[LeArc] Area Forecast Discussion 4/22/05

[Duane Whittingham]

FXUS63 KDVN 222022
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
322 PM CDT FRI APR 22 2005

.SYNOPSIS...SURFACE LOW WAS OVER SOUTHERN INDIANA THIS AFTERNOON
WITH SATELLITE IMAGERY SHOWING LARGE COMMA HEAD PATTERN OVER MIDWEST
WITH TIGHTLY WRAPPED UPPER LOW EVIDENT ON WATER VAPOR IMAGERY
SLIDING ACROSS FAR SOUTHERN IL. DEFORMATION ZONE SHOWERS CONFINED TO
MAINLY SE HALF OF CWA AT MID AFTERNOON AND SHOULD CONTINUE TO WANE.
UPSTREAM...TO THE NW...SHORTWAVE RIDING SE ACROSS SE MN WAS MOVING
OVER AREA WHERE SUNSHINE BROKE OUT EARLIER TODAY AND WHERE MODELS
PROGGED STEEP MID LEVEL LAPSE RATES. THIS HAS RESULTED IN BANDS OF
SHOWERS FROM SE MN TO CENTRAL IA WITH EVEN A FEW LIGHTNING STRIKES
SHOWING OVER N CENTRAL IA.
&&

.SHORT TERM...(TONIGHT THROUGH SATURDAY)...INITIAL CHALLENGE IS
SHOWERS AND THUNDERSTORM POTENTIAL FOR THIS EVENING...THEN
TEMPERATURES AS COLD AIR CONTINUES TO FILTER INTO REGION. ACTIVITY
OVER WESTERN IL TO SE IA WILL TAPER TO SPRINKLES LATE THIS AFTERNOON
AS DEFORMATION ZONE LIFT EXITS TO SOUTHEAST. HOWEVER...AT SAME
TIME...MID LEVEL Q-VECTOR CONVERGENCE ASSOCIATED WITH SHORTWAVE
SLIDING SE PROGGED BY MODELS TO MOVE ACROSS NORTHERN HALF OF CWA
THIS EVENING. MID LEVEL LAPSE RATES...SHOWN BY GFS OVER 7 DEG C/KM
OVER N CENTRAL IA MATCHES WELL WITH STRONGEST CELLS AND LIGHTNING
STRIKES. WILL THROW IN MENTION OF TSRA LATE AFTERNOON/EARLY EVENING
OVER E CENTRAL IA AND NW IL...WHERE STRONGEST FORCING OVERLAPS THIS
AXIS OF STEEP LAPSE RATES DIVING SE. WILL KEEP SCATTERED POPS GOING
AND RAISE THE EAST TO LIKELY FOR THIS EVENING.

ONCE THIS LIFT PASSES...COLD ADVECTION AND SUBSIDENCE WILL CLEAR
SKIES OUT FROM NW TO SE OVERNIGHT. TIGHT PRESSURE GRADIENT AND COLD
ADVECTION SHOULD KEEP LOWER LEVELS FROM DECOUPLING. WITH H85
TEMPERATURES AS LOW AS -8 DEG C AND SURFACE DEWPOINTS IN UPPER 20S
ADVECTING IN FROM NORTH TONIGHT...WILL BE A COLD NIGHT AND GUIDANCE
TEMPERATURES IN LOWER TO MID 30S LOOK REASONABLE. DRY AIR AND BREEZY
CONDITIONS SHOULD PRECLUDE FROST AND ONLY A COUPLE HOURS NEAR
FREEZING ANTICIPATED...SO WILL HOLD OFF ON HIGHLITE AND INSTEAD USE
HEADLINES IN PUBLIC FORECAST ZONES. ON SATURDAY...KEPT HIGHS ONLY IN
UPPER 40S TO LOWER 50S AND BROUGHT IN SLIGHT CHANCE FOR SHOWERS TO
NW IL AS UPPER LEVEL COLD POOL DROPS DOWN WITH REINFORCING H5 LOW.
..SHEETS..

&&

.LONG TERM (SATURDAY NIGHT AND SUNDAY )...
REGION WILL STILL BE UNDER THE INFLUENCE OF CYCLONIC FLOW AROUND
STACKED LOW PRESSURE ROTATING FROM THE OHIO VALLEY NORTH INTO THE
EASTERN GREAT LAKES.  MODELS SHOW HIGHEST RH WILL BE TO THE EAST OF
THE CWA AND ANTICIPATE CLEAR OR MOSTLY CLEAR SKIES DURING THE NIGHT.
COLD AIRMASS WEST OF THE LOW WILL BRING SUBFREEZING TEMPS TO THE
REGION SUNDAY MORNING. ENTIRE CWA SHOULD BE AT OR JUST BELOW
FREEZING SUNDAY MORNING WITH MINS FROM THE UPPER 20S N TO AROUND 32
IN THE SOUTH.  SURFACE PRESSURE GRADIENT SHOULD KEEP WINDS UP DURING
THE NIGHT AND WILL LIMIT ANY FROST FORMATION TO THE LOWER LYING
LOCATIONS AND MAINLY IN THE WESTERN SECTIONS OF THE CWA AT THAT.
TEMPS SUNDAY WILL AGAIN BE ON THE COOL SIDE WITH MAXES TOPPING OUT
IN THE LOW TO MID 50S EVEN WITH SOME SUNSHINE.  ...DLF...

(SUNDAY NIGHT THROUGH FRIDAY)...
MODELS ARE IN GOOD AGREEMENT WITH THE OVERALL PATTERN OF SPLIT FLOW
OVER THE U.S. DURING THE PERIOD...BUT ARE HAVING DIFFICULTY
RESOLVING THE S/W ENERGY MOVING SOUTH THROUGH THE NW FLOW.  THE GFS
CONTINUES TO BE MORE AGGRESSIVE WITH THESE S/W'S AND AS A RESULT
INDICATES COOL AND WET CONDITIONS FOR MOST OF THE PERIOD.  THE
ECMWF ON THE OTHER HAND CONTINUES TO SHOW A LESS DYNAMIC PATTERN.
WITH LITTLE CONFIDENCE IN EITHER MODEL WILL CONTINUE SPIRIT OF THE
PREVIOUS FORECAST PACKAGE WITH POPS FOR MONDAY INTO TUESDAY
ASSOCIATED WITH THE INITIAL S/W ROTATING THROUGH THE REGION.  AFTER
THAT WILL GO WITH A GENERALLY DRY AND COOL FORECAST OTHER THAN
SLIGHT CHANCE POPS THURSDAY AND FRIDAY WITH POTENTIAL FOR REGION TO
COME UNDER THE INFLUENCE OF SRN STREAM SYSTEM FAVORED BY THE ECMWF
OR THE NRN STREAM ENERGY DEPICTED BY THE GFS.  ...DLF...

&&

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

&&

$$

SHEETS/DLF





---------------------------------------------------------------------
Duane Whittingham (N9SSN) - Producer
Tom and Darryl Radio Shows
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Heard Fridays 9pm ET, Sundays 12am ET and Tues 2am ET (Folk)
An Independent Freeform Eclectic Radio Show.
http://www.tomanddarryl.org
http://www.wtnd.us


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