AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 915 PM CST SAT NOV 24 2001 UPDATED ZONES AROUND 615 PM TO ADD A CHANCE OF SHOWERS ACROSS EASTCENTRAL IL TONIGHT MAINLY THIS EVENING. MORE WIDESPREAD RAIN CONTINUES ALONG AND N OF THE IL RIVER CLOSER TO UPPER LEVEL LOW AND COLD POOL ALOFT OVER IA. SURFACE 989 MB LOW JUST EAST OF KMSP WITH ONE COLD FRONT OVER EASTERN INDIANA EAST OF I-65 AND ANOTHER FRONT OVER CENTRAL IA AND NW MO. 03Z/9 PM TEMPS SLIPPED TO 48 AT KGBG TO 59 AT KLWV WHILE DEWPOINTS IN MID TO UPPER 40S. SSW WINDS 12-24 MPH WITH GUSTS OF 18-35 MPH AND STRONGEST NEAR THE IL/IN BORDER. ONE BAND OF SHOWERS ALONG IL/IN BORDER ON LEADING EDGE OF LOW CLOUD DECK CIRCULATING AROUND DEEP LOW OVER IA. MORE WIDESPREAD LIGHT RAIN WITH A FEW EMBEDDED HEAVIER SHOWERS ALONG AND N OF THE IL RIVER. LOW TO BEGIN TO SLOWLY FILL IN AS IT LIFTS NE INTO WESTERN LAKE SUPERIOR BY 12Z/SUN. RUC/MESOETA CONTINUE CHANCE OF LIGHT QPF ALONG AND N OF IL RIVER OVERNIGHT AND DIMINISHING CHANCES SOUTH AS LOW BKN-OVC PREVAILS. AREAS ALONG AND S OF I-70 PROBABLY WILL BE DRY REST OF THE NIGHT...BUT KEEPING PROB40 CHANCE OF SHOWERS IN CASE ANY BANDS OF SHOWERS EXTEND AS FAR S AS I-70. SW WINDS STAY FAIRLY STRONG 15 TO 25 MPH WITH GUSTS AROUND 35 MPH POSSIBLE. LOWS IN THE LOWER 40S NW...MID 40S CENTRAL AND UPPER 40S SE APPEAR ON TRACK WITH WIND CHILLS IN THE 20S DEVELOPING. .ILX...NONE. $$ KH il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1045 PM EST SAT NOV 24 2001 MAIN FCST CONCERNS OVERNIGHT ARE PCPN TRENDS AND POTENTIAL FOR TSRA. WV IMAGERY AND RUC ANALYSIS INDICATED MID LVL CIRCULATION OVER ERN IA. AT THE SFC...A 989 LO WAS LOCATED NEAR KMSP WITH A STATIONARY FRONT EXTENDING TO THE NORTHEAST INTO WRN LK SUPERIOR. A PCPN BAND EXTENDED FROM NEAR KISQ-MUNISING TO THE SOUTH WITH TSRA INTO LOWER MI. THIS BAND ON THE EDGE OF THE DRY SLOT AND SFC LLVL CONVERGENCE/TROF WAS ALSO SUPPORTED BY PROXIMITY TO LEFT EXIT REGION OF 120 KT H3 JET AND STEEPENING 700-500 MB LAPSE RATES AOA 7C/KM WITH GOOD HGT FALLS AS SHRTWV NEAR BASE OF THE TORF PIVOTS TO THE NORTHEAST. ANOTHER BATCH OF SCT SHRA OVER CNTRL WI ASSOCIATED WITH THE MID LVL LO AND OCCLUDED FRONT WAS ALSO LIFTING TO THE NORTH. EXPECT THIS AREA TO SPREAD INTO UPR MI BTWN 06Z-12Z...PER RADAR TRENDS AND 00Z RUC. AXIS OF INSTABILITY SUPPORTING TSRA WL CONTINUE TO SHIFT TO THE EAST. SO... HAVE REMOVE TSRA WORDING FOR ALL BUT ERN PORTION OF THE CWA. STRONG WAA HAS PUSHED TEMPS UP TO NEAR RECORD HIGH THIS EVENING (52 AT KMQT VS. RECORD OF 55). AS LO LIFTS TO WRN UPR MI BY 12Z...COLDER AIR WRAPPING IN FROM THE SW WILL REMAIN MAINLY WEST OF UPR MI. SO...TEMPS SHOULD REMAIN MILD WITH OVERNIGHT LOWS NOT TOO MUCH BELOW CURRENT READINGS. .MQT...NONE. JLB mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 435 PM EST SAT NOV 24 2001 12Z RAOBS/LATEST WV LOOP AND RUC ANAL SHOW VIGOROUS NEGATIVELY TILTED SHRTWV MOVG NEWD THRU THE MID MS VALLEY AS 120KT H3 JET MAX LIFTS NE AHD OF SYS TO W OF HI AMPLITUDE/PERSISTENT RDG ALG E COAST. OCCLUDED LO PRES...WITH MSLP AT 984MB...MOVG N THRU WRN IA. WARM CONVEYOR BELT MSTR...WITH PW IN EXCESS OF 1 INCH AND DEEP SATURATION/H85 WND UP TO 50 KTS PER 12Z RAOBS... ADVCTG NWD INTO CWA IN STRG SLY FLOW AHD OF SYS. LINE OF HEAVIER SHRA IN ADVANCE OF H85 THETA-E SURGE/WND MAX HAS MOVED THRU CWA. LTG EARLIER...BUT NONE NOW AS CNVCTN MOVD N INTO NR MOIST ADIABATIC LAPSE RATE AND BCM MORE ELEVATED. LIFT WITHIN WARM CONVEYOR BELT ENHANCED BY UPR DVGC/ CONFLUENCE IN EXIT RGN OF LIFTING JET MAX. BACK EDGE OF WARM CONVEYOR BELT/LEADING EDGE OF DRY SLOT WITHIN JET AXIS HAS PUSHED INTO CWA. SOME -RA OBSVD UNDER UPR DRYING WELL IN ADVANCE OF MAIN BACKWASH MSTR/COLDER CLD TOPS OVR ERN NB...AND SOME TSRA HAVE RDVLPD OVR NE IA IN UNSTABLE AIR IN DRY SLOT. PCPN ALL RA IN NW LKS/NRN PLAINS AS COLD AIR REMAINS BOTTLED UP IN CAN. SFC FRZG LINE FM CNTRL ONTARIO TO SRN MB...BUT MUCH COLDER AIR LURKING UNDER BIG ARCTIC HI ACRS NW CAN. DESPITE PRESENCE OF 37KT WNDS AT 2K FT AGL PER 12Z GRB SDNG...HIER STABILITY N OF SFC WARM FNT TO S RESTRICTING MIXING OF THIS MOMENTUM TO SFC. ANOTHER VIGOROUS SHRTWV PLOWING INTO NRN CA ATTM. NMRS FCST CONCERNS THIS PACKAGE REVOLVING ARND TIMING/IMPACT OF OCCLUSION TO THE SW. MODELS REMAIN IN DECENT AGREEMENT SHOWING SFC LO CENTER REACHING WRN CWA BY 12Z SUN. HOWEVER...CURRENT TRACK OF SFC LO ALMOST DUE N WOULD SUG LO CENTER MAY END UP A BIT FARTHER W THAN FCST...NOT UNRSNBL CONSIDERING INTENSITY OF SYS ATTM. SFC LO SHUD FOLLOW H5/H7 CENTER MORE CLOSELY (FCST TO TRACK THRU ERN MN)... SO XPCT LO CENTER WL BE CLOSER TO DLH THAN IWD AT 12Z SUN. THIS ADJUSTMENT WL RESULT IN A SLOWER RETURN OF DEEPER BACKWASH MSTR AND COLDER AIR TNGT/SUN. FOR TNGT...BACK EDGE OF WARM CONVEYOR BELT WL MARCH SW TO NE ACRS CWA THIS EVNG AHD OF OCCLUDED FNT PASSAGE...SO SHRA TO BCM MORE SCT. LTG TRENDS AND ARRIVAL OF ETA H9 LI (MULYR ABV NR SFC STABILITY) AOB 0 ONLY AFTR ARRIVAL OF DRIER AIR/H7-3 QVECTOR DVGC SUG TSRA A SML CHC...BUT HAVE KEPT IN MENTION SINCE TSRA DVLPG IN UNSTABLE AIR TO THE S AND FOR CONTINUITY. APRCH OF VIGOROUS H7-3 QVECTOR CNVGC IN LEFT EXIT OF H3 JET MAX COINCIDES WITH ARRIVAL OF DRIEST AIR