[LeArc] Forecast Discussion : MLI@ 1/26/03 2:21:03 AM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 260833
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 AM CST SUN JAN 26 2003

RUNNING LATE WITH ISC GRIDS...SORRY! 

VORT MAX RESPONSIBLE FOR SNOW AND WIDESPREAD 1/2 TO 1 INCH AMOUNTS SOUTHERN
HALF NOW EXITING STAGE RIGHT. MAIN VORT LOBE DROPPING THROUGH
SOUTHERN MN AND WI. THIS FEATURE IN CONJUNCTION WITH LEFT EXIT REGION
OF 110+ KT UPPER JET CORE IN NORTHERN PLAINS GENERATING 
SECONDARY BAND OF SNOW WITH VISIBILITIES FOR SHORT TIME DROPPING BELOW 2 MILES
AT FEW SITES. LATEST SURFACE ANALYSIS SHOWS ARCTIC AIR SURGING 
BACK INTO REGION WITH CENTER OF BITTER COLD DOME PUSHING INTO DAKOTAS.
STRENGTHENING PRESSURE GRADIENT KEEPING WINDS IN RANGE OF 10-20 MPH WITH
OCCASIONAL GUSTS TO NEAR 25 MPH AT TIMES. 

VERY ACTIVE AND CHANGEABLE PATTERN UNFOLDING AS ADVERTISED WITH MANY FORECAST
CHALLENGES NEXT FEW DAYS. IMMEDIATE CONCERNS THIS MORNING ARE 
WITH SNOW CHCS EARLY ON AND POTENTIAL FOR ADDITIONAL ACCUMS...THEN FOCUS 
SHIFTS TO BRISK WINDS...WIND CHILLS AND TEMPERATURES. BEYOND...CONCERNS WITH 
SNOW CHCS LATE TONIGHT/MON AND ACCUMS WITH STRONG WARM ADVECTION...TEMPS AND 
PCPN CHCS LATE MON NIGHT/TUE.
 
NEAR TERM...FORCING IN FORM OF UPPER DIVERGENCE AND PVA TO RESULT IN
SHORT PERIOD OF SN/--SN EARLY THIS MORNING MOST LOCATIONS. NOWCASTING TOOLS 
SUGGEST BEST FORCING TO SLIDE E/SE FROM CENTRAL IA THROUGH CWA NEXT 
FEW HOURS WITH ADDITIONAL ACCUMS OF FEW TENTHS OF AN INCH POSSIBLE. SN/--SN 
TO EXIT BY 12Z-15Z WITH MODERATE-STRONG SUBSIDENCE LEADING TO CLEARING 
SKIES DEPICTED ON SATELLITE COMING INTO FAR NORTHERN IA ATTIM. WILL BASE FIRST 
PERIOD WORDING ON LATEST RADAR/SATELLITE TRENDS. BRUNT OF ARCTIC BLAST
TO ROTATE THROUGH TODAY WITH TEMPS CONTINUING TO FALL INTO MID MORNING BEFORE
GOING STEADY THEN RISING FEW DEGS. GRADIENT TO KEEP WINDS IN 15 TO 25 MPH
RANGE THIS MORNING AND WHEN COMBINED WITH TEMPS NEAR ZERO...PRODUCES WIND CHILLS
NEARING 20 BELOW...BORDERLINE FOR ADVISORY (20-30 BELOW). 
SINCE HORSE ALREADY OUT OF THE BARN AND IT WILL BE CLOSE...WILL GO AHEAD AND
CONTINUE WITH WIND CHILL ADVISORY FOR THIS MORNING. CONDITONS WILL IMPROVE 
THIS AFTERNOON AS THE CENTER OF THE HIGH APPROACHES AND WINDS DIMINISH.

