Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 062350
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
650 PM CDT FRI MAY 6 2016

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 242 PM CDT FRI MAY 6 2016

MAIN FORECAST FOCUS TO BE ON THE PASSAGE OF A COLD FRONT TONIGHT
AND POTENTIAL FOR ANY THUNDERSTORMS TO DEVELOP.

THE 19Z MSAS SURFACE ANALYSIS SHOWED THIS COLD FRONT STRETCHED
FROM AN AREA OF LOW PRESSURE OVER CENTRAL ONTARIO SOUTHWEST
THROUGH NE MN...AND CONTINUING INTO CENTRAL SECTIONS OF SD.
PRECIPITATION HAS BEEN A BIT SPOTTY SO FAR...DESPITE TEMPERATURES
IN NE MN SOARING TO 90 DEGREES.

THIS COLD FRONT IS FORECAST TO DROP SE INTO NORTHERN WI THIS
EVENING AND PASS THROUGH CENTRAL/EAST-CENTRAL WI AROUND OR SHORTLY
AFTER MIDNIGHT. MODELS INDICATE SOME MODEST MID-LEVEL INSTABILITY
(STEEP LAPSE RATES/8H LI`S AROUND -2)...ALTHOUGH THERE IS EVIDENCE
OF A LOW-LEVEL CAP FROM FORECAST SOUNDINGS. THEREFORE...ANTICIPATE
A SCATTERED LINE OF HIGH-BASED SHOWERS/THUNDERSTORMS TO ACCOMPANY
THE FRONTAL PASSAGE. INSTABILITY OVERALL IS GENERALLY WEAK...SO DO
NOT EXPECT ANY STORMS TO BE STRONG OR SEVERE. WINDS WILL VEER TO
THE NORTH AND BRIEFLY GUST...ESPECIALLY OVER EASTERN WI WHERE THE
WINDS WOULD FUNNEL DOWN THE BAY OR ALONG THE LAKESHORE. MIN
TEMPERATURES WILL BE MILD WITH READINGS ONLY FALLING INTO THE MID
TO UPPER 40S NORTH/DOOR COUNTY...50-55 DEGREE RANGE SOUTH.

SOME CLEARING WILL OCCUR BEHIND THE FRONTAL PASSAGE SATURDAY
MORNING...HOWEVER SOME BUILD-UP OF MID CLOUDS IS ADVERTISED BY THE
MODELS FOR SATURDAY AFTERNOON AS COOLER AIR ALOFT INTERACTS WITH
THE STRONG MAY SUN AND SHORTWAVE ENERGY MOVES INTO THE GREAT LAKES
AS AN UPPER TROUGH ROTATES THROUGH THE REGION. DO NOT BELIEVE THAT
THERE WILL BE ENOUGH MOISTURE LEFT BEHIND THE FRONT TO ALLOW ANY
PRECIPITATION TO DEVELOP...JUST MORE CLOUDS IN THE AFTERNOON. MAX
TEMPERATURES WILL BE MORE SEASONAL WITH READINGS AROUND 60 DEGREES
LAKESIDE...LOWER TO MIDDLE 60S NORTH-CENTRAL AND MID TO UPPER 60S
ELSEWHERE.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 242 PM CDT FRI MAY 6 2016

MODEL GUIDANCE CONTINUES THE TREND OF SPLIT FLOW ACROSS THE
CONTINENT THROUGH NEXT WEEK. THERE WILL BE AT LEAST A COUPLE
CHANCES FOR PRECIPITATION IN THIS PERIOD...BUT SUBTLE DIFFERENCES
BETWEEN MODELS IN THE INTERACTION OF LOWS IN BOTH THE NORTHERN AND
SOUTHERN STREAMS MAKE PRECISE TIMING DIFFICULT. THE RESULT IS A
SMATTERING OF POPS THROUGHOUT THE PERIOD. THERE APPEARS TO BE
SUFFICIENT INSTABILITY TO MENTION SOME POTENTIAL FOR THUNDERSTORMS
EARLY IN THE WEEK...WHILE MENTIONS OF THUNDER HAVE LARGELY BEEN
REMOVED AS THE WEEK PROGRESSES.


