403
FXUS65 KTFX 260235
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
835 PM MDT MON MAR 25 2019
UPDATE
ONLY WEATHER UPDATE THIS EVENING WAS TO GENERALLY INCREASE
OVERNIGHT RELATIVE HUMIDITY. THIS CHANGE WAS TO HELP CREATE MORE
OF A CHANCE FOR FOG OVER THE NORTHEAST TFX PLAINS (INCLUDING THE
HAVRE AREA) AND IN SOME SOUTHWEST VALLEYS. THE REMAINDER OF THE
FORECAST IS ON TRACK.
DID MAKE SOME CHANGES TO HYDROLOGIC STATEMENTS, BUT DETAILS ARE IN
THE HYDROLOGY SECTION.
SYNOPSIS
HIGH PRESSURE MOVING ACROSS THE REGION WILL BRING DRY CONDITIONS
THROUGH EARLY TUESDAY AFTERNOON WITH TEMPERATURES ALSO WARMING TO
SLIGHTLY ABOVE SEASONAL AVERAGES TUESDAY AFTERNOON. MORE RAIN AND
SNOW SHOWERS WILL START TO AFFECT THE REGION BY TUESDAY EVENING,
ESPECIALLY IN WESTERN AND SOUTHWESTERN MT. MUCH OF THE STATE WILL
LIKELY SEE RAIN AND/OR SNOW BETWEEN WEDNESDAY NIGHT AND THURSDAY
ALONG WITH A RETURN TO COOLER THAN AVERAGE TEMPERATURES.
AVIATION
UPDATED 530 PM MDT MON MAR 25 2019
VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT 24 HOURS ACROSS THE
FORECAST AREA. MOISTURE IN THE SOUTHWEST FLOW ALOFT WILL CAUSE MID
AND HIGH LEVEL CLOUDINESS TO INCREASE OVER THE AREA. A DISTURBANCE
MAY BRING SOME MAINLY MOUNTAIN PRECIPITATION TO THE NORTHWEST
PORTION OF THE FORECAST AREA (INCLUDING KCTB) BETWEEN 09Z AND 18Z.
PATCHY FOG MAY ALSO DEVELOP IN SOME SOUTHWEST VALLEYS (INCLUDING
KHLN/KBZN) AND ALONG THE MILK RIVER (INCLUDING KHVR). HOWEVER, THE
INCREASING HIGH CLOUDS MAY HINDER ITS DEVELOPMENT, SO HAVE STAYED
WITH A VCFG FOG MENTION TO EXPRESS LOW CONFIDENCE IN FOG DIRECTLY
IMPACTING THESE TERMINALS. OVERALL, SOUTHWEST DOWNSLOPE WINDS WILL
INCREASE WITH THE PASSAGE OF THIS DISTURBANCE OVER THE PLAINS,
LEAVING THE MAIN CHANCE FOR PRECIPITATION OVER THE MOUNTAINS AFTER
18Z. COULSTON
HYDROLOGY
THE FLOOD ADVISORIES REMAIN IN EFFECT FOR CASCADE, CHOUTEAU, JUDITH
BASIN, FERGUS, PONDERA, AND TETON COUNTIES BASICALLY UNTIL FURTHER
NOTICE. LATEST REPORTS INDICATE THAT SOME WATER HAS RECEDED, BUT
THERE ARE STILL REPORTS OF MINOR FLOODING OVER MULTIPLE ROADWAYS IN
THE AREA ALONG WITH STANDING WATER IN FIELDS. MILD TEMPERATURES
THROUGH TUESDAY SHOULD INCREASE THE RATE OF MELTING AND RUNOFF, AND
MAY EXTEND ISSUES INTO SOUTHWESTERN MONTANA. THE THREAT FOR
PRECIPITATION FOR WEDNESDAY THROUGH THURSDAY COULD ALSO EXACERBATE
ONGOING FLOODING.
HAVE ALSO RECEIVED REPORTS OF SNOWMELT CAUSING WATER TO BACK UP IN
CULVERTS AND FLOW OVER SOME ROADS ACROSS PORTIONS OF SOUTHWEST
MONTANA (PRIMARILY BROADWATER, MADISON, AND GALLATIN COUNTIES AT
THIS TIME). WITH CONTINUED WARMING EXPECTED THERE, AS WELL AS AN
INCREASED THREAT FOR PRECIPITATION LATER THIS WEEK, THE POTENTIAL
FOR FURTHER MINOR FLOODING WILL INCREASE. WILL THEREFORE ISSUE A
FLOOD ADVISORY FOR ALL OF SOUTHWEST MONTANA, EXTENDING NORTH INTO
LEWIS AND CLARK COUNTY.
