62°F
Updated:
9/22/2023
04:08:00am

Forecast Discussion
NWS Omaha/Valley, NE
000 FXUS63 KOAX 220440 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1140 PM CDT Thu Sep 21 2023 ...Updated Aviation Forecast Discussion... .DISCUSSION... Issued at 325 PM CDT Thu Sep 21 2023 Key Messages: - Scattered showers and thunderstorms are expected to move into eastern Nebraska overnight tonight, with the threat of strong gusty winds, large hail (particularly southwest of a line from Seward to Beatrice), and lightning. - The Friday severe weather risk is conditional, depending on the strength of the capping inversion. However, if storms are able to develop, there will be the risk for severe wind gusts and large hail up to 2 inches in diameter. - Numerous severe thunderstorms are possible across the region Saturday afternoon and evening. All mode of severe weather will be possible. - Lingering showers and clouds will persist across the region through Monday, giving way to clear and dry conditions Tuesday through the end of the forecast period. ...TODAY AND TONIGHT... 12Z UPPER AIR ANALYSIS SHOWS A LONG WAVE TROUGH POSITIONED OVER THE WESTERN CONUS WITH STRONG DIFFLUENT FLOW OVER THE ROCKIES AND HIGH PLAINS. 500 MB ANALYSIS SHOWS AN EMBEDDED SHORTWAVE TROUGH ROUNDING THE EASTERN SIDE OF THE LONGWAVE TROUGH AND IS EXPECTED TO EJECT OUT INTO THE CENTRAL HIGH PLAINS THIS AFTERNOON. AT THE SURFACE, CURRENT OBS SHOWS EAST/SOUTHEASTERLY WINDS AT 10 TO 20 MPH ACROSS THE REGION. WHILE SOUTHEAST NEBRASKA AND SOUTHWEST IOWA WILL SEE HIGHS IN THE LOW 80S, A COLD POOL LEFT OVER FROM MORNING CONVECTION SHOULD KEEP TEMPERATURES IN THE 60S AND LOW 70S FOR PORTIONS OF NORTHEAST NEBRASKA. TONIGHT, WITH THE EJECTION OF THE AFOREMENTIONED SHORTWAVE TROUGH AND MODEST LOW LEVEL MOISTURE WITH DEW POINTS IN THE 60S, SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS PORTIONS OF CENTRAL NEBRASKA. THESE STORMS ARE EXPECTED TO GROW UPSCALE AND RESULT IN A CLUSTER OF STORMS, POSSIBLE AND MCS, WHICH WILL MOVE INTO OUR REGION FROM THE WEST. CURRENT GUIDANCE SUGGESTS THE MOST LIKELY TIME FRAME THESE STORMS WILL MOVE INTO EASTERN NEBRASKA WILL BE AROUND 11PM, WITH THE HIGHEST CHANCES OF RAIN BEING BETWEEN MIDNIGHT AND 4AM. THESE STORMS WILL POSE THE RISK FOR STRONG GUSTY WINDS AND SMALL HAIL, BUT THIS THREAT SHOULD REMAIN WEST OF US- 81, AS AREAS EAST OF THE HIGHWAY WILL HAVE LIMITED INSTABILITY WITH THE DEVELOPMENT OF A STRONG CAPPING INVERSION ASSOCIATED WITH THE NOCTURNAL BOUNDARY LAYER AND STRONG WARM AIR ADVECTION IN THE 850- 700MB LAYER. ...FRIDAY AND FRIDAY NIGHT... SCATTERED SHOWERS (30-40%) ARE EXPECTED TO LINGER ACROSS THE REGION FRIDAY MORNING, WITH RAIN ENDING BY 11AM. OVER THE COURSE OF THE AFTERNOON, FLOW AT THE SURFACE IS EXPECTED TO VEER AND BECOME MORE SOUTHERLY WITH THE DEVELOPMENT OF A SURFACE TROUGH ASSOCIATED WITH THE EJECTION OF ANOTHER SHORTWAVE TROUGH INTO THE CENTRAL PLAINS. THIS WILL ALLOW MODEST MOISTURE TRANSPORT INTO THE REGION FROM THE SOUTH, WITH DEWPOINTS INCREASING TO THE MID AND UPPER 60S. HOWEVER, EVEN THOUGH THERE IS SUFFICIENT LOW LEVEL MOISTURE AND SUBSTANTIAL DYNAMIC FORCING THAT WILL MOVE INTO THE REGION TOMORROW AFTERNOON, A STRONG FLOW (25-40 KNOTS) IN THE 850-700 HPA LAYER WILL ADVECT WARM AIR INTO THE REGION FROM THE SOUTH/SOUTHWEST. THIS WILL HELP REINFORCE THE CAPPING INVERSION OVER THE COURSE OF THE DAY, CREATING A CONDITIONAL RISK FOR STRONG TO SEVERE THUNDERSTORMS ACROSS NORTHEAST NEBRASKA. IF FLOW IN THIS LAYER TAKES ON A MORE WESTERLY COMPONENT, STORM INITIATION MAY BE INHIBITED ALTOGETHER ACROSS THE REGION. IF FLOW IN THIS LAYER TAKES ON MORE OF AN EASTERLY COMPONENT, WARM AIR ADVECTION WILL BE WEAKER CONTRIBUTING TO A WEAKER CAPPING INVERSION AND ALLOWING MORE GREATER COVERAGE OF STORMS LATER IN THE EVENING AND OVERNIGHT