493
FXUS63 KDVN 221726
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1226 PM CDT FRI OCT 22 2021
..AVIATION UPDATE
SYNOPSIS
ISSUED AT 220 AM CDT FRI OCT 22 2021
LATEST GOES NIGHTTIME MICROPHYSICS IMAGERY EARLY THIS MORNING
SHOWS PERSISTENT LOW LEVEL STRATUS ACROSS THE SOUTHEAST HALF OF
THE CWA. 00Z DVN/ILX SOUNDINGS SHOWED A RATHER STRONG INVERSION
AROUND 900MB TRAPPING THESE CLOUDS. LOOKING FURTHER UPSTREAM, MID
AND HIGH LEVEL CLOUDS ARE TRACKING SOUTHEAST OUT OF THE NORTHERN
PLAINS AND INTO SOUTHERN MN AND NORTHERN IA.
2AM SURFACE OBSERVATIONS SHOW TEMPERATURES MAINLY IN THE MIDDLE
30S ALONG AND NORTH OF A LINE FROM SIGOURNEY, TO CEDAR RAPIDS, TO
FREEPORT. THIS IS WHERE THERE ARE NO CLOUDS AND WHERE FROST IS
LIKELY THIS MORNING. ELSEWHERE, TEMPERATURES WERE IN THE 40S
UNDERNEATH THE STRATUS CLOUDS.
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 220 AM CDT FRI OCT 22 2021
FORECAST FOCUS TODAY IS ON CLOUD AND TEMPERATURE TRENDS AND
CHANCE FOR FROST TONIGHT. NO CHANGE TO FROST HEADLINES FOR THIS
MORNING.
AN UPPER LEVEL WAVE WILL TRACK EAST ACROSS THE CWA TODAY,
BRINGING AN INCREASE IN CLOUDS. KEPT THE TREND FROM PREVIOUS
FORECASTS AND WENT WITH THE LOWER SIDE OF GUIDANCE FOR
TEMPERATURES. HIGHS IN THE LOW TO MID 50S ARE FORECAST, SIMILAR TO
WHAT OCCURRED YESTERDAY. LATEST RAP SHOWS ENOUGH LIFT AND
MOISTURE WITH THE WAVE TO WARRANT ADDING SOME SLIGHT CHANCE
POPS/SPRINKLES TO THE FORECAST FOR A FEW HOURS IN THE AFTERNOON.
ANY PRECIPITATION THAT REACHES THE GROUND, WILL BE A FEW
HUNDREDTHS AT BEST.
CLOUDS WILL BEGIN TO DIMINISH THIS EVENING BEHIND THE PASSAGE OF
THE AFOREMENTIONED SHORTWAVE, ALONG WITH DECREASING WINDS. THIS
WILL SET THE STAGE FOR TEMPERATURES DROPPING INTO THE LOW TO MID
30S OVERNIGHT AND FROST HEADLINES WILL BE NEEDED. WILL LET THE
DAYSHIFT MAKE THE FINAL CALL ON LOCATION OF HEADLINES ONCE THE
CURRENT FROST ADVISORY EXPIRES. AT THIS TIME, AREAS ALONG AND
NORTH OF I-80 WILL HAVE THE BEST CHANCES OF FROST FORMATION EARLY
SATURDAY. IF WINDS GO COMPLETELY CALM, THERE IS SOME POTENTIAL FOR
AREAS IN RIVER VALLEYS AND NORTH OF HIGHWAY 20 TO SEE TEMPERATURES
DROP INTO THE UPPER 20S. WILL PASS THIS CONCERN ON TO THE NEXT
SHIFT.
LONG TERM
(SATURDAY THROUGH THURSDAY)
ISSUED AT 240 AM CDT FRI OCT 22 2021
KEY MESSAGES:
1. QUIET DAY SATURDAY.
2. ACTIVE PERIOD FOR REST OF THE LONG TERM.
3. HEAVY RAIN EVENT FORECAST ALONG THE MO/IA BORDER AND EAST INTO IL
ON SUNDAY.
