FXUS63 KDVN 302045
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 PM CST MON NOV 30 2009

.SYNOPSIS...
SUBSIDENCE IN UPPER LEVEL NW FLOW AND BROAD FLAT RIDGING AT THE 
SURFACE WERE PROVIDING CLEAR SKIES AND SEASONABLE TEMPERATURES 
ACROSS THE FORECAST AREA THIS AFTERNOON. THIS NW FLOW WAS BETWEEN AN 
UPPER TROUGH AXIS OVER THE EASTERN GREAT LAKES AND UPSTREAM RIDGE 
AXIS OVER THE NORTHERN ROCKIES. 12Z ANALYSIS AND LATEST WV IMAGERY 
INDICATED A CUTOFF UPPER LOW NEAR BAJA CA FLANKED BY A RIDGE TO THE 
NORTH OVER THE GREAT BASIN. THIS SPLIT FLOW PATTERN WILL KEEP QUIET 
AND SEASONABLY WARM WEATHER IN PLACE FOR ONE MORE DAY...THEN MID TO 
LATE WEEK FEATURES CHANGES TO A COLDER...MORE ACTIVE PATTERN.  
&&

.SHORT TERM...TONIGHT AND TUESDAY...
TEMPERATURES ARE THE MAIN CHALLENGE AS PREFRONTAL WARMING BOOSTS 
HIGHS TO WELL ABOVE NORMAL TUE AFTERNOON. TONIGHT...SKIES WILL 
LIKELY REMAIN MOSTLY CLEAR AS THE NEXT ROUND OF MID AND HIGH CLOUDS 
ASSOCIATED WITH A SHORTWAVE MOVING INTO THE NRN GREAT LAKES LOOKS TO 
JUST BRUSH ONLY THE NE IN THE EVENING. A LIGHT SURFACE PRESSURE 
GRADIENT...AND INCREASING WARM ADVECTION IN W-SW FLOW ALOFT WILL 
LIKELY KEEP SURFACE WINDS IN THE 5 TO 10 KT RANGE TO PREVENT 
SIGNIFICANT DECOUPLING AND COOLING. HOWEVER...WITH SHORT TERM MODELS 
TRENDING A BIT TOO MOIST AT THE SURFACE SO FAR TODAY COMPARED TO 
SURFACE OBSERVATIONS...MOS MINS MAY BE A BIT TOO WARM AND HAVE 
TRENDED NEAR TO BELOW...IN THE UPPER 20S NORTH TO LOWER 30S SOUTH.

TUE...SHORTWAVE CURRENTLY MOVING ACROSS SOUTHERN BC SENDS A SURFACE 
LOW ACROSS THE NORTHERN PLAINS. MODELS IN GENERAL AGREEMENT WITH THE 
SURFACE COLD FRONT NOT REACHING THE NW CWFA UNTIL EVENING...KEEPING 
THE AREA IN PREFRONTAL WARMING THROUGH THE DAY. MODEL FORECAST 
SOUNDINGS SUPPORT MIXING TO AROUND 925 MB AT BEST...WHICH WOULD 
SUPPORT HIGHS IN THE 50S...POSSIBLY APPROACHING 60 IN THE FAR SOUTH 
UNDER NEAR FULL SUNSHINE. 
..SHEETS..     

.LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT WILL BE VERY INTERESTING 
REGARDING THE MID WEEK SYSTEM. FIRST...TUESDAY NIGHT WILL BE QUIET 
AND DRY.

WEDNESDAY/WEDNESDAY NIGHT...ALL MODELS HAVE SUDDENLY JUMPED 
NORTHWEST WITH THE STORM TRACK. TWO THINGS ARE CAUSING THIS TO 
OCCUR. FIRST...THE SOUTHERN STREAM UPPER LOW WAS POORLY SAMPLED ALL 
WEEKEND DUE TO NO RAOBS FROM NORTHERN MEXICO. SECOND...THE NORTHERN 
STREAM SHORTWAVE IS STRONGER PER CANADIAN RAOBS AND WATER VAPOR THAN 
WHAT THE MODELS DEPICTED YESTERDAY WHICH IS CAUSING IT TO DIG 
FURTHER TO THE SOUTH/WEST. THE NET RESULT FROM BOTH IS TO PULL THE 
SOUTHERN SYSTEM FURTHER NORTH...ALA FUJIWARA.

