HAMweather.com Area Forecast Discussion for County Warning Area DVN

Thu, 16 Feb 2012 07:05:44 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1112 PM CST WED FEB 15 2012

.AVIATION...
A COLD FRONT WILL SWEEP THROUGH EASTERN IOWA AND WESTERN ILLINOIS
THROUGH 09Z EARLY THIS MORNING...AND AS THIS OCCURS...THE IFR TO
LIFR CONDITIONS WITH FOG AND VERY LOW CIGS WILL RAPIDLY IMPROVE TO
MVFR...THEN A HOUR OR TWO LATER...VFR. NORTHWEST WINDS OF 10
KTS WILL CONTINUE THROUGH THE PERIOD AFTER 09Z. MOSTLY CLEAR SKIES
AND GOOD VISIBILITY WILL CONTINUE THROUGH THE DAY THURSDAY AND
THURSDAY EVENING.
..ERVIN..

.PREV DISCUSSION... /ISSUED 325 PM CST WED FEB 15 2012/

SYNOPSIS...
LATEST WV IMAGERY INDICATED A MID LEVEL SHORTWAVE ALONG THE SOUTH CENTRAL
KS/OK BORDER. AHEAD OF THIS MAIN WAVE...WEAK VORT MAXES EMBEDDED
IN THE W-SW FLOW ALOFT WERE PRODUCING SHOWERS OVER S AND SE IA
INTO W CENTRAL IL...AND OVER SW IA. MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS WERE MUCH FURTHER SOUTH FROM AR...MO INTO THE OHIO
VALLEY IN THE PRIMARY AXIS OF GULF MOISTURE AND WARM AIR ADVECTION THAT
EXTENDED FROM THE TX COAST INTO EASTERN KS AT 12Z...BUT HAS SINCE
BEEN SHUNTED EASTWARD BY A W-SW 850 MB FLOW SHOWN BY THE PROFILER
NETWORK ACROSS THE SOUTHERN PLAINS INTO THE MID MS VALLEY. THIS WAS ALSO
IN AN AREA OF BETTER JET LEVEL SUPPORT. AT THE SURFACE...MSAS
INDICATED WEAK LOW PRESSURE OVER CENTRAL OK WITH A TROUGH
EXTENDING NORTH INTO CENTRAL IA. AFTER A SUNNY START THIS
MORNING...LATEST VISIBLE SATELLITE IMAGERY INDICATED LOW CLOUDS
HAD OVERSPREAD ALL BUT THE FAR WEST CENTRAL AND NORTHWEST PORTIONS
OF THE DVN FORECAST AREA.

SHORT TERM...TONIGHT AND THURSDAY...
PRIMARY FOCUS IS ON PRECIPITATION TONIGHT AS THE PLAINS SYSTEM
SWEEPS BY TO THE SOUTH. 12Z MODELS HAVE TRENDED TOWARD A MUCH
WEAKER AND LESS ORGANIZED STRUCTURE AT THE SURFACE...SHOWING MORE
OF A AN ELONGATED LOW OR TROUGH THAT SWEEPS EAST TO LAKE MI BY
12Z. THE ECMWF HAD A SLIGHTLY BETTER VERIFICATION OF SURFACE
PRESSURE FIELDS AT 18Z COMPARED TO OTHER MODELS AND HAVE THUS
WEIGHTED THE FORECAST MORE HEAVILY IN ITS FAVOR.

SHORT TERM TRENDS INDICATE SCATTERED SHOWERS TO CONTINUE OVER THE 
SOUTH TO SOUTHEAST HALF OF THE FORECAST AREA LATE THIS AFTERNOON 
WITH ANOTHER ROUND THIS EVENING FURTHER NORTH AS THE PRIMARY FORCING 
AHEAD OF THE WEAKENING MID LEVEL SHORTWAVE...PRODUCING SHOWERS OUT 
WEST FROM NE KS INTO SW IA MOVES EASTWARD. HAVE THUS CONTINUED THE 
HIGH CHANCE TO CATEGORICAL POPS ACROSS THE SOUTHERN 2/3RDS OF THE 
FORECAST AREA FOR THIS EVENING...THEN HASTENED THE DEMISE OF 
MEASURABLE PRECIPITATION AS DOWNWARD MID LEVEL MOTION AND DRY AIR AT 
THE MID LEVELS QUICKLY FOLLOWS FROM WEST TO EAST AFTER MIDNIGHT. ALL 
MODELS NOW DEPICT THE FORCING...AND SUPPORT FOR PRECIPITATION... 
EXITING EAST BEFORE THE LOW LEVELS BECOME COLD ENOUGH TO SUPPORT
SNOW OR ANY MIXED OR FREEZING PRECIPITATION AT THE SURFACE. ALONG
THESE LINES...WILL KEEP A MARGIN OF ERROR MIX OF RAIN AND WET SNOW
GOING LATE TONIGHT IN THE NORTH...BUT HAVE REMOVED ANY MENTION OF
MEASURABLE ACCUMULATIONS. WITH GULF MOISTURE ALREADY SHUNTED EAST
AND BEING WRUNG OUT BY CONVECTION IN THE MID MS VALLEY...QPF
AMOUNTS HAVE BEEN LOWERED...WITH A ONLY A FEW HUNDREDTHS CENTRAL
AND NORTH UP TO PERHAPS ONE OR TWO TENTHS IN THE SOUTH. WITH
FORECAST SOUNDINGS SHOWING SHARP MID LEVEL DRYING AND LINGERING
LOW LEVEL MOISTURE AFTER MIDNIGHT...HAVE ADDED PATCHY FOG AND
DRIZZLE OVER THE ENTIRE AREA OVER MAINLY THE CENTRAL AND EAST.
SLIGHTLY STRONGER W-NW WINDS...AND ADVECTION OF DRIER AND COOLER
AIR SHOULD LIMIT THIS POTENTIAL IN THE WEST BASED ON CURRENT
FORECAST TIMING.