ALF AND INTENSE ISENTROPIC DESCENT ON 295K SFC (H775)...SO SHRA COVG SHUD REMAIN SCT. ETA SLOWEST AT RUSHING BACKWASH MSTR EWD TO JUST FAR W BEFORE 12Z SUN...SO FOLLOWED ITS GUIDANCE. WENT WITH HIER FWC FCST MINS PER ABV ADJUSTMENTS...NUMBERS CONSISTENT WITH OBSVD DWPTS IN DRY SLOT. ALTHOUGH THERE MAY BE A DCRS IN LLVL STABILITY FOLLOWING OCCLUDED FROPA THIS EVNG...ETA FCST SDNGS SHOW STABLE LYR NR THE SFC LINGERING. ALL MODELS SHOW A DCRS IN PRES GRADIENT FOLLOWING FROPA AS WELL...SO HAVE DOWNPLAYED WNDS. ON SUN...SFC LO CENTER FCST TO MOVE MORE RPDLY NE TO NR JAMES BAY BY EVNG. AS UPR SHRTWV OPENS UP...DECAYING BACKWASH MSTR TRAVERSES CWA WITH LINGERING CYC FLOW BEHIND SFC LO UNDER H7-3 QVECTOR DVGC/RISING HGTS. IN A SWITCH FM YDAY...ETA NOW SLOWER DRIVING SHALLOW COLD AIR SE IN WAKE OF THE CYC AND PREFERRED. FCST SDNGS SHOW SHARP INVRN DVLPG ARND 3K FEET AS COLD AIR OOZES UNDER FAIRLY WARM AIR ALF. THIS LO INVRN WL RESTRICT DEPTH OF INSTABILITY AND LES POTENTIAL. BUT ANY LINGERING SPRINKLES IN BACKWASH WL CHG TO FLURRIES OVR THE WRN 4 ZNS...WHERE ETA SHOWS H100-85 THKNS DROPPING BLO 1300M BY 00Z MON. WRN HALF OF CWA WL SEE MAX TEMPS IN THE MRNG/EARLY AFTN WITH TEMPS FALLING LATER TOWARD 32 AT IWD BY EVNG. DURG SUN NGT INTO MON...UPR RDG AXIS BTWN DEPARTING LO PRES AND APRCHG SYS NOW COMING ASHORE IN CA MOVES OVR NW LKS AS SFC RDG AXIS AND SHALLOW COLD AIR CONT TO POUR SE INTO CWA. ETA FCST SDNGS SHOW MOIST LYR LINGERING BLO 3K INVRN WITH GRDLY VEERING LLVL WND FM NW TO NE. LYRS ABV 5K FEET EXHIBIT CONSIDERABLE DRYING. SINCE TEMPS WITHIN MOIST LYR OVR CNTRL ZNS NEVER FALL BLO -10C (TO PREVENT ICE NUCLEATION)...XPCT UPSLOPE ENHANCED PCPN TO BE IN THE FORM OF -DZ/ -FZDZ. OVR THE W...ETA INDICATES LOWEST TEMPS WITHIN MOIST LYR REACHING -12C (LK-COLDEST LYR DELTA T NR 17C) BY LATE SUN NGT. BUT LO INVRN AND NEUTRAL TO ACYC NE FLOW IN THE ABSENCE OF UPR DYNAMICS NOT FVRBL FOR SGNFT LES THESE ZNS. SO WL TREND FCST OF -DZ/-FZDZ/ FLURRIES TOWARD MAINLY JUST FLURRIES. FOR THE E AND S...ABSENCE OF SGNT UPSLOPE FLOW WL LIMIT POTENTIAL FOR -DZ/FLURRIES. USED ETA BLYR TEMPS FOR MIN TEMPS FCST SUN NGT. DURG DAY ON MON...12Z MODELS SHOW CA SHRTWV/SFC LO REACHING IA BY 00Z TUE. PER PMDHMD...PREFER SLOWER AVN/CAN TIMING ON ARRIVAL OF ASSOCIATED UPR DYNAMICS. HOWEVER...AVN DEPICTS ENUF UPR DVGC/H7-3 QVECTOR CNVGC DVLPG IN THE AFTN OVR THE WRN ZNS TO REACH GREATER SATURATION (H85-5 RH OVR 80 PCT) AND TO GENERATE QPF THERE. HOWEVER...WL GO MORE THAN CHCY POPS ATTM DUE TO DRYNESS OF MID LVLS IN ANTECEDENT AIRMASS. FCST SDNGS SHOW AIRMASS COLD ENUF FOR ALL SN. CONCERNED THAT ELY FLOW MAY ALLOW SOME LK ENHANCEMENT FOR KEWEENAW ZNS...BUT HI STABILITY WITH LINGERING INVRN ARND 3K FT SHUD REDUCE THIS POTENTIAL...AT LEAST WELL IN ADVANCE OF SYS. XPCT ENUF DRY AIR TO LINGER IN THE MID LVLS OVR THE E AND CNTRL WITH TEMPS IN THE MOIST LYR STILL ABV -10C TO PRECLUDE MORE THAN -DZ/-FZDZ IN UPSLOPE AREAS. SOME IMPORTANT TRENDS IN THE LONGER TERM FOR THE NEXT STORM SYSTEM TO IMPACT THE GRT LKS ON TUE. 00Z MODELS TRENDED TOWARD A HIER AMPLITUDE TROF OVR THE PLAINS AND A RDG OFF THE E CST. THE RESULT IS A WEAKER SHRTWV/SOMEWHAT FLATTER SFC LO THAT LIFTS OUT TOWARD THE GRT LKS (IN SHARPER UPR CONFLUENCE BTWN WRN TROF/ERN RDG)...WITH THE TRACK OF THE SFC LO FARTHER S THAN EARLIER FCST AS SHALLOW COLD AIR ASSOCIATED WITH MAMMOTH HI OVR NW CAN OOZES S INTO CONUS AND PUSHES MAIN BAROCLINIC ZN A BIT FARTHER S. 12Z MODELS HAVE CONTD THIS TREND AND SHOW WEAKENING SFC LO ELONGATING E THRU THE CTNRL LKS DURG TUE WITH SHARP H7-3 QVECTOR CNVGC/H4-2 DVGC OVR CWA. AVN DEPICTS DEEPEST MSTR OVR THE NRN HALF OF CWA...COLD AIR MAY BE TOO SHALLOW ACRS THE S FOR BEST LIFT. AIRMASS OVR CNTRL/WRN ZNS WL BE COLD ENUF FOR ALL SN...BUT EVEN IN THE E FALLING THKNS IN THE FACE OF WAD WITH UPR SHRTWV GOING TO THE S SUGS MIX WL GRDLY CHG TO ALL SN BY TUE AM. LLVL WND FIELD TOO E FOR SGNFT LK ENHANCEMENT...XCPT OVR THE KEWEENAW ZNS...WHERE FCST H85 TEMPS ARND -6 RESULT IN LK-H85 DELTA T ARND 10-11C. PSBL LINGERING INVRN MAY LIMIT IMPACT THOUGH. NOT MUCH AGREEMENT ON PATTERN AFTR TUE...BUT ECMWF HAS BEEN MOST CONSISTENT WITH FCST PAST COUPLE OF RUNS. SO FOLLOWING ITS GUIDANCE MORE CLOSELY FOR THE EXTENDED PD...WHICH PROMISES TO BE AN ACTIVE PD WITH A NUMBER OF STRG PAC DISTURBANCES EMBEDDED WITHIN A MORE ZONAL FLOW THAT FEATURES PLENTY OF COLD AIR IN CAN TO BE TAPPED. ECMWF... WITH SUPPORT FM MAJORITY OF CANADIAN ENSEMBLE MEMBERS...INDICATES THAT AT LEAST A GOOD CHUNK OF WRN TROF GETS KICKED NE IN THU-FRI TIME FRAME IN ADVANCE OF ANOTHER STRG DISTURBANCE RIDING INTO THE W. WL MAINTAIN GOING FCST FOR SN/SHSN ON THU-FRI WITH DRY WX ON SAT. TEMPS THRU THE EXTENDED PD SHUD FALL STEADILY WITH GRDLY LWRG HGTS/ RISING MSLP FCST. COORDINATED WITH APX. .MQT...NONE. KC mi SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 328 PM EST SAT NOV 24 2001 THE LATEST SURFACE ANALYSIS AND WATER VAPOR LOOP HAS NEARLY VERTICALLY STACKED STRONG OCCLUDED SYSTEM CENTERED OVER WESTERN IOWA. THE OCCLUDED FRONT CURRENTLY EXTENDS ACROSS CENTRAL IOWA AND BACK ACROSS NORTHERN ILLINOIS. AHEAD OF THIS FRONT...AREA RADARS SHOW AN EXTENSIVE AREA