• Event summary
• Snowfall map (graphic)
• Snowfall amounts (text)
• Forecast history
• Excerpts from Area Forecast Discussions issued by WFO Norman:

Excerpts from Area Forecast Discussions issued by WFO Norman:

• Tuesday , 17 Dec, 318 PM
• Wednesday, 18 Dec, 400 AM
• Wednesday, 18 Dec, 335 PM
• Thursday, 19 Dec, 401 AM
• Thursday, 19 Dec, 700 AM
• Thursday, 19 Dec, 242 PM
• Friday, 20 Dec, 409 AM
• Friday, 20 Dec, 300 PM
• Saturday, 21 Dec, 338 AM
• Saturday, 21 Dec, 958 AM
• Saturday, 21 Dec, 158 PM
• Saturday, 21 Dec. 930 PM
• Sunday, 22 Dec. 328 AM
• Sunday, 22 Dec. 220 PM
• Sunday, 22 Dec. 950 PM
• Monday, 23 Dec. 350 AM
• Monday, 23 Dec. 340 PM

ISSUED 318 PM CST TUE DEC 17 2002

GOING INTO SUNDAY...[MODELS] SOMEWHAT SIMILAR IN LONGWAVE TROUGH OVER THE FAR W U.S. NEXT ISSUE IS TIMING OR INFLUENCE OF THIS SYSTEM AS GFS HAS SHORTWAVE EJECTING OUT LATE MONDAY INTO TUESDAY. SINCE CANADIAN AND ECMWF TROUGHS ARE FORECAST TO BE FARTHER E THIS COULD BE EARLY MONDAY INTO TUESDAY. ALSO...GFS SHOWS BOUNDARY LAYER MOISTURE TO SURGE QUICKLY N-WARD INTO AT LEAST E OKLAHOMA BY LATE MONDAY. WITH TIMING CONCERNS WILL LIKELY REMOVE POPS FROM SUNDAY AND INTRODUCE CHANCES OF RAIN/MAYBE THUNDER INTO EASTERN 2/3 OF FORECAST AREA MONDAY AND TUESDAY.

ISSUED 400 AM CST WED DEC 18 2002

...EXTENDED PERIODS LOOK GOOD. THERE ARE STILL SOME INCONSISTENCIES BETWEEN THE MODELS. MRF HAS A TROUGH DIGGING ALONG THE CA COAST AND MOVING THROUGH THE AREA AS AN OPEN TROUGH MON/TUE. HOWEVER THE ECMWF HAS THIS SYSTEM SLOWING DOWN...STRENGTHENING AND BECOMING A CLOSED LOW. DUE TO THE INCONSISTENCIES WILL NOT MAKE ANY BIG CHANGES TO LATER PERIODS.

ISSUED 335 PM CST WED DEC 18 2002

THERE WILL BE BETTER CHANCES OF PRECIPITATION WITH THE SYSTEM MOVING INTO THE S PLAINS FROM THE SW U.S. EARLY OR MID NEXT WEEK. THE MEDIUM-RANGE MODELS DO NOT AGREE ON THE TIMING HOWEVER. THE ECMWF IS STRONGER AND SLOWER WITH THE UPPER SYSTEM THAN THE MRF. WILL INCREASE TO CHANCE POPS IN THE S FOR TUESDAY...BUT OTHERWISE WILL KEEP POPS IN THE EXTENDED AT SLIGHT CHANCE.

ISSUED 401 AM CST THU DEC 19 2002

NEXT MAJOR SYSTEM WILL COME THROUGH THE BEGINNING OF NEXT WEEK...STILL SOME DISAGREEMENT BETWEEN MEDIUM RANGE MODELS ON STRENGTH OF THIS SYSTEM. EXTENDED POPS INTO W ZONES MON THRU TUE AND INTRODUCED WINTER PRECIP MON NIGHT THRU TUE NIGHT...DUE TO COLD 850 MB TEMPS AND THICKNESSES ASSOCIATED WITH THIS UPPER LEVEL TROUGH.

