Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 300812
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
312 AM CDT THU JUL 30 2015

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 243 AM CDT THU JUL 30 2015

A FAIRLY VIGOROUS UPPER LEVEL DISTURBANCE...SHOWN ON WATER VAPOR
IMAGERY TRACKING THROUGH SOUTHERN MANITOBA AND SASKATCHEWAN...WILL
TRACK ALONG THE WISCONSIN AND MICHIGAN BORDER THIS
AFTERNOON...COMBINED WITH A SURGE OF HIGHER THETA-E AIR IN THIS
REGION. THIS WILL SET THE STAGE FOR THE POSSIBILITY OF SHOWERS AND
THUNDERSTORMS ACROSS THE NORTH. NWP MODELS AND HI-RES MODELS ARE
IN GENERAL AGREEMENT ON THE TIMING AND LOCATION OF THESE
SHOWERS...SAVE FOR THE CANADIAN MODEL WHICH IS STILL DRY. MODEL
SOUNDINGS SHOW A FAIRLY UNSTABLE ATMOSPHERE IN PLACE ACROSS
NORTHERN WISCONSIN THIS AFTERNOON...WITH MUCAPES OF 500 TO 700
J/KG. GIVEN THE FORCING AND INSTABILITY IN PLACE WILL RAISE POPS
ACROSS THE NORTH THIS AFTERNOON AND INCREASE THE COVERAGE OF POPS
FURTHER SOUTH. COVERAGE THIS AFTERNOON COULD ACTUALLY BE MORE
WIDESPREAD THAN THE AREA EXPERIENCED WITH THE COLD FRONT THAT
PASSED THROUGH YESTERDAY MORNING. STORMS THAT DEVELOP COULD
PRODUCE STRONG GUSTY WINDS AS MID LEVEL WINDS WILL STILL BE FAIRLY
GUSTY. SURFACE WINDS ARE EXPECTED TO GUST TO 20 TO 25 MPH...LOWER
THAN THEY WERE YESTERDAY AFTERNOON. HIGHS TODAY SHOULD GET INTO
THE UPPER 70S ACROSS THE NORTH...WITH LOW TO MID 80S FURTHER
SOUTH.

SHOWERS AND THUNDERSTORMS MAY LINGER INTO THE EARLY EVENING...BUT
SHOULD DISSIPATE WITH THE LOSS OF DAYTIME HEATING RATHER QUICKLY.
OVERNIGHT LOWS ARE EXPECTED TO DROP INTO THE UPPER 50S TO LOWER
60S.

ANOTHER MID LEVEL SHORTWAVE WILL TRACK THROUGH ON
FRIDAY...BRINGING A RENEWED CHANCE FOR SHOWERS AND THUNDERSTORMS
DURING THE AFTERNOON HOURS. HOWEVER INSTABILITY VALUES WILL BE
MUCH LESS THAN TODAY...THEREFORE WILL STAY WITH THE SLIGHT CHANCE
POPS FRIDAY AFTERNOON. TEMPERATURES ON FRIDAY WILL BE SIMILAR TO
TODAY WITH HIGHS IN THE UPPER 70S TO LOWER 80S.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 243 AM CDT THU JUL 30 2015

THE LATEST MEDIUM RANGE ENSEMBLE GUIDANCE CONTINUES TO INDICATE THAT
NORTHWEST UPPER FLOW WILL PREVAIL THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK...BETWEEN SUB-TROPICAL RIDGING OVER THE ROCKIES AND
TROUGHING OVER ONTARIO.  SOME AMPLIFICATION IN THE PATTERN WILL
OCCUR BY THE MIDDLE OF NEXT WEEK...WHICH THE ECMWF SHOWS BETTER THAN
THE GFS.  WILL CONTINUE TO SIDE WITH THE ECMWF FOR MUCH OF THIS
FORECAST.

