Lexington Weather

Lexington, Massachusetts, USA

56°F

5/20/2024 10:02pm

Lexington Conditions: Clear
Temperature: 56.1°F / 13.4°C
Dew Point: 52.0°F
Relative Humidity: 86%
Wind: Calm, 10-min avg: Calm, gust: 3 mph
Barometer: 29.96 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for North Platte, NE

        
000
FXUS63 KLBF 190909
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
409 AM CDT Sun May 19 2024

.KEY MESSAGES...

- The Storm Prediction Center has maintained a Slight Risk
  (level 2 of 5) for western Nebraska Sunday, mainly for areas 
  west of Highway 83 with large hail and damaging winds the main
  concerns.

- Additional strong to severe thunderstorms are possible on
  Monday though the main concern is likely to be the threat of 
  heavy rain Monday night into Tuesday.

- Cooler temperatures arrive around the middle of the week. Confidence
  in seeing a frost or freeze event remains low.

- A return to normal temperatures with active weather is
  expected for the latter half of the upcoming week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 407 AM CDT Sun May 19 2024

Early morning radar and satellite analysis depict a broad area of 
moderate to heavy rainfall lifting north and east out of western 
Kansas into far southwest and south central Nebraska. This activity 
is largely being driven by a modest shortwave ejecting ahead of 
larger scale troughing taking shape across the western CONUS. DCVA 
and WAA in the low-levels are helping provide broad ascent across 
the local area. Though instability declines quickly with northward 
extent, non-zero MUCAPE values and values reaching as high as 1000-
1500 j/kg have reached the Nebraska/Kansas border and will continue 
to translate north through the morning. This should allow for a 
continuation of rain and thunderstorm chances this morning. Given 
the magnitude of instability and deep-layer shear exceeding 35 
knots, cannot completely rule out stronger storms capable of at 
least small hail during the late morning, mainly for areas east of 
Highway 83. Lift is expected to wane by early afternoon as the main 
shortwave departs to the north and east. This should lead to an 
appreciable break during the day with dry conditions likely for at 
least the majority of the early afternoon.

Residual cloud cover as well as rain will likely hamper diurnal 
temperatures during the day. NWP model spread for high temperatures 
today vary widely for central Nebraska with discrepancies nearing 10 
degF. Higher resolution guidance is more bullish on afternoon high 
temperatures. This is largely due to quicker departure of 
rain/clouds as well as continued strong southerly flow in the lower 
levels which will support advection of warmer air into the area. 
Afternoon dew points will steadily climb with many locations 
climbing into the middle to upper 50s and even a few locations 
potentially seeing values in the lower 60s. While confidence is 
fairly limited for the immediate short range, the going forecast 
calls for afternoon highs in the middle 70s to middle 80s east to 
west. With the expected overlap of greatest surface temperatures and 
greatest low-level moisture, moderate instability will develop as 
west-southwesterly flow aloft will advect a stout EML over the 
region. This will yield moderate to strong instability immediately 
east of a sharpening dryline that will stretch from the Black Hills 
south into far northeast Colorado. With adequate deep layer shear 
already in place, organized severe convection is appearing more 
likely. The latest SPC Day 1 Outlook has expanded the pre-existing 
Slight Risk (level 2 of 5) north and east with the coverage now 
including most if not all locations between the Highway 385 and 
Highway 83 corridors. Forecast soundings, while depicting fairly 
strong capping that will need to be overcome, show long/straight 
hodographs above 1km with the majority of the instability located 
within and above the hail growth zone. With non-zero SCP values and 
moderate storm relative inflow at the surface, believe hail up to 
golf ball size will be possible with discrete convection early on. 
Gradually, upscale growth due to merging cold pools in an area of 
1000+ j/kg DCAPE and delta theta-e values falling below -20 degC 
should support more of a damaging wind threat. This will likely 
persist into the evening as rich theta-e air continues to be 
advected into what will likely be a maturing MCS. Only when this 
system begins to encounter recycled air originating from strong 
convection across Kansas will a weakening trend become likely. This 
will generally be around Midnight with the majority of activity 
likely having exited the local area by then. Precipitation amounts 
from this activity will be fairly variable. While a few localized 
areas may see 1.00" or more, most locations will likely remain in 
the 0.25-0.50" range.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 407 AM CDT Sun May 19 2024