OF RAINFALL MOVING ACROSS SE MICHIGAN SURGING NNE WITHIN THE WARM SECTOR. THE MAIN FORECAST CHALLENGE WILL BE SEVERE WEATHER POTENTIAL TONIGHT AS THE OCCLUDED FRONT PASSES ACROSS THE FORECAST AREA AND THEN WIND SPEEDS ON SUNDAY. THE 12Z MODELS INITIALIZED THE CENTRAL PLAINS SYSTEM WELL AND ARE IN GOOD AGREEMENT IN TIMING SURFACE AND UPPER LEVEL FEATURES. THE LATEST RUC AND MESO ETA CONTINUE TO SHOW FORCING AND DEEP MOISTURE ASSOCIATED WITH WARM CONVEYOR BELT PRECIP PUSHING ACROSS THE FORECAST AREA EARLY THIS EVENING...THEN EXITING TO THE EAST BETWEEN 22Z AND 01Z. LIGHTNING PLOT HAS SHOWN VERY FEW STRIKES ACROSS INDIANA AND MICHIGAN THIS AFTERNOON (WIDESPREAD CONVECTION ACROSS THE DEEP SOUTH MAY BE INTERSECTING SOME MOISTURE TRANSPORT NORTHWARD THUS DECREASING THE INSTABILITY). AM CONCERNED THAT SEVERE POTENTIAL MAY EXIST LATER THIS EVENING ALONG/AHEAD OF THE OCCLUDED FRONTAL BOUNDARY. THE 18Z MESO ETA SOLUTION SHOWS AN AREA OF HIGH 700-500MB OMEGA MOVING EAST ACROSS LOWER MICHIGAN BETWEEN 02Z AND 06Z TONIGHT. THIS AREA OF LIFT IS ALONG THE OCCLUDED FRONT AND AHEAD OF A POTENT SHORT WAVE THAT LIFTS INTO SOUTHERN LOWER MICHIGAN BY 06Z. MID LEVEL LAPSE RATES ARE PROGGED TO RISE TO 7 C/KM ALONG THIS FEATURE AS 500MB TEMPS COOL IN ADVANCE OF THE APPROACHING UPPER LOW AND MID LEVEL DRYING SHOULD ENHANCE CONVECTIVE POTENTIAL. ALTHOUGH 900MB COMPUTED LIS PER THE MESO ETA ARE ON THE ORDER 0 TO -2C...THE LATEST RUC MODEL SOUNDINGS INCREASE 900MB LIS TO -4C BY 06Z TONIGHT ACROSS THE MICHIGAN/OHIO BORDER. THE SPC SLIGHT RISK ACROSS THE AREA FOR THESE THUNDERSTORMS ALSO LOOKS WARRANTED GIVEN THE WIND FIELD (MESO ETA MODEL SOUNDINGS SHOW 50 TO 65 KT WINDS IN THE 2-5K FT LAYER...WITH 500MB WINDS OF 80KTS). NORNTHERN INDIANA 17Z PROFILER DATA CONFIRMS THESE STRONGER WINDS AS IT SHOWED 55KT AT 1000M. THUS IF CONVECTIVE DOWNDRAFTS ARE ABLE TO MIX SOME OF THESE STRONGER WINDS DOWN TO THE SURFACE...SOME OF THE THUNDERSTORMS WILL BECOME CAPABLE OF PRODUCING DAMAGING WIND GUSTS. AFTER A BRIEF PERIOD IN THE DRY SLOT LATE TONIGHT...DEEP WRAP AROUND MOISTURE PUSHES BACK INTO THE FORECAST AREA AROUND 12Z. DPVA AHEAD OF A SECONDARY SHORT WAVE ROUNDING THE BASE OF THE UPPER LOW SHOULD LEND ENOUGH FORCING TO CARRY SCT POPS. STRONGEST LOW LEVEL CAA SHOULD OCCUR ACROSS SE MICHIGAN BETWEEN 09Z AND 12Z. THIS MAY LEAD TO DAYTIME HIGHS OCCURRING RIGHT AROUND 6 AM. THROUGH THE AFTERNOON...CAA IS NOT ALL THAT IMPRESSIVE (WITH 850MB TEMPS PROGGED TO ONLY DROP TO AROUND 0 DEG C BY 00Z)...THUS DO NOT EXPECT A SIGNIFICANT TEMPERATURE DROP DURING THE AFTERNOON. WITH A FAIRLY TIGHT PRESSURE GRADIENT ACROSS THE GREAT LAKES AND UNDER COLD ADVECTION...SHOULD BE FAIRLY WINDY. ETA MODEL SOUNDINGS SHOW WINDS OF 35 TO 40 KNOTS WITHIN THE MIXED LAYER. FOR NOW I WILL HIGHLIGHT SOME HIGHER WIND GUSTS IN THE ZONES...BUT KEEP THINGS UNDER ADVISORY CRITERIA. LATER SHIFTS WILL HAVE TO MONITOR THIS. THE UPPER LEVEL TROUGH AND SURFACE LOW QUICKLY MOVE INTO CANADA DURING SUN AFTERNOON AND EVENING. LARGE SCALE SUBSIDENCE AND DRYING SHOULD SLOWLY BRING AN END TO THE SCATTERED SHOWERS FROM SOUTH TO NORTH DURING THE AFTERNOON AND EVENING. ETA MODEL SOUNDINGS WANT TO HOLD ON TO SOME LINGERING MOISTURE BELOW 800MB. WITH 900-700MB DIVERGENCE AND ANTICYCLONIC SURFACE FLOW DEVELOPING MONDAY NIGHT...I WILL AT LEAST HAVE SKIES BECOMING PARTLY CLOUDY. LOW LEVEL WARM AIR ADVECTION QUICKLY BEGINS MONDAY NIGHT...WARMING 850MB TEMPS TO +6C BY MONDAY AFTERNOON. RIDGING ALOFT ON MONDAY WILL PROVIDE WARM AND DRY CONDITIONS. EXTENDED DISCUSSION...JET MAXIMUMS ORIGINATING OUT OF THE NORTH PACIFIC WILL CONTINUE TO CARVE OUT A LONG WAVE TROUGH ACROSS THE CENTRAL US. WITH SEVERAL IMPULSES DEVELOPING SURFACE LOW PRESSURE SYSTEMS ACROSS THE CENTRAL AND EASTERN US...THIS WILL BE A RATHER ACTIVE WEEK. ATTENTION FIRST TURNS TO ANOTHER LOW PRESSURE SYSTEM TO MOVE INTO THE GREAT LAKES ON TUESDAY ORIGINATING OUT OF THE CENTRAL PLAINS. PREFER THE FASTER AVN/MRF/ETAXX SOLUTION WITH THE TRACK OF THE SURFACE LOW GIVEN THE LOWER AMPLITUDE OF THE 500MB TROUGH. SE MICHIGANS BEST SHOT OF PRECIP WILL THUS COME MONDAY NIGHT INTO EARLY TUESDAY VIA THE WARM CONVEYOR BELT GIVEN THIS SCENARIO. BEING WITHIN THE WARM SECTOR...THIS STILL LOOKS TO BE AN ALL RAIN EVENT. ALL THE MEDIUM RANGE MODELS ARE IN FAIRLY GOOD AGREEMENT IN THE DEEPENING OF THE LONG WAVE TROUGH OVER THE CENTRAL US ON WEDNESDAY WITH SURFACE CYCLOGENESIS OVER THE GULF COASTAL STATES. THE MEDIUM RANGE MODEL SOLUTIONS DIVERGE IN BOTH THEIR HANDLING OF THE UPPER TROUGH AND IN THE TRACK OF THE SURFACE LOW. THE ETAXX...GLOBAL AND UKMET SOLUTIONS BRING THE LOW NNE INTO OHIO ON THURSDAY...THEN LIFT THE LOW NE ACROSS THE EASTERN GREAT LAKES THURSDAY NIGHT INTO FRIDAY. THE MRF SOLUTION IS AN OUTLIER WITH DEVELOPMENT OF THE SURFACE LOW ALONG THE EAST COAST (WHICH WOULD SUGGEST A DRY FORECAST FOR SE MICHIGAN). GIVEN THE BETTER CONSENSUS OF THE ETAXX...GLOBAL AND UKMET...I WILL FOLLOW THEIR SOLUTIONS MORE CLOSELY. ENOUGH COLD AIR IS PROGGED ON THE BACK SIDE OF THE SURFACE LOW TO DEVELOP AN ACCUMULATING SNOWFALL EVENT. HOWEVER...PRECIP TYPE OVER SE MICHIGAN WILL DEPEND ON THE EXACT TRACK OF THE SURFACE