ISSUED 700 AM CST THU DEC 19 2002

WE ARE GOING TO ISSUE A WINTER STORM OUTLOOK FOR POSSIBLE HEAVY SNOW NEXT MON-TUE. 06Z GFS/AVN IS CONSISTENT WITH PREVIOUS RUNS AND IN FACT IS SLIGHTLY COOLER WITH THICKNESS VALUES OVER THE AREA MON NIGHT. EVOLVING PATTERN...AT LEAST AS PROGGED BY THE AVN...IS A NEARLY-CLASSIC OK HEAVY SNOW PATTERN IN ALL RESPECTS. COLD SURFACE RIDGE SETS UP E-W ACROSS N TIER OF U.S. WITH CENTER OVER N PLAINS PROVIDING THE COLD AIR. SURFACE LOW SHIFTS FROM AZ/NM TO TX COAST...NE SURFACE WINDS ACROSS AREA...UPPER LOW COMING OUT OF AZ/NM. ALTHO MODELS OFTEN END UP TOO FAST AND TOO FAR N WITH THESE SYSTEMS...HAVE NOT SEEN A TREND IN RECENT RUNS TO SLOW IT DOWN OR NUDGE IT FARTHER S. PER YESTERDAY'S MEDIUM-RANGE DISCUSSIONS...ENSEMBLES HAVE TENDED TO SUPPORT THE [FASTER] SOLUTIONS. EVEN IF IT WERE TO TRACK FARTHER S...OUR S ZONES WOULD LIKELY BE UNDER THE GUN. DECISION TO ISSUE AN OUTLOOK IS BASED ON PROJECTED TIMING. SNOW POSSIBLY BEGINNING ON MONDAY - THE MONDAY BEFORE XMAS - AND CONTINUING INTO XMAS EVE. OUTLOOK WILL BE OUT BY AROUND 730 AM.

ISSUED 242 PM CST THU DEC 19 2002

ALTHOUGH THE MODELS ARE IN FAIR AGREEMENT WITH REGARD TO THE SPEED OF THE [APPROACHING UPPER] TROUGH...ANSWERS REGARDING AIR COLD ENOUGH TO SUPPORT SNOW REMAINS THE LARGEST UNCERTAINTY AT THIS POINT. THE GFS HAS BEEN AND CONTINUES TO BE THE COLDEST OF ALL THE MODELS WITH ENSEMBLE MEMBERS CONSISTENT WITH THE OPERATIONAL RUN IN SHOWING THE 5400 M THICKNESS CONTOUR ACROSS FAR N OK LATE MONDAY. FOR THIS REASON...HAVE BROUGHT THE MENTION OF A CHANCE OF A RAIN/SNOW MIX INTO THE AREA A BIT EARLIER FROM THE PREVIOUS FORECAST.

PLAN TO REISSUE THE WINTER STORM OUTLOOK...ITS IMPORTANT TO UNDERSTAND THAT SPECIFICS REGARDING THE POTENTIAL FOR WINTERY WEATHER EARLY NEXT WEEK ARE STILL UNCLEAR.

ISSUED 409 AM CST FRI DEC 20 2002

STILL LOOKS LIKE PRECIP WILL HOLD OFF UNTIL SUN NIGHT WHEN WARM ADVECTION DEVELOPING AHEAD OF THE MAIN [TROUGH] BEGINS TO AFFECT THE AREA. PRECIP TYPE WILL BE THE QUESTION AS WE GET INTO MONDAY. WILL NOT GET TOO DETAILED THAT FAR OUT WITH PLENTY OF UNCERTAINTY AT THIS TIME. WILL CONTINUE GENERAL TREND OF MAINLY RAIN SE HALF WITH RAIN/SNOW NW MONDAY. WILL GRADUALLY BRING WINTERY PRECIP FARTHER SE OVERNIGHT MONDAY INTO TUESDAY BEFORE PRECIP ENDS FROM THE W LATE TUESDAY.

ISSUED 300 PM CST FRI DEC 20 2002

FOCUS SHIFTS TO SUNDAY NIGHT WITH APPROACHING E PAC LOW RESULTING IN A RATHER DEEP PATTERN OF ISENTROPIC UPGLIDE OVER S/SW PARTS OF THE AREA LATE IN THE NIGHT. AS STRONG S/SE FLOW CONTINUES ABOVE THE SURFACE...BELIEVE RAIN WILL DEVELOP AND SPREAD N-WARD ACROSS THE S HALF OF THE AREA ON MONDAY WITH SNOW POSSIBLE TO THE N. LATEST [ETA] RESEMBLES THE COLDER AND MORE PESSIMISTIC SNOWY FORECAST THAT THE GFS HAS SHOWN THE PAST COUPLE DAYS. GIVEN THIS CONTINUITY...BELIEVE ITS APPROPRIATE TO BEGIN INCREASING THE PROBABILITY OF SNOW OVER A LARGER PART OF THE AREA FOR MONDAY THROUGH TUESDAY WHILE STILL TRYING TO AVOID TOO MANY SPECIFICS.

