000
FXUS65 KBYZ 172055
AFDBYZ
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BILLINGS MT
255 PM MDT SAT MAY 17 2008
.SHORT TERM...VALID FOR SUN AND MON...
SHORT TERM MODELS IN GOOD AGREEMENT FOR NEXT 12 TO 24 HOURS. QUIET
WEATHER OVER REGION WITH DRY NORTHWEST FLOW ALOFT AS HIGH PRESSURE
RIDGE SITS OVER WEST. A FEW MID TO UPPER LEVEL CLOUDS EXPECTED AS
RIDGE LOOKS A BIT DIRTY UPSTREAM.
SUNDAY AND MONDAY...
SURFACE LOW PROGGED TO DEEPEN ACROSS NORTHEAST MONTANA
AND DROP SOUTHEAST BY SUNDAY EVENING AS COLD FRONT GETS DRAGGED
INTO NORTHERN SECTIONS BY DISTURBANCE ROUNDING RIDGE UP IN CANADA.
PRESSURE GRADIENT WILL TIGHTEN IN RESPONSE CREATING WINDY
CONDITIONS ACROSS MUCH OF OUR FORECAST AREA.
POCKET OF INSTABILITY WITH NOTABLE EQUIVALENT POTENTIAL VORTICITY
WORKS IN BEHIND THIS BY SUNDAY NIGHT INTO MONDAY ACROSS EASTERN
ZONES. NAM MORE AGGRESSIVE PAINTING LIGHT CONVECTIVE PRECIP OVER
FORECAST AREA...BUT GFS DOES SHOW CONDENSATION PRESSURE DEFICITS
LOW ENOUGH TO INDICATE A FEW SHOWERS MAY REACH GROUND. SO HAVE
INTRODUCED SLIGHT CHANCE POPS OVER EAST SUNDAY NIGHT INTO MONDAY
MORNING...AND EXTENDED SLIGHT CHANCE INTO CENTRAL ZONES AS WELL
LATE MONDAY.
GUIDANCE NUMBERS ALSO COOLING MONDAY OFF QUITE A BIT...THIS SEEMS
REASONABLE GIVEN NORTH TO NORTHEAST LOW LEVEL WINDS AND UPSTREAM
TEMPS. WILL STILL KEEP WEST A LITTLE OVER GUIDANCE FOR NOW AS
BELIEVE COOLER AIR TO STAY MAINLY EAST WITH MOMENTUM OF SYSTEM.
FIRE WEATHER ISSUES...LOW RELATIVE HUMIDITY VALUES AND GUSTY WINDS
ARE EXPECTED SUNDAY. HOWEVER...AT THIS TIME FUELS ARE REPORTED TO
BE GREEN...AND FIRE WEATHER DANGERS REPORTED ACROSS OUR DISTRICTS
IS LOW TO MODERATE. THEREFORE...WILL NOT ISSUE FIRE WEATHER
HIGHLIGHTS FOR NOW. WILL UPDATE FIRE WEATHER FORECAST TO INSERT
HEADLINE TO RAISE AWARENESS OF WEATHER CONDITIONS SUNDAY.
HYDROLOGY ISSUES...AFTER CONFERENCE WITH RFC...RIVER FORECASTS FOR
LIVINGSTON ON YELLOWSTONE ADJUSTED UPWARD. CONFIDENCE INCREASING
THAT SOME FLOODING MAY OCCUR WITH WARM TEMPS AND PLENTY OF
SNOWPACK. WILL BE ISSUING RIVER FLOOD WATCH FOR WESTERN AREAS AND
ALSO CARBON COUNTY. BT
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
CONFIDENCE INCREASING FOR A GOOD CHANCE OF MOISTURE THE MIDDLE OF
THIS WEEK AS WELL AS ASSOCIATED COOLER TEMPERATURES. AT THIS
TIME HOWEVER...GFS SHOWING THAT DURATION OF THE STORM WOULD NOT BE
AS LONG AS ECMWF SUGGESTS.
