337 FXUS63 KDVN 190430 AFDDVN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 1130 PM CDT MON MAR 18 2013 .SYNOPSIS... ISSUED AT 331 PM CDT MON MAR 18 2013 AT 20Z...A STRONG COLD FRONT EXTENDED SOUTH FROM LOW PRESSURE OVER NORTHERN MN SOUTHWARD THROUGH THE FORECAST AREA ROUGHLY ALONG THE MS RIVER. THIS FRONT WAS ASSOCIATED WITH A STRONG UPPER LEVEL SHORTWAVE PASSING THROUGH MN AND IA THIS AFTERNOON. BEHIND THE FRONT...W-NW WINDS WERE SUSTAINED FROM 20 TO 30 MPH WITH GUSTS TO AROUND 40 MPH IN EAST CENTRAL IA. THIS WAS CAUSING SOME BLOWING AND DRIFTING OF THE MORNING SNOWFALL THAT TOTALED 2-3...AND LOCALLY AS HIGH AS 4 INCHES. NORTH OF HIGHWAY 30. TEMPERATURES WERE FALLING INTO THE MID AND UPPER 20S BEHIND THE FRONT WHILE OUT AHEAD READINGS WERE IN THE 30S...AND EVEN 40S IN THE FAR SOUTH WERE SUNSHINE WAS BREAKING THROUGH THE STATUS. WHILE THE BULK OF THE SNOW HAD EXITED TO THE EAST INTO NORTH CENTRAL IL...SOME PATCHY DRIZZLE OR FREEZING DRIZZLE WAS OBSERVED LOCALLY...AND ALSO INDICATED BY RADAR WEAK RETURNS IMMEDIATELY BEHIND THE COLD FRONT. && .UPDATE... ISSUED AT 855 PM CD /ISSUED 858 PM CDT MON MAR 18 2013/ T MON MAR 18 2013 CLOUDS HAVE RAPIDLY DECREASED IN STRONG SUBSIDENCE OVER IOWA EARLY THIS EVENING...AND THIS TREND SHOULD CONTINUE INTO ILLINOIS OVER THE NEXT FEW HOURS. FLURRIES AND SOME NARROW SNOW SHOWER STREAKS CONTINUE IN THE CLOUDY AREAS...BUT THIS ACTIVITY TOO IS DECREASING. I HAVE ADDED BLOWING SNOW TO THE FAR NORTH...WHERE SOME REPORTS OF SLICK ICE FORMATION FROM DRIFTING SNOW IS BEING REPORTED. TEMPERATURES ARE DROPPING FAST...ALREADY IN THE TEENS TO LOWER 20S OVER THE CENTRAL AND NORTHERN CWA. ALL TOLD...LOWS IN THE SINGLE DIGITS STILL SEEM ON TRACK FOR THE NORTH 1/3. ERVIN && .SHORT TERM...(THIS EVENING THROUGH TUESDAY) ISSUED AT 331 PM CDT MON MAR 18 2013 UNSEASONABLY COLD TEMPERATURES AND STRONG WINDS ARE THE IMMEDIATE FORECAST CONCERNS. SURFACE OBSERVATIONS WERE INDICATING AREAS OF SUSTAINED WINDS OF NEAR 30 MPH AT TIMES WITH GUSTS APPROACHING 45 MPH IN THE PUSH OF STRONG SUBSIDENCE AND COLD AIR ADVECTION OVER EAST CENTRAL IA BACK INTO NORTH CENTRAL IA. WHILE POCKETS OF THESE ADVISORY LEVEL CONDITIONS WILL LIKELY CONTINUE...CURRENTLY DO NOT EXPECT WIDESPREAD SUSTAINED SPEEDS OF THIS MAGNITUDE AS THIS POST FRONTAL SURGE SHOULD BE TRANSITIONAL AND THE SURFACE PRESSURE GRADIENT DOES NO APPEAR STRONG ENOUGH TO WARRANT ADVISORY LEVEL WINDS TO CONTINUE INTO THIS EVENING. THERE WILL BE A CONTINUED RISK OF DRIFTING SNOW AND POSSIBLE BLOWING SNOW ACROSS THE NORTH... ESPECIALLY ON NORTH-SOUTH ROADS OVER THE NEXT SEVERAL HOURS. HOWEVER...GIVEN THE NATURE OF THE WET SNOW THAT FELL AT TEMPERATURES NEAR FREEZING THIS MORNING...DO NOT ANTICIPATE ENOUGH BLOWING SNOW TO JUSTIFY AN ADVISORY. OTHERWISE...WILL LIKELY SEE CONTINUED FLURRIES INTO