Severe Thunderstorm Warning 16, NWS Gaylord, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
407 PM EDT SAT JUN 9 2001

LATEST SURFACE ANALYSIS CONTINUES TO SHOW HIGH PRESSURE IN CONTROL
OF THE WEATHER ACROSS THE GREAT LAKES REGION. HOWEVER...A WEAK SHORT
WAVE MOVING ACROSS MICHIGAN ALOFT IS WORKING WITH MODEST INSTABILITY
TO CAUSE SCATTERED SHOWERS AND THUNDERSTORMS. MAIN CONCERNS THIS
PACKAGE REVOLVE AROUND SHOWER AND THUNDERSTORM CHANCES THROUGH THE
SHORT TERM.

12Z MODELS ONLY IN FAIR AGREEMENT...ESPECIALLY WITH RESPECT TO THE
NEXT MAIN SHORT WAVE TO MOVE THROUGH THE REGION ON SUNDAY. THE AVN
IS FASTER AND STRONGER THAN THE ETA AND TO A LESSER DEGREE THE NGM.
SOME OF THE STRENGTH OF THE AVN APPEARS TO BE DUE TO CONVECTIVE
FEEDBACK FROM A MCS THAT SHOULD FIRE OVER THE NORTHERN PLAINS
TONIGHT. SO...HAVE GENERALLY FOLLOWED THE ETA SOLUTION...BUT HAVE
SPED UP THE MOVEMENT OF THE WAVE A BIT. GUIDANCE TEMPERATURES
GENERALLY CLOSE AND REASONABLE...SO HAVE NOT STRAYED TOO FAR.

TONIGHT...UPPER WAVE CENTERED OVER LOWER MICHIGAN WILL EXIT THE
REGION THIS EVENING. WILL CARRY A CHANCE OF SHOWERS AND
THUNDERSTORMS AREAWIDE FOR THE EVENING UNTIL THE WAVE EXITS AND THE
HEATING OF THE DAY SUBSIDES.

SUNDAY AND SUNDAY NIGHT...NEXT SHORT WAVE (CURRENTLY OVER MONTANA)
MOVES INTO THE REGION AND HAS DECENT DPVA ASSOCIATED WITH IT. OTHER
POSITIVE FACTORS FOR CONVECTION INCLUDE MODEST RRQ JET FORCING AND
STEEP SURFACE TO 500 MB LAPSE RATES (ABOUT 7 C/KM). MODEL SOUNDINGS
YIELD CAPE VALUES BY AFTERNOON OF 1000-1500 J/KG. WIND FIELDS
INCREASE BY AFTERNOON AS WELL...SO SOME OF THE THUNDERSTORMS HAVE
THE POTENTIAL TO BE SEVERE. CONVECTION WILL CONTINUE INTO THE NIGHT
TIME HOURS...ENDING AS THE WAVE EXITS THE REGION BY MORNING.

MONDAY AND MONDAY NIGHT...A MOSTLY QUIET AND MILDER PERIOD AS
SOUTHWEST LOW LEVEL FLOW PERSISTS AND WEAK UPPER RIDGING BUILDS BACK
INTO THE REGION. ANOTHER WAVE IS FORECAST TO RIDE UP THE BACK SIDE
OF THE RIDGE BY THE OVERNIGHT HOURS...BRINGING ANOTHER CHANCE OF
SHOWERS AND THUNDERSTORMS BY MORNING.

EXTENDED DISCUSSION...MODELS IN DECENT AGREEMENT TODAY...THOUGH MOST
HAVE TRENDED MORE AMPLIFIED ALOFT AND SLOWER WITH THE FRONTAL
PASSAGE AND ASSOCIATED PRECIPITATION FOR MID TO LATE WEEK (THE
CANADIAN HAS BEEN CONSISTENTLY SLOWER THROUGHOUT). THE CANADIAN AND
MRF ARE IN BEST AGREEMENT AND WILL LEAN TOWARD THEIR TIMING GIVEN
RECENT TRENDS. CURRENT CANADIAN/MRF TIMING IS ALSO SUPPORTED FAIRLY
WELL BY THEIR ENSEMBLE MEMBERS. FOLLOWING THIS THINKING...HAVE
PULLED SHOWER AND STORM MENTION FROM WEDNESDAY AND SHIFTED IT LATER
INTO THE THURSDAY/FRIDAY TIME FRAME. ONE OTHER CONCERN COMES
TUES?DAY...WHERE MODELS HINT AT A PIECE OF ENERGY LIFTING OUT OF THE
WESTERN U.S. TROF AND BRINING A CHANCE OF SHOWERS/STORMS WITH IT.
THE LATEST AVN EXTENSION ALSO SUPPORTS ADDING SHOWERS/STORMS TO
TUESDAY.

.APX...NONE.

BAK