THE MISSOURI RIVER AT LANDUSKY (NEAR THE FRED ROBINSON BRIDGE)
IS CURRENTLY STAYING JUST BELOW MODERATE FLOOD STAGE (29.0 FEET)
AS OF MONDAY EVENING, SO AM CONTINUING THE FLOOD WARNING UNTIL
FURTHER NOTICE, WITH THE LATEST FORECAST HAVING THE RIVER FALL
BELOW FLOOD STAGE EARLY TUESDAY AFTERNOON. THE MAIN INFLOW LOOKS
TO BE FROM THE JUDITH RIVER, WITH RUNOFF FROM JUDITH BASIN AND
FERGUS COUNTIES, LIKELY EXACERBATED BY ICE BLOCKAGE ON THE
MISSOURI.
-HOENISCH/KREDENSOR/COULSTON
PREV DISCUSSION
/ISSUED 530 PM MDT MON MAR 25 2019/
TONIGHT THROUGH TUESDAY NIGHT...
AN UPPER LEVEL RIDGE SHIFTS EAST ACROSS THE NORTHERN ROCKIES AND
MONTANA TONIGHT FOR DRY CONDITIONS AND SEASONABLY COOL TEMPERATURES.
ON TUESDAY, A WEAK SHORTWAVE EJECTING OUT OF A LARGE UPPER LOW
EDGING TOWARD THE WEST COAST MOVES UP THROUGH SW FLOW ALOFT AND
ACROSS ID AND WESTERN MT LATE TUESDAY AND TUESDAY NIGHT. THIS
FEATURE WILL PUSH A WEAK COLD FRONT EAST ACROSS THE REGION TUESDAY
AFTERNOON AND EVENING WITH SHOWERS DEVELOPING ALONG THE FRONT AND
INCREASES AS THE FRONT MOVES SOUTHWARD IN THE EVENING. ENOUGH WEAK
INSTABILITY MAY BE PRESENT TUESDAY AFTERNOON AND EVENING FOR AN
ISOLATED THUNDERSTORM, PRIMARILY SOUTH OF A LINE FROM HELENA EAST TO
LEWISTOWN. HOENISCH
WEDNESDAY THROUGH NEXT MONDAY...
SOME PRECIP MAY HANG ON OVER SW MONTANA THROUGH THE DAY WEDNESDAY AS
THAT SHORTWAVE DEPARTS AND THE NEXT MAJOR SYSTEM MOVES ONSHORE THE
WEST COAST. THIS SYSTEM WILL REALLY GET INTO GEAR OVER THE SOUTHERN
PART OF THE CWA LATER WED AFTERNOON OR EVENING, THEN CONTINUE
IMPACTING THE AREA THROUGH THURSDAY NIGHT. THERE REMAINS SOME MODEL
DISAGREEMENT ON THE NORTHWARD EXTEND OF PRECIP, THOUGH IT APPEARS
LIKELY THAT MUCH OF THE HI-LINE EAST OF GLACIER COUNTY COULD BE
LOCKED OUT OF ANY SIGNIFICANT RAIN OR SNOW. SNOW TOTALS WERE
INCREASED A BIT OVERALL, WITH 1 TO 5 INCHES EXPECTED FOR THE PLAINS
SOUTH OF A LINE FROM CONRAD THROUGH CENTRAL FERGUS COUNTY, AS WELL
AS FOR MANY OF THE SOUTHWEST VALLEYS FROM HELENA SOUTHWARD. MOST OF
THE MOUNTAINS ARE FORECAST TO GET 5-10 INCHES OF SNOW, BUT SOME OF
THE SOUTHERN MOUNTAINS, PARTICULARLY THE RANGES IN MADISON AND
GALLATIN COUNTIES, COULD SEE OVER A FOOT.
THIS SYSTEM WILL START TO WIND DOWN DURING THE DAY FRI, BUT SOME
PRECIP COULD LINGER OVER SW MT DURING THAT TIME, UNTIL UPPER RIDGING
PUSHES INTO THE AREA FRI NIGHT. SATURDAY CURRENTLY LOOKS CLEAR AND
DRY, BUT MODELS DISAGREE ON WHETHER THE NEXT SYSTEM WILL PUSH INTO
THE AREA ON SUN, OR HOLD OFF UNTIL THE MON/TUE TIME FRAME. -KREDENSOR
PRELIMINARY POINT TEMPS/POPS
GTF 33 53 30 44 / 0 10 10 20
CTB 29 53 26 44 / 10 10 0 10
HLN 20 48 20 41 / 0 20 20 30
BZN 18 48 21 43 / 0 10 20 40
WEY 14 50 20 49 / 0 10 20 40
DLN 24 44 25 41 / 0 10 20 30
HVR 28 56 28 45 / 0 0 0 0
LWT 30 58 30 45 / 0 10 30 20
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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