THIS WILL RESULT IN SNOW LIKELY N OF A STILLWATER TO CHEYENNE LINE DURING THE DAY MONDAY WITH A BROAD UNCERTAINTY ZONE OF RAIN AND/OR SNOW LIKELY S-WARD TO A SEMINOLE TO ALTUS TO QUANAH TX LINE. ETA/AVN SUGGEST THIS ENTIRE AREA COULD TRANSITION TO ALL SNOW DURING THE DAY BUT FEEL ITS BEST TO KEEP THE HIGHEST CONFIDENCE OF ALL SNOW TO AREAS FARTHER N UNTIL CONFIDENCE INCREASES.

THE POTENTIAL EXISTS FOR A SIGNIFICANT WINTER STORM OVER PARTS OF THE AREA WITH HEAVY SNOW APPEARING LIKELY FOR SOME PARTS OF THE AREA...HOWEVER IT IS IMPORTANT TO UNDERSTAND THAT THE EVENT IS OVER 4 DAYS AWAY AND THAT THE FORECAST IS BASED ALMOST ENTIRELY ON COMPUTER MODELS THAT ARE OFTEN CLOSE TO REALITY BUT ARE ALSO SOMETIMES UNABLE TO RESOLVE SMALL-SCALE FEATURES THAT CRITICALLY AFFECT THE EVOLUTION OF THE STORM SYSTEM. THE UPPER LOW THAT IS EXPECTED TO INFLUENCE THE AREA IS STILL OVER THE EASTERN PACIFIC AND COULD BEHAVE QUITE DIFFERENTLY FROM WHAT THE MODELS ARE INDICATING. ALTHOUGH CONFIDENCE IN A SIGNIFICANT SNOW EVENT HAS INCREASED...THERE IS STILL CONSIDERABLE UNCERTAINTY AS TO HOW MUCH SNOW WILL FALL AND WHAT AREAS WILL BE AFFECTED. PLEASE BE PATIENT AS THE FORECAST WILL LIKELY EXPERIENCE MANY CHANGES OVER THE NEXT SEVERAL DAYS.

ISSUED 338 AM CST SAT DEC 21 2002

THINGS GET MORE INTERESTING MONDAY AND MONDAY NIGHT AS COOLER AIR GRADUALLY FILTERS INTO THE AREA FROM THE N. DID NOT MAKE ANY BIG CHANGES TO [FORECAST] MONDAY WITH BEST CHANCES FOR SNOW IN THE N...RAIN IN THE SE...AND MIXED PRECIP CENTRAL. EXPECT WINTERY PRECIP AREA TO CONTINUE TO MIGRATE FARTHER S-WARD INTO THE AREA MONDAY NIGHT AS COLD AIR DEEPENS.

ISSUED 958 AM CST SAT DEC 21 2002

QUICK LOOK AT NEW AVN/ETA SUGGESTS A SLIGHTLY SLOWER AND MORE S-WARD SCENARIO POSSIBLY DEVELOPING FOR AT LEAST MONDAY. STILL PREMATURE TO MAKE ANY CHANGES AT THIS POINT...BUT AT LEAST INITIALLY THIS WOULD SUGGEST THAT POPS MAY BE REDUCED OR POSSIBLY ELIMINATED ACROSS N HALF OF OK MONDAY MORNING...WITH PRECIPITATION PERHAPS DEVELOPING IN THESE AREAS BY AFTERNOON.