LOW...WHICH AT THIS TIME IS TOO EARLY TO PIN DOWN. SO I WILL MENTION THE CHANCE OF BOTH RAIN AND SNOW IN THE ZONES. GIVEN THAT THE MRF SOLUTION SEEMS TOO FAR EAST WITH THE COLD AIR...I WILL CONTINUE WITH TEMPS A FEW DEGREES ABOVE FMR GUIDANCE. .DTX...GALE WARNING...TONIGHT AND SUNDAY...LAKES HURON AND ST CLAIR. CONSIDINE mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1124 AM EST SAT NOV 24 2001 MAIN CONCERN THIS FCST PACKAGE IS -SHRA/TSRA THIS AFTN AND TNGT. WV IMAGERY CONT TO SHOW GULF MSTR BEING DRAWN INTO THE UPR GRTLKS AND UPR MS VALLEY THIS AM BY THE DEEP LOW OVR SE NE. SFC ANLYS SHOWING A STATIONARY FNT STRETCHES ACRS E CNTRL ONT THRU NW LK SUPERIOR TO A LOW OVR SW IA. A CDFNT REACHES S FM THE IA LOW TO THE TX GULF CST AND IS CHANNELING LOW LVL MSTR INTO THE UPR GRTLKS AS WELL. RUC INDC MEAN SFC-500MB RH OF >90PCT OVR MOST OF UPR MS VALLEY AND THE UPR GRTLKS THIS AM. THE SFC LOW IS SLIGHTLY DEEPER THAN ANY OF MDLS INDC. HOWEVER...AVN WAS DOING THE BEST ON PROJECTING THE STRENGTH OF THIS LOW. AVN CONT TO BE A LTL DEEPER THAN ETA AND NGM IS WEAKER. THUS AVN IS PULLING THE UPR LVL LOW INTO W LK SUPERIOR OVRNGT...WHILE ETA IS MOVING IT INTO W U.P. ETA AND RUC ARE IN GOOD AGREEMENT IN THE POSITIONING AND STRENGTH OF SFC LOW BY 00Z. NGM CONT TO APPEAR TOO WEAK. THUS LOOKING FOR A COMPROMISE BTWN AVN AND ETA. A WEAK SHRTW WILL CYCLE THRU THE FCST AREA THIS AFTN. WHILE A STRONGER SHRTWV WILL ROTATE ARND THE IA LOW AND REACH INTO SRN WI BY 00Z SUN. CYC FLOW ARND THE ASSOC SFC LOW...AS IT SLIDES INTO SE MN...WILL KEEP THE WND OUT OF THE E AND SE DRAWING WRM MST AIR INTO FCST AREA THRU OUT THE AFTN. THIS WILL A FAIR AMNT OF 300K ISENTROPIC LIFT OVR THE FCST AREA THRU THE AFTN. THE ISENTROPIC ENERGY WILL FALL OFF BY THIS EVE WHILE 850-700MB Q-VEC CONVERGENCE AND SHRTWV ENERGY INCR ACRS FCST AREA. COND LOOK MOST FAVORABLE FOR THE GENERAL RA OCCURRING THIS AFTN TO CHG OVR TO MORE -SHRA AND POSSIBLE TSRA BY LATE AFTN AND EARLY EVE OVR FA. UNDER CLDY SKIES WITH -SHRA...XPC TEMPS TO CHG LTL AND REMAIN CLOSE TO GUIDANCE. THE LOW WILL SLIDE ACRS W U.P. INTO W LK SUPERIOR OVRNGT. SHRTWV ENERGY ASSOC WITH THIS WILL ALSO SWING THRU THE AREA. A DRY SLOT WILL SWING THRU THE AREA AFT MIDNIGHT. WITH WRAP ARND MSTR BRINGING MSTR BACK INTO THE AREA BY SR. Q-VEC CONVERGENCE AND ISENTROPIC LIFT WILL KEEP SHRA GOING INTO THE EARLY MORNING HRS SPCLLY OVR THE E CWA. CLD CVR WILL KEEP TEMPS FM FALLING OFF VERY MUCH OVRNGT. THE GRAD WILL WEAKEN AS THE LOW MOV INTO FCST AREA...AND WNDS WILL FALL OFF. .MQT...GALE WRNG LK SUPERIOR. DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 1005 AM CST SAT NOV 24 2001 WELL...MORNING SOUNDING DENOTES PLENTY OF KINEMATICS...BUT NOT MUCH THERMODYNAMICS...YET. THE SWEAT INDEX CAME IN AT 355...0-3 KM SRH OF 600 M2/S2...AND THE 0-6 STORM MOTION IS 34 KTS AND 30 DEGREES RIGHT OF THE AVERAGE WIND. THE K INDEX IS 34...BUT THE LIFTED INDEX IS 0....AND NO CAPE TO SPEAK OF. LATEST RUC AND MSAS LOOP HAS 1000-850 THETA E RIDGE WITH LEADING LINE OF SHRA/TSRA. CELL IN MONTGOMERY COUNTY BOWED OUT AND SHOWED 50 KTS AT 4000 FT...AND RADAR OPERATOR ISSUED A SVRBNA. MAIN LOW IS WRAPPED TIGHT OVER THE MO/NE BORDER...WITH AN ATTACHED COLD FRONT FROM LIT INTO ERN TX. FOR THE MOMENT...PRE-FRONTAL SQUALL LINE CONTINUES TO RACE ALONG ERN MS & WRN AL...WITH ADDITIONAL CONVECTION DEVELOPING IN THE WARM SECTOR EAST OF THE SQUALL LINE. THE PRIMARY THREATS WILL BE WIND DAMAGE FOR OUR CWA...BUT ISOLATED IN NATURE. IN ALABAMA...THE THREAT IS TORNADIC IN NATURE...AND THERE THREAT IS MUCH GREATER. LATER THIS AFTERNOON...AS THE FRONT MOVES THROUGH...THE INSTABILITY WILL INCREASE...AND THE THREAT FOR SEVERE WEATHER INCREASES... MAINLY FROM 20Z-02Z. FOR THE MEANTIME...PRESSURE GRADIENT...THE MAIN STORY WITH MOST OBSERVATIONS IN THE 20 TO 30 KT AND GUSTY RANGE. I'LL UPDATE THE ZONES TO ADDRESS WIND ISSUES. .BNA...TORNADO WATCH FOR COUNTIES ALONG AND WEST OF I-65 TIL 11 AM JDG tn TEXAS/OKLAHOMA PANHANDLES FORECAST DISCUSSION NATIONAL WEATHER SERVICE AMARILLO TX 1128 AM CST SAT NOV 24 2001 WINDS AT LIBERAL WERE SUSTAINED INTO THE WIND ADVISORY CATEGORY WITH STRONGER WINDS CURRENTLY SPREADING SOUTH INTO THE EASTERN HALF OF THE OKLAHOMA PANHANDLE AND NORTHEASTERN TEXAS PANHANDLE. THE 6 HOUR RUC FORECASTS WIND ADVISORY CRITERIA TO CONTINUE THROUGH THE REMAINDER OF THE AFTERNOON. THEREFORE...A WIND ADVISORY HAS BEEN PUT OUT FOR THE AFTERNOON AND MATCHES UP WELL WITH CWAS TO THE NORTH AND EAST. .AMA... TX...WIND ADVISORY FOR THIS AFTERNOON ZONES 004-005-010. OK...WIND ADVISORY FOR THIS AFTERNOON ZONES 002-003. CB tx AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE BLACKSBURG, VA 915 AM EST SAT NOV 24 2001 RADAR AND OBS SHOWING ENOUGH LIGHT RAIN AND DRIZZLE TO ENHANCE WORDING OF FCST THIS MORNING. MODELS KEEP GOOD UPSLOPE 8H WINDS THRU 18Z AND LAMP DATA STILL SHOWING CLOUDS HOLDING IN. ALSO WL TRIM MAX TEMPS BASED ON CLOUD COVER...LATEST RUC AND LAMP DATA. WL HAVE SOME CLEARING IN THE WRN COUNTIES BY THIS AFTN WITH MAXES STILL IN THE LOWER TO MID 60S. .RNK... NC...NONE. VA...NONE. WV...NONE. AMS va AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 110 AM EST SUN NOV 25 