Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 021016 AAA
AFDDVN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
516 AM CDT SUN AUG 2 2015

.UPDATE...
ISSUED AT 514 AM CDT SUN AUG 2 2015

THE VORT MAX MOVING INTO OUR AREA ALONG WITH THE H85 THETAE
PUSH....SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ACROSS WESTERN
AND SOUTHERN IA EARLY THIS AM. HRRR SUGGESTS THAT THESE STORMS
CONTINUE TO FIRE CLOSER TO US AND THEN MOVE THROUGH OUR AREA. AS A
RESULT OF THE TRENDS AND GUIDANCE...DECIDED TO INCREASE POPS AFTER
12Z ACROSS MY WESTERN ZONES. MAY NEED TO INCREASE TO LIKELYS IF
CURRENT HRRR IS CORRECT.

&&

.SYNOPSIS...
ISSUED AT 329 AM CDT SUN AUG 2 2015

AN AGITATED ACCAS DECK ASSOCIATED WITH A QUICK MOVING VORT MAX IN
THE STEERING FLOW WAS LOCATED FROM ESCANABA MI TO HASTINGS NE.
EXTREMELY ISOLATED CONVECTION HAS FORMED IN THIS BAND AS IT
MARCHES TO THE SE AT AROUND 20 KTS. AT THE SFC...DEWPOINTS ARE
POOLING ACROSS THE AREA AND RELATIVELY CLEAR SKIES REMAIN ACROSS
THE AREA. WITH THE POOLING MOISTURE....TEMPS HAVE BEEN SLOW TO
DROP ACROSS THE AREA. GUIDANCE SUGGESTS AN H85 THETAE PUSH OF
NEAR 50 DEGREES INTO THE AREA NEAR 12Z. THIS AND THE VORT MAX WILL
DOMINATE OUR WEATHER IN THE NEXT 6 TO 12 HOURS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 329 AM CDT SUN AUG 2 2015

MAIN FORECAST CONCERN FOR THE SHORT ARE THE CHANCES FOR
THUNDERSTORMS AND RAIN TODAY. THERE ARE TWO CHANCES WITH THE FIRST
ONE EITHER ONGOING AT 12Z OR STARTING SHORTLY THEREAFTER. THE
OTHER IS ASSOCIATED WITH A COLD FRONT THAT WILL MOVE THROUGH THE
AREA TODAY AND INTO TONIGHT. SOME OF THE STORMS LATER THIS
AFTERNOON AND EVENING COULD BE STRONG TO SEVERE.

THIS MORNING THE ACCAS DECK MOVING INTO THE AREA WILL ENCOUNTER AN
H85 THETAE PUSH. THESE TWO ARE FORECAST TO BE COINCIDENT ACROSS
THE CWA NEAR 12Z. THIS COULD LEAD TO THE DEVELOPMENT OF SHOWERS
AND THUNDERSTORMS ACROSS THE AREA. LARGE SCALE MODELS HINT AT THIS
POSSIBLY HAPPENING...HOWEVER THE MESOSCALE NATURE OF THE FORCINGS
ARE DIFFICULT FOR THE MODELS TO HANDLE CORRECTLY. PERUSING THE
CAMS...WHICH DO BETTER WITH MESOSCALE FEATURES...IT IS CLEAR THAT
THESE MODELS DO SUGGEST ADDITIONAL THUNDERSTORM DEVELOPMENT THIS
MORNING WITH THE WAVE. AT THIS TIME...THESE STORMS ARE NOT
EXPECTED TO BE SEVERE. A STRONG STORM WITH SMALL HAIL COULD BE
POSSIBLE. I DO NOT HAVE HIGH CONFIDENCE IN THIS OCCURRING SO
DECIDED TO GO WITH SCHC POPS UNTIL THE ACCAS BECOMES BETTER
AGITATED. ANY STORMS THIS AM COULD LEAVE OFBS THAT MAY
INFLUENCE CONVECTION LATER.

THIS AFTERNOON...GUIDANCE SUGGESTS THAT MIXING WILL RESULT IN HIGH
TEMPS IN THE 90S ACROSS THE AREA. SOUNDINGS INDICATE THE EML HAS
RESULTED IN DRIER AIR ALOFT. AS THIS DRIER AIR IS MIXED DOWN...THE
TEMPS SHOULD INCREASE AND DEWPOINTS SHOULD LOWER. USED MOSGUIDE
FOR THE DEWPOINTS AS THEY SEEMED TO HAVE A BETTER HANDLE ON WHAT
WAS GOING ON NOW AND MIXING THE DEWPOINTS LOWER THIS PM. AS A
RESULT...HEAT INDICES WILL REMAIN BELOW CRITERIA.

LATE THIS AFTERNOON A COLD FRONT WILL MOVE THROUGH THE AREA.
LOOKING AT THE THUNDERSTORM POTENTIAL...THERE WILL BE SUFFICIENT
DEEP LAYER SHEAR FOR ISOLATED CELLS. WITH THE MAIN FORCING TO THE
NORTH...THESE STORMS MAY BE SLOWER TO GROW UPSCALE INTO A MCS.
LAPSE RATES IN THE MID LEVELS SUGGEST THAT HAIL WILL BE THE MAIN
THREAT. WITH THE HIGH TEMPS AND LIKELY HIGHER STORM
BASES...DAMAGING WINDS COULD ALSO BE POSSIBLE. LOW LEVEL SHEAR
AND HODOS ARE INDICATIVE OF THE POSSIBILITY OF TORNADOES AS WELL.
IN FACT THEY ARE VERY FAVORABLE FOR POSSIBLE TORNADOES.
HOWEVER...THE THERMODYNAMIC ENVIRONMENT IS NOT. I THINK THE THREAT
OF TORNADOES IS HIGHER WITH AN MCS INSTEAD OF A SUPERCELL STORM
THAT MAY BE THE FIRST MODE OF DEVELOPMENT. REGARDLESS THERE IS A
THREAT FOR SEVERE WEATHER FROM THESE STORMS.