ISSUED 158 PM CST SAT DEC 21 2002

UPPER SYSTEM EXPECTED TO GENERATE SURFACE LOW IN W TX SUNDAY NIGHT INTO TUESDAY...THIS WILL PUT OK IN NE BOUNDARY LAYER WINDS WHICH WILL BRING COOL AND INITIALLY DRY AIR INTO THE STATE MONDAY. NEW MODELS TREND THE UPPER SYSTEM TO APPROACH OK 12 HR OR SO LATER AND SLIGHTLY TO THE S FROM PREVIOUS RUNS. BUT IN KEEPING WITH PAST TRENDS...LIFT APPEARS TO BE PLENTIFUL AS IT APPROACHES N TX AND OK MONDAY NIGHT. WITH MODEL SOLUTIONS LIGHTLY SLOWER TODAY...HEFTY PRECIP CHANCES WERE PUSHED BACK INTO LATE MONDAY AFTERNOON AND MONDAY NIGHT FOR THE N HALF. WARM ADVECTION SHOULD START RAIN IN THE S MONDAY MORNING. NEW MODELS ALSO TREND IN HAVING COLDER AIR MOVING INTO W OK SOONER WITH THE NE SURFACE FLOW. ALTHOUGH THE TIMING OF THE LIKELY SNOW HAS BEEN PUSHED BACK UNTIL MONDAY NIGHT AND TUESDAY...THIS SYSTEM IS EXPECTED TO BRING ENOUGH [LIFT] FOR HEAVY SNOWFALL IN PARTS OF THE AREA.

ISSUED 930 PM CST SAT DEC 21

LATEST ETA/MESOETA...AND TO AN EXTENT THE 18Z AVN...POINT TO STRONG POSSIBILITY OF PRECIPITATION BEGINNING ACROSS NW OK SUNDAY NIGHT-EARLY MONDAY...AS LEAD DISTURBANCE EJECTS. THERE WILL BE AN INITIAL MOISTENING PHASE ASSOCIATED WITH ANY PRECIP...BUT FEEL IT IS PRUDENT TO INCREASE POPS ACROSS THE N ON MONDAY AND ADD THEM TO W CENTRAL AND NW OK SUNDAY NIGHT. AS STATED IN DAY SHIFT PRODUCTS...WINTER STORM HEADLINES LIKELY NEXT 24 HOURS.

ISSUED 328 AM CST SUN DEC 22

DESPITE POOR INITIALIZATION AT 00Z BY THE ETA WITH THIS SYSTEM...ETA/GFS COME INTO PRETTY GOOD AGREEMENT WITH THE MOVEMENT OF THIS SYSTEM THROUGH THE S ROCKIES AND INTO THE PLAINS. LOOKS LIKE TWO-PRONGED SHOT AT THE AREA AS INITIAL LIFT ASSOCIATED WITH DEVELOPING WARM ADVECTION AND FAVORABLE UPPER JET PATTERN AFFECTS THE AREA FROM LATE TONIGHT INTO MONDAY. BOTH ETA AND GFS INDICATE SHORTWAVE EJECTING NE ACROSS THE AREA MONDAY/MONDAY NIGHT AHEAD OF THE MAIN LOW. LOOKS LIKE PRECIP SHOULD TAPER OFF AS THE FEATURE MOVES BY. MAIN LOW COMES OUT TUESDAY BUT BY THAT TIME BETTER MOISTURE HAS SHIFTED TO THE E OF THE AREA AND UPPER JET PATTERN IS LESS FAVORABLE. AS IS USUALLY THE CASE MAIN FORECAST PROBLEM WILL BE PRECIP TYPE AND HOW RAPIDLY WINTER TYPE PRECIP SPREADS SE INTO THE AREA. FOR TONIGHT AIR MASS OVER THE AREA WILL INITIALLY BE FAIRLY DRY BUT SHOULD BEGIN TO MOISTEN UP AS WARM ADVECTION/ISENTROPIC LIFT DEVELOP AHEAD OF THE APPROACHING UPPER LOW. EXPECT PRECIP TO DEVELOP LATE TONIGHT AS LIFT STRENGTHENS. N AND W SHOULD BE COLD ENOUGH FOR ANY PRECIP TO CHANGE OVER TO SNOW FAIRLY QUICKLY. ETA TEMPERATURE/THICKNESS IS COLDER THAN THE GFS. LOOK AT BUFR SOUNDINGS SHOWS PRECIP CHANGING TO SNOW FROM SW THROUGH CENTRAL SECTIONS DURING THE MORNING. THIS MAY BE A BIT FAST...ESPECIALLY IF THE WARMER GFS IS CORRECT. WILL COMPROMISE A BIT AND INDICATE PRECIP CHANGING TO SNOW FROM SW INTO CENTRAL SECTIONS AROUND MIDDAY MONDAY. POTENTIAL FOR ACCUMULATING SNOWS LOOKS SUFFICIENT TO GO WITH A WATCH FOR ABOUT THE NW 2/3RDS OF THE AREA. WILL CONTINUE WITH POPS FOR TUESDAY BUT AT THIS TIME LOOKS THAT ANY PRECIP THAT FALLS WILL BE LIGHT.

