Severe Thunderstorm Warning 20, NWS Billings, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
210 PM MDT SUN JUN 20 2004

.SHORT TERM...VALID FOR MON AND TUE...

THUNDERSTORMS HAVE DEVELOPED OVER SOUTHERN TIER IN ASSOCIATION
WITH ID SHORTWAVE. OTHER STORMS WERE OVER THE NW FORECAST AREA. HAVE
RAISED EVENING POPS ALONG SOUTHERN TIER AS SHORTWAVE OVER ID SINKS
S. EFFECTS FROM VORT WILL BE SOUTH OF AREA BY 12Z. BOTH MODELS HAD STEEP
AFTERNOON AND EVENING LAPSE RATES WITH DEEPEST INSTABILITY OVER THE
MOUNTAINS MON AND TUE WITH ETA SHOWING MORE PRECIPITATION THAN GFS. ETA
APPEARED A BIT OVERDONE WITH PRECIPITATION GIVEN LIMITED SOURCES OF
LIFT. ANOTHER SHORTWAVE FORECAST TO ROTATE SE THROUGH E MT/W DAKOTAS ON
MON. SHADED POPS WESTWARD DUE TO VORT LOBE MOVING THROUGH E ZONES AROUND
18Z. PIECES OF WEAK VORT ENERGY WILL ROTATE THROUGH THE AREA MON NIGHT
AND TUE IN CYCLONIC NW FLOW ALOFT. REMOVED POPS MON NIGHT AS AFTERNOON
CONVECTION SHOULD DISSIPATE WITH LOSS OF DAYTIME HEATING. CONTINUED THE
SLIGHT CHANCE POPS FOR TUE OVER THE E UNDER CYCLONIC FLOW. ALSO SOME
FRONTOGENESIS PROGGED OVER SW MTNS TUE SO CONTINUED POPS THERE. MADE
ONLY MINOR CHANGES TO TEMPERATURES. RAISED TEMPERATURES ON TUE AS
700 TEMPS PROGGED BETWEEN +2 AND +8 DEGREES C. ARTHUR

.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...

NW FLOW ALOFT PERSISTS ACROSS THE REGION THROUGH THE EXTENDED PERIOD.
MODELS CONTINUE TO SHOW GOOD AGREEMENT BETWEEN EACH OTHER AND SEE NO
REAL REASON TO MAKE ANY CHANGES. THE NW FLOW WILL CONTINUE TO BRING A
SERIES OF WEAK DISTURBANCES TO THE REGION RESULTING IN ISOLATED SHOWER
ACTIVITY OVER PORTIONS OF SC/SE MT...MAINLY THE MTNS AND THIS ALREADY
COORD WELL IN PREVIOUS FORECAST PACKAGE. ONE ITEM FOR SUBSEQUENT
SHIFTS TO WATCH IS THE PLACEMENT OF THE HUDSON LOW AND WRAP AROUND
FEATURES WITH FALLING THICKNESS VALUES BEYOND DAY 6 TIME FRAME...IF
THE LOW OFF THE PACIFIC COAST DOES NOT MOVE INLAND THIS WOULD ALLOW FOR
SLIGHTLY COOLER TEMPS TO INVADE THE EASTERN PORTION OF THE STATE. GIVEN
THAT A WEAK RIDGE LINGERS OVER THE WESTERN PORTION OF THE REGION AND ANY
UNCERTAINTIES THAT COULD DEVELOP IN LATER MODEL RUNS WILL LET PRESENT
FORECAST STAND AND MAKE CHANGES AS NEEDED FOR COORD WITH SURROUNDING
OFFICES. SPRINGER

&&

.PRELIMINARY POINT TEMP/POPS...

    MON     TUE     WED     THU     FRI     SAT     SUN
-----------------------------------------------------------
BIL 050/071 053/077 054/080 053/078 053/083 052/083 052/083
    20/B    00/B    00/B    00/B    00/B    00/B    00/B
LVM 044/070 043/076 046/075 046/075 045/077 044/077 044/077
    20/B    00/B    00/B    00/B    00/B    00/B    00/B
HDN 053/072 050/077 054/079 054/078 053/082 052/082 052/082
    20/B    02/T    20/B    00/B    00/B    00/B    00/B
MLS 048/070 053/074 056/077 053/075 055/079 054/079 054/079
    22/T    02/T    20/B    00/B    00/B    00/B    00/B
4BQ 052/071 051/075 053/079 053/075 052/079 051/079 051/079
    22/T    02/T    20/B    00/B    00/B    00/B    00/B
BHK 046/066 048/074 050/075 047/074 052/076 051/076 051/076
    22/T    02/T    20/B    00/B    00/B    00/B    00/B
SHR 045/068 046/075 049/078 049/076 048/079 047/079 047/079
    32/T    02/T    20/B    00/B    01/B    11/B    10/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&