TUESDAY...COLD LOOKS TO HAVE SLOWED DOWN A BIT...BUT AREA WILL BE
UNDER DEEP SOUTHWEST FLOW BY TUESDAY NIGHT. THIS WILL BRING THIS
CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA. GFS/ECMWF
CONTINUE TO BE IN PRETTY GOOD ON THE TIMING OF THE FRONT AT THIS
TIME INTO EASTERN ZONES BY 12Z WEDNESDAY.
WEDNESDAY...GOOD AGREEMENT STILL AT THIS TIME UPPER TROUGH WILL BE
WELL INTO WESTERN MONTANA. THIS SHOULD SET UP A FAIRLY LARGE AREA
OF MOISTURE AND CLOUD ACROSS THE AREA THROUGH THE NIGHT. HAVE
BEGIN TO LOWER TEMPERATURES TOWARDS ENSEMBLE MINIMUMS BUT WITH SOME
UNCERTAINTY WITH TIMING WILL NOT GO AS COLD AS IT COULD BE IF
SYSTEM IS IN PLACE AT THAT TIME.
THURSDAY...STILL PRETTY GOOD AGREEMENT BUT GFS STARTING TO TREND
STRONGER AND FURTHER SOUTH WITH ENERGY WHILE STRONG WITH NORTHERN
BRANCH OF THE SYSTEM. ECMWF/UKMET/GEM HOWEVER CONTINUE TO KEEP MORE
ENERGY FURTHER NORTH KEEPING SYSTEM CLOSED OFF FURTHER NORTH. THIS
WOULD RESULT IN A WETTER AND COOLER FORECAST AND WILL CONTINUE TO
TREND TO THIS AND RAISE POPS EVEN MORE INTO HIGH SCATTERED.
FRIDAY...BIGGEST DIFFERENCE SHOWING UP IN ECWMF/GFS WITH GFS
CLOSING ENERGY WELL TO THE SOUTH NEAR BAJA CALIFORNIA. ECMWF ON
THE OTHER HAND SHOWING A VERY UNSETTLED PATTERN FOR OUR AREA WITH
A DEEP SOUTHERN FETCH ACROSS WESTERN UNITED STATES. UKMET WOULD
TEND TO SUPPORT THIS PATTERN AS WELL SO WILL KEEP HIGHER SCATTERED
POPS GOING.
NO CHANGES BEYOND FRIDAY AS THINGS STILL LOOK UNCERTAIN WITH AT
LEAST SOME POPS NEAR CLIMATOLOGY. RASCH
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL ACROSS THE AREA TONIGHT AND TOMORROW.
A WEAK COLD FRONT WILL SOUTH INTO EASTERN ZONES TOMORROW AFTERNOON
AND BRING A SLIGHT CHANCE OF A THUNDERSTORM IN THE AFTERNOON AND
EVENING. RASCH
&&
.PRELIMINARY POINT TEMP/POPS...
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 057/089 057/081 052/086 049/057 044/056 041/062 044/063
00/N 02/T 02/T 35/W 55/W 54/R 32/R
LVM 053/084 052/076 048/081 043/054 038/052 036/055 040/058
00/N 01/B 03/T 35/W 55/W 54/R 33/R
HDN 054/090 055/082 051/086 049/062 043/057 040/064 044/063
00/N 02/T 02/T 25/W 55/W 54/R 32/R
MLS 054/087 057/077 052/083 050/064 046/057 043/061 046/063
02/T 22/T 00/B 24/W 45/W 54/R 32/R
4BQ 051/086 055/078 050/083 049/063 044/057 042/062 043/061
01/N 12/T 00/B 24/W 55/W 54/R 32/R
BHK 050/083 053/071 048/078 048/064 044/055 042/059 042/060
02/T 22/T 00/B 24/W 45/W 54/R 32/R
SHR 048/085 051/077 046/080 046/058 042/053 037/059 040/059
00/N 02/T 12/T 25/W 55/W 54/R 32/R
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLOOD WATCH THROUGH TUESDAY FOR MTZ034-039-041-056-064>067.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