2001 SFC LOW PRES SITUATED INVOF MN/WI BDR WITH OCFNT/CDFNT COMBINATION EXTENDING TO ERN IN-ERN TN AT 04Z WHILE SFC DWPNTS UP TO THE 55-65 RANGE E OF APLCNS PA-GA AND PRES GRAD TIGHT ENOUGH TO BRING SOME G30 NR APLCNS. SATPIX HAVE PRETTY GOOD ENHANCEMENT THRU OH...MI AND INTO RGN NR WRN QUE BDR WITH ACTIVE 04Z HRLY LTG PLOT ROUGHLY ALG KTVC-KFWA LN. MOST OF THE MSTR ON 00Z KALY SOUNDING IS WI 4 THSD FT OF SFC...BUT ENOUGH TO PROMPT PTCHY DRZL. KPIT SOUNDING MORE MSTR RICH IN THE AC REACHES AND KIPT DID RECORD MEASURABLE PCPN...MEAN- WHILE KLWX SOUNDING WAS AT OR APCHG SATURATION BLO H7. RUC H3 ANLYS HAD 00Z RDG POSITION OVR CNTRL NY WITH JET ACRS ERN MT-OK-WRN TN-ERN WI/LK MI. PCPN MAY BE RELATIVELY SPARSE DURG THE MRNG...SAVE FOR SW CORNER OF DIST...OF COURSE IGNORING FOREMENTIONED DRZL AS SGFNT FORCING MAY WAIT TIL MIDDAY IN WRN DIST AND MID AFTN ACRS ERN DIST. CONVECTIVE POTENTIAL QUESTIONABLE PER WARM AIR INVOF H8. OTHER WILD CARD IS TRIPLE PT TRAJ...BUT LEANING AGAINST ATTM. FNT MAKES IT TO VCNTY OF FINGER LKS THIS EVNG AND TO THE E OF CT RIVER VLY BY SR MON...ALLOWING SW MID-LVL FLOW TO RECOVER TEMPS TO MILD AND THEN SOME LVLS...SPCLY SINCE POST-FNTL ENVIRONMENT DOES LTL TO LWR H10-H5 THKNSS. WHETHER SCDNRY FNTL SYSTEM WL HOLD TOGETHER ENOUGH TO GENERATE PCPN MON IS LOOKING LIKE A POOR PROSPECT. TUE NGT INTO WED LOOKS TO BE NEXT BEST SHOT AS AVN RUN TRACKS SFC LOW ACRS SRN FRINGE OF ONTARIO INTO SW QUE...BUT AN UP-THE-APLCNS LOW BRINGS THU THE CHC OF CONNECTING WITH SOME GULF MSTR...THEN SOME NW FLOW FRI TO ALLOW MORE SEASONABLE CONDS AND CHC OF LK EFFECT SHSN. MCKINLEY/KHH .ALY...NY ERN/VT EXTRM SRN/MA EXTRM WRN/CT NW...NONE. ny AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 928 AM MST SUN NOV 25 2001 THE CURRENT FORECAST IS ON TRACK. SOME WARM ADVECTION SNOWS WERE MOVING THROUGH THE CWA AHEAD OF THE MAIN UPPER TROUGH OVER UT/AZ. ACCUMULATIONS WILL BE LIGHT WITH THIS BAND...MAINLY 1-2 INCHES OR LESS. A MODEST CONCERN TODAY IS THE CHANCE FOR FOG AND FREEZING DRIZZLE...ESPECIALLY GIVEN THE CLOUD TOP TEMPERATURES OF -10 TO -15C OVER PARTS OF THE CWA. A MORNING UPDATE MAY BE NEEDED FOR THIS... OTHERWISE NO MAJOR CHANGES TO THE ZONES ARE EXPECTED. DEEP EASTERLY UPSLOPE FLOW WILL DEVELOP TODAY IN ADVANCE OF THE APPROACHING STORM...WHICH SHOULD SETUP THE EASTERN BLACK HILLS AS A FAVORABLE LOCATION FOR ENHANCED SNOWFALL TONIGHT. HOWEVER...THE MAIN ACTION SHOULD STILL OCCUR OVER SOUTH-CENTRAL SD WHERE LOW- LEVEL CONVERGENCE AND FRONTOGENESIS WILL BE MAXIMIZED. THE 12Z AVN/RUC STILL APPEAR TO HAVE THE BEST HANDLE ON THE UPCOMING STORM...AND THUS THESE MODELS WILL BE FOLLOWED FOR THE AFTERNOON ZONE PACKAGE. .UNR...WINT STM WATCH TONIGHT AND MONDAY EAST OF THE BLKHLS. MJB sd SOUTH CENTRAL AND SOUTHEAST COLORADO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO COLORADO 131 PM MST SUN NOV 25 2001 ACTIVE WX PATTERN TO CONTINUE OVER THE NEXT 5-7 DAYS. CURRENTLY/MODELS: LATEST WATER VAPOR IMAGERY/RUC 400MB ANALYSIS LOOPS SHOWED ULJ BEGINNING TO ENTER EXTREME SWRN CO/NWRN NM. BAROCLINIC LEAF CLOUD STRUCTURE DEVELOPING INTO COMMA CLOUD OVER WRN CO/NERN UT PER IR SATELLITE IMAGERY. DEFORMATION ZONE OVER SWRN CO MTNS/SAN LUIS VALLEY HAS HELPED PRODUCED HVYSNW BURSTS. 4-6 INCHES OF SNOW HAVE FALLEN IN PORTIONS OF SAN LUIS VALLEY. HVYSNW CONTINUES ALONG THE S/W FACING SLOPES OF ERN SAN JUAN MTNS. SO FAR...12+ INCHES AROUND THE WOLF CREEK AREA. MID LEVEL LAPSE RATES RATHER UNSTABLE WITH A FEW CLOUD TO GROUND LIGHTNING STRIKES IN THE VICINITY OF THE LFQ OF ULJ NEAR SWRN CO. NOTED MID/UPPER LEVEL "DRY" SLOT HAS ENTERED SWRN CO...BUT SOME CONVECTIVE POPPING IN SWRN CO MTNS. POTENTIAL HVYSNW SHOULD START TO SHUTDOWN FOR SWRN CO MTNS BY EARLY THIS EVE. PRECIP HAVING A TOUGH TIME PUSHING OFF THE SERN MTNS THANKS TO MOD DOWNSLOPE FLOW. AT THE SFC...MOD PRESSURE FALLS IN WRN CO AND WRN KS. AT 18Z...LOWEST PRESSURE WAS NEAR KLHX/KSPD DUE TO WARMER TEMPS... NEAR 70F IN BACA CO. KIND OF A KLHX LOW FORMATION. STREAMLINES ACTUALLY SHOW POTENTIAL CENTROID DEVELOPMENT JUST SE OF KLIC. STRONG PRESSURE RISES BEGINNING TO MOVE INTO SWRN CO FROM UT/AZ PER MSAS DATA. APPEARS LEE SIDE CYCLOGENESIS IS ABOUT TO GET UNDERWAY...OR "LEAP" FROM WRN CO. MODELS ARE STILL FAIRLY CONGRUENT WITH SYNOPTIC SCALE PATTERN THROUGH 48HRS. PLAN TO STICK WITH THE ETA/MESO-ETA DUE TO BETTER TERRAIN RESOLUTION. TNGT: 80-110KT ULJ PROGGED TO RACE ACROSS NRN NM INTO EXTREME SERN CO THIS EVE WITH DEEP CYCLOGENESIS OVER E CNTRL CO THIS EVE...THEN MIGRATES INTO CNTRL PLAINS OVRNGT. ASSOCIATED STRONG SHORTWAVE FCST OVER EXTREME SERN CO...WHICH PUTS SE CO IN A TROUBLESOME SPOT. THIS WILL BE NEAR THE CUSP OF COMMA CLOUD STRUCTURE (NEAR DEFORMATION ZONE) BETWEEN 00Z-06Z. DEFORMATION ZONE SHSN BURSTS ALREADY OCCURRING OVER SERN CO MTNS AND REDEVELOPING OVER SWRN CO MTNS. ETA HAS A FAIRLY HEALTHY IMPLIED VERTICAL ASCENT AREA OVER SERN CO LATE THIS AFTN/EARLY EVENING THEN SHIFTS IT ALONG AND N OF PALMER DIVIDE THIS EVE PER 700-300MB DIV Q. ALSO...STRENGTHENING SFC WINDS WILL PICKUP OUT OF THE N-NW THIS EVE. MID LEVEL LAPSE RATES REMAIN STEEP WITH 7-8 C/KM OVERHEAD. WITH ALL THIS IN MIND...IT COULD SUPPORT A