PUBLIC FORECAST DISCUSSION FOR 4PM ZONE ISSUANCE
AFDCHI SURFACE RIDGE OVER THE AREA...WITH VERY DRY AIR IN LOW LEVELS.
MODELS ARE CONSISTENT IN BRINGING WARMER AIR UP INTO THE REGION
AHEAD OF THE NEXT WEAK WAVE...SO WILL WORD AS EVENING LOW WITH
STEADY TEMPS THEREAFTER. VERY WEAK LIFT ON THURSDAY MEANS MAINLY
FLURRIES...WITH A SMALL CHANCE OF LIGHT ACCUMS FAR S AND SE CWA.
A CHANCE OF LK EFFECT SHSN POST FRONTAL...THEN TEMPS COOL OFF SOME
UNDER UNUSUAL ENE/WSW UPPER PATTERN.
TEMPS TO REMAIN BELOW NORMAL THROUGH THE EXTENDED...WITH SAT AND TUE
THE BEST CHANCES FOR LIMITED PRECIP.
.CHI...NONE
JHV
AVIATION DISCUSSION FOR 18Z TAFS WRITTEN AT NOON...
SURFACE ANALYSIS SHOWS WARM FRONT IN CENTRAL IOWA...WITH ARCTIC
FRONT EXTENDING FROM NORTH DAKOTA INTO CENTRAL ONTARIO. CURRENT
SHIELD OF LIGHT SNOW IN MINNESOTA ASSOCIATED WITH 265 AND 270 K
ISENTROPIC LIFT. THIS IS FORECAST TO PASS NORTH OF TERMINALS THIS
AFTERNOON...LEAVING THE TERMINAL AREAS WITH A MID DECK OF 6 KFT
ASSOCIATED WITH A BIT OF WARM ADVECTION AND LIFTING ALONG THE WARM
FRONT...AS SEEN ON ACARS AND AREA PROFILERS.
WARM FRONT TO PASS TONIGHT...KEEPING WINDS AROUND 24008KT OR SO.
INCREASED WARM ADVECTION WILL ALLOW CLOUD DECK TO DESCEND TO ABOUT 5
KFT OVERNIGHT. DEWPOINTS WILL CLIMB TO MID OR UPPER 20S BY
MORNING...WITH THE COLD FRONT FORECAST TO APPROACH FROM THE NW
DURING THE MID MORNING. FEEL REAL SHARP WIND SHIFT WILL COME AT OR
JUST AFTER MID DAY WITH ADVECTION OF DRY AIR. THIS WILL ALSO BE THE
MECHANISM FOR SOME LIGHT SNOW TO DEVELOP...ALONG AND BEHIND THE
FRONT. SNOW SHOULD NOT REDUCE VISIBILITIES LESS THAN 4 OR 5 SM...BUT
THINK CLOUD DECK WILL DESCEND TO ABOUT 3KFT AS THE FRONT APPROACHES.
ROGOWSKI/WHW
AREA FORECAST DISCUSSION...CORRECTION
NWS CHICAGO IL
AFDCHI 1200 PM CST WED FEB 5 2003
AVIATION DISCUSSION FOR 18Z TAFS WRITTEN AT NOON...
SURFACE ANALYSIS SHOWS WARM FRONT IN CENTRAL IOWA...WITH ARCTIC
FRONT EXTENDING FROM NORTH DAKOTA INTO CENTRAL ONTARIO. CURRENT
SHIELD OF LIGHT SNOW IN MINNESOTA ASSOCIATED WITH 265 AND 270 K
ISENTROPIC LIFT. THIS IS FORECAST TO PASS NORTH OF TERMINALS THIS
AFTERNOON...LEAVING THE TERMINAL AREAS WITH A MID DECK OF 6 KFT
ASSOCIATED WITH A BIT OF WARM ADVECTION AND LIFTING ALONG THE WARM
FRONT...AS SEEN ON ACARS AND AREA PROFILERS.
WARM FRONT TO PASS TONIGHT...KEEPING WINDS AROUND 24008KT OR SO.
INCREASED WARM ADVECTION WILL ALLOW CLOUD DECK TO DESCEND TO ABOUT 5
KFT OVERNIGHT. DEWPOINTS WILL CLIMB TO MID OR UPPER 20S BY
MORNING...WITH THE COLD FRONT FORECAST TO APPROACH FROM THE NW
DURING THE MID MORNING. FEEL REAL SHARP WIND SHIFT WILL COME AT OR
JUST AFTER MID DAY WITH ADVECTION OF DRY AIR. THIS WILL ALSO BE THE
MECHANISM FOR SOME LIGHT SNOW TO DEVELOP...ALONG AND BEHIND THE
FRONT. SNOW SHOULD NOT REDUCE VISIBILITIES LESS THAN 4 OR 5 SM...BUT
THINK CLOUD DECK WILL DESCEND TO ABOUT 3KFT AS THE FRONT APPROACHES.