Monday and Tuesday...Largely expect Monday to begin fairly quiet as 
the area is caught between the smaller scale system departing to the 
east and approaching large scale trough from the west. Deepening 
trough to the west will begin to approach the central CONUS by early 
morning Monday. Height falls are unlikely to increase markedly until 
the latter half of the day though which should limit the arrival of 
the greatest rain chances. Opted to decrease PoPs during the day as 
a result. This was done by blending in SREF/HREF PoPs. As a result, 
only Slight Chance PoPs (< 20%) exist for the early afternoon with 
only a slight increase of up to 35% (Chance category) expected by 
late afternoon for the eastern Panhandle. PoPs will maximize Monday 
evening into early Tuesday as the main PV anomaly overspreads the 
area. An attendant surface low lifting southwest to northeast across 
central Kansas will help promote strong lift within a anomalously 
moist environment where PWATs will likely exceed 1.00" in the pre-
convective environment. PoPs overnight Monday into Tuesday will 
likely near 100% for most locations in the local forecast area, as 
confidence remains high in a noteworthy rainfall event. The ECMWF 
Extreme Forecast Index (EFI) continues to highlight this with values 
exceeding 0.8 and Shift of Tails values of 0-2, suggesting the 
extreme values of the ensemble suite exceed the 90th percentile in 
the model climatology. Both EPS and GEFS ensemble products show 
increased probabilities of exceeding 1.00" total QPF for Monday 
night through Tuesday afternoon with the EPS the more bullish 
solution of the two. The 24-hour mean values from both ensemble 
suites exceed 1.00" in the maxima with the EPS nearing 1.75" for 
mean QPF. Deterministic solutions show widespread 1.00-2.00" 
rainfall with localized amounts closer to 3.50". It's important to 
note that unlike typical convective heavy rainfall scenarios, these 
amounts are being achieved in closer to 6 hour timeframe versus 
shorter periods. This should limit, but not negate, the threat for 
flash flooding. As the main trough aloft lifts north and east into 
the upper Mississippi Valley, precipitation will wind down and 
likely end by late in the day Tuesday. The PoPs inherited from the 
NBM maintain Slight Chance and Chance categories right through 
Tuesday evening and into Wednesday but deterministic solutions 
suggest there should be a notable break for the latter half of the 
daytime Tuesday so expecting these to be cleaned up with later 
forecasts. Temperatures will be trending cooler with a values 
falling into the 60s to low 70s Monday and 50s-60s by Tuesday.

A fairly active pattern will persist through the middle of next week 
as a stalled out upper-low allows smaller scale disturbances to 
pivot through the area. While day-to-day predictability remains 
fairly low confidence for now, ensemble signals point to Friday into 
early Saturday as the next appreciable chance in the local area. 
This will be attributed to a stronger cold front expected to dive 
south through the area. For now, precipitation chances will favor 
eastern Nebraska with decreasing probabilities as one goes west. 
That said, finer details like timing and placement of key features 
are unlikely to be confidently located until we're closer to 48-72 
hours out so expect the forecast to waver somewhat in the coming 
days. Ahead of this, temperatures will recover to seasonable values 
for Thursday and possibly Friday before falling once again in the 
wake of the front. The exact magnitude of cold air moving in remains 
to be seen but a brief cooldown is likely and the current forecast 
highs for Friday and Saturday include temperatures falling to around 
10 degrees below normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 102 AM CDT Sun May 19 2024

The main aviation concern will be the development of rain and 
thunderstorms during the day on Sunday. Confidence remains low on 
timing and location, but at this time the best chance to see 
thunderstorms will be in the afternoon mainly across southwest 
Nebraska and into the Sandhills. Large hail and strong gusts will be 
the main threats as well as reductions in visibility due to intense 
falling rain. The strongest storms should remain south of KVTN.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Kulik