AREA FORECAST DISCUSSION
NWS SAN FRANCISCO CA
AFDMTR 935 PM PST WED JAN 29 2003
CLEAR SKIES PREVAIL OVER MOST OF OUR DISTRICT THIS EVENING AS THE
AXIS OF THE LARGE-SCALE UPPER LEVEL RIDGE REMAINS PARKED OVER THE
WEST COAST. THE ONLY SIGNIFICANT CONCERN AT PRESENT IS WHETHER AREAS
OF DENSE FOG WILL AGAIN DEVELOP LATE TONIGHT AND THURSDAY MORNING.
LATEST SATELLITE FOG PRODUCT IMAGERY SHOWS SOME FOG DEVELOPMENT
OCCURRING IN MARIN COUNTY IN THE VICINITY OF THE PT REYES PENINSULA
AND TOMALES BAY. THIS SATELLITE IMAGERY ALSO SHOWS THAT THE AREA OF
PERSISTENT FOG IN THE NORTHERN SAN JOAQUIN VALLEY HAS MOVED INTO THE
EASTERN PORTION OF CONTRA COSTA COUNTY AND EXTREME NORTHEASTERN
ALAMEDA COUNTY. A SPOTTER IN OAKLEY...IN FAR NORTHEASTERN CONTRA
COSTA COUNTY...REPORTED A VISIBILITY OF 1/8 MILE AT ABOUT 815 PM.
THE PRESENT FORECAST CALLS FOR AREAS OF FOG OVERNIGHT IN THE NORTH
AND CENTRAL SFO BAY AREA...AND INCLUDES MENTION OF THE FOG BECOMING
LOCALLY DENSE AFTER MIDNIGHT. THIS APPEARS TO BE ON-TRACK AND NO
UPDATES ARE CURRENTLY PLANNED...BUT WILL CONTINUE TO MONITOR IN CASE
A DENSE FOG ADVISORY IS NEEDED LATER TONIGHT.
THURSDAY THROUGH FRIDAY...LITTLE CHANGE IN OUR WEATHER CONDITIONS IS
EXPECTED. THEN LATE FRIDAY NIGHT AND SATURDAY...A MODERATELY STRONG
UPPER-LEVEL DISTURBANCE IS PROJECTED TO MOVE RAPIDLY THROUGH OUR
DISTRICT. THIS SYSTEM...PRESENTLY CENTERED ABOUT 1200 MILES NNW OF
HAWAII...WAS FLOWN EARLIER TODAY BY THE WINTER STORM RECON PROGRAM
AND THUS SAMPLED WITH TARGETED DROPSONDES FROM THE NOAA G-IV
AIRCRAFT. IN ADDITION...A US AIR FORCE C-130 PROVIDED DROPSONDE AND
FLIGHT LEVEL DATA ACROSS A BROAD REGION OFFSHORE FROM THE PACIFIC
NORTHWEST. THESE DATA WERE INCORPORATED INTO THE 00Z NCEP MODEL
RUNS...AND THUS THE INITIAL MODEL STATE OVER THE TYPICALLY DATA
SPARSE CENTRAL AND EASTERN PACIFIC OCEAN SHOULD BE MUCH BETTER
DEFINED THAN USUAL. THAT SAID...THE JUST-RECEIVED 00Z GFS MODEL
OUTPUT SHOWS A SOLUTION FOR THE FRIDAY NIGHT/SATURDAY SYSTEM THAT IS
GENERALLY QUITE SIMILAR TO THAT FROM THE EARLIER 18Z RUN...THOUGH
JUST A BIT SLOWER AND A TAD STRONGER. WITH THE LATEST MODEL RUNS THE
GFS HAS NOW FINALLY COME INTO GOOD AGREEMENT WITH WHAT HAS BEEN
CONSISTENTLY PROJECTED BY ALL THE ECMWF AND UKMET MODEL RUNS OVER THE
PAST TWO DAYS. DESPITE THE RATHER ROBUST UPPER-LEVEL DYNAMICS...BOTH
THE GFS AND...ESPECIALLY...THE ETA MODEL OUTPUT QPF ARE QUITE
LIMITED AND SUGGEST LITTLE IF ANY PRECIP SOUTH OF SFO...WITH EVEN THE
NORTHERN PORTIONS OF OUR DISTRICT GETTING ONLY QUITE LIGHT AMOUNTS.
THIS DISPARITY BETWEEN PROJECTED UPPER LEVEL DYNAMICS AND QPF APPEARS
TO BE A CONSEQUENCE OF THE COMBINATION OF ONLY VERY MINIMAL
ASSOCIATED SURFACE DEVELOPMENT AND A QUITE LIMITED AVAILABLE MOISTURE
SUPPLY.