TONIGHT...WILL BE VERY COLD WITH MAIN CONCERN ON HOW LOW WILL WE GO THIS EVE
WITH CLEAR SKIES...LIGHT WINDS AND FRESH LIGHT SNOW COVER. 
CURRENT FORECAST UNDERCUTS GUIDANCE BY NEARLY CAT WHICH LOOKS GOOD AND WILL
STAY FAIRLY CLOSE. RIDGE AXIS QUICKLY DEPARTS OVERNIGHT WITH
SOUTHERLY WINDS AND WARM ADVECTION COMMENCING BRINGING INCREASE IN CLOUDS AND
STEADY OR SLOWLY RISING TEMPS. NEXT CONCERN BECOMES CHANCE OF SNOW. 
AVN/GFS AND ETA SATURATE COLUMN WESTERN 1/3RD OR SO BY 12Z MON AND ADVERTISE
DRY LOW LEVELS STILL YET TO OVERCOME ALONG AND EAST OF MISSISSIPPI.
FOR NOW WILL GO WITH FLURRIES AND CHANCE OF SNOW ROUGHLY ALONG AND WEST
OF LINE FROM CEDAR RAPIDS TO MOUNT PLEASANT...AND WILL BRING MENTION OF FLURRIES
TO THE RIVER AND KEEP IT DRY FAR EAST. 

MONDAY - STRONG WARM ADVECTION AND DECENT FORCING SUGGESTS LIKELY POPS MOST
LOCATIONS FOR PERIOD OF SNOW WITH ACCUMS OF UP TO 1 INCH.
LATER MODEL RUNS WILL CLARIFY STRENGTH AND EXTENT OF MOISTURE BUT CAN/T RULE
OUT SOME 2-3 INCH AMOUNTS IF ALL COMES TOGETHER JUST RIGHT.
SOME HEFTY ADVECTION FOR SURE WITH META SHOWING H85 TEMPS ACROSS STATE OF
IA AT 18Z RANGING FROM -11C NORTHEAST TO +8C SOUTHWEST...WOW!
MY GUESS IS THAT SHOULD BE GOOD ENOUGH TO GENERATE MORE THAN JUST CLOUDS!
TEMPS MONDAY TO BE QUITE TRICKY. TEMPS PROBABLY STRUGGLE MOST OF THE
DAY WITH CLOUDS AND PCPN...THEN SURGE QUICKLY TOWARD SUNSET...WITH HIGHS
LIKELY OCCURRING AFTER DARK! 
 
NEXT CHALLENGE IS PCPN CHANCES LATE MON NIGHT-TUE. AVN/GFS MAY BE UP TO USUAL
TRICKS WITH QPF BOMB OVER CWA WITH AMOUNTS OF AROUND 1/3RD OF AN INCH.
HOWEVER...GIVEN STRENGTH OF ADVECTION AND POSITION OF HIGH OFF MID ATLANTIC
NEVER KNOW. MOST MODELS INDICATING SOME PCPN AHEAD OF FRONT JUST
QUESTION OF HOW MUCH. BASED ON THIS AND GUIDANCE POPS IN HIGH CHC TO 
LIKELY CAT FEEL UNCOMFORTABLE WITH CURRENT DRY FORECAST AND WILL INSERT CHC POPS
AND LET DAY CREW RE-EVALUATE. PCPN TYPE WILL BE TRICKY AS WELL AND FOR NOW
WILL GO WITH RAIN/SNOW. 

DUE TO TIME CONSTRAINTS WILL LEAVE EXTENDED PRETTY MUCH ALONE. 

DMX...THANX FOR COORD!

.DVN...
IA...WIND CHILL ADVISORY THIS MORNING FOR AREAS NEAR AND NORTH OF ALINE FROM
WILLIAMSBURG TO IOWA CITY AND CLINTON.
IL...WIND CHILL ADVISORY THIS MORNING FOR AREAS NEAR AND NORTHWEST OF A LINE
FROM THOMSON TO FREEPORT.
MO...NONE.


MCCLURE