SATURDAY NIGHT THRU SUNDAY NIGHT...
WEATHER CONDITIONS SHOULD BE LARGELY QUIET DURING THIS PERIOD WITH
A RIDGE OF HIGH PRESSURE DRIFTING EASTWARD ACROSS THE AREA. THE
NAM SUGGESTS SOME SCATTERED SHOWERS SATURDAY NIGHT AT THE
BEGINNING OF THE PERIOD AS AN UPPER LEVEL VORT MAX QUICKLY SHOOTS
THROUGH THE GREAT LAKES...AND THERE IS SOME SUPPORT FROM THE SREF
AND THE NCAR WRF ENSEMBLE WHICH HAVE A FEW WETTER MEMBERS.
HOWEVER...EXPECT THAT MOISTURE WILL LARGELY BE LACKING AND THE END
RESULT WILL BE DRY. ALSO SPURRED BY A RELATIVE LACK OF ATMOSPHERIC
MOISTURE...EXPECT RELATIVE HUMIDITY TO AGAIN BE LOW...SIMILAR TO
TODAY AND THE FORECAST FOR TOMORROW. THE PROLONGED PERIOD OF LOW
RH SHOULD HELP MAKE FINE FUELS RECEPTIVE TO FIRE IGNITION AND
GROWTH...AND A GREATER OPPORTUNITY FOR IGNITIONS SHOULD EXIST WITH
OPENING WEEKEND FOR THE FISHING SEASON. HOWEVER...IN THE WAKE OF A
COLD FRONT...TEMPERATURES SHOULD BE COOLER AND WINDS CALMER THAN
TODAY...SO NO FIRE WEATHER HEADLINES ARE ANTICIPATED AT THIS TIME.

NEXT WEEK...
A MORE SIGNIFICANT CHANCE FOR RAIN WITH AN OCCASIONAL
THUNDERSTORM LOOK TO MOVE INTO THE REGION EARLY NEXT WEEK. THE
BEST OPPORTUNITY FOR ELEVATED INSTABILITY AND ANY POTENTIAL
THUNDER LOOKS TO COME MONDAY NIGHT INTO TUESDAY. THIS IS STILL
FAIRLY LIMITED...SO NOT REALLY CONCERNED ABOUT SEVERE WEATHER AT
ALL. ONSET OF PRECIPITATION IS SOMEWHAT IN QUESTION...AND WILL
LARGELY DEPEND ON HOW QUICKLY A SOUTHERLY FLOW OF LOW LEVEL MOIST
AIR CAN OVERCOME THE CURRENT DRYNESS. THERE MAY BE A RELATIVE LULL
IN THE PRECIP MIDWEEK AS THE FIRST UPPER LOW WEAKENS AND DEPARTS
THE REGION...BUT THE AFOREMENTIONED DIFFICULTY IN PARSING THE
SUBTLE DIFFERENCES IN GUIDANCE MAKE IT HARD TO DELINEATE WHERE ANY
DRY PERIODS MAY OCCUR RIGHT NOW. A SECOND UPPER LOW WILL BRING
MORE PRECIP BY LATE WEEK.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 636 PM CDT FRI MAY 6 2016

MAIN AVIATION CONCERNS INCLUDE HIGH-BASED TSTMS WITH GUSTY WINDS
OVER NORTHERN WI THIS EVENING...BORDERLINE LLWS CONDITIONS
TONIGHT...AND A WIND SHIFT WITH A COLD FRONTAL PASSAGE.

EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE TAF PERIOD...ASIDE
FROM THE POSSIBILITY OF BRIEF MVFR VSBYS WITH TSTMS OVER NORTHERN
WI THIS EVG.

A LINE OF SHOWERS AND SCT TSTMS WAS MOVG THROUGH NW/NC WI EARLY
THIS EVG...IN ASSOCIATION WITH A COLD FRONTAL PASSAGE. THE STORMS
HAD EARLIER PRODUCED SMALL HAIL AND WIND GUSTS TO 25-40 KTS...BUT
WERE SHOWING SIGNS OF WEAKENING OVER THE PAST HOUR. THE REMNANTS
OF THESE STORMS SHOULD AFFECT THE RHI TAF SITE DURING THE MID TO
LATE EVENING...BUT CONFIDENCE IN PCPN TRENDS FOR THE OTHER TAF
SITES WAS TOO LOW TO MENTION IN THE TAFS AT THIS TIME.

THE COLD FRONT IS EXPECTED TO MOVE THROUGH RHI 03-04Z...AUW/CWA
05-06Z...AND GRB/ATW/MTW 07-08Z. WINDS WILL SWITCH TO THE NORTH
AND GUST TO 20-25 KTS AFTER THE FRONTAL PASSAGE.

BORDERLINE LLWS WILL DEVELOP THIS EVG...AND GRADUALLY WANE LATE
TONIGHT.

&&

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

$$

SHORT TERM.....KALLAS
LONG TERM......LUCHS
AVIATION.......KIECKBUSCH


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