THE EVENING IN THE STEEP LOW LEVEL LAPSE RATES AS COLD AIR STRONG ADVECTION CONTINUES UNDER 850 MB TEMPERATURES DROPPING INTO THE SUBZERO TEENS CELSIUS OVERNIGHT. LOOKING AT UPSTREAM TEMPERATURES AND THERMAL PROFILES...HAVE STAYED WITH LOWS IN THE SINGLE DIGITS TO LOWER TEENS ACROSS THE NORTH WHERE RECENT SNOWFALL WILL AMPLIFY THE IMPACT OF THE INCOMING COLD AIRMASS. INCOMING MID LEVEL SUBSIDENCE SHOULD BRING AT LEAST PARTIAL CLEARING OVER THE AREA...ALLOWING THE CENTRAL FORECAST AREA AND MUCH OF THE SOUTH TO BOTTOM OUT IN THE TEENS. WITH WINDS REMAINING AT LEAST 15 TO 25 MPH THROUGH THE NIGHT...WIND CHILLS TOWARD MORNING WILL LIKELY DROP BELOW ZERO ACROSS THE NORTH. TUESDAY...THE PRESSURE GRADIENT BETWEEN THE SURFACE LOW MOVING SLOWLY AWAY ACROSS THE UPPER GREAT LAKES AND HIGH PRESSURE RIDGE MOVING INTO THE PLAINS WILL KEEP WINDS RATHER BLUSTERY THROUGH THE DAY. EVEN WITH SUNSHINE...THE ARCTIC-LIKE AIRMASS AND LIMITED WARMING DUE TO THE SNOW COVER ACROSS MAINLY THE NORTH SHOULD LIMIT HIGHS TO THE UPPER 20S TO LOWER 30S. MIXING TO 925 MB SUPPORTS HIGHS IN THE UPPER 30S TO LOWER 40S ACROSS THE FAR SOUTH WHERE LITTLE SNOW FELL TODAY. THESE TEMPERATURES WILL BE AT LEAST 15 DEGREES BELOW NORMAL FOR MID MARCH. .LONG TERM...(TUESDAY NIGHT THROUGH MONDAY) ISSUED AT 331 PM CDT MON MAR 18 2013 THE ACTIVE WX PATTERN THAT THE AREA HAS BEEN IN FOR ROUGHLY A MONTH WILL BRIEFLY QUIET DOWN. HOWEVER...THE COLDER THAN NORMAL CONDITIONS WILL CONTINUE. REFER TO THE CLIMATE SECTION FOR MORE INFORMATION. TUES NIGHT A VORT MAX PASSES JUST SOUTH OF THE CWFA. 850-700MB CONDENSATION PRESSURE DEFICITS DROP BUT FOR THE MOST PART THE 1000-850MB CONDENSATION PRESSURE DEFICITS DO NOT. THE WRF IS THE LONE EXCEPTION AND CONTINUES TO SUGGEST THE POTENTIAL FOR PRECIP REACHING THE GROUND. FCST SOUNDINGS SHOW A CONSIDERABLE AMOUNT OF DRY AIR IN THE LOWER LEVELS...EXCEPT THE WRF WHICH IS SATURATED. TAKING INTO ACCOUNT THE VARIOUS BIASES OF THE MODELS...HAVE OPTED TO GO DRY TUES NIGHT. RADAR WILL LIKELY SHOW A NICE BAND OF VIRGA STARTING LATE TUESDAY AFTERNOON AND INTO TUES EVENING FROM SOUTHERN IOWA INTO NORTHERN MISSOURI. WED THROUGH THURSDAY QUIET AND DRY CONDITIONS WILL BE SEEN AS THE NEXT CANADIAN HIGH BUILDS INTO THE MIDWEST. TEMPERATURES WILL AVERAGE WELL BELOW NORMAL. THURSDAY NIGHT ON... MODEL CONSENSUS HAS DRY CONDITIONS THURS NIGHT/FRIDAY. STARTING FRI NIGHT THROUGH MONDAY THE MODEL CONSENSUS HAS INCREASING AMOUNTS OF SCHC POPS OR CHC POPS...MAINLY ATTRIBUTED TO THE GFS. THIS TIME FRAME IS DURING A RE-ALIGNMENT OF THE LONGWAVE PATTERN ACROSS THE NORTHERN HEMISPHERE. DURING SUCH RE-ALIGNMENTS...MODEL PREDICTABILITY DROPS SIGNIFICANTLY AND RUN TO RUN CONTINUITY BECOMES VERY POOR. ADDITIONALLY...WE ARE IN THE SPRING SEASON WHICH ALSO CAUSES MODEL PREDICTABILITY TO DROP. THE 