BY MIDDAY SATURDAY CLEARING SKIES CAN BE EXPECTED...ALONG WITH BREEZY
CONDITIONS AS MODERATE NORTHWESTERLY FLOW DEVELOPS AT THE SURFACE AND
ALOFT. THEREAFTER...RENEWED LARGE SCALE RIDGING RETURNS US TO A
DRY AND BENIGN WEATHER PATTERN AS WE HEAD INTO THE FIRST PART OF
THE COMING WEEK.
ALL POPS ZERO. BLIER
SFO...TNGT...SCA...POINT SUR TO PT PIEDRAS BLANCAS.
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
AFDDDC 251 AM CST THU JAN 30 2003
DAYS 1-2...
THE MAIN CONCERN FOR THE SHORT TERM WILL BE TEMPERATURES.
THE WATER VAPOR LOOP AND 00Z ANALYSIS SHOWS THE LATEST SHORTWAVE
TROUGH ON ITS WAY AWAY FROM THE AREA, LEAVING NORTHWESTERLY FLOW
ALOFT OVER THE NORTHERN AND CENTRAL PLAINS. AT THE SURFACE, HIGH
PRESSURE SLID OUT INTO THE MISSISSIPPI VALLEY AND A SURFACE TROUGH
HAS DEVELOPED IN THE LEE OF THE ROCKIES.
THE SHORT TERM MODELS SEEMED TO HAVE INITIALIZED WELL AND ARE IN
GOOD GENERAL AGREEMENT. ALL KEEP SURFACE WINDS FROM THE SOUTHWEST
AND WEST TODAY, CREATING A GOOD SETUP FOR DOWNSLOPE. MODEL 850
TEMPS RANGE FROM 10 C IN THE EAST TO NEARLY 15 C IN THE WEST.
NORTHWESTERLY FLOW ALOFT MAY BRING IN SOME CIRRUS CLOUDS, BUT THINK
THERE SHOULD STILL BE ENOUGH INSOLATION TO MIX OUT WELL, AND ALONG
WITH DOWNSLOPING SURFACE WINDS, TEMPS SHOULD GET UP INTO THE LOWER
TO MID 60S. TONIGHT, ANOTHER SHORTWAVE TROUGH MOVES THROUGH THE
NORTHERN PLAINS AND INTO THE UPPER MS VALLEY, BRINGING THE SURFACE
TROUGH OUT OF THE WESTERN PLAINS AND PULLING A WEAK FRONT THROUGH
THE CWA. ALL OF THE PRECIPITATION WILL BE TO THE NORTH, BUT A FEW
SCATTERED CLOUDS COULD COME OUR WAY. WINDS WILL SHIFT TO A MORE
NORTHERLY DIRECTION, BUT TEMPERATURES WITH THIS SYSTEM WILL NOT BE
BITTERLY COLD, WITH 850 MB TEMPS NOT EVEN GOING BELOW ZERO ACCORDING
TO THE MODELS. THUS, WILL KEEP TONIGHTS LOWS IN THE UPPER 20S TO
NEAR 30. WINDS WILL SHIFT AROUND AGAIN TO THE SOUTHWEST BY LATE
AFTERNOON ON FRIDAY AS ANOTHER LEE SURFACE TROUGH DEVELOPS.
DOWNSLOPING WILL AGAIN BE A FACTOR, BUT WITH 850 TEMPS AROUND 5
DEGREES COOLER THAN THURSDAY, WILL KEEP FRIDAYS HIGHS SEVERAL
DEGREES COOLER THAN THE DAY BEFORE. SOUTHWEST TO WEST WINDS WILL
CONTINUE INTO FRIDAY NIGHT, KEEPING TEMPERATURES FROM DROPPING TOO
MUCH.
DAYS 3-7...
WEATHER SYSTEM THAT IS FORECAST TO AFFECT THE CENTRAL PLAINS IN THE
SUN-MON TIME FRAME STARTING TO LOOK MORE INTERESTING ON THE 00Z
MODEL RUNS. SYSTEM IS NOW OVER THE EASTERN PACIFIC AND WAS SAMPLED
WELL YESTERDAY EVENING BY AIRCRAFT/DROPSONDES ASSOCIATED WITH THE
WINTER STORM RECON PROGRAM.