DISCUSSION:
PATTERN FAVORS AN ACTIVE STORM TRACK ACROSS OUR AREA THROUGH THE
LONG TERM. RIDGING ON SATURDAY WILL QUICKLY TURN TO SW WITH RETURN
FLOW AND STALLED OUT WARM FRONT ACROSS THE SOUTHERN CWA. IMPRESSIVE
FGEN AND THE UPPER LEVEL LOW MOVING ACROSS THE AREA WILL LEAD TO
WIDESPREAD RAIN AND SOME THUNDERSTORMS. MORE TEMPORARY RIDGING IS
EXPECTED MONDAY INTO TUESDAY BEFORE THE FLOW TURNS SOUTHWEST AND AN
OPEN WAVE MOVES ACROSS THE AREA, BRINGING RAIN TO THE AREA ONCE
AGAIN.
MAIN FORECAST CHALLENGE TURNS TO SUNDAY'S SYSTEM AND HEAVY RAINFALL.
GUIDANCE IS IN GOOD AGREEMENT WITH A FILLING LOW MOVING TOWARDS THE
AREA. A WARM FRONT WILL MAKE IT TO NEAR THE MO/IA BORDER.
OVERRRUNING PRECIP WILL OVERSPREAD OUR AREA THROUGH THE MORNING.
SHOWERS AND STORMS ARE EXPECTED, ESPECIALLY NEAR THE WARM FRONT
ACROSS SOUTHERN IOWA. THE UPPER LEVEL LOW AND SFC LOW MOVE EAST
ALONG THE FRONT. EVENTUALLY THE WRAP AROUND WILL SLOWLY EXIT THE
AREA THROUGH MONDAY AS THE CLOSED LOW LUMBERS TO THE EAST.
LOW LEVEL SHEAR IS IMPRESSIVE AND ANY SURFACE BASED STORM THAT COULD
BE NEAR THE WARM FRONT COULD TAKE ON LOW LEVEL ROTATION. THE MAIN
QUESTION FOR ANY SEVERE WOULD BE HOW MUCH CAPE IS POSSIBLE. WITH
THE STALLED SFC FRONT AND ROBUST LIFT OVER THE FRONT, THINK THAT THE
SEVERE THREAT WILL BE LIMITED AND MAINLY SOUTH OF THE CWA. IF WE
CAN GET SOME CLEARING, THEN IT IS POSSIBLE FOR SEVERE WEATHER NEAR
THE SFC FRONT. GFS HAS THIS INTO OUR SOUTHERN CWA BY 30 MILES OR
SO. ANY CHANGE IN THE PLACEMENT OF THE WARM SECTOR WILL GREATLY
AFFECT ANY SEVERE THREAT. THE LARGER IMPACT LOOKS TO BE HEAVY RAIN.
SYNOPTIC MODELS SUGGEST 2 TO 3 INCHES OF RAIN WITH THIS EVENT ACROSS
THE SOUTHERN CWA. LOOKING AT ENSEMBLE GUIDANCE, LOOKS LIKE THIS
COULD END UP 2 TO 4 INCHES OF RAIN WITH ISOLATED POCKETS OF HIGHER
AMOUNTS. THE 00Z NAMNEST, UP TO 12Z SUNDAY HAS A 6+ BULLSEYE IN
SOUTH CENTRAL IOWA. THE SYNOPTIC SETUP POINTS TO A HIGH CONFIDENCE
HEAVY RAIN EVENT. THE HEAVIEST BAND MAY ONLY FALL IN A 1 TO 2
COUNTY WIDE BAND AND IS DIFFICULT TO NAIL DOWN AT THE CURRENT TIME.
LOOKING TO FFG ACROSS THIS AREA, WE COULD SEE SOME ISOLATED FLASH
FLOODING. LATER FORECASTS CAN REFINE TOTALS AND AREAS WHERE THE
HEAVIEST IS EXPECTED. WPC HAS A SMALL SLIGHT RISK FOR EXCESSIVE
RAINFALL. FURTHER NORTH HALF TO 1.5 INCHES OF RAIN IS EXPECTED
ACROSS THE REST OF THE CWA.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1225 PM CDT FRI OCT 22 2021
SURFACE HIGH PRESSURE WILL BRING VFR WEATHER WITH GOOD VISIBILITY
AND SOME PASSING MID LEVEL CLOUDS THROUGH THE PERIOD. WINDS WILL
REMAIN NORTHWESTERLY AROUND 3-8 KTS.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SYNOPSIS...GROSS
SHORT TERM...GROSS
LONG TERM...GIBBS
AVIATION...ERVIN
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