE NEXT INCOMING SYSTEM THAT NOW MOVES IN SAT. IN THE
LONGER RANGE MODELS CONTINUE TO SHOW A LOT OF VARIANCE IN OUR AREA.
MOST SOLUTIONS...PARTICULARLY THE ECMWF...SHOW QUITE A BIT OF
CYCLONIC FLOW OVER OUR AREA AND THE NE PAC THRU WED. THE MRF/AVN
SHOWS THE MOST RIDGING ALONG 130W BY TUE OR WED OF NEXT WEEK.
.SHORT TERM...
WITH THE PASSAGE OF THE FRONT EARLIER THIS EVENING ONSHORE GRADIENTS
AND WESTERLY WINDS THROUGH THE STRAIT AND CHEHALIS GAP ARE
INCREASING. A PGTSND CONVERGENCE ZONE APPEARS TO BE SETTING UP N OF
KPAE PER KATX RADAR WHILE MODERATE PCPN IS BEING REPORTED IN THE
MOUNTAINS. EXPECT UPSLOPE PCPN AND CONVERGENCE TO CONTINUE OVERNIGHT
SO WILL MAINTAIN THE SN ADVISORY FOR THE CASCADES AND PASSES. RIDGING
BUILDS RAPIDLY INLAND FRI MORNING WHICH WILL STABILIZE THE AMS AND
KILL THE ONSHR GRADIENTS...HENCE ENDING THE PCPN AND CONVERGENCE
ZONES BY 15-18Z. THE MAIN DIFFERENCE TONIGHT CONCERNS THE SPEED AT
WHICH THE NEXT SYSTEM NOW NEARING 145W MOVES EWD. WARM ADVECTION PCPN
SHOULD REACH THE COAST FRI EVENING THEN MOVE INLAND LATE FRI NIGHT.
SAT COULD BE AN ALL DAY RAIN WITH A LATE AFTN FROPA IN THE INTERIOR.
THE AFTN FORECASTS...BASED ON PREVIOUS MODEL GUIDANCE...APPEAR TOO
DRY AND SLOW. SO WILL UPDATE FRI NIGHT AND SAT PERIODS.
.EXTENDED...
LOOKS SHOWERY SUN AS A MEAN TROUGH SETS UP ALONG 130W. CURRENT
FORECASTS FOR MON AND TUE MAY BE A BIT OPTIMISTIC...BUT WILL AWAIT
NEW GUIDANCE BEFORE MAKING CHANGES BEYOND SAT NIGHT PERIOD.
UIL 827+ SEA 3237 OLM 6238 ALBRECHT
.SEW...SNOW ADVISORY TONIGHT NORTH W SLOPES NORTH AND CENTRAL
CASCADES AND PASSES.
SMALL CRAFT ADVISORY COAST...STRAIT OF JUAN DE FUCA...
PUGET SOUND AND HOOD CANAL.
.KATX...VCP21/CSR21...OPERATIONAL.