GFS INDICATING A SPLIT SYSTEM WITH MORE ENERGY COMING OUT ACROSS NEW
MEXICO AND THE TEX PANHANDLE. ECMWF MODEL HAS BEEN THE MOST
AGGRESSIVE WITH THIS SYSTEM AND IS NOW CLOSING IT OFF AT H5 WITH THE
VORT MAX TRACKING FROM THE FOUR CORNERS REGION EAST ALONG THE KS/OK
BORDER. CANADIAN BRINGS THE SYSTEM OUT MORE OPEN AND FARTHER NORTH
BUT IS TRENDING TOWARD A DEEPER AND MORE SOUTHERN TRACK COMPARED TO
PREVIOUS RUNS. MODEL RUNS ARE ALSO SLOWING THE SYSTEM DOWN A LITTLE
WHICH MAKES SENSE WITH IT DIGGING MORE. APPEARS THE BEST LOW LEVEL
MOISTURE WILL BE SHUNTED OFF TO THE EAST AS H85 FLOW IS FORECAST TO
BE SOUTHWESTERLY AHEAD OF THE SYSTEM. THINK AT LEAST SOME GULF
MOISTURE SHOULD GET ENTRAINED INTO THE SYSTEM AS IT MOVES OUT. WITH
THIS IN MIND WILL INCREASE POPS INTO THE CHANCE CATEGORY FOR LATE
SUNDAY AND CONTINUE INTO SUNDAY NIGHT.
MORE UNCERTAINTY INVOLVED WITH THE SYSTEM FORECAST TO AFFECT THE
PLAINS BY MIDWEEK. LATEST RUN OF THE GFS HAS FLOPPED 180 DEG WITH
THIS SYSTEM AND NOW HAS THE UPPER LOW DIGGING INTO THE INTERMOUNTAIN
WEST WHILE THE UPPER RIDGE PUNCHES UP INTO WESTERN CANADA. CURRENT
EXTENDED AND 8 TO 10 DAY FORECAST INDICATING THE POSSIBILITY FOR
PRECIPITATION ALONG WITH COOLER TEMPS SO WILL LEAVE AS IS.
PRELIMINARY GUIDANCE FOR COORDINATION ONLY. OFFICIAL FORECASTS ARE
CONTAINED WITHIN THE DODGE CITY ZONE FORECAST.
DDC 63 29 60 33 / 0 0 0 0
GCK 63 29 62 32 / 0 0 0 0
EHA 66 30 64 33 / 0 0 0 0
LBL 64 30 63 33 / 0 0 0 0
HYS 62 28 58 30 / 0 0 0 0
P28 60 31 57 31 / 0 0 0 0
.DDC...NONE.
RITTERLING/GERARD
AREA FORECAST DISCUSSION
NWS SPRINGFIELD MO
AFDSGF 205 AM CST THU JAN 30 2003
SHORT TERM CONCERNS MAINLY DEAL WITH AVIATION/TRAVEL.
LATEST 11-3.9U FOG IMAGERY DEPICTS A VERY SHALLOW STRATUS DECK THAT
CONTINUES TO SLOSH ALONG AND SOUTH OF THE MISSOURI OZARKS TERRAIN IN
LIGHT FLOW REGIME UNDERNEATH SURFACE RIDGE. SPECTACULAR VIEW OUTSIDE
AT THE MOMENT WITH MODERATE ICE CRYSTALS FALLING FROM THE LOW
CEILINGS INTO AN ALREADY SATURATED BOUNDARY LAYER. ALTHOUGH THE
SCENERY IS PRETTY...THIS IS GOING TO LEAD TO SIGNIFICANT RIME ICING
PROBLEMS AS VISIBILITIES REMAIN LOW WITH SE WINDS NOW PROVIDING
ADDITIONAL OROGRAPHIC ASCENT. TRAVELERS SHOULD BE AWARE OF THE LOW
VISIBILITIES AND BLACK ICE THAT WILL LIKELY PERSIST THROUGH
SUNRISE...ESPECIALLY ALONG THE OZARKS PLATEAU. HAVE OPTED TO ISSUE A
FREEZING FOG ADVISORY FOR LOCATIONS ALONG AND SOUTH OF A JOPLIN TO
VICHY LINE THRU 9 AM (NPW WILL BE OUT SHORTLY).
FOR TODAY...WINDS WILL GRADUALLY VEER INTO THE SE AND S AS SURFACE
RIDGE AXIS SLIDES EAST OF THE AREA. RESIDUAL FOG/LOW STRATUS SHOULD
MIX OUT BY MID MORNING...WITH ABUNDANT SUNSHINE EXPECTED EVERYWHERE
BY AFTERNOON. MODEST MID LEVEL WARM ADVECTION AHEAD OF BROAD LEE
TROUGH SHOULD ALLOW TEMPS THIS AFTERNOON TO REACH THE MID 40S
CENTRAL MO TO THE LOWER 50S IN FAR SW MO AND SE KS.