PRETTY GOOD POTENTIAL FOR SNOW BURSTS(+SHSN) IN AND NEAR SERN CO MTNS AND THE VICINITY OF THE PALMER DIVIDE THIS EVE. ELSEWHERE...THE OROGRAPHIC ASCENT SNOW MACHINE SHOULD SHUTDOWN FOR THE SW MTNS THIS EVE AND SWITCH TO THE CNTRL MTNS. DEEP SUBSIDENCE MOVES INTO CWA AFTER 06Z. CURRENT PLANS ARE TO DROP ADVISORY FOR SAN LUIS VALLEY AND CONTINUE SWRN CO MTN WARNING/ADVISORY THIS EVE AND CNTRL MTNS TNGT. WILL GO WITH SHSN "LIKELY" SE MTNS THIS EVE WITH ACCUMULATIONS 1-4 INCHES. FOR THE SERN CO PLAINS...AS SYSTEM "BOMBS OUT" ACROSS WRN KS...PRESSURE GRADIENT WINDS WILL PICK UP. ALL INGREDIENTS FOR MTN WAVE DEVELOPMENT NOT REALLY JUXTAPOSED...HOWEVER PRESSURE GRADIENT AND ANY PRECIP(VIRGA BOMBS) COULD "GOOSE" WIND GUSTS TO NEAR MARGINAL HIGH WIND WARNING GUST CRITERION. PLAN TO STICK WITH STRONGLY WORDED WIND FORECAST IN ZFP. ETA/MESO-ETA NOT PRINTING MUCH QPF...IF AT ALL...FOR SERN CO. SYSTEM'S COMMA HEAD WILL FLIRT WITH KIOWA/CROWLEY/EL PASO COUNTIES TNGT. WILL CHECK RADAR/METAR/RUC TRENDS FOR FINAL DECISION. MAY NEED TO TWEAK SAN LUIS VALLEY TEMPS DOWN A LITTLE TNGT WITH FRESH SNOW COVER. CLOUDS AND WINDS WILL DETERMINE HOW FAR THE TEMP DROPS...THOUGH. MON: CYCLONE MIGRATES INTO THE UPPER MS RVR VALLEY BY MON AFTN. STILL MOD LOWER TROP WIND FIELD MUCH OF THE DAY AND DOWNSLOPE FLOW FOR SERN CO MTNS/PLAINS...WITH SOME FAVORED OROGRAPHIC ASCENT FOR CNTRL MTNS. PLAN TO STICK NEAR MESO-ETA MAX TEMPS FOR MON. MON NGT-TUE: STILL LOOKS LIKE A "CHUNK" OF MODIFIED ARCTIC AIR MASS WILL "OOZE" DOWN THE HIGH PLAINS INTO THE CNTRL ROCKIES FROM N CNTRL US/CAN LATE MON NGT-TUE. SYNOPTIC PATTERN BECOMES COMPLEX... THOUGH. ULJ TRACK REMAINS ACROSS GREAT BASIN INTO DEEP DESERT SW THROUGH SRN PLAINS. ETA HAS WEAK TROUGHNESS OVER CNTRL ROCKIES... WHILE AVN TRIES TO ACTUALLY CLOSE OFF A LOW OVER NERN CO TUE AFTN. NOT SURE IF I AM READY TO BUY INTO THIS SOLUTION. 48-60HR ETA SHOWING LITTLE IN THE WAY OF POTENTIAL VERTICAL ASCENT MOTION ON TUE. COLDER AIR MASS TO TAKEOVER MUCH OF CO WITH 700MB TEMPS PROGGED TO BE -12C TO -16C. CANNOT DISCERN ANY SIGNIFICANT OROGRAPHIC ASCENT EVENT...YET. WITH SUCH COLD TEMPS...ANY LITTLE ASCENT COULD SQUEEZE OUT SOME LIGHT SNOW/FLURRIES. CONFLICT BETWEEN FWC AND MAV MOS. FWC ABOUT 10-15 DEGS WARMER THAN MAV FOR TUE. IF LOW CLOUDS/ELY LOW LEVEL FLOW DEVELOPS ALONG AND E I-25...WOULD GIVE THE MAV THE NOD...BUT MAV NOT FORECASTING THESE CONDITIONS AND WILL PROBABLY GET A CORRECT TEMP FORECAST FOR ALL THE WRONG REASONS. MES0- ETA SHOWING 850-700MB LEVELS/LAYER HAVING RH OF 70% OR GREATER. IF THERE ARE ANY BREAKS IN THE CLOUDS TUE AM...THE COMBINATION OF SUN AND COLD AIR SHOULD PROMOTE A REDEVELOPMENT OF CLOUDS. TOUGH CALL THIS FAR OUT AND PLAN TO STICK WITH CURRENT FORECAST OF LOW POPS. WED: PATTERN STARTS TO CHANGE WITH SHORTWAVES MOVING E THROUGH CNTRL US AND THE APPROACH OF THE NEXT PACIFIC SYSTEM. TEMPS MAY TRY TO RECOVERY AS THE LOW LEVEL COLD AIR MASS RECEDES FROM CO AND LEE SIDE TROUGH DEVELOPS. CURRENT FORECAST LOOKS GOOD. THU-SUN: UNSETTLED WEATHER PATTERN FOR THE REMAINDER OF THE WEEK INTO NEXT WEEKEND. NEXT SYSTEM..."OPEN WAVE"...PROGGED FOR THU NGT- FRI AS IT RACES THROUGH WLY FLOW. THIS WOULD SUPPORT THE POTENTIAL FOR MORE SNOWFALL ALONG THE CONTDVD AND WWD. NOT MUCH HOPE FOR SERN CO MTNS/PLAINS. ALSO...TEMPS SHOULD BE MODERATING THU INTO THE WEEKEND. NOT MUCH IN THE WAY OF ANY CHANGES. .PUB...WINTER STORM WARNING...61...THIS EVE SNOW/BLOWING SNOW ADVISORY...60...THIS EVE SNOW/BLOWING SNOW ADVISORY...58/59...TNGT. METZE co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 140 PM MST SUN NOV 25 2001 FORECAST CONCERNS ARE SNOW AMOUNTS/WINDS AND DEALING WITH THE COLDEST AIR OF THE WINTER SEASON. STRONG CYCLOGENESIS WILL OCCUR EAST OF THE ROCKIES EARLY THIS EVENING AS AN INTENSE LOW PRESSURE AREA MOVES FROM SOUTHEAST COLORADO NORTHEAST THROUGH THE NORTHWEST TRI-STATE AREA AND INTO SOUTH CENTRAL NEBRASKA BY MORNING. THE AVN IS THE MOST CONSISTENT WHEN COMPARED TO ITS PREVIOUS RUN AS WELL AS THE LATEST RUCII FROM FSL AT 6Z THIS EVENING WITH REGARD TO THE POSITION OF THE SURFACE LOW. GIVEN THE TRACK OF THE AVN...INSTABILITY PROGS SUGGEST SOME ELEVATED TRW EARLY TONIGHT OVER THE NORTHERN HALF OF THE CWA...PRIMARILY NORTH OF INTERSTATE 70. DRYSLOT WORKS INTO THE SOUTHERN PORTION OF THE AREA KEEPING PRECIP CHANCES ON THE LOW SIDE. OTHERWISE...EXPECT SOME SNOW OVER THE NORTHWEST CWA BY 6Z...SPREADING SOUTH AND WEST ON THE BACKSIDE OF THE INTENSIFYING LOW. EXPECT VERY WINDY CONDITIONS ON THE BACK SIDE OF THE LOW WITH WARMER TEMPS OVER THE EAST AND SOUTH AND COLDER TEMPS NORTH AND WEST. AS FAR AS ANY ACCUMULATIONS...MORE CONFIDENCE IN COLDER AIR WITH THIS SYSTEM THAN THE LAST...WILL MENTION 1-3 INCHES OVER NORTHERN YUMA COUNTY WITH AN INCH OR LESS OVER ALL BUT THE FAR SOUTHERN AND EASTERN CWA WHERE NO ACCUMULATION IS EXPECTED. SURFACE LOW CONTINUES NORTHEAST ON MONDAY WITH SNOWFALL SPREADING FROM SOUTHWEST TO NORTHEAST. IT WILL BE VERY WINDY AND MUCH COLDER. WILL GO CHANCE POPS WITH NO ADDITIONAL ACCUMULATION. SUBSIDENCE AND SURFACE HIGH NOSE INTO THE AREA BRINGING AN END TO THE PRECIP BUT ALLOWING VERY COLD AIR TO CONTINUE POURING IN. ELONGATED