THE QUESTION NOW IS WHAT TO DO. INSTINCT TELLS ME THERE IS MORE TO 
THIS EVENT THAN WHAT THE MODELS CURRENTLY INDICATE. INTERESTINGLY... 
HVY RAIN TECHNIQUES SHOW A NARROW RIBBON OF HIGHER PWS RUNNING FROM 
NORTHERN MO INTO NORTHEAST ILLINOIS WITH NICE SPEED/MOISTURE 
CONVERGENCE. ADD TO THIS GOOD FRONTOGENETICAL FORCING AND LIKELY 
EVAPORATIVE COOLING. WAA WING TOOL SHOWS VERY STRONG FORCING 
DEVELOPING OVER THE CWFA AND MOVING EAST WITH TIME.

SO...THE PLAN IS THAT ADDITIONAL PHASING OF THE NORTHERN/SOUTHERN 
STREAMS WILL OCCUR OVER THE NEXT 24 HRS AS THE SOUTHERN STREAM GETS 
BETTER SAMPLED FROM RAOBS. THIS PHASING WILL PULL THE SOUTHERN 
SYSTEM A BIT FURTHER NORTH/WEST. AS A RESULT...I HAVE INTRODUCED 
SCHC POPS WED AFTERNOON/EVENING OVER THE SOUTHEAST THIRD OF THE 
CWFA. IF A NARROW BAND DEVELOPS...ANY PRECIP WILL CHANGE OVER TO SN 
DUE TO EVAPORATIVE COOLING. POTENTIAL DRY SLOT MAY END THE PRECIP 
LATE WED NIGHT OR FLURRIES MAY DEVELOP AS THE FIRST OF SEVERAL VORT 
MAXES ROTATES DOWN FROM THE NORTHERN SYSTEM. SUBSEQUENT SHIFTS WILL 
HAVE TO WATCH TRENDS CAREFULLY AND BE READY TO MADE MORE SIGNIFICANT 
CHANGES TO THE FCST.

THURS THROUGH SATURDAY WILL FEATURE WELL BELOW NORMAL TEMPERATURES 
AS THE UPPER LOW OF THE NORTHERN SYSTEM ROTATES THROUGH THE AREA. 
MODELS CONTINUE TO TREND COLDER WITH H85 TEMPS OF AT LEAST -15C AND 
925MB TEMPS RANGING FROM -7 TO -10C. FLURRIES AND SHSN ARE EXPECTED 
WITH EVERY VORT MAX THAT ROTATES THROUGH THE AREA. COOLED MAX TEMPS 
DOWN FOR THURSDAY A LITTLE BUT COOLED FRI/SAT MAX TEMPS DOWN 
CONSIDERABLY. MAX TEMPS IN THE 20S SHOULD BE SEEN FRIDAY AS THE CORE 
OF THE COLD AIR MOVES THROUGH.

SUNDAY/MONDAY...TEMPERATURES WILL SLOWLY MODERATE TO NEAR NORMAL AS 
WAA IN THE LOW LEVELS PUSHES THE COLD AIR OUT OF THE AREA.
...08...

&&

.AVIATION...
MOSTLY CLEAR SKIES AND VFR CONDITIONS WILL PREVAIL OVERNIGHT INTO 
TUESDAY AS A WEAK RIDGE AXIS PASSES THROUGH THE REGION. SOUTHWEST 
WINDS WILL DECREASE TO LESS THAN 10 KTS AROUND SUNSET...THEN 
INCREASE TO 10 TO 15 KTS TUESDAY MORNING. 
..SHEETS..

&&

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

&&

$$

SHEETS/08