ISSUED 220 PM CST SUN DEC 22

UPPER LOW WAS MOVING ACROSS CENTRAL BAJA CALIFORNIA EARLY SUNDAY AFTERNOON. ALTHOUGH WATER VAPOR SATELLITE DEPICTION IS DIFFICULT TO RECONCILE WITH NEAR-TERM MODEL FORECASTS...ASSOCIATED STRONG UPPER JET IS EXPECTED TO BE IN A FAVORABLE POSITION MONDAY TO GENERATE STRONG LIFT ACROSS OK AND ADJACENT PARTS OF N TX.

NEAR-SURFACE DEWPOINTS IN THE UPPER TEENS AND LOWER 20S SUNDAY AFTERNOON ARE EXPECTED TO RISE ONLY MODESTLY OVERNIGHT AS MOISTURE ADVECTION IS EXPECTED TO BE STRONGER ABOVE THE SURFACE LAYER. THIS CONDITION AND INTERPRETED MODEL SOUNDINGS SUGGEST THAT AS PRECIP DEVELOPS MONDAY MORNING IN SW OK IT COULD INITIALLY BE RAIN FOR A SHORT PERIOD WITH BELOW-FREEZING SURFACE TEMPERATURES. HOWEVER, ANY PERIOD OF FREEZING PRECIP IS EXPECTED TO BE BRIEF AS THE SNOW-MAKING LAYER IS EXPECTED TO BE SUFFICIENTLY COLD AND RELATIVELY DRY TO GENERATE ALL SNOW SOON AFTER.

WITH THE OBSERVED DISCREPANCY BETWEEN WATER VAPOR LOOPS AND NEAR-TERM FORECAST MODEL TRACKS OF THE UPPER SYSTEM...THE ZONE OF HEAVIER SNOWFALL REMAINS QUITE UNCERTAIN. HOWEVER...ISENTROPIC LIFT...MOISTURE ADVECTION AND THE ORIENTATION OF FRONTOGENESIS WILL PROVIDE NECESSARY CONDITIONS FOR SNOWFALL...ESPECIALLY FROM SW TO CENTRAL OK. LIFT EXPECTED WITH THE UPPER SYSTEM SHOULD ENHANCE AMOUNTS DEPENDING ON ITS TRACK.

WINTER STORM WATCH WILL BE DELAYED IN NW OK UNTIL MONDAY MORNING. THE WATCH WILL BE EXTENDED THROUGH MONDAY NIGHT AND WILL PICK UP A FEW MORE COUNTIES TO THE SE OF THE ONE ISSUED PREVIOUSLY. IT WILL INDICATE SIMILAR RAIN-SNOW TRANSITION TIMING TO THE CURRENT WATCH.

ISSUED 950 PM CST SUN DEC 22

NEW MODEL DATA ARE THROWING BIG WRENCH IN CURRENT FORECAST. 00Z ETA/MESOETA HAVE STRONG SIGNAL THAT CHANGEOVER OF RAIN TO SNOW WILL BE DELAYED ACROSS S CENTRAL OK AND PARTS OF WESTERN N TX...WITH TRANSITION NOT UNTIL MIDNIGHT TOMORROW NIGHT. ALSO...FOR CENTRAL OK...TRANSITION IS DELAYED UNTIL LATE AFTERNOON/EVENING. HIGH AMOUNTS OF LIQUID QPF WILL BE GENERATED IN AREA OF STRONG WARM ADVECTION/FRONTOGENETICAL FORCING DURING THE DAY AND EVENING...BUT MOST EXPECTED TO FALL BEFORE CHANGE OVER. THIS WILL TRANSLATE INTO LEAVING S AREAS IN WATCH FOR MONDAY AFTERNOON AND MONDAY NIGHT.