TROUGH OVER THE CENTRAL US KEEPING INFLUENCE OF COLD HIGH PRESSURE OVER THE AREA THROUGH EARLY WEDNESDAY BEFORE SURFACE TROUGH DEVELOPS ALONG THE FRONT RANGE. LESS COLD WOULD BE THE BEST TERM FOR WEDNESDAYS HIGHS. EXTENDED...LESS COLD CONTINUES THURSDAY AND EARLY FRIDAY. DISTURBANCE TO MOVE THROUGH FRIDAY CONTINUES TO SHOW SIGNS OF MATERIALIZING BASED ON COMPARISON OF PREVIOUS AND CURRENT RUNS OF MRF AND ECMWF. THEN COLD AIR AGAIN FOR FRIDAY NIGHT AND SATURDAY. COULD SEE SOME PRECIP FRIDAY LATE. SUNDAY LOOKS LIKE AN AVERAGE DAY RIGHT NOW. TEMPS NEAR NORMAL ON THURSDAY AND FRIDAY...THEN DROP A BIT BELOW NORMAL FOR SATURDAY AND BACK TO NEAR NORMAL FOR SUNDAY. .GLD...WIND ADVISORY TONIGHT WEST OF A LINE FROM RED WILLOW COUNTY NEBRASKA TO GOVE COUNTY KANSAS. WIND ADVISORY MONDAY FOR THE ENTIRE COUNTY WARNING AREA. THEDE/DORN ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 450 PM EST SUN NOV 25 2001 12Z RAOBS/LATEST WV LOOP AND RUC ANAL SHOW AN ACTIVE UPR FLOW WITH SVRL POTENT SHRTWVS EMBEDDED WITHIN GENERAL WSW FLOW ALF BTWN MEAN TROF OVR W AND HIER AMPLITUDE RDG OFF E COAST. SHRTWV THAT BROUGHT YDAYS RA NOW MOVG INTO SE ONTARIO AND WEAKENING AS SYS RAMS INTO PERSISTENT ERN RDG AND HIEST H3 WNDS NOW TO E. OCCLUDED SFC LO MOVG INTO SE ONTARIO WITH CYC FLOW IN ITS WAKE OVR CWA. PCPN SHIELD WITHIN BACKWASH MSTR HAS DIMINISHED CONSIDERABLY...BUT SOME SPRINKLES NOTED ON 88D OVR THE ECNTRL ZNS. CYC FLOW AND LO CLD IS WDSPRD ARND SYS...AND 12Z INL SDNG SHOWS VERY MOIST MIXED LYR BLO INVRN AT H85. ISOBARS TAKE ON A MORE NEUTRAL TO ACYC ORIENTATION ACRS SCNTRL CAN INTO THE PLAINS ON SRN FLANK OF SPRAWLING ARCTIC HI ACRS NW CAN AND UNDER UPR RDGING BTWN GRT LKS SHRTWV AND NEXT SHRTWV IN CNTRL ROCKIES. SHALLOW COLD AIR ADVCTG S IN CROSS ISOBARIC NNELY FLOW ACRS SCNTRL CAN INTO NRN PLAINS IN ADVANCE OF THIS HI. 12Z CYQD SDNG INDICATES EVEN LWR INVRN THAN AT INL WITH HGT JUST 50MB ABV SFC. BIS SDNG SHOWS VERY DRY MID LVL AIR UNDER UPR RDG WITH SUBSIDENCE INVRN AT H75...ANOTHER LWR INVRN AT H9 REFLECTS ARRIVAL OF SHALLOW COLD AIR THERE THIS MRNG. NXT SYS IN ROCKIES MORE POTENT THAN THE DEPARTING GRT LKS SHRTWV. 150KT H3 JET MAX ANALYZD DIGGING INTO SCNTRL CA AT 12Z CAUSED 00Z TO 12Z H3 HGT FALLS UP TO 250M ACRS THE SRN ROCKIES...AND POCKET OF H5 TEMPS BLO -30C ADVCTG INTO SHRTWV TROF. 12Z ETA/AVN ANAL APPEAR TO HAVE GOOD HANDLE ON LOCATION OF UPR JET. ALTHOUGH PW ACRS PLAINS IN ADVANCE OF SYS LESS THAN 0.50 INCHES AS RETURN FLOW FM GLFMEX HAS NOT HAD A CHC TO GET SETUP AGAIN IN WAKE OF DEPARTING SHRTWV...HI CLD AHD OF INCOMING SHRTWV STREAMING EWD THRU PLAINS UPR RDG AXIS. FCST CONCERNS ARE MANY THIS PACKAGE AND REVOLVE ARND APRCHG ROCKIES STORM SYS AND GOING HEADLINES WITH PSBL EXPANSION OF WATCH FARTHER E. MODELS ARE RELATIVELY CONSISTENT IN MASS FIELDS...BUT THERE ARE SOME DIFFERENCES AS DISCUSSED BLO. SO USED A MODEL MIX FOR RATHER COMPLICATED FCST. RELATIVELY QUIET WX SHUD PREVAIL TNGT AS UPR RDG/DRY AIR ALF IN PLAINS MOVE OVHD WHILE LLVL FLOW BCMS MORE NEUTRAL/ACYC AS SHALLOW COLD WEDGE POURS SE IN WAKE OF DEPARTING LO PRES SKIRTING QUICKLY TOWARD QUEBEC. FCST ETA SDNGS CONT TO EXHIBIT QUITE A BIT OF MSTR TRAPPED BLO LO INVRN ARND 3-4K FT. ETA SHOWS TEMPS WITHIN MOIST LYR REACHING AS LOW AS -12C AT CMX (LO ENUF FOR ICE NUCLEATION)...BUT ONLY -8C AT MQT AND IMT (NOT LO ENUF). AS LLVL WND FIELD VEERS FM NW TO NNE OVRNGT...XPCT LIKELIHOOD OF FZDZ MAINLY OVR HIER TERRAIN IN BARAGA-MQT ZNS AFTR MIDNGT...WHILE DZ BCMS MORE FLURRIES OVR THE FAR W ESPECIALLY WITH LOSS OF UPSLOPING THERE. CONFIDENCE IN FCST OF FZDZ HIER DUE TO OBSERVATION OF THIS PCPN TYPE ATTM IN CNTRL ONTARIO... AND XPCTD LONG FETCH/MOISTENING ACRS LK SUP AND UPSLOPE. LO INVRN AND NEUTRAL/ACYC FLOW ARE NOT FVRBL FOR LES OVR WRN ZNS EVEN THOUGH LK-INVRN HGT DELTA-T NR 17C. PREFER ETA BLYR FCST TEMPS FOR MINS OVR FWC GUIDANCE...SINCE MOS USUALLY POOR DOWNWND OF LK AND WITH SHALLOW COLD AIR. AS UPR JET MAX ROUNDS BASE OF UPR TROF LATE TNGT...MODELS SHOW SHRTWV LIFTING NE TOWARD GRT LKS WITH TIGHTENING PRES GRADIENT/ INCRSG ELY FLOW AS HI PRES BLDS TO THE N. BY 00Z TUE...SHRTWV/SFC LO PRES PROGGED TO REACH IA. MODELS SHOW AXIS OF PW CLOSE TO 0.75 INCH SURGING NWD FM GLF AHD OF SYS INTO WI TOWARD 00Z. AVN DEPICTS UPR DVGC/ QVECTOR CNVGC IN LEFT EXIT OF H3 JET MAX ARRIVING OVR WRN ZNS DURG THE AFTN...WITH PCPN BRKG OUT THEN. ALTHOUGH UPR DVGC AND H85-7 FRONTOGEN IN CROSS ISOBARIC LLVL FLOW BTWN APRCHG SFC LO/HI MAY ENHANCE UVV BY LATE IN DAY...PREFER LWR AVN QPF (ETA FCSTS ALMOST 0.50 INCH AT IWD/AVN CLOSER TO 0.25 INCH) AS ETA FCST SDNGS SHOW PERSISTENT DRY WEDGE BTWN 5K AND 8K FEET AND DRY ADVCTN (DESPITE LIFT) ON 285K TO 295K SFCS WITH JUST 2G/KG AVBL NR H7-75. PARADOXICALLY...AVN SHOWS MORE MOIST ADVCTN EARLIER THAN ETA...BUT THINK ETA CLOSER TO REALITY WITH MSTR PROFILE GIVEN DRYNESS OF ANTECEDENT AIRMASS AND CURRENT LACK OF ANY GULF CONNECTION. SHALLOWNESS OF COLDER AIR TO THE S AND E SUG WEAKER OVRRNG/ MOISTENING. SO FCST POPS RANGE FM CATEGORICAL OVR THE W TO UNDER 30 PCT OVR THE E (DRY THERE ALL DAY). UP TO 3 INCHES/2 INCHES SN AT IWD/CMX DURG AFTN. ALTHOUGH GROSS MODEL OUTPUT SUGS LK ENHANCEMENT