HOURS. WITH ANY STORMS THAT DEVELOP, LARGE HAIL AND STRONG DAMAGING WINDS WILL BE THE PRIMARY HAZARD, BUT A TORNADO CANNOT BE RULED OUT. ...SATURDAY AND SATURDAY NIGHT... THE LONGWAVE TROUGH OUT WEST IS EXPECTED TO EJECT INTO THE NORTHERN PLAINS SATURDAY AFTERNOON. THIS WILL CONTRIBUTE TO THE DEVELOPMENT OF A SURFACE LOW IN CENTRAL SOUTH DAKOTA THAT WILL TRACK TO THE NORTHEAST, AND A SECONDARY LOW WHICH IS EXPECTED TO DEVELOP ACROSS NORTHEASTERN KANSAS. AT THE SURFACE, A DRY LINE IS EXPECTED TO DEVELOP IN CENTRAL NEBRASKA AND MIX EASTWARD INTO THE REGION DURING THE AFTERNOON HOURS. AHEAD OF THE DRYLINE, SURFACE DEW POINTS WILL BE IN THE 60S, WITH TEMPERATURES REACHING INTO THE 80S. THIS WILL ALLOW FOR MODEST INSTABILITY TO OVERSPREAD THE REGION, WITH MLCAPE 1000-2000 J/KG. UNLIKE FRIDAY, THE CAPPING INVERSION IS EXPECTED TO WEAKEN ALLOWING FOR THUNDERSTORM DEVELOPMENT ALONG THE DRYLINE BY 4PM. WITH CROSS BOUNDARY FLOW, BULK SHEAR 40-50 KNOTS AND 0-3KM SRH BETWEEN 200 AND 300 M^2/S^2, A LINE OF SUPERCELLS APPEARS PROBABLE WITH ALL MODES OF SEVERE WEATHER POSSIBLE. THERE IS STILL UNCERTAINTY WITH HOW FAR WEST THESE STORMS WILL DEVELOP, BUT MODEL CONSENSUS IS THAT A LINE OF STRONG TO SEVERE THUNDERSTORMS WILL DEVELOP BY THE TIME THE DRY LINE REACHES THE MISSOURI RIVER. STORMS SHOULD BE EAST AND SOUTH OF THE REGION BY MIDNIGHT. ...SUNDAY THROUGH THURSDAY... THE WEEKEND STORM SYSTEM IS EXPECTED TO BECOME CUTOFF AND LINGER IN THE NORTHERN PLAINS/UPPER MIDWEST THROUGH MONDAY NEXT WEEK. THIS WILL BRING CLOUDS AND SCATTERED LIGHT RAIN SHOWERS TO PORTIONS OF NORTHEAST NEBRASKA AND WESTERN IOWA. BY TUESDAY THE SYSTEM SHOULD MOVE EAST OF OUR AREA BRINGING CLEARER AND DRIER CONDITIONS TO THE REGION FOR THE END OF THE FORECAST PERIOD. TEMPERATURES DURING THIS TIME ARE EXPECTED TO BE AVERAGE, WITH HIGHS IN THE MID AND UPPER 70S AND LOWS IN THE LOW 50S. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1137 PM CDT Thu Sep 21 2023 VFR conditions at TAF issuance, but MVFR conditions potentially developing by 10-12z, then back to VFR by 22z at KLNK/KOMA and 23/04z at KOFK. We`ll also have to contend with shower and thunderstorm chances early in the TAF, the best chance for thunderstorms appears to be be at KLNK 08-10z, and KOMA 10-12z. There may also be spotty showers in the clouds Friday afternoon into the evening, but too far out to reliably forecast at this time. Southeast winds generally less than 12 knots through the period. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Darrah AVIATION...DeWald
NWS OAX Office Area Forecast Discussion
Forecast Discussion
NWS Hastings, NE
000 FXUS63 KGID 220517 AFDGID AREA FORECAST DISCUSSION National Weather Service Hastings NE 1217 AM CDT Fri Sep 22 2023 .UPDATE... Issued at 1214 AM CDT Fri Sep 22 2023 UPDATE Issued at 956 PM CDT Thu Sep 21 2023 The tornado watch for portions of south central Nebraska and north central Kansas has been allowed to expire. while the threat for tornadoes has diminished, a few strong to marginally severe thunderstorms remain possible early this morning. The main hazards with the stronger storms will be strong winds and heavy rainfall, which may result in localized flooding. && .DISCUSSION...(This evening through Thursday) Issued at 133 PM CDT Thu Sep 21 2023 Key Messages: * Thunderstorms chances the next 48 hours or so are main focus of the forecast, and to what extent the area could see severe weather. * The forecast returns to "mostly dry" in the mid/longer period with temperatures at or slightly above seasonal normals. Deck of low/mid level clouds across the forecast in response to deep moisture return and warm advection ahead of western US trough and lead shortwave moving in Colorado region. Surface dewpoints "up there" for late September...well into the 60s. With the clouds have come