LATEST GUIDANCE INDICATES THAT HIGHEST SNOW AMOUNTS MAY BE FARTHER N THAN CURRENTLY FORECAST. WILL MAKE THIS ADJUSTMENT TO CENTRAL AND N SECTIONS OF CURRENT WATCH...AND MAKE THE WATCH A WINTER STORM WARNING FOR MONDAY AND MONDAY NIGHT. WILL INDICATE TIME DIFFERENCES AND AMOUNTS IN THE WARNING SEGMENTS...BUT BIGGEST CHANGE WILL BE TO INCREASE ACCUMULATIONS ACROSS N OK.

ISSUED 350 AM CST MON DEC 23

SW UPPER LOW PROGGED TO COME OUT IN 2 PIECES...THE FIRST LIFTING NE TOWARD TX PANHANDLE/W OK BY THIS EVENING AND 2ND SHEARING OUT AND WEAKENING E-WARD TONIGHT/TUESDAY. APPEARS MOST IF NOT ALL OF THE WEATHER HERE MAY OCCUR WITH THE FIRST PIECE TODAY INTO THIS EVENING...WHICH UNFORTUNATELY IS THE CRITICAL PERIOD REGARDING PRECIP TYPE. NONE OF THE MODELS MAY HAVE A GOOD HANDLE ON THIS SYSTEM INITIALLY...SO NOT SURE ANY OF THEM ARE GOING TO DO A VERY GOOD JOB WITH THE SYSTEM AS A WHOLE...MUCH LESS THE MESOSCALE DETAILS. BASED ON CURRENT RADAR...THERE IS STRONG SUSPICION THAT MODELS IN GENERAL ARE UNDERFORECASTING THE SNOW POTENTIAL. GFS...BY VIRTUE OF ITS BETTER RUN TO RUN CONSISTENCY...IS PREFERRED THIS MORNING. GFS IS A BIT COOLER THAN ETA/MESOETA WITH THICKNESSES AND 850 MB TEMPERATURES THROUGH THIS EVENING...AND GIVEN THE CURRENT SURFACE DEWPOINTS IN LOWER 20S ACROSS PARTS OF CENTRAL/N OK AM LEANING TOWARD THE COOLER GFS AND A QUICKER CHANGEOVER FROM RAIN TO SLEET/SNOW TODAY. SLEET/SNOW ALREADY BEING REPORTED IN PARTS OF CENTRAL OK...BUT MUCH OF THE I-44 CORRIDOR MAY REMAIN IN OR NEAR THE CRITICAL CHANGEOVER ZONE LATER TODAY...INCLUDING LAWTON AND OKLAHOMA CITY AREAS. MOST LIKELY AREA FOR HEAVY SNOW REMAINS ACROSS ROUGHLY THE NW 30 TO 40 PERCENT OF THE AREA...WHERE 5-10 INCHES APPEAR LIKELY WITH LOCALLY HIGHER ACCUMULATIONS. IT MAY BE A STRUGGLE TO ATTAIN WARNING-LEVEL ACCUMULATIONS IN MUCH OF THE I-44 CORRIDOR. WATCH/WARNING AREAS WILL NOT CHANGE THIS MORNING...WITH WATCH CONTINUED TONIGHT ACROSS MOST OF THE TX ZONES INTO S CENTRAL OK.

ISSUED 340 PM CST MON DEC 23

MAIN LIFTING MECHANISM FOR PRECIP IS LEAVING OUR FORECAST AREA AT THIS TIME. SOME RESIDUAL SNOW IS STILL FALLING ACROSS N-CENTRAL OK...AND IS EXPECTED TO DIMINISH FURTHER THIS EVENING. AS THE UPPER SYSTEM DRAGS ITSELF ACROSS OUR N BORDER OVERNIGHT...AN INCH OR TWO OF NEW SNOW WILL BE POSSIBLE. ALTHOUGH THIS IN ITSELF DOES NOT WARRANT AN ADVISORY...THE NEW SNOW WILL FALL IN AREAS THAT HAVE JUST RECEIVED SEVERAL INCHES OF NEW SNOW. SO...A SNOW ADVISORY WILL COVER OUR NORTHERN TWO ROWS OF COUNTIES UNTIL MIDNIGHT.