OVR KEWEENAW WITH H85 TEMPS ARND -6C LATE IN DAY (DELTA-T 11C)... FEEL SHARP LO INVRN AND DIRECTIONAL SHEAR THRU INVRN LVL WL MITIGATE THIS IMPACT. GIVEN CROSS ISOBARIC FLOW AND FRONTOGEN...PREFER LWR FWC GUIDANCE MAX TEMPS WITH LTL DIURNAL INCRS IN TEMP UNDER GRAY SKIES. AS UPR SHRTWV CONTS TO GRIND NE INTO COLD HI PRES BLDG INTO ONTARIO MON NGT INTO TUE...SFC LO WEAKENS AND ELONGATES EWD INTO CNTRL LKS ON SRN FLANK OF LLVL ARCTIC AIR OOZING SWD. ETA SHOWS SATURATION OCCURRING OVR CWA TMRW NGT NW TO SE AS PERSISTENT ELY FLOW OVRRNS COLD AIR/MSTR TO THE S GETS ENTRAINED INTO SYS AND CCB STRUCTURE DVLPS IN STRG ELY FLOW N OF H7 LO TRACK. ETA SHOWS 3G/KG AVBL IN MOIST AXIS LIFTING NWD AHD OF STORM SYS BTWN 06Z AND 18Z TUE...WHEN HEAVIEST SN SHUD FALL ACRS NW ZNS WITH MSTR CNVGC/UPR DVGC IN LEFT EXIT OF JET/ H85-3 QVECTOR CNVGC/H85-7 FRONTOGEN ALL IN PHASE AND UPSLOPE FLOW WL EXACERBATE PCPN RATES. INCRSG PRES GRADIENT AND ENHANCED AGEOSTROPHIC CROSS ISOBARIC FLOW SUG A GOOD BET FOR HI WNDS (ETA SHOWS WND SPEEDS OVR 30 MPH NR THE SFC)...SO HAVE ADDED WINDY WORDING TO ALL ZNS EXPOSED TO LK AND HIT BLSN HARDER. WL HIT SN ACCUMS HARDEST OVR KEWEENAW AND BARAGA/MQT...WHERE ENELY FLOW MAY ALSO ADD LK ENHANCEMENT EVEN THOUGH SAME LIMITING FACTORS FOR THIS IMPACT REMAIN. GIVEN AVAILABILITY OF 3G/KG (6 INCHES/12 HRS) AND JET/ FRONTOGEN AND UPSLOPE/PSBL LK ENHANCEMENTS...WL GO UP TO 10 INCHES HERE THIS 12HR PD. OVR THE S...IT APPEARS COLD AIR WL BE TOO SHALLOW TO KEEP PCPN FM BEING ALL SN AND PREVENT DEEP SATURATION FOR TOO LONG. HAVE OPTED TO ADD ALGER/LUCE INTO WINTER STORM WATCH PER NCEP MDT RISK OF 6 INCHES OR MORE AND AS INCRSGLY SHEARED H5 VORT MAX TRACKS TO THE S AND MAGNITUDE OF CROSS ISOBARIC FLOW/CAD SHUD KEEP LLVLS COLD ENUF FOR ALL SN. WRNG CRITERIA HERE WL BE MORE MARGINAL (XPCT ARND 8 INCHES/12 HRS)...AND WATCH MAY END UP GOING TO ADVY... BUT BLSN POTENTIAL SGNFT EVEN HERE. AFTR 18Z...INCREASINGLY ELONGATED SYS LOSES MSTR CONNECTION AND BEST UPR DYNAMICS...SO ALL THAT REMAINS IS DECAYING CCB WITH SHEARED H5 SHRTWV TO THE S INTO WED. 00Z OPERATIONAL EXTENDED MODELS PROMISE A RATHER ACTIVE PATTERN FOR LATE WEEK INTO NXT WEEKEND AS A SERIES OF STRG DISTURBANCES RIDING INTO THE W COAST AMPLIFY IN THE MEAN TROF ACRS CNTRL NAMERICA CAUSED BY THE BUILD UP OF COLD AIR UNDER MAMMOTH ARCTIC HI PRES IN CNTRL CAN. THIS SCENARIO SUPPORTED BY PRESENCE OF SVRL IMPRESSIVE LOOKING DISTURBANCES OVR THE GLFAK AND ERN PAC PER WV IMAGERY. ONE SHRTWV IN ERN PAC LOOKS STRGR THAN FCST...SO HAVE DOUBTS THAT MODELS HAVE TRENDED WEAKER FOR THIS SHRTWV PROGGED TO REACH NW LKS IN THU-FRI TIMEFRAME. TIMING OF THESE INDIVIDUAL SHRTWVS IN FAST MOVG FLOW WL BE UNCERTAIN AT BEST...AND HAVE LTL CONFIDENCE IN TRYING TO PINPOINT A DRY DAY AND BELIEVING THE SLIM MAJORITY OF THE OPERATIONAL MODELS AND CAN ENSEMBLE MEMBERS THAT SUG FRI WL BE DRY. WL CARRY A CHC OF SN EACH DAY WITH RECENT DRY WX AND RECORD WARMTH OVER. COORDINATED WITH APX/GRB/DLH. .MQT...WINTER STORM WATCH LATE MON AFTN AND TUE MIZ002-009. WINTER STORM WATCH MON NIGHT AND TUE MIZ001-003>005-010>011. WINTER STORM WATCH LATE MON NIGHT AND TUE MIZ006-007. KC mi AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 1251 PM MST SUN NOV 25 2001 THE EVOLUTION OF THE UPCOMING WINTER STORM IS BECOMING CLEARER THIS AFTERNOON PER THE SATELLITE IMAGES AND RUC2 PROGS. THE AVN HAS THE BEST HANDLE ON THE SITUATION...BUT THE ETA HAS TRENDED MORE TOWARD THE AVN...AND IS NOT TOO FAR OFF. MOREOVER...THE MM5 AND CANADIAN MODELS ALSO LEND SUPPORT TO THE AVN/RUC SCENERIO. FOR TONIGHT...STRONG WARM ADVECTION...FRONTOGENESIS...AND JET STREAK DYNAMICS WILL LEAD TO A LARGE ZONE OF LIFT ACROSS THE CWFA...AND ESPECIALLY OVER SOUTHERN SD. DEEP...EAST UPSLOPE FLOW WILL FURTHER ENHANCE LIFT OVER THE EASTERN BLACK HILLS. THE AVN SUGGESTS THE LOW WILL BE SLOWER MOVING THAN PREVIOUSLY THOUGHT...WITH WRAPAROUND LIFT AND MOISTURE PERSISTING THROUGH MOST OF MONDAY. QPF FROM THE AVN SUPPORTS 24-HOUR SNOWFALL OF 8 TO 14 INCHES OVER SOUTH-CENTRAL SD ...WITH 4 TO 7 INCHES OVER THE BLACK HILLS...FOOTHILLS...AND MEADE/ ZIEBACH COUNTIES...AND 2 TO 5 INCHES OVER NORTHEASTERN WY THROUGH NORTHWESTERN SD. NORTH TO NORTHEAST WINDS OF 15 TO 35 MPH SHOULD DEVELOP OVER MUCH OF THE SD PLAINS EAST OF THE BLACK HILLS TONIGHT AND MONDAY. ACCORDINGLY...WINTER STORM WARNINGS AND WINTER WEATHER ADVISORIES HAVE BEEN ISSUED...EXCEPT FOR FAR NORTHWESTERN SD AND NORTHEASTERN WY. SOME LIGHT SNOW WILL LINGER INTO MONDAY NIGHT AND TUESDAY...BUT SNOWFALL SHOULD GENERALLY BE LIGHT. UPSLOPE FLOW FOR THE NORTHERN HILLS IS NOT EXPECTED TO MATERIALIZE WITH THIS SYSTEM. ALSO...IT IS POSSIBLE THAT ADVISORIES MAY BE NEEDED INTO MONDAY EVENING...BUT THIS CAN BE ADDRESSED LATER. FINALLY...MOS MINS ARE TOO LOW FOR TONIGHT GIVEN THE SURFACE DEWPOINTS...AND THIS ALSO CARRIES OVER INTO THE MAXES FOR MONDAY. IN THE EXTENDED...GENERALLY WESTERLY FLOW WILL BRING A MODERATION IN TEMPERATURES...BUT THERE WILL ALSO BE CONSIDERABLE WAVES...THUS ONE CANNOT RULE OUT A CHANCE OF SNOW FOR MOST OF THE PERIOD. .UNR...WINT STM WRNG FAR SWRN-WCNTRL-SCNTRL SD. .WINT WX ADVY BLKHLS-ERN/NRN FOOTHILLS-MEADE-ZIEBACH. MJB sd