scattered showers and cooler temperatures, especially across the northern forecast area which has had an outflow from morning thunderstorms in northeast Nebraska move through. Tonight the issue is thunderstorms, coverage and severity. The bottom line is there is uncertainty in both coverage and intensity but also enough "juice" to support some strong/severe storms for a time. First, the mid-level showers may perk up a bit as they move northeast across the areas the next 3-4 hours. Not looking for severe weather but a strong storm or two southeast of Hastings is possible. The main severe risk initially appears to be just west of the forecast, in southwest Nebraska on the lead edge of the deep moisture and differential heating. Initial storm development there could be severe in the later afternoon, but development farther into southern Nebraska in the 6 to 9 pm timeframe appears probable. This convection has the potential to produce large hail and strong winds. Some, discrete supercell in the early evening will be worth watching for a tornado, but personally think that is more likely just west. By mid/later evening, a decent low level jet will promote more development and sustainability to the east across much of the forecast area it appears. Again, severe storms possible, but overall severity should wane toward midnight. Should the storms develop in this manner, there will be some decent rain to measure in a few people`s rain gauge. The upper level low and and main front move through on Saturday morning. Prior to that, rain/storm chances Friday favor north of the forecast area. Although we display 40-50% rain chances north of I-80 tomorrow night, I think that may be too high. Same vote for Saturday, as the frontal timing and proximity of the low don`t suggest real great rain chances. Expect to see those chances tighten up and decrease Saturday in the east. Temperatures will drop a bit behind the front (from early this week) but still hold around normal for the weekend. Unfortunately, time has been sparse to look much at the longer term part of the forecast...roughly Sunday through Thursday. In general, an upper level ridge aloft will temporary assert itself for a few days keep much of the area mainly dry. Having said that, there small chances for showers/isolated thunderstorms. One is in the eastern areas Monday/Tuesday. Those are tied to the weekend upper low sort of shearing apart over eastern NE/IA. Pretty big assumption at this point and I would not be surprised if those eventually disappeared. And I would not bet too much on the rain chances later in the week just yet either. There is a LOT more dry than wet next week. Temperatures will be normal to slightly above normal (normal highs next week 73-79 degrees)which has been the trend much of September. And with morning lows in the lower/middle 50s, that is a pretty pleasant week for the first full week of autumn. Lighter winds early in the week will pick up and becoming more steady about midweek ahead of the potential trough by next weekend. && .AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Saturday) Issued at 1144 PM CDT Thu Sep 21 2023 -SHRA expected to end early this morning and behind the rain models bring in some IFR ceilings. The winds have been a little squirrely from the storms, but should become more easterly once this wave moves out. The models still vary in timing of lifting of ceilings so kept with afternoon timing for ceilings to lift. Some models hold the IFR ceilings all day. With all of the precip tonight, I would expect BR/FG Friday evening, so put 6BR to start off the potential for FG in future TAFS. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ UPDATE...Wekesser DISCUSSION...NOAA/NWS/Moritz AVIATION...Beda
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