12Z GFS HAS DONE A SIGNIFICANT CHANGE FROM PREVIOUS RUNS AND IS INDICATING A SIGNIFICANT STORM SYSTEM. BASED ON THE INCOMING 12Z LOW-RES ECMWF...DPROG/DT SUPPORTS A SHIFT TOWARD THE GFS SOLUTION. THE ENSEMBLES OF THE GFS WOULD TEND TO SUPPORT THE 12Z DETERMINISTIC RUN. WHETHER THE GFS SOLUTION WILL BE REALIZED IS NOT KNOWN YET. WHAT IS KNOWN IS THAT THE OVERALL PATTERN SUGGESTS THE POTENTIAL FOR VERY DYNAMIC SYSTEMS. VERY DYNAMIC SYSTEMS TEND TO HAVE NON LINEAR ASPECTS TO THEM WHICH MAKES PREDICTION MORE DIFFICULT. ..08.. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 1126 PM CDT MON MAR 18 2013 SUBSIDENCE BEHIND MONDAYS SNOW AND WIND HAS RESULTED IN WIDESPREAD CLEARING...AND NOW CLEAR SKIES ARE FOUND OVER ALL OF IOWA AND NORTHWEST ILLINOIS...OUTSIDE OF A FEW VERY THIN STRATUS FRACTUS CLOUDS NEAR DBQ...WHICH ARE OCCASIONALLY PICKED UP BY THE CEILOMETER...BUT ARE UNLIKELY TO BE REPRESENTATIVE OF AN ACTUAL BROKEN OR OVERCAST CIG. WINDS WILL REMAIN UP...NEAR 18KTS GUSTING 26KT THROUGH THE NIGHT AND TUESDAY...FROM THE WEST. WINDS WILL DECREASE TOWARDS 00Z WEDNESDAY...AS HIGH PRESSURE MOVES IN FROM THE WEST. ALL CONDITIONS WILL BE VFR...OUTSIDE OF THE VERY BRIEF PERIOD OF MVFR CIG AT DBQ OVERNIGHT. ERVIN && .CLIMATE... ISSUED AT 331 PM CDT MON MAR 18 2013 THE CURRENT 6-10 DAY AND 8-14 DAY OUTLOOK CONTINUES TO INDICATE TEMPERATURES REMAINING BELOW NORMAL. THE SIGNAL FOR PRECIPITATION IS MIXED SUGGESTING DRIER THAN NORMAL AND THEN AROUND OR SLIGHTLY ABOVE NORMAL. THE ENSEMBLE MEMBERS OF THE NAO AND AO REMAIN NEGATIVE THROUGH THE END OF THE MONTH SUPPORTING COLDER THAN NORMAL TEMPERATURES THROUGH AT LEAST THE END OF MARCH. THE ENSEMBLE MEMBERS OF THE AO ARE TIGHTLY CLUSTERED AND ARE PROGGED TO BE BRIEFLY NEAR THE EXTREME VALUE OF MINUS 6 WHICH STRONGLY SUPPORTS TEMPERATURES REMAINING BELOW NORMAL. BY EARLY APRIL MOST ENSEMBLE MEMBERS OF THE NAO AND AO REMAIN NEGATIVE SUGGESTING BELOW NORMAL TEMPERATURES WILL CONTINUE INTO THE FIRST WEEK OF APRIL. THE GLOBAL MODELS ARE SIGNALING THAT THE STABLE 3 WAVE PATTERN ACROSS THE NORTHERN HEMISPHERE WILL BREAK DOWN AND RE-ALIGN ITSELF INTO A 4 WAVE PATTERN WITH LONGWAVE TROFS ON BOTH COASTS OF NORTH AMERICA. THIS LONGWAVE PATTERN SUGGESTS THE SOUTHERN STREAM WILL BE THE MORE DOMINATE OF THE TWO JETS WHICH WOULD SUPPORT PRECIPITATION BEING SOMEWHAT LESS THAN NORMAL. HOWEVER...SUCH A LONGWAVE PATTERN ALSO SUGGESTS THE POTENTIAL FOR SEVERAL SIGNIFICANT STORM SYSTEMS AFFECTING THE CONUS SOMEWHERE EAST OF THE ROCKIES OVER THE NEXT 2 TO 3 WEEKS. IF THIS LONGWAVE PATTERN VERIFIES...THEN PRECIPITATION CHANCES WOULD BE ON THE INCREASE STARTING AROUND THE END OF THE MONTH. ..08.. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ UPDATE...ERVIN SYNOPSIS... SHORT TERM...SHEETS LONG TERM...08 AVIATION...ERVIN CLIMATE...08