SHORT WAVE ENERGY NOW PUNCHING THROUGH BRITISH COLUMBIA WILL CREST
THE WESTERN UPPER RIDGE THIS MORNING AND BEGIN ITS DECENT INTO THE
LOWER 48 THIS EVENING. AS INDICATED BY WATER VAPOR/IR
IMAGERY...EXPECT EXTENSIVE HIGH CLOUDINESS TO QUICKLY OVERSPREAD THE
AREA EARLY TONIGHT BUT NOT MUCH ELSE. SYSTEM WILL ONLY HAVE WHAT
MOISTURE IT BRINGS FROM THE PACIFIC AND SOME WEAK ADDITIONAL ASCENT
DRIVEN FROM FRONTOGENETIC FORCING ALONG DECENT MID-UPPER LEVEL
BAROCLINIC ZONE. WILL KEEP LOW CHANCE POPS ACROSS FAR NORTHEASTERN
SECTIONS FOR SOME LIGHT RAIN LATE TONIGHT/EARLY FRIDAY...BUT WOULD
BE SURPRISED TO SEE MORE THAN A HUNDREDTH OR TWO FROM TEASING
SHOWERS.
SKIES CLEAR OUT FRIDAY AFTERNOON...AND THEN THE "WINDS OF CHANGE"
ARRIVE. SIGNIFICANT STORM SYSTEM THAT WAS WELL SAMPLED BY NOAA/AIR
FORCE AIRCRAFT THIS EVENING OVER THE MID PACIFIC (THANKS NCEP) WILL
REACH THE WEST COAST FRIDAY EVENING...SHUNTING THE UPPER RIDGE AXIS
INTO THE COUNTRY'S MID SECTION. IN ADDITION TO RAPID HEIGHT
RISES...STRONGLY WESTERLY UPPER JET WILL INDUCE SIGNIFICANT LEE
TROUGHING AND CHINOOK FLOW OFF THE ROCKIES. WARM AIR WILL QUICKLY
ADVECT INTO THE REGION SATURDAY AS LOW LEVEL FLOW VEERS AND
STRENGTHENS IN RESPONSE TO LEE CYCLOGENESIS. EXPECT TO SEE HIGHS IN
THE 60S ACROSS WRN SECTIONS SATURDAY...AND AREAWIDE ON SUNDAY AS
THERMAL RIDGE AXIS BUILDS OVER THE AREA. STRONG GRADIENT WINDS WILL
HELP TO KEEP MINS WELL ABOVE NORMAL...BUT WILL ALSO LEAD TO
HEIGHTENED FIRE DANGER IF LOW LEVEL MOISTURE FAILS TO RETURN FAST
ENOUGH. COINCIDENTALLY...FIRE WEATHER FORECASTS RESUME WITH TOMORROW
AM'S SHIFT.
RAPID GULF MOISTURE RETURN IS EXPECTED SUNDAY AS UPPER TROUGH
DEEPENS AND FURTHER STRENGTHENS LEE CYCLONE...LEADING TO PRONOUNCED
CROSS-GULF FLOW. 00Z/30 GFS AND 12Z/29 ECMWF ARE IN EXCELLENT
AGREEMENT WITH CONTINUING THE TREND TOWARD A SLOWER FRONTAL
PROGRESSION ACROSS THE PLAINS AS SEVERAL SURFACE WAVES WILL LIKELY
EMANATE FROM A RATHER COMPLEX UPPER SYSTEM. WILL BRING INITIAL
CHANCE FOR SHOWERS/STORMS INTO THE AREA SUNDAY NIGHT AND CONTINUE
INTO MONDAY AS FRONT SWEEPS ACROSS THE AREA. SYNOPTIC SCALE SETUP
LOOKS FAVORABLE FOR A POTENTIAL SEVERE CONVECTIVE EPISODE ACROSS THE
MISS VALLEY REGION ON MONDAY IF MOISTURE RETURN IS AGGRESSIVE
ENOUGH. WILL CONTINUE TO MONITOR. HAVE ALSO MADE SIGNIFICANT UPWARD
ADJUSTMENTS TO TEMPERATURES SUNDAY NIGHT/EARLY MONDAY MORNING AHEAD
OF SURFACE FRONT.
.SGF...
.MO...FREEZING FOG ADVISORY FOR LOCATIONS ALONG AND SOUTH OF A
JOPLIN TO VICHY LINE...EFFECTIVE THRU 9 AM.
.KS...NONE.