LOOKING AT THE CAMS...THE NAM 4KM HAS THE BULK OF THE STORMS AND
BOWING STRUCTURES ACROSS WI AND E IL. THIS MODEL POPS SHORT LIVED
ISOLATED CELLS THAT STRUGGLE TO GROW UPSCALE INTO A MCS
STRUCTURES. THE WRFNMM AND ARW ARE EERILY SIMILAR IN WHICH A
FRONTAL MCS COMES THROUGH OUR AREA INSTEAD OF TO THE EAST.
REGARDLESS THESE MODELS PRODUCE STORMS AND THUS GIVE ME HIGHER
CONFIDENCE THAT CONVECTION WILL OCCUR. DID NOT GO HIGHER THAN CHC
AS I DO NOT HAVE AN IDEA OF WHICH OF THE SOLUTIONS WILL OCCUR.
LATER SHIFTS MAY BE ABLE TO INCREASE POPS ACROSS THE AREA AS THE
DAY PROGRESSES AND A CLEARER SOLUTION IS SEEN.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 329 AM CDT SUN AUG 2 2015

MONDAY AND MONDAY NIGHT... NORTHWEST FLOW ALOFT WILL DOMINATE EARLY IN THE
WEEK AS ANOMALOUSLY DEEP UPPER LOW (500 MB HEIGHTS OF 550-555 DECAMETERS
EQUATING TO ROUGHLY 2+ STANDARD DEVIATIONS BELOW CLIMO PER NAEFS) REMAINS
PARKED NEAR QUEBEC. THIS FLOW PATTERN COUPLED WITH HIGH PRESSURE RIDGE
BUILDING IN WILL RESULT IN COOLER (NEAR NORMAL) AND DRIER CONDITIONS
TO START THE WEEK. A SURFACE FRONT IS ANTICIPATED TO STALL OUT FROM THE
CENTRAL PLAINS TO THE APPALACHIANS BY MONDAY EVENING. ISENTROPIC LIFT AND
WEAK LOW AMPLITUDE SHORTWAVES WILL PROVIDE FOCUS FOR PRECIPITATION CHANCES
NEAR AND ON COOL SIDE OF BOUNDARY...WITH THE FAR SOUTHERN CWA POTENTIALLY IN
CLOSE PROXIMITY TO SOME OF THIS ACTIVITY.

TUESDAY AND TUESDAY NIGHT... OVERALL PATTERN NOT SHOWING MUCH CHANGE
DURING THIS PERIOD WITH UPPER LOW SLOW MOVING THROUGH ONTARIO... AND
CWA STAYING ON COOL SIDE OF STALLED FRONTAL ZONE FROM THE PLAINS THROUGH THE
MID-MISSISSIPPI VALLEY. THUS... MORE OF THE SAME WITH PLEASANT CONDITIONS
WITH NEAR TO SLIGHTLY BELOW NORMAL TEMPS AND COMFORTABLE HUMIDITY LEVELS...
AND ANY RAIN CHANCES MAINLY TO OUR SOUTH/WEST IN VICINITY OF STALLED FRONT
WITH SOUTHERN CWA STANDING ANY CHANCES FOR RAIN BEING IN CLOSER PROXIMITY TO
BOUNDARY.

WEDNESDAY THROUGH SATURDAY... CONTINUED GRADUAL DRAWN DOWN ON TEMPS TO BELOW
NORMAL EXPECTED INTO LATE WEEK WITH INFLUX OF COOLER AIR (850 MB TEMPS
LOWERING INTO RANGE OF 12-16C) IN WAKE OF DEPARTING ONTARIO UPPER LOW.
IN ADDITION...LIKELIHOOD OF INTERVALS OF CLOUDINESS WITH SERIES OF UPPER LEVEL
DISTURBANCES PROPAGATING THROUGH REGION IN THE SEMI-ZONAL TO NORTHWEST FLOW
TO AID IN KEEPING TEMPS BELOW NORMAL. WITH SURFACE FRONT NEARBY WILL MAINTAIN
RAIN CHANCES THROUGH THURSDAY THEN TRENDS SUPPORT DRYING OUT LATE WEEK INTO THE
WEEKEND WITH ANOTHER BOUT OF GREAT LAKES RIDGING AND INFLUX OF COOLER...DRIER AIR.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1145 PM CDT SAT AUG 1 2015

VFR CONDITIONS WILL BE SEEN THROUGH 15Z/02. THE PROBABILITY OF A
SHRA OR TSRA AFFECTING A TAF SITE THROUGH SUNRISE IS UNDER 10
PERCENT. IF A SHRA/TSRA WOULD AFFECT A TAF SITE...KDBQ WOULD HAVE
A SLIGHTLY BETTER CHANCE...AND ONLY A BRIEF PERIOD OF MVFR
CONDITIONS MIGHT BE SEEN. AFT 15Z/02 VFR CONDITIONS ARE EXPECTED
TO CONTINUE. A NEW ROUND OF CONVECTION IS EXPECTED AFT 18Z/02
ACROSS NORTHERN ILLINOIS.


&&

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

$$

UPDATE...GIBBS
SYNOPSIS...GIBBS
SHORT TERM...GIBBS
LONG TERM...05
AVIATION...08


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