THURSDAY...NW SURFACE WINDS...COLD AIR ADVECTION...AND MID LEVEL 
SUBSIDENCE SHOULD RESULT IN PARTLY TO MOSTLY SUNNY SKIES. 
ANTICIPATING SUNSHINE...TEMPERATURES SHOULD RECOVER FROM MORNING 
LOWS IN THE UPPER 20S TO LOWER 30S...INTO THE LOWER 40S BY
AFTERNOON ACROSS THE AREA. ..SHEETS..

LONG TERM...THURSDAY NIGHT THROUGH NEXT WEDNESDAY...
MAINLY QUIET WITH TEMPS GENERALLY NEAR TO ABOVE NORMAL. W/NW FLOW WILL
PREVAIL INTO THE WEEKEND. A WEAK CLIPPER TYPE SYSTEM IS PROGGED TO
PASS THROUGH PORTIONS OF THE UPPER MIDWEST FRI-FRI EVE. STILL SOME
DISAGREEMENT WITH THE EXACT TRACK. DPROG/DT OF HI-RES ECMWF AND GEM 
SHOWS A BIT OF A SOUTHWARD SHIFT ON TRACK WITH SYSTEM PASSING ACROSS 
OUR NORTHERN COUNTIES FRI EVE. MEANWHILE... DPROG/DT OF GFS SHOWS 
PRETTY GOOD CONSISTENCY PAST SEVERAL RUNS AND IT TAKES SHORTWAVE AND 
ATTENDANT SFC LOW NORTH OF CWA FRI EVE. NAM HAS SHIFTED OVER 150 MILES
NW FROM NCNTRL IN TO SE WI WITH BY FRI EVE WITH 12Z RUN. MOISTURE 
WILL BE LIMITED THUS TRACK CRITICAL FOR PCPN CHCS WITH MAIN CHCS 
BEING FOUND ALONG AND JUST LEFT OR NORTH OF SFC LOW IN THE 
COLDER AIR. DUE TO BETTER RUN TO RUN CONSISTENCY OF GFS IT WAS THE 
MODEL OF CHOICE... THUS I HAVE KEPT FCST DRY FOR NORTHERN COUNTIES FRI
NGT. 
 
ANOTHER AREA OF DISAGREEMENT AMONG THE MODELS IS PCPN POTENTIAL ALONG 
AND JUST BEHIND COLD FRONT FRI EVE. 12Z UKMET IS THE OUTLIER WITH 
A SLOWER SOLUTION WITH MORE PHASING OF ENERGY STREAMS AND DOES NOT 
SHOW FRONT PASSING UNTIL SAT AM. THE RESULT OF THIS IS THAT IT ALLOWS
MORE MOISTURE PRE-FRONTAL AND BETTER FORCING THUS THE MODEL IS WET WITH
0.1 TO 0.25 INCH OF PCPN OVER SE 1/3-1/2 OF THE CWA FRI NGT. MOST
OTHER MODELS OFFER NOT MUCH PHASING AND DEPICT SYSTEM WEAKENING 
OR OPENING UP WHILE PASSING ACROSS THE LOWER MISSISSIPPI VLY AND THE 
DEEP SOUTH OVER THE WEEKEND... WITH PCPN STAYING WELL TO OUR SOUTH.
WITH THIS BEING GENERAL CONSENSUS OF MODELS HAVE OPTED TO KEEP DRY FCST
FOR THE SOUTHERN COUNTIES FRI NGT-EARLY SAT. OTHERWISE... THIS LOOKS 
TO BE YET ANOTHER COLD FRONTAL PASSAGE THAT SERVES TO COOL US DOWN TO
NEAR NORMAL FOR A COUPLE OF DAYS. 

MON-WED... HIGHLY ACTIVE PACIFIC WAVE TRAIN CONTINUES... WITH NEXT 
SYSTEM TOWARD TUE-WED TIMEFRAME. CONSIDERABLE AMOUNT OF UNCERTAINTY WITH
HANDLING OF ENERGY IN SPLIT FLOW. LATEST ECMWF HAS SHIFTED NORTHERN
STREAM ENERGY SEVERAL HUNDRED MILES FARTHER NORTH OVER PAST THREE RUNS
AND NOW HAS MOST OF ENERGY PASSING TO OUR NORTH. THIS WOULD CERTAINLY BE
A WARMER SCENARIO AND A DRIER ONE WITH AREA SPLIT WITH NORTHERN STREAM
ENERGY PASSING WELL NORTH... WHILE BETTER MOISTURE TIED TO SOUTHERN
STREAM PASSING TO OUR SOUTH. THIS WOULD ALSO FIT THE OVERALL PATTERN 
OF THIS SO CALLED WINTER. HARD TO GO AGAINST SLIGHT CHC TO LOW CHC POPS
BY TUE INTO WED... WITH TEMPS ABOVE NORMAL.   ..05..

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.