ROGOWSKI/WHW
PRELIMINARY DISCUSSION FOR 4 AM PUBLIC ZONES
UPPER TROF MOVED E TODAY AND SKIES CLEARED OUT EXCEPT FOR NW IN E OF
GYY WHERE A FEW VERY LIGHT LAKE SNOW FLURRIES ARE STILL OCCURING.
THESE WILL END TODAY AS RIDGE MOVES OVER AREA AND WINDS TURN MORE SW.
WITH POLAR AND SUBTROPICAL JETS OVER S 1/2 US VERY STRONG FLOW TO
140KT. IN MEAN TIME CLOUDS AOA 030 OVER PLAINS HEADED EAST AND INTO
OUR AREA DURING AFTERNOON.
OVERALL PATTERN IS TO HAVE BROAD TROF SLOWLY SINK DOWN OVER N US AND
OVER OUR AREA FRIDAY MORNING AND TO S OF AREA BY EVE. IMPULSES MOVE
RAPIDLY TO E JUST S OF THIS ADVANCING NORTHERN TROF. THIS LEADS TO A
VERY SHEARED VORTICITY PATTERN OVER OUR NECK OF THE WOODS. NEW MOBILE
TROF THEN DROPS SE OVER AREA BY LATE SATURDAY TO REINFORCE THE COLD
AIR ON SUNDAY. WARMEST 850 TEMPS OVER AREA NEXT FEW DAYS ARE ON
SATURDAY MORNING 12Z AHEAD OF THE NEW TROF. STRONG SW SFC WINDS WITH
THIS TROF.
BY 12Z THURSDAY BOTH AVN/NGM MUCH MORE AGGRESSIVE WITH COLUMN RH THAN
THE ETA. AVN WAY OVERDONE AS USUAL BUT ETA PROBABLY A LITTLE
UNDERDONE. FOR ALL THE HIGH RH MAV POPS STILL ONLY 30% N AND A LITTLE
HIGHER S AS VERY LITTLE LIFT. BOTH OMEGA FIELDS AND Q-VECTOR
CONVERGENCE VERY WEAK LATE TONIGHT/THURSDAY. SOME WEAK UPPER LEVEL
DIVERGENCE OVER THE S COUNTIES LATE TONIGHT BUT THIS ABOVE FAVORED
SNOW TEMPERATURE GROWTH AREA. NEUTRAL TO VERY WEAK UPLIFT ON 280K
LEVEL TONIGHT/THURSDAY. WILL CONTINUE WITH THE EXISTING LO CHANCE
POPS OF LIGHT SNOW/FLURRIES. WILL ALSO CONTINUE WITH THREAT WEAK LAKE
EFFECT SNOW SHOWERS NW IN THURSDAY NIGHT AS NEW SURGE COLD AIR COMES
DOWN.
TEMP GUIDANC O.K. WITH ETA TOO WARM.
.CHI...NONE
AF
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 310 PM PST WED FEB 5 2003
.SYNOPSIS...HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH THE
MIDDLE OF NEXT WEEK. EXPECT MOSTLY CLEAR SKIES WITH AREAS OF LATE
NIGHT AND MORNING FOG.
.DISCUSSION...SATELLITE IMAGERY SHOWS STRATUS HAVING A HARD TIME
BURNING OFF OVER THE SOUTH SOUND WITH THE REST OF THE AREA CLEAR.
SURFACE GRADIENTS ARE A LITTLE BIT STRONGER OFFSHORE THIS AFTERNOON
BUT NOT BY MUCH VERSUS YESTERDAY. ACARS SOUNDINGS SHOW THE TOP OF THE
INVERSION AT AROUND 1600 FEET WITH LIGHT WINDS BELOW THE INVERSION.
SURFACE DEW POINTS ARE LITTLE CHANGED FROM YESTERDAY. NOT EXPECTING
MUCH CHANGE ON THURSDAY. WITH CLEAR SKIES ALONG THE EAST SLOPES
OFFSHORE GRADIENTS INCREASING SOME BUT NOT ENOUGH TO SCOUR OUT THE
WEST SIDE. MODEL SOUNDINGS CONTINUE TO SHOW A STRONG INVERSION AROUND
1300 FEET IN THE MORNINGS. GIVEN ALL THIS PERSISTENCE LOOKS TO BE A
GOOD FORECAST FOR THE SHORT TERM WITH THE ASA CONTINUING.
.EXTENDED...GFS SOLUTION HAS GOTTEN RID OF THE FUNKY LOW FROM THE
PREVIOUS TWO RUNS WITH THE CANADIAN MODEL NOW PICKING UP ON IT.
CURRENT GFS RUN LOOKS GOOD WITH UPPER LEVEL BLOCKING PATTERN
CONTINUING OFF THE COAST THROUGH THE PERIOD. ENSEMBLES HAVE NO
INDICATION OF THE LOW FROM THE PREVIOUS RUNS. SURFACE GRADIENTS
REMAINING OFFSHORE BUT NOT THAT STRONG. WILL KEEP THE PERSISTENCE
FORECAST GOING THROUGH THE EXTENDED. felton
UIL 0000 SEA 0000 OLM 0000
.KSEW...NONE.
.KATX...VCP32/CSR32...OPERATIONAL.