BOOKBINDER
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 830 PM PST WED JAN 29 2003
.SYNOPSIS...SCATTERED SHOWERS WILL DIMINISH OVER WESTERN WASHINGTON
TONIGHT...IN THE WAKE OF THE FRONT THAT MOVED THROUGH THE AREA LATE
WEDNESDAY. A STRONGER FRONTAL SYSTEM WILL ARRIVE THURSDAY...PRODUCING
WINDY CONDITIONS AND LOCALLY HEAVY RAINFALL LATER THURSDAY THROUGH
FRIDAY. COOLER WEATHER IS EXPECTED OVER THE WEEKEND...WITH A WEAKER
SYSTEM DUE INTO THE AREA SUNDAY.
.DISCUSSION...A PACIFIC FRONTAL SYSTEM HAS BEEN WORKING ITS WAY
THROUGH THE AREA TODAY...WITH THE OCCLUDED FRONT MAKING LANDFALL LATE
THIS AFTERNOON AND CROSSING THROUGH THE PUGET SOUND AREA EARLIER THIS
EVENING. PCPN SHOULD GRADUALLY DECREASE TONIGHT AS THE FRONT MOVES
ACROSS ERN WA. THOUGH WE DO HAVE LOW LEVEL WESTERLIES BEHIND THE
FRONT AND A SMALL SURFACE RIDGE MOVING ONTO THE COAST...AND RADAR IS
HINTING AT A WEAK PUGET SOUND CONVERGENCE ZONE.
IN THE BROADER PICTURE THERE IS A FLAT DIRTY UPPER RIDGE ALONG THE
PACIFIC NW COAST WITH THE LONGWAVE TROUGH POSITION OUT ALONG 160W.
THE NEXT SYSTEM UPSTREAM IS DEVELOPING AS IT MOVES NE OUT OF THE
LONGWAVE TROUGH. THIS SYSTEM LOOKS INTERESTING...AS SATELLITE IMAGERY
SHOWS A PLUME OF MOISTURE BLOSSOMING AT THE HEAD OF THE WARM CONVEYOR
BELT NEAR 40N/140W AND A FRONT THAT EXTENDS BACK TO THE BASE OF THE
TROUGH JUST N OF HAWAII NEAR 30N/160W. AIRCRAFT OBSERVATIONS INDICATE
AN UPPER LEVEL JET MAX OF 150 KT IS HELPING THE DEVELOPMENT OF THIS
FEATURE. THIS SYSTEM APPEARS SET TO PRODUCE LOTS OF PCPN WHEN IT
MOVES INTO WRN WA THU AFTERNOON...AS MODEL SOLUTIONS HAVE SHOWN FOR
THE PAST SEVERAL DAYS. IT STILL LOOKS LIKE THE 850 MB TEMPS WILL RISE
TO AROUND +6C IN THE WARM SECTOR THU NIGHT...WITH LOW LEVEL WINDS
AROUND 50 KT. THE HEAVY RAIN MIGHT NOT CONTINUE LONG ENOUGH FRI TO
CAUSE WIDESPREAD SERIOUS FLOODING...BUT THE MORE FLOOD-PRONE RIVERS
OF WRN WA CERTAINLY FACE THE POTENTIAL FOR FLOODING AND THE FLOOD
WATCH LOOKS GOOD.
THE COLD FRONT SHOULD TRAIL THROUGH THE AREA SLOWLY ON FRI. A SHARP
SURFACE TROUGH...CORRESPONDING TO THE BENT BACK OCCLUSION...WILL
SWING THROUGH THE AREA FRI NIGHT OR EARLY SAT. I THINK IT'S WORTH
MENTIONING SOME WINDS FOR THAT. ALSO THE GFS SHOWS WESTERLY 850 MB
FLOW AROUND 30 KT FRI NIGHT THROUGH SAT...WITH THE SNOW LEVEL
HOPEFULLY FALLING TO 3000 FT. SO THIS COULD PROVIDE ONE OF THE BETTER
MOUNTAIN SNOW EVENTS FOR THE CASCADES IN QUITE A WHILE. NO CHANGES TO
THE EXTENDED PERIOD...AS IT LOOKS LIKE A SYSTEM WILL MAKE IT OVER THE
RIDGE INTO THE AREA SUN...WITH A DIRTY RIDGE CONTINUING INTO NEXT
WEEK.
MCDONNAL
UIL 8+++ SEA 8+++ OLM 8+++
.KSEW...GALE WARNING COAST AND STRAIT OF JUAN DE FUCA.
.SMALL CRAFT ADVISORY CAMANO ISLAND TO POINT ROBERTS AND PUGET
SOUND AND HOOD CANAL.
.SNOW ADVISORY CASCADES TONIGHT.
.KATX...VCP21/CSR21...OPERATIONAL.