FRIDAY NIGHT THROUGH SATURDAY NIGHT...CHANNELED SHORTWAVES WILL BE
SWINGING ACROSS THE NORTHERN GREAT LAKES FRIDAY NIGHT.  THOUGH THEY
MAY BRING SCATTERED MID-CLOUDS AT TIMES...PROGGED SOUNDINGS ARE TOO
DRY FOR ANY SHOWER THREATS.  THIS TREND CONTINUES ON SATURDAY WHEN
ANY MID-LEVEL MOISTURE FROM SHORTWAVES WILL BECOME ENHANCED BY
DIURNAL INSTABILITY.  SOUNDINGS AGAIN HAVE TROUBLE SATURATING BELOW
700MB SO THINK THE ECMWF IS TOO PESSIMISTIC IN GENERATING PRECIP SAT
AFTERNOON.  WILL THEREFORE STAY WITH A DRY FORECAST.  PRECIP CHANCES
IMPROVE ON SATURDAY NIGHT AS THE LOW AND MID-LEVEL FLOW TEMPORARILY
BACK TO MORE OF A SOUTH OR EVEN SOUTHWEST DIRECTION.  THIS BACKING
FLOW WILL SUPPORT 925-700MB THETAE ADVECTION WHICH WILL BETTER
TARGET CENTRAL AND SOUTHERN WISCONSIN THAN FURTHER NORTH.  WILL
INCREASE PRECIP CHANCES SOME...BUT WILL NOT GET TOO AGGRESSIVE WITH
THE CURRENT DRY PATTERN.  NO SIGNIFICANT CHANGES TO TEMPS.

REST OF THE FORECAST...PRECIP CHANCES WILL LINGER INTO SUNDAY
MORNING...BUT MAY SEE A BREAK IN THE AFTERNOON AS THE WARM/MOIST
ADVECTION WEAKENS.  ANY BREAK WILL BE SHORT-LIVED HOWEVER...SINCE
THE NEXT CANADIAN COLD FRONT WILL ARRIVE SUNDAY NIGHT.  CHANCES OF
SHOWERS AND THUNDERSTORMS WILL BE WIDESPREAD ALONG THE FRONT...EVEN
IF MID-LEVEL FGEN WILL BE WEAKENING ALONG IT.  A COOLER AND DRIER
AIRMASS WILL THEN MOVE INTO THE REGION FOR MONDAY AND TUESDAY...WITH
AFTERNOON SHOWERS AND ISOLATED STORMS POSSIBLE...MAINLY ACROSS
NORTHERN WISCONSIN.  CONFIDENCE DECREASES BY WEDNESDAY AND
THURSDAY...BUT SOME INDICATIONS OF SHORTWAVES PROVIDING OCCASIONAL
PRECIP CHANCES DURING THIS TIME.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1133 PM CDT WED JUL 29 2015

CYCLONIC FLOW IS EXPECTED TO PERSIST ACROSS THE AREA THROUGH
THURSDAY NIGHT...BUT VFR CONDITIONS SHOULD PREVAIL. AN UPPER LEVEL
SHORT WAVE WAS FORECAST TO PASS THROUGH WISCONSIN DURING THE DAY
ON THURSDAY WITH SOME OF THE MODELS PRODUCING RAIN AND OTHERS NOT.
THE 00Z GFS/00Z CANADIAN WERE DRY...THE 00Z NAM ONLY SPIT OUT A
SMALL AREA OF LIGHT QPF...WHILE THE 12Z ECMWF AND 21Z SREF HAD
MORE WIDESPREAD AND HIGHER QPF. ANOTHER SHORT WAVE APPROACHES
WISCONSIN THURSDAY EVENING BUT MODELS WERE NOT IN AGREEMENT WITH
THAT SYSTEM EITHER. AS A RESULT...THE FORECAST REMAINS DRY WITH
ONLY SOME SCATTERED TO BROKEN VFR CIGS. WINDS WILL INCREASE AGAIN
DURING THE DAY BUT GUSTS WILL NOT BE NEARLY AS HIGH AS THEY WERE
DURING THE DAY ON WEDNESDAY.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....KURIMSKI
LONG TERM......MPC
AVIATION.......MG


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